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	2022-12-14: How Can Matter Be BOTH Liquid AND Gas? 20:01: ... all active galaxies glow at the maximum, and there are regions of such galaxies that are ...
	2022-11-23: How To See Black Holes By Catching Neutrinos 07:49: ... of cetus includes a lot of Milky Way stars, a lot of very distant galaxies, but there’s only one thing that is a plausible source of ... 08:08: It’s a beautiful spiral galaxy 47 million light years away. 08:12: Now a regular galaxy should not produce so many neutrinos. 08:25: As with most galaxies, including our own, there’s a gigantic black hole at its core. 08:34: But unlike most galaxies, M77's supermassive black hole is not quiet. 08:40: ... currently in a feeding phase - gas from the surrounding galaxy has been driven to the center, forming a whirlpool of searing plasma - ... 09:05: ... is not that powerful, it's known as a Seyfert galaxy, and the light of its accretion disk is hidden from us by a wreath of ... 09:17: Being one of the closest AGNs to our galaxy makes M77 a prime candidate as the source of neutrinos. 08:08: It’s a beautiful spiral galaxy 47 million light years away.
	2022-11-09: What If Humanity Is Among The First Spacefaring Civilizations? 00:55: Galaxies. 01:30: We are in fact on a typical planet, orbiting a typical star in a typical galaxy. 01:58: ... floating in a more typical environment: the freezing void between the galaxies. ... 11:54: ... to work out how to expand into space and another million to cross the galaxy at 10% light speed, this delay will have basically no effect on ...
	2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics? 17:10: In principle you could look at planets in other galaxies.
	2022-10-19: The Equation That Explains (Nearly) Everything! 15:40: ... are the most brilliant objects in the universe. They are the hearts of galaxies. Maelstroms of power and mystery shining out to us from across space and ...
	2022-10-12: The REAL Possibility of Mapping Alien Planets! 00:33: ... are billions of extrasolar   planets - exoplanets - in our galaxy. And we’re learning a ton about them - for example,   ... 01:25: ... You might recall these pictures of the black holes in the M31 galaxy and the center of the Milky Way.   These were taken by ... 04:36: ... produce highly distorted images,   like these stretched out galaxies seen  through the gravitational field of a   giant galaxy ... 06:05: ... it’s possible to reconstruct the image  from a messy galaxy lens, then it’s completely   straightforward to do it with the ... 12:52: ... be able to do this for many exoplanets.  And, actually, for distant galaxies and   black holes and literally anything else for  which ... 00:33: ... are billions of extrasolar   planets - exoplanets - in our galaxy. And we’re learning a ton about them - for example,   we’ve figured out ... 04:36: ... seen  through the gravitational field of a   giant galaxy cluster. If the alignment is close enough, we can see an Einstein Ring, like ... 06:05: ... it’s possible to reconstruct the image  from a messy galaxy lens, then it’s completely   straightforward to do it with the very ... 04:36: ... is what you get when   you try to reconstruct the original galaxy. The results are remarkably close to the originals.   We can go into the ...
	2022-09-21: Science of the James Webb Telescope Explained! 00:19: ... weeks now, and has seen some pretty amazing stuff, from colliding galaxies to planets and exoplanet atmospheres to the earliest, most distant ... 04:03: The very first galaxies shone with intense ultraviolet light as the dense, young gas of the early universe collapsed into the first stars. 04:28: JWST is designed to catch that light and has already observed galaxies much closer to the Big Bang than ever before. 04:34: JWST is also great at exploring galaxies of any epoch of cosmic time. 04:51: Combined with its sensitivity sensitified to the earliest galaxies this let’s us complete our map of galaxy evolution over cosmic history. 08:49: ... took of one apparently empty spot on the sky, but which reveals 10,000 galaxies back into the early ... 09:28: Those white blobby things are massive elliptical galaxies of the cluster, several billion light years away. 09:36: These arcs are much more distant galaxies whose light is warped by the gravitational field of the cluster. 09:49: And this bright star is, well, a star - in the milky Way galaxy. 04:51: Combined with its sensitivity sensitified to the earliest galaxies this let’s us complete our map of galaxy evolution over cosmic history.
	2022-09-14: Could the Higgs Boson Lead Us to Dark Matter? 01:40: We see its effect in the way galaxies move and in how the universe on the largest scales evolves. 04:18: If we were to find excess gamma radiation from high-density regions of our galaxy, then this might come from dark matter annihilations.
	2022-08-17: What If Dark Energy is a New Quantum Field? 03:33: ... of regular matter - like inside our solar system, or even inside our galaxy. But if you include the vast voids between the galaxies, the extremely ... 12:31: ... still accelerates - but that expansion is restricted to regions outside galaxies. The Milky Way survives a quintessence-dominated universe. That’s not ...
	2022-07-27: How Many States Of Matter Are There? 10:57: Astrophysicists routinely model the galaxies as a sort of fluid of stars, where the interactions are not electromagnetic, but gravitational. 11:05: So, galaxies are fluids of stars which themselves are made of plasmas of hydrogen made of frozen nuggets of quark matter. 11:14: So if sand and crowds and galaxies exhibit behaviors that resemble states of matter are these really actual states of matter?
	2022-07-20: What If We Live in a Superdeterministic Universe? 05:02: ... how far apart Alice and Bob’s labs are - across the campus or across the galaxy - the apparent influence should be ...
	2022-06-30: Could We Decode Alien Physics? 15:41: ... near  impossible for living things, the fact   that the galaxy could be completely filled with von Neumann probes from a single ... 15:07: ... thanks for helping us enhance the collective wisdom of the galaxy.    A quick announcement before   we get to comments: we’ll ... 15:41: ... probe - a self replicating device designed to propagate across the galaxy.   Even if interstellar travel is near  impossible for living things, ...
	2022-06-22: Is Interstellar Travel Impossible? 00:27: ... a galaxy where billions of planets have had billions of years to spawn ... 01:31: But none ever manage to populate the galaxy because sending living creatures between the stars is so difficult that it’s just not worth it. 03:36: The space between the stars in our galaxy is far from empty. 10:30: Moderate shielding is sufficient for nearby stars, and the ability to repair shielding might get us to more distant parts of the galaxy. 12:29: These things are accelerated in the monstrous magnetic fields of black holes and supernovae and of the galaxy itself.
	2022-06-01: What If Physics IS NOT Describing Reality? 13:31: ... the various acts of galactic cannibalism performed  by our galaxy. Let’s see what you had to ... 13:41: ... van Oosterhout asks what happens to  the central black holes of galaxies that the   milky way eats. The answer is simple - the ... 14:22: ... Ziak asks how galaxy interactions  affect the galactic habitable zone,   ... 15:25: ... Kosa asks about actual collisions between  stars when galaxies merge. Given that most of the   galaxy is empty space, what’s ... 16:52: ... of the traveling photons. And finally,   in a universe where galaxies shrink you’d expect  pygmy mammoths, which I’ve already told you ... 14:22: ... Ziak asks how galaxy interactions  affect the galactic habitable zone,   suggesting that it may ... 13:41: ... eats those black holes.   Eventually, anyway. If the swallowed galaxy is  big enough to have its own so-called supermassive   black ... 14:22: ... will move through many different   regions as it orbits the galaxy. It’ll be born in  a spiral arm probably, and then move in and out of ... 13:41: ... black hole, that black hole will end up in some  orbit within our galaxy’s gravitational well.   It’ll interact with stars, kicking them ...
	2022-05-25: The Evolution of the Modern Milky Way Galaxy 01:09: ... but are really snapshots of the incredibly  violent process of galaxy formation.   This is how all galaxies are made. We can  ... 01:41: ... what about our home galaxy? It would be nice  if we could learn the Milky Way’s true ... 02:19: ... Milky Way is a pretty typical barred  spiral galaxy. Our sun is in the disk,   on a minor outcropping of one of the ... 03:22: ... in our episode on the galactic habitable zone.   The first galaxies collapsed from very slight  over-dense regions in the hot hydrogen ... 05:11: ... For  example, stars that form from the gas of the   same galaxy tend to have similar amounts of heavy  elements in them, as the gas ... 05:58: ... slightly different, they may have drifted  to opposite sides of the galaxy by now.   But there are other orbital properties we can  ... 06:32: ... Suns worth of matter -   that it must have reshaped the galaxy and can be  thought of as the birth of the “modern” Milky ... 06:57: ... galaxy the Milky Way consumed has been  dubbed ‘Gaia-Enceladus’ - named ... 08:29: ... above and below its more slender counterpart.   Not all spiral galaxies have a thick disk, which  suggests something special happened to ... 09:11: ... into the halo, the crazy gravitational pulls   of the two galaxies slamming into each other  kicked up the orbits of many of the stars ... 09:42: ... lightly. But we can trace that history also.  When a dwarf galaxy gets too close to the Milky   Way it gets pulled thin as tidal ... 10:12: ... galaxy has dozens of known streams. Some of  the littlest ones are still ... 10:34: ... ago.   Since then, it’s wrapped all the way around  the galaxy, going up and over the poles and   coming back down to punch ... 11:10: ... the mass of the galaxy approaches, it pulls  the disk of the Milky Way up, but then when ... 11:57: ... we know of up  to 7 mergers in the history of   the galaxy and at least 42 distinct  streams surrounding the Milky ... 12:11: ... meal yet. The Milky Way’s two brightest satellite  galaxies, the Large and Small Magellanic Clouds,   are currently making ... 13:17: ... going to change with the final merger of our local   group of galaxies - when Andromeda and the  Milky Way collide. This is a major ... 13:54: ... and hungriest kid in the playground,   as we gobble up any galaxies foolish enough to stray into the Milky Way’s little patch of space ... 17:21: ... form   of the bound system — so I would think thank  galaxies that formed in an expanding universe   would be more puffed up ... 18:10: ... effect  due to the tiny vacuum energy inside   the galaxy. However the effect is minuscule, and  couldn’t really be ... 18:41: ... intergalactic space as expanding, but rather  that galaxies are shrinking. Jonathan Rose   has a similar hypothesis that ... 11:10: ... the mass of the galaxy approaches, it pulls  the disk of the Milky Way up, but then when ... 01:09: ... so it’s possible to stitch together a  frankenstein flipbook of galaxy evolution. ... 01:41: ... we know about the Milky Way of the present,   and of galaxy evolution in the general ... 02:19: ... a life of violence. So   let’s look at what we know about galaxy evolution  based on all the other galaxies in the ... 01:09: ... but are really snapshots of the incredibly  violent process of galaxy formation.   This is how all galaxies are made. We can  piece together a pretty ... 09:42: ... tidal  stream, and ultimately can be wrapped around   the galaxy multiple times. In the end  it disperses into the Milky Way’s ... 05:11: ... For  example, stars that form from the gas of the   same galaxy tend to have similar amounts of heavy  elements in them, as the gas that ... 06:57: ... a clear indication   that these stars were not born in our galaxy.  We’ve also found a group of 13 globular clusters   with ... 10:34: ... Gaia Enceladus breakfast   is the Sagittarius Dwarf Spheroidal Galaxy  which first fell in about 5 billion years ago.   Since then, ... 13:17: ... is a major merger,   because Andromeda is a full-blown spiral galaxy  in its own right. In fact it’s around twice as   massive as ... 06:57: ... a clear indication   that these stars were not born in our galaxy.  We’ve also found a group of 13 globular clusters   with matching ... 12:11: ... tails that make a great  loop all across the ‘bottom’ half of the galaxy,   a 600,000 lightyear long tail of  gas called the ‘Magellanic ... 14:38: ... start with the habitable zone: In that episode I said that parts of the galaxy   with too much heavy element abundance might not  produce life ...
	2022-05-18: What If the Galactic Habitable Zone LIMITS Intelligent Life? 00:00: ... wants to   kill us. In fact, a good fraction of our own  galaxy turns out to be utterly uninhabitable,   even for sun—like ... 01:07: ... of  the most perplexing mysteries of the universe? In   a galaxy of 200+ billion stars, why don’t we see  any other signs of ... 04:32: ... liquid water on the planet’s   surface. So it sounds like the galaxy should  be full of potential starting points for life,   ... 05:24: ... what are some of the factors that make  a region of the galaxy habitable or ... 06:28: ... parts of the Milky Way were wracked by  supernovae for much of the Galaxy’s ... 06:56: ... planetary systems could have formed in the first place. Our galaxies started   like all galaxies - as a slightly overdense ... 09:26: ... factors make the core the worst place in  the galaxy. The extreme density of stars will   have led to frequent close ... 10:04: ... core was forming, pristine  gas continued to pour into the Galaxy’s growing   gravitational field. It was swept up into  a ... 11:12: ... the Sun and solar   system are NOT special as far as our galaxy goes.  But now that we have so much back-story, perhaps   ... 12:04: ... discovered something unexpected: of all the stars  in the Galaxy that could currently support life,   most of them - 75% - have ... 13:03: ... a million years or less for one species   to colonise the galaxy - even if just with robotic  probes. But it seems that most ... 11:12: ... the Sun and solar   system are NOT special as far as our galaxy goes.  But now that we have so much back-story, perhaps   we can say ... 05:24: ... what are some of the factors that make  a region of the galaxy habitable or ... 04:32: ... liquid water on the planet’s   surface. So it sounds like the galaxy should  be full of potential starting points for life,   even if we ... 00:00: ... wants to   kill us. In fact, a good fraction of our own  galaxy turns out to be utterly uninhabitable,   even for sun—like stellar ... 04:32: ... that most stars have planets  - at least in the local part of the galaxy.   Kepler also revealed that there are around 40  billion Earth-analog ... 06:28: ... elements are produced in  massive stars and then spread through the galaxy   in supernova explosions. So a big factor  in determining the ... 06:56: ... further - beyond the formation  of the Sun to the formation of the Galaxy   to figure out where habitable planetary systems could have formed ... 08:01: ... so much. The metallicity of that  region is now the highest in the galaxy,   and high metallicity means too many planets  - in particular, too ... 04:32: ... that most stars have planets  - at least in the local part of the galaxy.   Kepler also revealed that there are around 40  billion Earth-analog ... 06:28: ... parts of the Milky Way were wracked by  supernovae for much of the Galaxy’s ... 10:04: ... core was forming, pristine  gas continued to pour into the Galaxy’s growing   gravitational field. It was swept up into  a ... 06:28: ... parts of the Milky Way were wracked by  supernovae for much of the Galaxy’s history. ...
	2022-05-04: Space DOES NOT Expand Everywhere 00:19: ... to reveal the universe is expanding on the largest scales. The distant galaxies are all racing away from us, and interpreted through the lens of ... 01:24: ... - planets orbit stars, stars orbit in the mutual gravity of their galaxies, galaxies whirl and collide in local groups and clusters. But if you ... 04:26: ... of the expanding universe that’s actually pretty useful here. Glue galaxies to a balloon and inflate. The galaxies recede from each other with ... 04:54: ... shape of the gridlines change. They pull towards massive objects like galaxies. ... 05:19: ... fight against the inward pull of gravity? Is the space inside, say, a galaxy growing but overcome by the gravitational attraction between the ... 06:04: ... expansion. In the balloon analogy it’s tempting to think of the galaxy as being held together despite the expanding material that it's attached ... 07:58: ... does an individual galaxy look like? If the galaxy causes gridlines to be pulled together on a ... 08:34: ... of the greater expansion comes from the receding view of distant galaxies. ... 11:59: ... to the amount of matter. But the ratio of empty space to matter inside galaxies doesn’t change. Now if the level of dark energy per unit volume were to ... 13:16: ... that we came into being soon enough to catch a glimpse of those receding galaxies - they will spend most of cosmic time far beyond the horizon, in which ... 05:19: ... fight against the inward pull of gravity? Is the space inside, say, a galaxy growing but overcome by the gravitational attraction between the ...
	2022-04-20: Does the Universe Create Itself? 07:43: ... on the other side of the lab - or on the other side of the galaxy. We’ve talked about this entanglement stuff in a previous ...
	2022-03-23: Where Is The Center of The Universe? 00:25: ... planet orbiting an ordinary star in the outskirts of an unremarkable galaxy. ... 01:46: Thanks to Edwin Hubble, we know that distant galaxies are racing away from us - and the further we look, the faster they’re moving. 02:05: The recession of the galaxies is just as well explained if all of space is expanding evenly everywhere. 02:12: Galaxies appear to be receding due the space between them stretching. 02:16: Most importantly, this looks the same no matter what galaxy you’re in. 11:35: ... out there are ways to make sense of Hubble’s observation of the receding galaxies that doesn’t require an infinite universe, nor a hyperspherically ...
	2022-03-08: Is the Proxima System Our Best Hope For Another Earth? 00:37: Alpha Centauri is the first and brightest of the constellation of the centaur, and the nearest star in our galaxy of 200 billion. 19:51: ... could explain the filaments and voids in the large scale distribution of galaxies in the universe, and whether they could explain the cosmic microwave ... 20:24: ... directly in the sense of cosmic strings causing string-like structure in galaxy ...
	2022-02-10: The Nature of Space and Time AMA 00:03: ... is that two types of motion are indistinguishable the motion of two galaxies moving apart because they're pinned to a to a space that's expanding ...
	2022-01-27: How Does Gravity Escape A Black Hole? 15:39: ... we showed of the inevitable collision of the Milky Way with the Andomeda Galaxy, Robert Herd asks the following: how can it be that in an expanding ... 16:04: Distant galaxies appear to be moving away because space on the largest scales is expanding evenly everywhere. 16:14: ... they’re close together, then the magnets will obviously form stars and galaxies. ... 16:25: ... back in our 3-body problem video, they asked how we can know that these galaxies will actually ... 15:39: ... we showed of the inevitable collision of the Milky Way with the Andomeda Galaxy, Robert Herd asks the following: how can it be that in an expanding universe, ...
	2022-01-19: How To Build The Universe in a Computer 00:03: In around four and a half billion years the Andromeda galaxy and our own Milky Way will finish their long mutual plummet. 00:16: Perhaps their denizens will look back with relief as the dislocated galaxies retreat on their future night skies. 00:30: ... be compacted to produce waves of supernovae, and the giant Milkdromeda galaxy will have been ... 00:59: And simulations of galaxy collisions are just the beginning. 01:40: He arrayed 37 light bulbs on a plane, each one representing billions of stars in a spiral galaxy disk. 02:37: ... so the two galaxies collided, just as with our modern supercomputer simulations, he ... 04:37: But if we want realistic simulations of say, a galaxy with its billions of stars, we need to do a bit better. 04:44: ... it’s improved nowhere near enough to do N-body simulations of entire galaxies using the method that I ... 05:26: ... simulation we’re trying to watch the detailed formation of individual galaxies, as well as the evolution of giant clusters of ... 07:57: ... gas is still everywhere - it flows into galaxies from beyond, where it rides the disk, fragments and collapses into ... 08:08: All of these processes are key parts of galaxy evolution and of star and planet formation, and so we’d better be able to simulate this too. 08:45: ... astrophysics, SPH codes are used to simulate  the flows of gas in galaxies and around quasars, used to simulate star and planet ... 08:58: SPH can even be used to do galaxy formation,   where the stars themselves are  treated as a type of fluid. 09:22: In your galaxy simulation you might need a separate prescription to describes how stars age and die. 10:02: ... can watch as galaxies form, with gas and dark matter interacting to produce waves of star ... 00:59: And simulations of galaxy collisions are just the beginning. 01:40: He arrayed 37 light bulbs on a plane, each one representing billions of stars in a spiral galaxy disk. 08:08: All of these processes are key parts of galaxy evolution and of star and planet formation, and so we’d better be able to simulate this too. 08:58: SPH can even be used to do galaxy formation,   where the stars themselves are  treated as a type of fluid. 09:22: In your galaxy simulation you might need a separate prescription to describes how stars age and die.
	2022-01-12: How To Simulate The Universe With DFT 06:18: In fact astrophysicists do huge galaxy simulations of millions of particles without doing millions-of-dimension calculations.
	2021-12-29: How to Find ALIEN Dyson Spheres 00:14: Any energy-hungry civilization more advanced than our own may leave an indisputable technological mark on the galaxy. 11:54: It would be incredibly difficult to detect such an object around a low mass star if it’s on the other side of the galaxy. 12:06: But that may not be true of other galaxies. 12:08: There are hundreds of billions of galaxies in the observable universe. 12:12: ... a single Dyson sphere's effects around individual stars at distant galaxies. But what if a civilization in one of those has occupied its entire home ... 12:33: ... by Penn State astronomer Jason Write used the WISE survey to look for galaxies that had too much infrared light compared to their visible ... 12:44: Now this is a bit tougher, because galaxies aren’t as simple as stars. 12:48: There can be a huge variation in the amount of IR that a galaxy produces. 12:53: But even accounting for this, the team found no evidence for galaxy-spanning civilizations in the 100,000 galaxies that they analysed. 13:11: In the past couple of years researchers have been thinking about Dyson spheres built around the supermassive black holes in the centers of galaxies. 13:55: ... future - one that could even leave our own astroengineering mark on the galaxy, perhaps to be noticed by younger species when they emerge in distant, ... 12:48: There can be a huge variation in the amount of IR that a galaxy produces. 12:53: But even accounting for this, the team found no evidence for galaxy-spanning civilizations in the 100,000 galaxies that they analysed.
	2021-12-20: What Happens If A Black Hole Hits Earth? 00:29: ... know there are plenty of these “stellar mass” black holes wandering the galaxy that we don’t see - but the chance of one coming close enough to cause ... 01:23: ... those little fluctuations in density eventually collapsed into stars and galaxies instead of black ... 02:27: ... holes all the way up to the supermassive black holes in the centers of galaxies. Over the decades, astronomers and cosmologists have managed to ... 15:30: ... point that I missed in that MOND episode. And that's that we’ve observed galaxies that seem to be >99% dark matter as well as a few that seem to lack ...
	2021-12-10: 2021 End of Year AMA! 00:02: ... deflected back towards each other by an intervening massive object a galaxy for example and reach us and so we can see the distant objects through ...
	2021-11-10: What If Our Understanding of Gravity Is Wrong? 00:24: ... the early 60s, Vera Rubin proved that the spiral galaxies are rotating so fast that they should fling themselves apart - ... 00:36: They would need at least 5 times as much  matter to provide the gravity needed to hold these galaxies together. 00:42: ... the gravity of visible matter is also way too weak to hold galaxy clusters together, or to bend the path of light to the degree seen in ... 01:22: The expected rotation rates of galaxies come  from applying our laws of gravity based on the observed mass. 02:11: In most galaxies, stars are somewhat concentrated  towards the centers, which means gravity should weaken towards the outskirts. 02:32: ... is supposed to add extra mass that’s more evenly distributed through galaxies, strengthening the gravitational field in the outskirts to explain the ... 04:08: If you tune the modification right you recover  the observed rotation curves for spiral galaxies very nicely without the need for extra mass. 04:17: ... minimum acceleration - to get the correct rotation curves for nearly all galaxies. ... 05:14: If you tune MOND to work for galaxies and then apply it to galaxy clusters, you do get rid of the need for some of the dark matter but not all of it. 06:35: ... galaxies all follow this tight relationship  between their speed of rotation ... 07:05: ... other hand, if you tune MOND to get the flat rotation curves of spiral galaxies, you automatically get the correct relationship  between rotation ... 08:50: ... possible to see if it gave the right result for the bending of light by galaxies, which wasn’t even possible with the original ... 10:58: ... into its deep gravitational wells and get to the business of forming galaxies. ... 12:07: ... see if the newly-dubbled  RelMOND - relativistic MOND - works for galaxy clusters and keeps stars from exploding  - but the authors are ... 12:33: ... I’ll just say that when galaxy clusters collide and the dark matter gets ripped away from the light ... 00:42: ... the gravity of visible matter is also way too weak to hold galaxy clusters together, or to bend the path of light to the degree seen in ... 05:14: If you tune MOND to work for galaxies and then apply it to galaxy clusters, you do get rid of the need for some of the dark matter but not all of it. 12:07: ... see if the newly-dubbled  RelMOND - relativistic MOND - works for galaxy clusters and keeps stars from exploding  - but the authors are ... 12:33: ... I’ll just say that when galaxy clusters collide and the dark matter gets ripped away from the light matter - it ...
	2021-09-15: Neutron Stars: The Most Extreme Objects in the Universe 10:06: ... these signals with LIGO right now, targeting   pulsars in our galaxy using their known rotation frequencies. They haven’t found anything ...
	2021-09-07: First Detection of Light from Behind a Black Hole 03:22: These things are pretty much only found in the very centers of galaxies, and pretty much every decent sized galaxy has one of these at their center. 09:38: The object is I Zwicky 1 - a so-called Seyfert galaxy, which is like a mini-quasar - this one around 100 million light years away. 13:21: ... because it would mean the number of FTL-capable civilizations in the galaxy would have to be enormous for the numbers to work ...
	2021-08-18: How Vacuum Decay Would Destroy The Universe 00:21: ... none of the familiar structures from atoms  to galaxies - would be possible. In fact,   for most possible ...
	2021-08-10: How to Communicate Across the Quantum Multiverse 16:27: ... rays that reach the earth. The magnetic fields then go on to add to the galaxy’s magnetic ...
	2021-08-03: How An Extreme New Star Could Change All Cosmology 15:05: ... how magnetism shapes our cosmos from the scale of planets up to entire galaxies. That magnetic episode .. attracted many ... 15:55: ... fields have any measurable effect on the orbits of stars around the galaxy. Not directly. The galactic magnetic field is very weak compared to the ... 17:08: ... magnetic fields do have important effects on scales from stars to galaxies - they’re still much, much weaker than gravity. Some people also hopped ...
	2021-07-21: How Magnetism Shapes The Universe 00:56: And it governs the formation of every major structure in the universe, from the smallest moon to the largest cluster of galaxies. 03:23: ... to this greater magnetic field of the solar system - and even of the galaxy. ... 04:55: About 4x the distance to Pluto, the Sun’s magnetic field connects to the field of the galaxy itself. 05:03: This is the heliopause, the boundary of the heliosphere, which defines the limit of the Sun’s influence in the galaxy. 05:11: Although it’s less of a sphere and more of a teardrop - dragged into that shape by the Sun’s orbital motion through the galaxy. 06:08: These specks tend to align with the local magnetic field of the Galaxy in exactly the same way as our iron filings align around a bar magnet. 06:56: The resulting map reveals a whirlwind of magnetism tangled through the galaxy. 07:05: Actually there’s a more traditional way to map the magnetic fields of galaxies. 08:21: We even have clear views of magnetic fields in many distant spiral galaxies. 08:39: And that plasma in turn drags the magnetic fields in orbit around the galaxy. 08:44: OK, so galaxies have magnetic fields. 10:17: ... same supernovae are expected to blast their own guts entirely out of the galaxy, which should result in all those newly-formed elements being lost to ... 10:34: That’s right - if you follow a magnetic field line too far, you may accidentally leave the galaxy. 10:39: But actually, these galactic fountains are incredibly important for building galaxies. 10:44: Their material tends to spill into the space around the galaxy before slowly raining back in, where it can be used for new star formation. 12:09: Thick flows of gas can be catapulted through the surrounding galaxy in powerful jets. 12:14: In some cases, these jets puncture the galaxy and plume out in radio lobes which can dwarf the entire galaxy that spawned them.
	2021-04-21: The NEW Warp Drive Possibilities 00:05: His whole “nothing travels faster than light” rule seems to ensure that exploration of even the local part of our galaxy will be an excruciating slow. 03:07: Or beyond the cosmic horizon, the expanding universe is carrying galaxies away from us faster than light. 12:47: And possibly also building a starship, to propel humanity into the galaxy on waves of warped space time.
	2021-04-13: What If Dark Matter Is Just Black Holes? 01:39: ... but it’s much more spread out than regular matter - for example, in our galaxy it forms a vast halo around twice the diameter of the Milky Way’s spiral ... 05:48: We see these “supermassive black holes” in the centers of essentially all galaxies. 05:53: Dark matter can’t be made of these or anything close to because they tend to fall to the centers of their galaxies pretty quickly. 08:24: ... best way to search for MACHOs in our galaxy is to monitor the stars in the galactic bulge or in our neighboring ... 09:46: ... I mentioned, the most massive black holes trickle to the center of our galaxy, but there’s an intermediate mass range from tens to thousands of solar ... 09:58: One way to test that is to look at dwarf galaxies. 10:01: ... galaxies are so small and dense that even black holes with tens of solar masses ... 10:11: ... of the structures of dwarf galaxies tells us that no more than 4% of the dark matter could be black holes of ... 10:20: ... existence of loosely bound binary star systems throughout our galaxy gives us similar constraints - if there were lots of black holes of ...
	2021-03-16: The NEW Crisis in Cosmology 01:16: ... Space on the largest scales   is stretching, throwing galaxies apart from  each other. We’ve talked about how ... 02:07: ... to nearby stars,   then more distant stars, then nearby  galaxies, then distant galaxies,  ... 02:36: ... if the Cepheid is in another galaxy,  you have the distance to that galaxy ... 03:13: ... partner. Using these supernovae to get distances   to galaxies halfway across the universe, they found something totally ... 06:22: ... distances from our good-ole Cepheid variables   in galaxies where both are observed. But those distant Cepheids are in turn ... 08:03: ... which tracked the motion of 100,000 stars in our local patch of the galaxy But to really nail down the lowest  rung of the distance ... 10:08: ... to look for vast ring-like patterns in the   way galaxies are scattered across the universe and use those rings as a sort of ... 10:40: ... hole - happens to be   closely aligned behind a more nearby galaxy. Then, that quasar’s light travels multiple paths ... 01:16: ... If we also know how far that light traveled - the distance to the galaxy - then we can figure   out the rate at which space is expanding ... 08:03: ... structure and motion of a good faction   of the Milky Way galaxy. Gaia is making the most accurate catalogue yet of parallax ... 10:40: ... hole - happens to be   closely aligned behind a more nearby galaxy. Then, that quasar’s light travels multiple paths through   this ... 02:36: ... so can find its distance.   And if the Cepheid is in another galaxy,  you have the distance to that galaxy ... 01:16: ... first figured this out. Long story short  - when a distant galaxy’s light travels to   us through the expanding universe it ...
	2021-02-17: Gravitational Wave Background Discovered? 00:00: ... colliding black holes well we've just taken it to the next level with a galaxy spanning gravitational wave detector that may have detected a ...
	2021-01-26: Is Dark Matter Made of Particles? 00:23: ... see the influence of dark matter in the orbits of stars and galaxies, in way light bends around galaxies and clusters, in the clumpiness of ... 03:05: ... the black lanes of dust that block the light from the center of our galaxy. ... 03:45: ... can map where dark matter is found by how it affects the rotation of galaxies, and how it drives the orbits of galaxies inside galaxy clusters, and by ... 04:21: They might collapse into dark matter galaxies or dark matter stars or dark matter people. 04:34: In fact, galaxies are really just shiny dustings of stars, sprinkled deep in the gravitational wells of massive reservoirs of dark matter. 05:06: In the early universe, that distance influenced the size of the seed structures which galaxies would later form from. 03:45: ... rotation of galaxies, and how it drives the orbits of galaxies inside galaxy clusters, and by the way it bends light around galaxies and ...
	2020-12-15: The Supernova At The End of Time 00:10: ... many very final-seeming fates await the Earth, then solar system, then galaxy, and ultimately the ...
	2020-11-18: The Arrow of Time and How to Reverse It 07:17: ... measure the velocities of particles across our universe - in the form of galaxies - we don’t see random motion. We see galaxies racing away from each ...
	2020-10-13: Do the Past and Future Exist? 14:36: ... mysterious absense of civilizations in our galaxy is sometimes explained in terms of a great filter - something reliably ...
	2020-09-08: The Truth About Beauty in Physics 09:23: Same with Newton’s gravity, derived from observations of apples and the moon, but it predicts the motions of galaxies.
	2020-08-17: How Stars Destroy Each Other 00:20: When our galaxy was a little younger there were two ordinary stars - perhaps not unlike our sun, and they danced together in binary orbit. 02:02: Our galaxy is full of these sorts of dysfunctional stellar relationships. 04:21: 50 or so classical novae go off in our galaxy every year. 07:09: ... start, you need to know that when you look at our galaxy in gamma rays - the highest energy light there is - the brightest points ... 10:05: Those supernovae are visible not just across the galaxy, but in galaxies across the universe.
	2020-07-28: What is a Theory of Everything: Livestream 00:00: ... the way things interact at the largest possible scales the scales of galaxies and super clusters of galaxies and all and the largest things in the ...
	2020-07-20: The Boundary Between Black Holes & Neutron Stars 03:04: Unfortunately, there are countless galaxies in a region that size, so to start with we have no idea in which galaxy the merger happened. 14:08: So, maybe then, there are antimatter galaxies out there. 14:25: ... there’s no way to directly test if distant galaxies are actually antimatter galaxies - they should emit exactly the same ...
	2020-06-30: Dissolving an Event Horizon 15:36: ... while it's low." And a gratifying number of Hitchhikers Guide to the Galaxy references: "The answer is 42." "Goodbye and thanks for all the fish." ...
	2020-06-22: Building Black Holes in a Lab 00:16: ... slingshot orbits around a patch of nothingness in the center of our galaxy, superheated disks of gas pouring into tiny spaces in quasars or X-ray ...
	2020-06-08: Can Viruses Travel Between Planets? 12:04: Perhaps DNA is the only possible basis for complex life, or perhaps panspermia seeded DNA-based life and DNA-preying viruses across the galaxy.
	2020-05-18: Mapping the Multiverse 16:27: So in an infinite universe, every definable galaxy or definable location ends up right here on top of us at some point in the rewind.
	2020-05-11: How Luminiferous Aether Led to Relativity 14:23: ... for an infinite universe the "size" is just the average distance between galaxies. Half that age and the galaxies were half the distance that they are ... 14:42: ... fraction of a second old, it was still infinite, even though ALL of the galaxies we can see were compacted into a tiny point. There were just infinitely ... 16:14: ... most distant horizon we can see is the same size as the local bubble of galaxies. Those poor cosmic background photons should have reached us billions of ...
	2020-05-04: How We Know The Universe is Ancient 00:55: ... to our discovery that there even is a universe outside the Milky Way galaxy. This is something we explored in our STELLAR series, but it’s worth a ... 01:35: ... or as Immanuel Kant called them, island universes. We now call them galaxies. It all changed in the 1920s. First Vesto Slipher found that the spiral ... 02:44: ... or redshifts and Hubble’s distances, we learned that essentially galaxies are racing away from us. And the further the galaxy the faster it seemed ... 03:09: ... We live in an evolving, expanding universe. The recession of the galaxies makes perfect sense in the context of Einstein’s then-new general theory ... 04:40: ... predict how long ago it happened. Think of it this way - if a particular galaxy is racing away from us, and we know how fast it’s moving and how far ... 06:06: ... the expansion rate has changed over time. You can’t just assume that the galaxies were always moving away at their current speeds. Now we’ll come back to ... 06:22: ... in something we call the Hubble constant, which just tells how fast a galaxy is moving away from us given its distance from us - the more distant, ... 07:07: ... problem with the observations. Edwin Hubble had got the distances to the galaxies wrong. It turns out that Cepheid variable stars come in two types, with ... 07:40: ... had observed a brighter variety of Cepheids in distant galaxies, but he then used a period- luminosity relationship measured from a ... 08:17: ... at Mt. Palomar to peer deeper than anyone had before into the Andromeda galaxy. With a newly calibrated Cepheid period- luminosity relation, and also ... 08:58: ... to explain another method astronomers had been using to get distances to galaxies, and so calculate the Hubble constant and the age of the universe. It’s ... 11:07: ... in dark matter - can be found by adding up the gravitational effect in galaxies and in galaxy clusters, and also by tracking the past expansion history ...
	2020-04-28: Space Time Livestream: Ask Matt Anything 00:00: ... curious about this piece what what can what can you tell them it's the galaxy the galaxy plane to the crowd but oh it is gold leaf and goals was ...
	2020-04-22: Will Wormholes Allow Fast Interstellar Travel? 14:59: ... Willenberg asks whether we've observed Fermi Bubbles in other galaxies. Actually yes. Google image search for "superbubbles". A lot of what ... 15:35: ... about the interstellar medium - isn't the space between the stars and galaxies an empty void? Actually no. Particularly within a galaxy, the space ... 16:33: And Leo Schultz was apparently already onto. Apparently I reside in a golden pyramid, floating above the galaxy. Well now I do. In my dreams at least. 14:59: ... Google image search for "superbubbles". A lot of what you'll see is the galaxy NGC 3079, which has very similar structures to the Fermi bubbles, in this ...
	2020-04-14: Was the Milky Way a Quasar? 00:00: The Milky Way galaxy is relatively calm by the destructive standards of the rest of the Universe, and compared to its own very violent past. 00:44: For example, the center of the Milky Way galaxy. 01:03: Yet as extreme as it may sound, the present-day Milky Way is actually relatively calm by the standards of many other galaxies in the Universe. 01:19: But across the Universe, there are loads of “active” galaxies - ones that harbour active galactic nuclei, or AGNs, at their centers. 01:36: The most powerful AGNs are called quasars, and they can shine a thousand times brighter than their surrounding galaxy. 02:58: In the case of the Milky Way it should form a vast ball that envelops the galaxy, thickening slightly towards the center. 03:47: Well, it turns out that the plane of the Galaxy also glows brightly in gamma rays. 06:36: Believe it or not, it’s not so uncommon for astronomers to witness storms of supernova explosions raging across a galaxy. 06:43: Or at least to catch a snapshot of a galaxy in the middle of such an event. 06:47: ... a galaxy has a lot of fresh gas and when that gas gets a shake - for example, if ... 09:23: AGN jets that get trapped within their galaxies tend to form more wedge-like shaped structures with internal structure - for example hotspots. 10:51: ... a handful of never-before-seen radio structures throughout the Galaxy — including two bubble-shaped structures extending above and below the ... 11:25: ... structures only extend 1400 light years above and below the plane of the Galaxy — leading astronomers to believe that they might be younger, more recent ... 06:47: ... if the galaxy is shaken by a collision or close interaction with another galaxy - then that gas can form stars at a really insane rate across the galaxy. ... 02:58: In the case of the Milky Way it should form a vast ball that envelops the galaxy, thickening slightly towards the center.
	2020-04-07: How We Know The Earth Is Ancient 03:43: ... way, Kant was also the first to have speculated about the existence of galaxies beyond the Milky way - Island Universes, as he called ... 10:35: ... proved that Immanuel Kant’s Island Universes were indeed other galaxies, many millions of light years away. The world simultaneously got a lot ...
	2020-03-24: How Black Holes Spin Space Time 01:01: ... havoc they wreak on their surroundings in distant quasars and in our own galaxy, and we’ve even taken an image of a black hole with the event horizon ... 06:48: ... a companion star or, in the case of quasars, a bunch of its host galaxy’s gas - the ISCO is expected to eventually be detectable as a dark circle ...
	2020-02-18: Does Consciousness Influence Quantum Mechanics? 14:26: ... also asked about this in the comments: if axions come from stars, would galaxies lose their dark matter and fly apart once the stars ... 14:37: This is a great image - galaxies falling apart as they turned into black holes and other stellar corpses.
	2020-02-11: Are Axions Dark Matter? 09:45: ... and forth between axions and photons by the magnetic fields of entire galaxies. That makes them invisible for part of their journey, so less likely to ...
	2020-01-27: Hacking the Nature of Reality 12:13: ... think that the largest structures in the universe today - galaxies and galaxy clusters - as collapsed from quantum fluctuations in the ... 12:27: ... observations - which in this case is the distribution of gigantic galaxies on the ... 16:14: ... be better at it because densities can be higher in the centers of small galaxies where those weaker active nuclei are ... 12:13: ... think that the largest structures in the universe today - galaxies and galaxy clusters - as collapsed from quantum fluctuations in the extremely early ...
	2020-01-20: Solving the Three Body Problem 06:20: ... millions of objects to simulate the formation and evolution of entire galaxies. But these numerical solutions didn’t begin with the invention artificial ...
	2020-01-13: How To Capture Black Holes 00:59: ... of binary black holes. And in very dense environments like the cores of galaxies, lone black holes may find each other and form a binary pair. However the ... 02:50: ... argument goes like this: we know that the center of almost every galaxy contains a supermassive black hole of millions to billions of times the ... 04:08: ... centers are, well, black. But occasionally gas from the surrounding galaxy will find its way into the galactic center and form an incandescent ... 05:37: ... in mass much, much faster than they could in almost anywhere else in the galaxy. So now we have one way for these black holes to get big. But in order to ... 10:18: ... contain hundreds of active galactic nuclei and many thousands of regular galaxies. Any of those could be the source of the black hole ... 10:40: ... we might see a temporary increase in the light from one of the active galaxies — a fading flash that is brightest at ultraviolet ...
	2020-01-06: How To Detect a Neutrino 07:51: ... ♪ enough to leave a bit of leftover stuff to produce the stars and galaxies and ♪ ♪ particle physicists that we see around us ...
	2019-12-17: Do Black Holes Create New Universes? 00:37: Tweak them too much and life, stars, galaxies, the universe as we know it wouldn’t exist.
	2019-12-09: The Doomsday Argument 00:08: We might hope for a trillion times that if we colonize the galaxy. 02:49: ... universe should have the maximum cosmological constant that would allow galaxies to form - and hence allow our ... 03:31: ... in a universe is proportional to the amount of mass that ends up forming galaxies in that ... 14:57: ... obvious example is that regular gravitational fields around stars and galaxies can be positively curved patches in a flat or hyperbolic ... 16:21: ... that is that the baryon acoustic oscillation signatures seen in galaxy clusters are an independent measure of curvature, and these point to a ...
	2019-12-02: Is The Universe Finite? 06:02: ... passes through a universe full of galaxies and galaxy clusters - all of which have enormous gravitational fields ... 08:39: In short - lensing by a cluster of galaxies tends to draw rays of light from different blobs together. 06:02: ... passes through a universe full of galaxies and galaxy clusters - all of which have enormous gravitational fields that act as lenses, ...
	2019-11-18: Can You Observe a Typical Universe? 00:45: ... of stars in the Milky Way, and that the Milky Way is an ordinary galaxy among 100s of billions of galaxies in the observable ... 01:20: It allows us to understand the origin of the Earth and the Milky Way by studying the ancient light of distant galaxies. 05:50: ... interesting that's happened since - from the formation of stars and galaxies to the evolution of life - has been powered by the slow increase in ... 08:33: For example a fluctuation the size of a galaxy is insanely more likely than one the size of our observable universe. 08:40: It’s much easier to produce 100s of billions of galaxy-sized fluctuations than a single fluctuation of 100s of billions of galaxies. 08:48: ... surely don’t need more than one galaxy to spawn a life-bearing planet - so there should be many more observers ... 08:40: It’s much easier to produce 100s of billions of galaxy-sized fluctuations than a single fluctuation of 100s of billions of galaxies.
	2019-11-11: Does Life Need a Multiverse to Exist? 01:44: ... our universe would be vastly different - and probably unable to produce galaxies, or stars, or ... 16:16: ... episode depressing - as in, sad to think we might be all alone in the galaxy. Well I know what you mean, but honestly, I find it kind of ... 16:27: I mean, what an awesome responsibility - to be among the first intelligent civilizations in our galaxy.
	2019-11-04: Why We Might Be Alone in the Universe 01:22: For example, in a planetary biosphere rather than floating in the void between the galaxies. 02:33: For example, if there’s only one life-bearing planet in the galaxy, or in the universe, you’re going to be on it. 03:05: ... opportunities for technical life to have emerged and spread through our galaxy and the apparent lack of galactic ... 04:45: The Kepler mission has revealed there should be 10 billion or so in our galaxy - 40 billion if we permit other star types. 05:02: ... had a tiny head start on us then it could have colonized the galaxy by ... 12:03: The Fermi paradox surely has a solution, and that solution may be that the galaxy is as empty as it looks. 04:45: The Kepler mission has revealed there should be 10 billion or so in our galaxy - 40 billion if we permit other star types. 07:31: Now, this could be an incredibly rare scenario, even galaxy-wide.
	2019-10-21: Is Time Travel Impossible? 01:15: Do a trip around the galaxy at close to the speed of light and very little time might pass from the perspective of the traveler.
	2019-10-15: Loop Quantum Gravity Explained 00:16: ... atoms and subatomic particles with that of the vast scales of planets, galaxies, and the entire ... 14:38: ... black hole merger, but the gravitational wave from it was deflected by a galaxy or something on its way to us - it was gravitationally lensed so as to ...
	2019-09-30: How Many Universes Are There? 06:31: ... universe would have restarted its accelerating expansion too quickly for galaxies and stars and life to ever ...
	2019-09-23: Is Pluto a Planet? 01:00: ... classify galaxies based on their shape, black holes based on how they feed and how they're ...
	2019-09-16: Could We Terraform Mars? 00:13: Life will blossom in our path and eventually the galaxy will shimmer with beautiful Earth-like orbs. 01:08: We’ll need to terraform Mars, as our first step to terraforming the galaxy.
	2019-08-26: How To Become an Astrophysicist + Challenge Question! 00:00: ... Space Telescope to help unravel the connection between quasars and galaxies As many others also found the two evolved hand-in-hand Each influencing ...
	2019-08-19: What Happened Before the Big Bang? 07:19: These same fluctuations collapsed under their own gravity to become the first galaxies. 10:51: ... realized that Vesta Slifer's observations of receding galaxies could be explained by an expanding universe and solved Einstein's ... 11:07: ... that before Hubble, we had no idea what the distances were to Slifer's galaxies and so we couldn't properly test this expanding universe ...
	2019-07-25: Deciphering The Vast Scale of the Universe 00:21: In that tiny area covered there are almost 10,000 entire galaxies. 00:43: Less than a century ago we didn’t know that a universe existed beyond our own Milky Way Galaxy. 00:49: ... and our understanding has grown enormously – to include countless galaxies to the cosmic horizon and almost to the beginning of ... 01:41: That’s not to say we’d never seen other galaxies – Andromeda is visible to the naked eye – if you have good vision. 01:48: And many nearby galaxies were visible as fuzzy blobs in our early telescopes. 01:53: But as far as we knew they were just clouds of gas inside our own galaxy. 03:25: Now there are some clever ways to measure distances to stars within the Milky Way galaxy. 03:32: But in another galaxy? 04:36: ... Andromeda Nebula became the Andromeda galaxy and with more distance measurements it became clear that all spiral ... 04:50: ... his distances with Vesto Slipher’s velocities to discover that the galaxies all appear to be racing away from the Milky Way – paving the way for the ... 06:23: ... we’re zipping past the hundreds of billions of stars of our Milky Way galaxy at a few hundred billion times the speed of ... 06:34: ... gives us an incredible understanding of the shape and motion of our home galaxy – once imagined to be the entire universe and now our very familiar ... 06:50: As we zoom out, now at several trillion times the speed of light, our local group of galaxies comes into view. 07:10: Every dot we see is a known galaxy, it’s position, velocity, and even stellar content measured and cataloged. 07:18: ... latest studies of galaxy motion reveal that Virgo, the Milky Way, and a hundred thousand more ... 07:32: ... speed of light we see the extent of our modern mapping of the universe – galaxies assembled into many vast filaments, flowing together on rivers of dark ... 07:58: They look small from here, but each is a maelstrom of gas falling into a giant black hole, and each shines out from the core of its own galaxy. 08:10: And so we just flew through an atlas of the some of the first galaxies to ever form. 08:16: ... see these most distant quasars, as well as the earliest galaxies or even black holes or worlds around other stars, Mt. Wilson's Hooker ... 07:18: ... latest studies of galaxy motion reveal that Virgo, the Milky Way, and a hundred thousand more galaxies ...
	2019-07-18: Did Time Start at the Big Bang? 00:25: ... of the retreating galaxies by Edwin Hubble and Vesto Slipher, combined with Einstein's - then - ...
	2019-07-01: Thorium and the Future of Nuclear Energy 15:29: ... In a recent episode we talked about how black holes influence the galaxies they formed in often by killing them Let's see what you had to say Steve ... 16:45: ... holes or active galactic nuclei are Typically in bowl-like elliptical galaxies. So orientation isn't as meaningful as in a spiral ... 16:59: ... active galactic nuclei tend to live in spiral galaxies for example Seyfert galaxies and they can have their Jets pointing in ... 17:49: ... more resources to investigating all West themed planets in elliptical galaxies I don't know, Oppie. I just don't ...
	2019-06-20: The Quasar from The Beginning of Time 03:40: For example, viewed in visible light, the Andromeda galaxy shows us newborn stars. 05:53: Now, that gas collapsed into the very first stars, then the very first galaxies.
	2019-06-17: How Black Holes Kill Galaxies 00:08: ... if that weren't enough we soon realized that every single decent sized Galaxy contains such a Supermassive Black Hole While in the beginning of the ... 01:35: ... itself depends on the total mass of the Galaxy including Dark Matter so why shouldn't a Galaxy and its Black Hole be ... 02:54: ... opposed to 'Top-down' which would have the large galaxies collapsing directly from the gas Now, Based on our understanding of ... 04:05: ... Things: In order for the Black Hole to grow in lock step with the galaxy you need to get a consistent proportion of new material down into the ... 05:09: how does a galaxy know to stop growing when its 1000 times larger than the Central Black Hole? 05:14: ... the best contender is that the black holes kill galaxies and by "kill" , I mean make them dead which I guess is the usual sense ... 05:24: ... in Astronomy, a dead galaxy refers to its current star formation activity in particular, the largest ... 06:33: ... of them involve a Quasar switching on and blasting the crap out of the galaxy's gas rewinding a bit to the whole galaxy formation thing when galaxies ... 07:21: ... dump an enormous amount of energy into the gas through the surrounding galaxy that can do two things It can drive gas out of the galaxy and prevent ... 10:44: Surely enough to shut down those galaxies' further growth. 10:49: ... the modern universe Giant Dead galaxies harbor fossil quasars supermassive Black Holes whose close connection to ... 12:04: ... that neutron star collisions are rare so that only lucky parts of the galaxies have a high abundance of the products of those ... 12:17: ... these collisions are rare they are common enough that most of the galaxy gets a decent amount of all the stable products of neutron star ... 04:05: ... of the Galaxy That's challenging, given how messy and varied the whole galaxy assembly process seems to be Second Observation seem to indicate that early Black ... 01:35: ... Holes somehow extend their nefarious influence throughout the entire Galaxy disrupting its ability to grow To understand this We first need to understand how ... 02:54: ... the nature of Dark Matter and Dark Energy we expect 'Bottom up Galaxy formation' this is what we see in our simulations of the Universe and also mostly ... 06:33: ... blasting the crap out of the galaxy's gas rewinding a bit to the whole galaxy formation thing when galaxies collide or even get stirred up a bit by eating a ... 01:35: ... itself depends on the total mass of the Galaxy including Dark Matter so why shouldn't a Galaxy and its Black Hole be closely ... 05:24: ... in Astronomy, a dead galaxy refers to its current star formation activity in particular, the largest ... 07:21: ... formation and its own feeding the end result is that Black Hole mass and Galaxy size are closely linked and in the largest galaxies our red dead ellipticals ... 06:33: ... of them involve a Quasar switching on and blasting the crap out of the galaxy's gas rewinding a bit to the whole galaxy formation thing when galaxies ...
	2019-06-06: The Alchemy of Neutron Star Collisions 02:47: ... supernovae at producing heavy elements and getting the mountains of the galaxy now that we've spotted these elements around the site of a neutron star ...
	2019-05-16: The Cosmic Dark Ages 00:24: ... past in motion. In fact we’re able to see some of the first stars and galaxies to ever form. But if we look beyond, both in distance and in time, there ... 03:52: ... galaxies – proto-galaxies – formed stars at a prodigious rate, and around these ... 04:46: ... story, but how do we know any of this? We do see a handful of primitive galaxies shining out from this time, including one from right near the beginning ... 03:52: ... with only tattered fragments of neutral gas drifting between the growing galaxy clusters. ...
	2019-05-09: Why Quantum Computing Requires Quantum Cryptography 14:46: ... we're covering comments from the last two videos - our episode on the galaxy without dark matter, and our coverage of the event horizon telescope's ... 15:19: One of dark matter's definig qualities is that it doesn't clump together - it remains diffusely spread out through our galaxy.
	2019-05-01: The Real Science of the EHT Black Hole 00:54: The beast in question is the supermassive black hole in the center of the M87 elliptical galaxy. 05:26: ... supermassive black hole at the heart of the M87 galaxy is currently active – it’s currently surrounded by an accretion disk – a ... 05:46: We see that jet extending 5000 light years outside the galaxy. 07:29: ... whipped into a near-light-speed vortex before being blasted through the galaxy ... 09:19: ... the rotational axis rotation based on the jet that we see leaving the galaxy. ...
	2019-04-24: No Dark Matter = Proof of Dark Matter? 00:03: ... is an exotic unknown substance may have come from the discovery of two galaxies that appear to have no dark matter at all today on spacetime journal ...
	2019-04-03: The Edge of an Infinite Universe 17:29: After some millions of years watching the galaxies fall apart, the last phase of the destruction of the solar system would happen pretty fast.
	2019-03-28: Could the Universe End by Tearing Apart Every Atom? 00:05: ... Galaxies ripped to shreds, Stars obliterated cats and dogs living together and ... 00:25: ... isn't a big deal at least for those of us safe and sound in nice galaxies like the Milky Way here the galaxy's gravitational field is plenty ... 01:55: ... Galaxies will eventually be so far apart that they can't see each other let alone ... 07:32: Eventually, we won't even be able to see the nearest galaxies because they'll be moving away too quickly. 07:38: But as long as we have a nice gravitationally bound galaxy to live in, the cosmic event horizon can never shrink to a size smaller than that galaxy. 07:47: ... not the case if dark energy increases. After our galaxy is disrupted by the increasing dark energy there's no protection from ... 09:15: ... messy until near the end, around a billion years before the big rip, galaxy clusters are ripped apart. At 60 million years and counting, the Milky ... 09:44: And so there should be a handful of galaxies still visible to us. 09:48: There are some millions of years of fun as we watch those galaxies disassemble and the constellations of stars in the Milky Way fly apart. 12:53: ... will still end in a long cold heat death in which the stars of our galaxy wink out become black holes and then evaporate over an unthinkably long ... 00:25: ... minuscule effect of dark energy it's in the vast tracts of space between galaxy clusters over countless trillions of cubic light-years of emptiness the dark ... 09:15: ... messy until near the end, around a billion years before the big rip, galaxy clusters are ripped apart. At 60 million years and counting, the Milky Way is ... 12:53: ... will still end in a long cold heat death in which the stars of our galaxy wink out become black holes and then evaporate over an unthinkably long ... 00:25: ... those of us safe and sound in nice galaxies like the Milky Way here the galaxy's gravitational field is plenty strong enough to resist the minuscule ...
	2019-03-20: Is Dark Energy Getting Stronger? 02:32: We see its effect in the rotation and movement of galaxies and in the bending of light due its space-warping gravity. 07:31: ... are vast winds that spray into the galaxy, giant jets that can punch out into intergalactic space, and also, ... 12:06: It’s not strong enough to have any effect on the space inside a galaxy, so the Milky Way, and certainly the solar system are safe. 12:15: ... stronger, then eventually it could cause the universe to expand inside galaxies, inside planetary systems, and eventually even inside ... 07:31: ... are vast winds that spray into the galaxy, giant jets that can punch out into intergalactic space, and also, hovering ...
	2019-03-06: The Impossibility of Perpetual Motion Machines 13:47: ... contaminating microwaves mostly come from our galaxy - there's a lot from the dust in between the stars, and also from ... 15:07: ... of the baryon acoustic oscillations frozen into both the CMB and in galaxy rings were blurred out quite a bit because the universe took a moment to ... 13:47: ... contaminating microwaves mostly come from our galaxy - there's a lot from the dust in between the stars, and also from ... 15:07: ... of the baryon acoustic oscillations frozen into both the CMB and in galaxy rings were blurred out quite a bit because the universe took a moment to ...
	2019-02-20: Secrets of the Cosmic Microwave Background 02:05: ... Recombination As the universe evolved those frozen shells collapsed into galaxies We still see them today Interwoven patterns of rings drawn in galaxies ... 12:34: ... and energy that's all of the atoms in all of the stars in all of the galaxies basically everything you can see The remaining 95% is the so-called Dark ... 14:23: ... clear about that So you should actually have overlapping bubbles of galaxies throughout the Universe But we only see a 2D projection of that Universe ...
	2019-02-07: Sound Waves from the Beginning of Time 00:04: Invisible to the naked eye, Our night sky is scattered with the hundreds of billions of galaxies that fill the known universe. 00:11: ... the stars, these galaxies form constellations, Hidden patterns that echo the reverberations of ... 01:22: They are the fossils of the first sound waves in the universe, imprinted on the distribution of galaxies on the sky. 06:46: ... and helium could begin the long work of collapsing into stars and galaxies work of collapsing into stars and galaxies as the universe continued to ... 07:22: Well, crazily, we can still see those rings, not made of plasma or gas, but made of galaxies. 08:17: Then, what it looks like now in the arrangement of galaxies. 08:35: Collapse that web into galaxies over the age of the universe, and at first glance, it looks like a random smattering of galaxies on the sky. 08:45: Detecting it required the most detailed surveys of the heavens ever conducted: It required galaxy redshift surveys. 08:54: Redshift is just the amount by which a galaxy's light has been stretched as it travelled through the expanding universe. 09:01: The more stretching, the longer that light has travelled, and so the more distant that galaxy must be. 09:08: ... gives distance. And with careful measurements of galaxies' positions on the sky, a redshift survey can produce a three-dimensional ... 09:18: With a galaxy redshift survey in hand, how do you find patterns in what looks like a random splattering of tens to hundreds of thousands of galaxies? 09:27: ... you expect that galaxies should mostly form in the centers of those primordial density ... 09:37: But you should also have a slight overabundance of galaxies at exactly 150 megaparsecs from those clusters. 10:01: Within that slice, tally up the distances on the sky between every pair of galaxies. 10:07: You should see a lot of galaxies that are close together. 10:13: They should also see a slight excess of galaxy pairs with separations of 150 megaparsecs. 10:21: These are the galaxy pairs where one is at the center of the dark matter peak, and one is on the surrounding ring. 10:36: ... in 2005 by the Sloan Digital Sky Survey in the northern hemisphere galaxies, and the 2dF survey in the ... 12:39: I mean think about it. There are rings in the sky inscribed in galaxies, frozen echoes of the very first sound waves to reverberate across space-time. 10:13: They should also see a slight excess of galaxy pairs with separations of 150 megaparsecs. 10:21: These are the galaxy pairs where one is at the center of the dark matter peak, and one is on the surrounding ring. 08:45: Detecting it required the most detailed surveys of the heavens ever conducted: It required galaxy redshift surveys. 09:18: With a galaxy redshift survey in hand, how do you find patterns in what looks like a random splattering of tens to hundreds of thousands of galaxies? 08:45: Detecting it required the most detailed surveys of the heavens ever conducted: It required galaxy redshift surveys. 08:54: Redshift is just the amount by which a galaxy's light has been stretched as it travelled through the expanding universe.
	2019-01-24: The Crisis in Cosmology 00:36: ...that there are galaxies outside the Milky Way,... 00:45: ...far outside the Milky Way, and so must be galaxies in their own right. 00:53: ...Hubble revealed that the galaxies are not only receding from us,... 01:07: The galaxies appear to be racing away from us, because the intervening space is expanding. 01:18: ... (H0) It tells us how fast the galaxies appear to be retreating from us, dependent on their distance apart But, ... 02:29: Km/s, that's for the recession speed of a given galaxy. 02:46: ...we'd expect the galaxy to be retreating from us at an additional 75 kilometers per second. 02:54: ...meant measuring the recession velocity and distance for as many galaxies as possible. 03:05: This is the lengthening of the wavelength of light from that galaxy,... 03:27: Measuring Cepheid periods in other galaxies gave Hubble their true brightnesses,... 06:07: The SHOES project measures the recession of galaxies up to around 2 billion light years away. 07:50: ...would go on to collapse into the vast clusters of galaxies of the modern universe. 14:26: ...due to the gravitational fields of more nearby galaxies.
	2019-01-09: Are Dark Matter And Dark Energy The Same? 00:32: And it’s pretty wild: negative mass particles continuously popping into existence between the galaxies. 01:18: So, dark matter: the galaxies are spinning too fast. 01:31: So we conclude that galaxies, and for that matter the universe, has 5-10 times as much matter as we can actually see. 06:32: Those simulations showed that galaxies do indeed spin more quickly when surrounded by negative mass particles. 06:39: ... is because the positive mass in the galaxy attracts a halo of negative mass, but at the same time that positive ... 06:50: This confines the galaxy from the outside so it can spin faster than if it were held together by its gravity alone. 12:41: Those galaxy rotation simulations are fascinating. 06:39: ... is because the positive mass in the galaxy attracts a halo of negative mass, but at the same time that positive mass is ... 12:41: Those galaxy rotation simulations are fascinating.
	2018-12-12: Quantum Physics in a Mirror Universe 00:02: ... origin was extremely improbable if it only had to happen once in the galaxy then we can consider abiogenesis mechanisms that are tens of billions of ...
	2018-12-06: Did Life on Earth Come from Space? 00:03: ... the abiogenesis is so unlikely that it only happened once in the entire galaxy and that once was not on earth what if primitive life arrived on earth ... 00:37: ... panspermia stars may be constantly spraying their germy life through the galaxies in some respects it sounds like levitating into space and becoming your ...
	2018-11-21: 'Oumuamua Is Not Aliens 09:01: ... every star that passed before us shed its vast cloud of comets into the galaxy, that would make plenty enough interstellar trash to explain ...
	2018-11-14: Supersymmetric Particle Found? 00:11: And we have one, the galaxy. 00:14: And the particles the galaxy flings at us may have finally revealed particles beyond the standard model.
	2018-10-25: Will We Ever Find Alien Life? 00:06: The silence of the galaxy and the resulting Fermi paradox has perplexed us for over half a century. 00:36: ... short, in a galaxy of hundreds of billions of stars, each of which having billions of years ... 01:11: A series of very recent surveys of our galaxy reveal none of the above while, at the same time, proving the abundance of potentially habitable worlds. 06:51: ... of the age of the Milky Way, and someone should have colonized the galaxy by now, yet we see ... 10:13: It also means we have a long, lonely future as one of the galaxy's only advanced species. 10:28: ... such thorough reliability that literally none ever leave a mark on the Galaxy. ... 12:15: So which will come first, spreading human civilization across the galaxy or humanity's doom? 01:11: A series of very recent surveys of our galaxy reveal none of the above while, at the same time, proving the abundance of potentially habitable worlds. 10:13: It also means we have a long, lonely future as one of the galaxy's only advanced species.
	2018-10-18: What are the Strings in String Theory? 03:58: ... Planck scale, roughly the scale of the difference between the Milky Way galaxy and your living ...
	2018-10-03: How to Detect Extra Dimensions 01:42: ... spectrum and, ultimately, with the discovery of the distant galaxy in which the explosion ... 07:48: In our hypothetical universe with four spatial dimensions, gravity is already weak on the scale of the solar system and the galaxy.
	2018-09-12: How Much Information is in the Universe? 00:19: Hundreds of billions of galaxies, each with hundreds of billions of stars, each with rather a lot of particles in them. 00:25: ... planets, and the particles, and radiation in between the stars and galaxies, not to mention space itself, with its fluctuating quantum fields, dark ... 08:14: And there are some hundreds of billions of galaxies in the universe, each with its own supermassive black hole.
	2018-08-23: How Will the Universe End? 02:13: ... episodes, we looked at the long series of ends of the world and of the galaxy that are in store for us, from disasters that will almost certainly ... 02:32: ... left us in a sorry state-- the merged Milky Way-Andromeda Galaxy comprised of nothing but stellar remnants, the ultradense neutron stars ... 03:13: ... out, the accelerating expansion of the universe will have dragged all galaxies beyond the Virgo Supercluster outside of the cosmic event ... 03:40: There'll be no evidence of a universe beyond the local galaxy and no evidence that there was ever a Big Bang. 04:40: The next destructive event is that every planetary system in the galaxy will eventually be disrupted by close encounters between stellar remnants. 05:04: The next calamity to befall the combined Milky Way-Andromeda Galaxy and, in fact, every galaxy will be its complete dissolution. 05:19: The remnants, mostly black dwarfs but also the diaspora of frozen planets and similar substellar objects, will be flung out of the galaxy. 05:33: ... to an estimate by Freeman Dyson, 90% to 99% of our galaxy's stars will be scattered into the void in something like 10 to the power ... 05:58: What happens after the Age of Galaxies depends on a critical question. 07:13: Some will be the remnant black holes of individual stars that were flung from galaxies long ago. 07:23: These monsters once grew in the cores of the now-forgotten galaxies. 07:27: Now they are all that's left of those galaxies. 07:30: Some have grown to masses of up to 100 trillion suns, having swallowed good-sized bites from entire galaxy clusters. 02:32: ... left us in a sorry state-- the merged Milky Way-Andromeda Galaxy comprised of nothing but stellar remnants, the ultradense neutron stars and black ... 05:33: ... to an estimate by Freeman Dyson, 90% to 99% of our galaxy's stars will be scattered into the void in something like 10 to the power ...
	2018-05-16: Noether's Theorem and The Symmetries of Reality 11:05: ... objects, detect the effects of weak gravitational lensing in distant galaxies, and see more distant supernovae, monitoring more distant quasars for ...
	2018-05-09: How Gaia Changed Astronomy Forever 00:18: Our understanding of our own galaxy will never be the same again. 01:23: The result is a 3D dynamical atlas of our quadrant of the galaxy. 01:44: From there, it stares outwards to the galaxy. 04:23: Moving on to stellar velocities, the galaxy is a dynamic place. 05:27: We can map things like stellar streams and detailed substructure that tell us about the history of our galaxies formation. 05:34: ... have already found evidence in the Gaia data that our galaxy was disturbed hundreds of millions of years ago, probably by an ... 05:46: And mapping globular clusters and dwarf galaxy orbits also tells us about future interactions with the Milky Way. 06:59: This dynamical information will be a powerful tool in understanding the dark matter distribution of the galaxy. 07:11: These dynamically connected flows of stars, once bound together as a globular clusters or dwarf galaxies. 07:51: Gaia has also mapped the position and brightnesses of over half a million quasars-- the cause of distant active galaxies. 08:14: Every generation, we improve our maps-- first, our maps of the world and now, our maps of the galaxy, filling in unexplored regions. 05:46: And mapping globular clusters and dwarf galaxy orbits also tells us about future interactions with the Milky Way.
	2018-05-02: The Star at the End of Time 00:00: [MUSIC PLAYING] If our descendants or any conscious being is around to witness the very distant future of our galaxy, what will they see? 00:30: ... to existence through the countless generations as we watch the Andromeda Galaxy merge with the Milky Way, forming a vast elliptical ... 06:21: So what does this mean for the future of our galaxy and for any life that exists then? 06:26: Well, long before the first red dwarfs approach the ends of their lives, there will be no other living stars left in the galaxy. 09:24: Joshua Hillerup asks whether dynamical friction leads to less dark matter near the centers of galaxies since dark matter's not very dense. 09:34: Yeah, dark matter is expected to be more evenly spread through the galaxy than things like stars and black holes. 09:54: ... asks how we'd be able to tell that the supermassive black hole in our galaxy center is in itself a dense swarm of smaller black holes in a shared ... 00:30: ... to existence through the countless generations as we watch the Andromeda Galaxy merge with the Milky Way, forming a vast elliptical ...
	2018-04-25: Black Hole Swarms 00:16: [MUSIC PLAYING] The core of our galaxy is a wild place. 00:58: ... swarm of smaller black holes that have reigned in from the surrounding galaxy. ... 01:07: ... "A Density Cusp of Quiesce X-ray Binaries in the Central Parsec of the Galaxy." In it, these astrophysicists find powerful evidence that our own Milky ... 01:56: And the densest, stellar objects, like black holes, sink to the centers of galaxies or star clusters. 02:51: As a black hole orbits the galaxy, it tugs on its neighboring stars. 03:46: Our galaxy is surrounded by these things called globular clusters. 04:30: Those black holes would then, sink even further to the center of the galaxy. 05:21: These X-ray binaries are seen throughout the galaxy. 07:35: Now, that's tens of thousands of times the black hole density anywhere else in the galaxy so yeah, it's a swarm of black holes. 08:05: ... black holes are so densely packed in the centers of galaxies, then we should probably know that, if we want to understand the source ...
	2018-04-18: Using Stars to See Gravitational Waves 00:14: In some cases, we're going to need a gravitational wave observatory the size of a galaxy. 03:49: ... mass black holes, supermassive black holes that live in the centers of galaxies, we need to observe gravitational waves in the 0.1 million hertz to 0.1 ... 05:34: We'd need a network of perfect timing devices scattered across the galaxy. 06:27: This galaxy scale observatory is already in operation and has placed valuable limits on the amplitude of the gravitational wave background. 07:52: ... observe this effect in the dense star fields of galactic cores if those galaxies also contain binary supermassive black holes that are generating ... 06:27: This galaxy scale observatory is already in operation and has placed valuable limits on the amplitude of the gravitational wave background.
	2018-04-11: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!) 10:10: ... energy into the most random possible state, little eddies of order, like galaxies, stars, planets, and life naturally ... 12:44: But the accelerating expansion of the universe will prevent any photons emitted today from galaxies at that distance or beyond from ever reaching us.
	2018-03-28: The Andromeda-Milky Way Collision 00:03: ... event to take place in the history of the night sky as the Andromeda Galaxy plows headlong into our own Milky ... 00:30: That's M31, the Andromeda Galaxy. 00:51: Andromeda is also racing towards our galaxy at 110 kilometers per second. 01:10: At around four billion years from now, it'll crash through the Milky Way, and both galaxies will be utterly disrupted in the monumental collision. 01:25: The Andromeda Galaxy was our first clue that there existed a universe outside the Milky Way. 01:41: ... whether Andromeda was a much smaller cloud of gas, a nebula inside our galaxy, or whether it was a galaxy in its own right at a much greater ... 02:45: Those Cepheids appeared extremely faint in Edwin Hubble's observations due to the galaxy's great distance. 03:01: Hubble went on to combine distance measurements to many galaxies with measurements of their velocities to discover the expansion of the universe. 03:16: Almost all of Slipher's galaxies seem to be moving away from us. 03:32: But Doppler shift measurements only gives the line of sight velocity, the component of the galaxy's motion directly towards or away from us. 03:44: If the galaxy has enough sideways or transverse velocity, then it could miss us completely. 03:55: The galaxy is so far away that its motion relative to background galaxies is almost imperceptible. 04:32: They mapped the locations of thousands of stars in Andromeda between 2002 and 2010 and compared them to background galaxies. 05:20: They also included the Triangulum, or Pinwheel Galaxy, the third-largest member of the Local Group. 05:30: The giant spiral galaxies fall together, and the little Triangulum Galaxy joins the party. 05:35: The first impact in around four billion years completely disrupts the spiral structure of both galaxies, creating these amazing tidal tails. 05:43: We see these in other distant galaxies, like the Antennae, which are currently in the process of collision. 05:49: ... Andromeda's core travels on for a bit before falling back, and the two galaxies merge into a vast football-shaped elliptical galaxy in around six ... 06:00: Both galaxies contain a supermassive black hole, which will fall towards the center of the new merged galaxy. 06:09: Gravitational interactions with stars slingshots those stars into larger orbits or even completely out of the galaxy. 06:37: There's also a chance that gas throughout the galaxy will be shocked into a storm of new star formation. 07:17: One big question is where we will land when the new uber galaxy settles. 07:33: Most end up in the outer parts of the merged galaxy, but many have orbits that periodically plunge them through the central regions. 07:40: ... travel far enough from the center to make dashes through the Triangulum galaxy before that galaxy also gets gobbled by the giant ... 08:08: Well, for around two billion years after the initial impact, our sky will be full of a galactic train wreck as the two galaxies settle down. 08:37: ... and whose spiral structure helped us guess the shape of our own galaxy. ... 08:56: Astronomers in the distant future will see only a single featureless orb in the sky, and the next nearest galaxies will be very far and fast receding. 10:25: ... thing, there's the consistency of the dark matter mass measurements of galaxies and galaxy clusters from gravitational lensing versus ... 05:30: The giant spiral galaxies fall together, and the little Triangulum Galaxy joins the party. 00:03: ... event to take place in the history of the night sky as the Andromeda Galaxy plows headlong into our own Milky ... 07:17: One big question is where we will land when the new uber galaxy settles. 02:45: Those Cepheids appeared extremely faint in Edwin Hubble's observations due to the galaxy's great distance. 03:32: But Doppler shift measurements only gives the line of sight velocity, the component of the galaxy's motion directly towards or away from us. 02:45: Those Cepheids appeared extremely faint in Edwin Hubble's observations due to the galaxy's great distance. 03:32: But Doppler shift measurements only gives the line of sight velocity, the component of the galaxy's motion directly towards or away from us.
	2018-03-21: Scientists Have Detected the First Stars 02:13: Before long, some of that early hydrogen gas collapsed to form the very first stars, long before the first galaxies formed.
	2018-02-21: The Death of the Sun 08:47: ... point to watch the sun's inevitable death, and to look to the greater galaxy for a new home across far reaches of space ...
	2018-01-31: Kronos: Devourer Of Worlds 00:50: And they form in the many thousands before being ejected from their birth clusters to wander the galaxy. 01:32: These wide binaries are actually extremely useful tools for understanding star formation and the environment of the galaxy they live in. 03:29: The stars' velocities tell us that they're moving in lockstep together around the galaxy.
	2018-01-17: Horizon Radiation 14:45: All that said, I love the idea of stars twinkling meaningfully at each other from across the galaxy.
	2018-01-10: What Do Stars Sound Like? 11:30: Now, it may eventually happen as the sun wanders the galaxy and encounters new neighbors, but it's still spectacularly unlikely.
	2017-12-20: Extinction by Gamma-Ray Burst 03:16: Roughly once per day, the jet from such an explosion in a distant galaxy reaches the earth and is detected by the Swift or Fermi satellites. 06:50: ... on the rates of GRBs we see in other galaxies and on the population of stars in the Milky Way, it's estimated that ... 11:53: ... there's a chance that some stars/solar systems will be ejected from the galaxy when the Milky Way collides with ... 12:03: Recent studies suggest that there's a 3% chance that the Sun will jump galaxies on Andromeda's first fly by. 12:16: And some stars will be sling-shotted out of the galaxy by the two supermassive black holes of Andromeda and the Milky Way as they fall together. 12:30: Dark everywhere except for the gigantic elliptical galaxy Milkdromeda, the final result of the merger. 12:39: We have a few billion years to come up with a better name for that galaxy. 12:30: Dark everywhere except for the gigantic elliptical galaxy Milkdromeda, the final result of the merger. 03:16: Roughly once per day, the jet from such an explosion in a distant galaxy reaches the earth and is detected by the Swift or Fermi satellites.
	2017-12-13: The Origin of 'Oumuamua, Our First Interstellar Visitor 06:46: Our sun, as it moves around the galaxy, passes through this field of debris.
	2017-12-06: Understanding the Uncertainty Principle with Quantum Fourier Series 13:53: Hanny's Voorweep is a wee blob of light right next to a spiral galaxy. 13:58: ... to be the light echo from a dead quasar that was once in that galaxy, so the cloud of gas ionized by the last burp of energy from an active ... 13:45: Danny [INAUDIBLE] reminded me of the coolest object found in "GalaxyZoo," discovered by a Dutch schoolteacher, Hanny van Arkel.
	2017-11-29: Citizen Science + Zero-Point Challenge Answer 01:52: These exploding stars show up as transient point of light, typically in very distant galaxies. 04:09: This project used citizen scientists to classify the morphological types of nearly 1 million galaxies. 09:37: And exclusively for challenge winners and Patreon supporters, we have astrochicken von Neumann, conqueror of the galaxy. 04:04: And of course, the Zooniverse's first and founding project, GalaxyZoo.
	2017-11-02: The Vacuum Catastrophe 09:42: They're too hot to pull into the deep dark matter wells that we see in galaxy clusters.
	2017-10-25: The Missing Mass Mystery 00:18: ... have revealed an observable universe full of hundreds of billions of galaxies, each of them with as many ... 00:33: The shining light of these stars illuminates or is conspicuously absorbed by gas and dust within those galaxies. 01:12: Yet, what if I told you that all of the stars and galaxies and galaxy clusters only comprise 10% of the light sector? 01:26: We think it must exist as extremely diffuse gas in between the galaxies. 01:59: Its gravity holds galaxies together and governed to the growth of large-scale structure in our universe throughout cosmic time. 03:23: ... 10 times as much hydrogen to start with than we actually see today in galaxies and ... 04:00: These speckles are fluctuations in density that would later collapse to become the galaxy clusters. 05:02: Again, we calculate that they should be way more baryonic matter than we see in galaxies. 05:08: ... work and collapse these faint fluctuations into gargantuan clusters of galaxies. ... 05:37: In the nexuses between filaments matter is dense enough for galaxies to form. 05:43: Now surveys of galaxies confirm that this is what the large-scale structure of the universe looks like. 05:50: And yet, when we add up the mass from those galaxies, most of the baryonic matter predicted by a theory is missing. 05:59: Well, our best guess is that it's in the form of a very diffuse plasma, atoms stripped of their electrons in between the galaxies. 06:15: We typically see that stuff inside galaxy clusters where the plasma is relatively dense and is energized by the light of the galaxies themselves. 06:39: Absorption features in the light of distant quasars reveal this gas lurking between clusters of galaxies. 07:12: ... is the giant filaments that form the cosmic web stretching in between galaxy ... 07:30: See, the vast tidal effects of nearby galaxies create shocks that can heat those baryons to hundreds of thousands or even millions of Kelvin. 08:01: And so those solitary baryons could add up to more mass than all of the galaxies in the universe. 08:47: So if there's enough of this stuff, then the CMB map should be slightly hotter directly in between galaxies that are connected by filaments. 09:10: ... filaments, which they assumed was between pairs of nearby massive galaxies, the type typically found in giant dark matter ... 09:31: And so the researchers needed to add together the results from many, many galaxy pairs. 09:38: used a million galaxy pairs, while Tanimura et al. 10:22: ... intergalactic space, still flowing with rivers of dark matter into the galaxy ... 10:35: As those baryons fall into the dense nexuses of the cosmic web, they'll feed galaxies with material to form new stars. 01:12: Yet, what if I told you that all of the stars and galaxies and galaxy clusters only comprise 10% of the light sector? 04:00: These speckles are fluctuations in density that would later collapse to become the galaxy clusters. 06:15: We typically see that stuff inside galaxy clusters where the plasma is relatively dense and is energized by the light of the galaxies themselves. 07:12: ... is the giant filaments that form the cosmic web stretching in between galaxy clusters. ... 10:22: ... intergalactic space, still flowing with rivers of dark matter into the galaxy clusters. ... 09:31: And so the researchers needed to add together the results from many, many galaxy pairs. 09:38: used a million galaxy pairs, while Tanimura et al.
	2017-10-11: Absolute Cold 09:03: So they probably lose angular momentum by dragging against gas in the center of galaxies, but we don't know how long that takes. 09:15: Dylan Burris asks, what besides a supermassive black hole lives in the centers of galaxies? 09:31: ... black holes, that have fallen towards the center from the surrounding galaxy. ... 09:39: And when galaxies get stirred up by an interaction or collision with another galaxy, we expect that gas will be driven into the core also.
	2017-10-04: When Quasars Collide STJC 01:31: These things live in the dead centers of pretty much every decent-size galaxy. 01:44: The ones in the course of galaxies contain the mass of a million two billion Suns. 01:59: Did they get most of their mass from eating gas and stars from their surrounding galaxy? 02:04: Or do they mostly grow when smaller SMBHs find each other and merge during galaxy collisions? 02:11: We know a lot more about the first process because we've been watching SMBHs munching on their host galaxies for half a century now. 02:45: When gas from the surrounding galaxy falls into and feeds the central supermassive black hole, you get an active galactic nucleus-- AGN. 03:03: But lower down the power scale, we have Seyfert galaxies, which typically contain a single SMBH weighing in at millions of solar masses. 03:12: Now, the purported binary black holes in this new study were found in a known Seyfert galaxy. 03:18: That means they're feeding on their surrounding galaxy, and they're approaching merger. 03:32: The Seyfert galaxy in question is Markarian 533, which is around 400 million light-years away. 03:38: The black holes are around one light-year apart in the center of the galaxy. 05:08: Those jets can blast through the surrounding galaxy and beyond, carrying their magnetic fields with them. 05:27: ... changes or as the jets smash into denser regions of the surrounding galaxy. ... 07:12: Like I said earlier, we already knew this sort of thing must happen when galaxies grow by merging with each other. 07:19: And the SMBHs of these galaxies must eventually fall towards the new merged galactic core. 09:48: And this galaxy is so dusty that it's hard to peer into the core at other wavelengths of light. 09:54: However, careful observations of the stars in the galaxy can help us figure out the masses of the black holes and look for signs of galaxy mergers. 02:04: Or do they mostly grow when smaller SMBHs find each other and merge during galaxy collisions? 02:45: When gas from the surrounding galaxy falls into and feeds the central supermassive black hole, you get an active galactic nucleus-- AGN. 09:54: However, careful observations of the stars in the galaxy can help us figure out the masses of the black holes and look for signs of galaxy mergers. 09:19: ... to detect the actual merger of a supermassive black hole binary with a galaxy-sized gravitational wave observatory called a pulsar timing ...
	2017-09-20: The Future of Space Telescopes 08:19: However, it would be able to see x-rays right down to the event horizons of super massive black holes in distant galaxies.
	2017-09-13: Neutron Stars Collide in New LIGO Signal? 06:12: And in this case, it's from the suspected galaxy that the wave came from. 06:17: But how do we locate the galaxy? 06:38: ... a flash of gamma radiation-- so the highest energy light-- from a galaxy 130 million light years ... 07:58: It's NGC 4993, a known lenticular galaxy. 08:03: We rarely see supernovae from this galaxy type because their most massive stars have long since exploded to leave neutron stars and black holes. 09:12: But the neutron stars' thin iron crust is likely bombarded with neutrons and blasted outwards, spraying a ton of r-process elements into the galaxy. 06:38: ... a flash of gamma radiation-- so the highest energy light-- from a galaxy 130 million light years ... 08:03: We rarely see supernovae from this galaxy type because their most massive stars have long since exploded to leave neutron stars and black holes.
	2017-08-30: White Holes 00:50: ... that quasars, x-ray binaries, even the center of our own Milky Way galaxy harbor these gravitational monstrosities, but the mathematics that ...
	2017-08-24: First Detection of Life 09:57: There are billions and billions of potentially water-bearing Earth-like planets in our galaxy alone.
	2017-08-10: The One-Electron Universe 10:48: ... supporters-- introducing Astro Chicken Von Neumann, conqueror of the galaxy. ... 10:59: ... week, we talked about the controversial evidence that many galaxies in the observable universe are drifting very slightly towards a point ... 12:04: ... if all galaxies have a slight preferred direction to one point on the sky, then the way ... 12:20: This is why you need so many galaxies across the sky to do this.
	2017-08-02: Dark Flow 00:28: Stars orbit within galaxies. 00:30: Galaxies whirl within the gravitational fields of giant clusters. 00:37: Distant galaxies are thrust apart from each other as the space between them grows. 00:51: The random motion of galaxies-- what we call peculiar motion-- should also have no preferred direction. 01:05: ... of the cosmic microwave background suggest that galaxy clusters across the cosmos may be moving ever so slightly towards the ... 02:43: In that reference frame, if you added together the peculiar velocities of all galaxies in the universe, you'd expect them to cancel out. 02:51: After all, those galaxies formed from the hot hydrogen plasma that produced the CMB. 02:56: So the peculiar motion of galaxies can be defined as motion relative to the cosmic microwave background. 03:13: Doing so has seemed to reveal that the motions of galaxies does not cancel out. 03:39: ... the most massive galaxy clusters in our universe are vast conglomerations of thousands of ... 04:11: This allows astronomers to find extremely distant galaxy clusters just by studying the CMB. 04:24: ... a galaxy cluster has some extra peculiar velocity in addition to the Hubble flow, ... 07:26: Since 1973, we've noticed that galaxies in the local part of the universe seem to be drawn in that direction due to an unseen gravitational influence. 07:36: ... hundreds of millions of light years and several hundred entire galaxy ... 07:50: ... is not causing the dark flow, because that flow seems to affect galaxies across the observable universe, or to two and a half billion light years ... 08:58: ... of much more stuff, a different bubble of observable universe with more galaxies, more clusters, more dark ... 04:24: ... a galaxy cluster has some extra peculiar velocity in addition to the Hubble flow, then ... 01:05: ... of the cosmic microwave background suggest that galaxy clusters across the cosmos may be moving ever so slightly towards the same point ... 03:39: ... the most massive galaxy clusters in our universe are vast conglomerations of thousands of galaxies and ... 04:11: This allows astronomers to find extremely distant galaxy clusters just by studying the CMB. 07:36: ... hundreds of millions of light years and several hundred entire galaxy clusters. ...
	2017-07-26: The Secrets of Feynman Diagrams 11:42: One will be an exclusive for challenge winners and Patreon supporters-- introducing the mighty Astro Chicken Von Neumann, conqueror of the galaxy.
	2017-06-07: Supervoids vs Colliding Universes! 04:05: A photon entering a matter-rich galaxy cluster gets an energy boost as it falls into the cluster's gravitational well. 04:47: But the galaxies have spread a little further out as it exits the void, so it doesn't get pulled out as strongly. 05:33: ... in Outback New South Wales to perform a spectroscopic survey of 7,000 galaxies in the direction of the cold spot and out to a redshift of ... 05:46: ... in layman's terms, they split the light from those galaxies into component wavelengths and determined the shift in the wavelengths ... 06:03: ... gave distances to those galaxies, which ultimately allowed them to build an accurate 3D atlas of galaxies ... 12:36: You can see galaxies forming in the very early universe, but they're incredibly faint. 12:41: And we need the largest telescopes in the world to even detect the entire galaxy, let alone any individual stars. 12:48: ... measure the metallicity of a star or a galaxy, you need to be able to split the light into a spectrum and look for ... 13:04: Right now, efforts are focused on computational modeling of populations of stars to predict the overall light that we expect to come from a galaxy. 13:17: [INAUDIBLE] et al., 2015, found a galaxy in the old universe whose light is very hard to explain without a lot of pop three stars. 04:05: A photon entering a matter-rich galaxy cluster gets an energy boost as it falls into the cluster's gravitational well.
	2017-05-31: The Fate of the First Stars 01:01: ... as supernovae, and spread their element-enriched guts through the galaxy, long before the sun was even a twinkle in the eye of a giant molecular ... 01:54: Pop one stars formed the most recently, and are still forming today, typically in the disks of spiral galaxies. 02:12: They were born long ago, when galaxies like the Milky Way were still forming in the early universe. 02:32: ... were the first ever stars, shining in the first ever proto galaxies, born of the pristine hydrogen and helium gas that filled the universe ... 09:15: ... of times the mass of the sun, that we find lurking in the centers of galaxies. ... 09:52: ... there long wanderings through the galaxy, they may have collected enough dust in their atmospheres to disguise ... 10:12: When we look out into the universe, as far as our telescopes can see, we do see primitive looking galaxies shining out from the earliest of times. 10:26: It's hard to make sense of this light, unless there are a ton of population three stars in those galaxies. 01:01: ... as supernovae, and spread their element-enriched guts through the galaxy, long before the sun was even a twinkle in the eye of a giant molecular ...
	2017-05-17: Martian Evolution 00:06: It's fun to think about humanity settling the galaxy, outposts of familiar Homo sapiens spread among the stars.
	2017-05-03: Are We Living in an Ancestor Simulation? ft. Neil deGrasse Tyson 08:31: We're on a typical planet around a typical star in a typical galaxy, with one exception. 12:27: There we talk about how confident we can really be in our understanding of the galaxy and the universe and of scientific knowledge in general.
	2017-04-26: Are You a Boltzmann Brain? 04:26: ... occasionally converge into a dense environment like a black hole or a galaxy, or into a complex arrangement like a teapot or a box DVD set of the ... 05:16: ... work" performed by that increase in entropy includes the formation of galaxies, stars, planets, Alan Tudyk-- indeed, the entire process of ... 07:15: A single galaxy should be enough.
	2017-04-19: The Oh My God Particle 06:10: For lower energy cosmic rays, it's believed that many, and perhaps most, come from supernova explosions within our galaxy. 06:29: The higher the energy of the cosmic ray, though, the more likely it is to have originated from outside our galaxy. 07:45: See, they must have come from nearby, from close enough to our galaxy to not be wiped out by the CMB.
	2017-04-05: Telescopes on the Moon 02:01: Here's a UV picture of the pinwheel galaxy taken by LUT.
	2017-03-22: Superluminal Time Travel + Time Warp Challenge Answer 00:20: The reality of the vast scale of our universe, even with our galaxy, is inconvenient for tales of star-hopping adventure or warring galactic empires.
	2017-03-15: Time Crystals! 11:27: The answer is that, yeah, it's rare, but there are a lot of stars in the galaxy.
	2017-03-01: The Treasures of Trappist-1 08:38: ... that M dwarfs are the most numerous stars in the galaxy, we may have seeing a giant boost in the number of possible homes for ...
	2017-02-15: Telescopes of Tomorrow 02:23: This will provide another set of baby pictures, the formation of the very first stars and galaxies in our universe. 02:36: Light from these earliest of galaxies has been traveling through our expanding universe since near the beginning of time. 02:55: Webb will help us learn whether stars form galaxies or galaxies form stars and the role of dark matter in the whole process. 08:44: We'll be able to track the motion of rogue high-velocity stars whizzing through our galaxy.
	2017-02-02: The Geometry of Causality 11:38: David, we're naming an entire galaxy after you. 11:41: It's a beautiful barred spiral galaxy in the Fornax cluster.
	2017-01-25: Why Quasars are so Awesome 00:37: Pulsars-- city-size atoms that beam deathrays through the galaxy. 01:11: That's surrounded by a solar system-sized whirlpool of superheated plasma that shines brighter than an entire galaxy. 03:24: ... it appeared at that distance, the weird object had to be emitting many galaxies worth of light from a seemingly impossibly small region of ... 03:37: ... swarms of neutron stars, an alien civilization harnessing their entire galaxy's power, bright, fast-moving objects being ejected by our own galaxy's ... 04:04: Well, it turns out that every decent sized galaxy has one at its core. 04:12: One way this can happen is when galaxies merge and grow. 04:50: And this same light drives powerful winds of gas back out into the surrounding galaxy. 05:28: Then, we only see hints of the central monster because it lights up gas in the surrounding galaxy. 05:34: ... an edge-on quasar has powerful jets, we see them blasting through the galaxy and even filling intergalactic space with beautiful radio ... 05:45: We call these radio galaxies. 07:29: As the first galaxies coalesced from this gas, the universe entered a long period of violent star formation. 07:36: As galaxies coalesced, they went through starburst phases, producing new stars at insane rates. 07:59: These forming galaxies were continuously blasted with energetic radiation and cosmic rays. 08:20: ... some of this gas found its way into the nuclei of galaxies, it encountered there the supermassive black holes that had been growing ... 08:35: Each burst of quasar activity in a given galaxy probably only lasts 10 million years or so. 08:42: However, that's enough to heat gas throughout the galaxy. 09:02: Galaxies had formed, but were no longer wracked by supernovae. 09:21: The much weaker, Seyfert galaxies are more common. 09:45: ... in a few billion years, when the Andromeda galaxy and the Milky Way inevitably collide and their supermassive black holes ... 03:37: ... swarms of neutron stars, an alien civilization harnessing their entire galaxy's power, bright, fast-moving objects being ejected by our own galaxy's ...
	2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer 01:00: This gives us things like quasars, supermassive black holes in galaxy cores that feed on a superheated whirlpool of gas. 01:55: By the way, almost all galaxies have these lurking at their cores. 03:55: Interferometry is going to be used to study much smaller black holes in our galaxy, the remnants of dead stars. 01:00: This gives us things like quasars, supermassive black holes in galaxy cores that feed on a superheated whirlpool of gas.
	2016-12-21: Have They Seen Us? 00:57: ... bubble of chatter is, as I speak, spreading out into the galaxy at the speed of light, the unmistakable signature of an emerging ... 12:20: ... civilizations would need to be extremely common throughout our galaxy-- and I mean tens of millions of them across the Milky Way-- for there to ... 12:35: If anyone else inhabits this very local region of the galaxy, then they may have been aware of us for some time now.
	2016-11-09: Did Dark Energy Just Disappear? 08:38: Counting galaxies and weighing dark matter tells us that Omega-m is probably around 0.3, but it's at least around 0.2.
	2016-11-02: Quantum Vortices and Superconductivity + Drake Equation Challenge Answers 02:52: I asked you to figure out some probabilities regarding the existence of other technological civilizations in our galaxy. 06:34: That tells me that we may be the only advanced-ish civilization to have emerged in the local region, but probably not within the whole galaxy. 08:10: Also, if you extend that estimate to the entire Milky Way, then you get something like 100,000 Type II civilizations in our galaxy.
	2016-10-19: The First Humans on Mars 10:09: ... if we find many PBH's spread through the galaxy and even outside the galaxy, their distribution may tell us that it was ... 10:24: A few of you also asked whether the supermassive black holes that we find at the centers of galaxies could be primordial black holes.
	2016-10-12: Black Holes from the Dawn of Time 02:19: These density fluctuations were enough to kick-start the formation of galaxies, but certainly not enough to immediately collapse into black holes. 05:27: In stars in our galaxy, in distant quasars, even in gamma ray bursts. 05:44: As the heavier ones buzz around the galaxy, they should pull apart loosely bound binary systems and have an effect on the structure of star clusters. 07:43: It's possible that certain types of very short gamma ray bursts are these final flashes from PBHs evaporating in our galaxy.
	2016-10-05: Are We Alone? Galactic Civilization Challenge 00:11: The famous Drake Equation tries to estimate the number of technological civilizations currently existing in our galaxy. 00:19: ... sociological factors, each of which narrows the range of stars in our galaxy that may have produced a surviving ... 02:20: ... Kepler mission allowed us to estimate that our galaxy boasts something like 14 billion terrestrial planets in the Goldilocks ... 03:57: ... humans to be the only advanced civilization to have ever appeared in our galaxy-- ever-- then there would need to be only a 1 in 60 billion chance for any ... 04:13: If the true probability of producing civilizations is higher, then there have been-- and perhaps still are-- advanced species in our galaxy. 02:20: ... Kepler mission allowed us to estimate that our galaxy boasts something like 14 billion terrestrial planets in the Goldilocks zone of ...
	2016-09-14: Self-Replicating Robots and Galactic Domination 00:16: I mean spacecraft capable of replicating themselves and exponentially spreading across the galaxy. 00:30: Our galaxy is depressingly natural looking. 00:47: Even the unusual denizens of the galaxy like pulsars and black holes just do what they do. 01:00: As far as we've seen, humanity is the only species ever to build anything bigger than a beaver dam in the entire galaxy. 01:08: ... or exploration should have been able to cross, even colonize the entire galaxy. ... 01:52: Today I want to argue that even if these points are true, there are reasons to expect a galaxy full of the evidence of past technological life. 02:06: ... to build copies of themselves to continue exploration of the galaxy. ... 04:35: Let me outline how such a device could populate the galaxy with robotic probes. 06:30: It might take several million years to cross the galaxy this way. 06:34: But the exponential nature of the process means that the entire galaxy would be covered in these things in that amount of time. 06:53: And B, once a successful probe is built, the galaxy will be swarming with them in 10 million years, max. 07:28: There are, at a minimum, tens of billions of terrestrial planets with liquid water in our galaxy. 07:46: ... species, that still means tens of thousands of planets in our galaxy get tech at some ...
	2016-08-24: Should We Build a Dyson Sphere? 09:23: Maybe this is why we don't see Dyson swarms all through the galaxy.
	2016-08-10: How the Quantum Eraser Rewrites the Past 11:02: The only black holes that we know for sure are buzzing around our galaxy are stellar remnant black holes.
	2016-08-03: Can We Survive the Destruction of the Earth? ft. Neal Stephenson 10:09: ... two, get the hell out of the solar system and start colonizing the galaxy beyond the 30-light-year range of a supernova and beyond the width of a ...
	2016-06-22: Planck's Constant and The Origin of Quantum Mechanics 12:50: ... the other hand, if the light source is large, for example, an entire galaxy, then it's easy for at least part of the galaxy to be located directly on ... 13:10: That Einstein ring is actually the galaxy that hosts the quasar.
	2016-06-15: The Strange Universe of Gravitational Lensing 03:25: At its most spectacular, we see extreme warping of the shapes of distant galaxies. 03:30: ... their light travels through the deep gravitational wells of intervening galaxies and galaxy clusters, they are greatly magnified in brightness and ... 04:09: ... and light source that will collapse those distorted images into the true galaxies that created ... 04:27: We've weighed many galaxies and galaxy clusters this way. 05:07: You can see the nearby spiral galaxy, whose gravitational field bends spacetime to create these paths. 05:14: To see multiple quasar images, you need a near-perfect alignment between the lensing galaxy and the quasar. 06:13: ... passing through the starry lens galaxy brightens and dims due to the gravitational fields of individual stars ... 06:50: Weak gravitational lensing slightly warps the shapes of essentially all galaxies in the universe. 06:57: When we look at hundreds or thousands of galaxies, we can spot correlations in the way their elongations are aligned. 09:23: But look through a telescope at very distant galaxies, and all are brightened, shifted and warped by the weird lens of a curved spacetime. 06:13: ... passing through the starry lens galaxy brightens and dims due to the gravitational fields of individual stars in that ... 03:30: ... travels through the deep gravitational wells of intervening galaxies and galaxy clusters, they are greatly magnified in brightness and stretched into arcs and ... 04:27: We've weighed many galaxies and galaxy clusters this way.
	2016-05-04: Will Starshot's Insterstellar Journey Succeed? 00:25: We were so sure that these were just steps on the inevitable path to our exploration of the galaxy. 10:33: Sandeep Siwach would like to know why dark energy only effects the space between galaxies and not within galaxies. 10:49: The density of matter inside galaxies is much, much higher than in between galaxies and even much, much higher than the average for the universe. 11:25: We do that by finding independent distances to white dwarf supernovae in nearby galaxies. 11:33: ... another type of standard candle, to get an independent distance to the galaxy in which a supernova ... 11:42: Cepheid variables are then calibrated as standard candles based on cepheid's in our own galaxy.
	2016-04-27: What Does Dark Energy Really Do? 01:14: In fact, measuring the past expansion history should tell us the future expansion without ever having to count any galaxies. 06:03: ... of astronomers spent years catching white dwarf supernovae exploding in galaxies billions of light years away to measure the past expansion history of ... 07:53: Let's take a mathematical ride into the far future, when the galaxies will be so far away that the density of the universe will be basically zero. 11:03: Our galaxy surveys have worked for decades to measure brightnesses, redshifts, stellar compositions, and more of many millions of galaxies. 11:23: These surveys don't measure dark matter content of all of their galaxy clusters. 11:03: Our galaxy surveys have worked for decades to measure brightnesses, redshifts, stellar compositions, and more of many millions of galaxies.
	2016-04-13: Will the Universe Expand Forever? 00:38: Combined with observations of the redshifts of galaxies, this showed us that the fabric of space itself is expanding. 03:40: ... dark energy-- the universe also has an escape velocity that lets distant galaxies escape each other's gravitational ... 04:13: ... because, on its largest scales, billions of light years, all of the galaxies and galaxy clusters are very evenly dusted across all of ... 04:26: ... we ignore the bumps and wiggles caused by individual galaxies, the resulting smooth universe lets us reduce those 10 Einstein equations ... 04:54: Although it's more accurate to think of it as the average distance between galaxies. 06:56: ... will eventually fall back inwards, and we'll see many of those distant galaxies up very close and personal as the universe undergoes the Big ... 07:14: We measure it from the redshifts of galaxies as well as other independent methods. 07:36: Astronomers worked for decades to weigh up the galaxies across vast swaths of the universe, including their dark matter. 08:07: In a way, we're lucky to be living in an era where we can still even see the distant galaxies. 12:21: It collapsed into the Sun's sibling stars, which are also scattered across the galaxy by now. 04:13: ... on its largest scales, billions of light years, all of the galaxies and galaxy clusters are very evenly dusted across all of ...
	2016-04-06: We Are Star Stuff 00:00: ... our body were forged in violent stellar alchemy and spread through the galaxy in past ... 09:04: This is also seen as a supernova, and it also laces the galaxy with heavy elements.
	2016-03-30: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners! 00:48: It was only recently, April 2015, that astronomers finally pinpointed a galaxy that an FRB came from. 00:55: It was an elliptical galaxy 6 billion light years away.
	2016-03-23: How Cosmic Inflation Flattened the Universe 10:15: ... Schneider asks, "Why does dark matter in a galaxy seem to form a sphere?" Well, this is because dark matter doesn't really ... 11:04: This is also true of the stars in a eliptical galaxies. 11:14: The reason spiral galaxies are discy is that those discs formed before the stars actually formed, back when the material was mostly gas.
	2016-03-16: Why is the Earth Round and the Milky Way Flat? 00:23: It loves building spheres like stars, planets, and moons, and disks like spiral galaxies, solar systems, and some crazy stuff like quasars. 01:53: disk-shaped things like galaxies and solar systems have circular symmetry. 08:20: This is not true of things like spiral galaxies, solar systems, and the whirlpools of gas around quasars. 09:50: Pretty much the same thing happens with spiral galaxies like the Milky Way, except on a much, much larger scale. 10:20: They don't just give us our beautiful globe of the Earth, our spiral Milky Way Galaxy.
	2016-03-09: Cosmic Microwave Background Challenge 01:00: We're looking at an ocean of orangey, red-hot plasma that would later collapse into galaxies, and people, and stuff. 02:10: ... the time it reaches us, right now, the universe has expanded so that the galaxies and clusters that those blobs evolve into are now 1,100 times further ...
	2016-03-02: What’s Wrong With the Big Bang Theory? 00:00: [MUSIC PLAYING] When we look out at distant galaxies, we see that they are all racing away from us. 04:05: And pack all of the galaxies in the entire observable universe into a space 10 to the power of minus 20th of the width of a proton. 10:19: That's if it were even valid to extrapolate that expansion to the scale of objects or even to galaxies. 10:38: That works on the largest scales in which galaxies and galaxy clusters are a speckled foam on top of a much vaster space time. 10:48: It doesn't work in galaxies or solar systems. 10:38: That works on the largest scales in which galaxies and galaxy clusters are a speckled foam on top of a much vaster space time.
	2016-02-24: Why the Big Bang Definitely Happened 01:42: Light from distant galaxies is red shifted, stretched to longer wavelengths. 01:47: And the further away the galaxy is, the more its light is stretched. 05:16: Very, very tiny fluctuations that would let it collapse on themselves to form galaxies and clusters of galaxies. 05:23: ... evolution from a smattering of tiny fluctuations to a network of giant galaxy clusters, is also evidence that the Big Bang picture is ... 05:36: When we look to vast distances, we're also looking back in time and we see the very first galaxies soon after they collapsed from these blobs. 05:46: ... we expect them to be violent places with galaxies colliding and merging with each other, rich in the raw materials of star ... 06:03: We see galaxies back when the universe was 5% its current age. 06:08: And they look very different to galaxies today. 06:29: ... was created, and those ripples should still be visible in the way that galaxies are spread out on the ... 05:23: ... evolution from a smattering of tiny fluctuations to a network of giant galaxy clusters, is also evidence that the Big Bang picture is ...
	2016-02-11: LIGO's First Detection of Gravitational Waves! 01:35: Since then, ripples from mergers of black hole pairs in distant galaxies have changed the shape of spacetime here on Earth. 03:44: It's expected that an observable merger of two black holes will happen only once every 10,000 years in any given galaxy. 03:52: So we need to watch a lot of galaxies. 04:05: That means we're watching millions of galaxies. 06:48: ... see the slow ringing of binary white dwarf stars in our own galaxy, as well as the final dance of pairs of truly gigantic, supermassive ...
	2016-01-27: The Origin of Matter and Time 00:40: Galaxies are things. 10:44: One takes a fast trip around the galaxy.
	2015-12-16: The Higgs Mechanism Explained 09:05: ... stars near the core of a galaxy with merging super massive black holes should have temperatures raised ...
	2015-12-09: How to Build a Black Hole 02:09: The collapsing outer shells ricochet off this impossibly dense nugget in a supernova explosion, enriching the galaxy with juicy new elements.
	2015-11-18: 5 Ways to Stop a Killer Asteroid 08:44: ... of others, note that any civilization advanced enough to colonize the galaxy would also be advanced enough to choose not to do ... 10:30: ... would only have to arise once in the galaxy, which allows the initial event of abiogenesis to be very unlikely, and ... 10:42: The big challenge is getting life-infested rocks to spread through the galaxy. 10:59: Well, I choose the ending where Shepard saves the galaxy. 09:01: ... needs to make a different choice to not stay at home, and we have galaxy-wide ...
	2015-11-05: Why Haven't We Found Alien Life? 00:37: Many of them have been around long enough to produce a civilization that could have easily colonized the entire galaxy by now. 01:28: Humanity may be one of the very first interstellar species in the history of the galaxy. 02:32: ... each of these was or how frequently these conditions are met through the galaxy. ... 03:36: And in fact, so fast that our galaxy probably should be brimming with at least simple life. 06:55: Questionable, but it would mean that life only needs to evolve once from scratch in any given galaxy. 07:27: However, both suggest that the galaxy should be teeming with slimeball planets filled with life. 07:59: So it's entirely possible that we'll soon discover that the galaxy is filled with life. 09:19: ... life is common, then of the billions of Earth-like planets in the galaxy, only a tiny fraction needed to have a small head start on us in order to ... 10:12: ... watch and maybe guide as other intelligent life emerges throughout the galaxy? ...
	2015-10-28: Is The Alcubierre Warp Drive Possible? 00:17: Star Trek warp drives zip around the galaxy at hundreds of times the speed of light. 01:19: So when are we going to be warping around the galaxy? 01:40: ... in this episode, the expansion of the universe means that very distant galaxies are moving apart from each other faster than light, even if the galaxies ... 06:38: So when are we going to be warping around the galaxy? 07:38: And this should actually allow it to detect binary star systems in our galaxy.
	2015-10-22: Have Gravitational Waves Been Discovered?!? 03:54: They happen in any given galaxy once every several thousand years. 03:58: Any g-wave that we're likely to spot is going to come from a distant galaxy, hundreds of millions of light-years away. 06:51: LIGO really just scratched the minimum sensitivity needed to spot merging neutron stars and black holes in relatively nearby galaxies. 11:05: ... born too late to explore the Earth, born too early to explore the galaxy, born just in time to watch PBS "Space ... 03:58: Any g-wave that we're likely to spot is going to come from a distant galaxy, hundreds of millions of light-years away.
	2015-10-15: 5 REAL Possibilities for Interstellar Travel 00:21: Is our galaxy littered with the remains of single planet civilizations as Elon Musk has asked? 09:55: ... drives don't pan out, these are what we'll want to actually explore the galaxy with near light speeds dilating apparent travel time down to human ... 00:21: Is our galaxy littered with the remains of single planet civilizations as Elon Musk has asked?
	2015-10-07: The Speed of Light is NOT About Light 11:06: Now replace the markers with galaxies, and that's basically what's happening with our universe.
	2015-09-30: What Happens At The Edge Of The Universe? 00:32: The universe is infinite because general relativity tells us that the universe is demonstrably flat and therefore the galaxies go on forever. 01:37: ... is currently 46 billion light years to whatever galaxy or galaxy clusters that blob evolved into, racing away from us with the ... 03:44: This means that there are galaxies that we can see now that we could never reach or even communicate with. 04:55: And presumably, a pretty similar distribution of galaxies and clusters all around you. 05:12: It's lumpy on small scales due to stars and galaxies, but smooth on large, sort of like ripples on the ocean. 05:18: Measurements of the distribution of galaxies and the CMB confirm this flatness with very high, but not infinite, precision. 08:16: The same with galaxy clusters. 08:18: The galaxy orbits give us a mass for the dark matter in the clusters and the lensing gives us a mass consistent with this. 08:31: Dark matter is cold and clumpy, which means it can bunch together to form galaxies. 08:51: By comparison, the cold hydrogen gas that fills our galaxy clumps together in giant clouds. 01:37: ... is currently 46 billion light years to whatever galaxy or galaxy clusters that blob evolved into, racing away from us with the expanding universe, ... 08:16: The same with galaxy clusters. 08:18: The galaxy orbits give us a mass for the dark matter in the clusters and the lensing gives us a mass consistent with this.
	2015-09-23: Does Dark Matter BREAK Physics? 00:00: [MUSIC PLAYING] Dark matter literally binds the galaxy together. 00:18: The Milky Way galaxy is spinning so fast that it should be scattering its stars into the void. 01:09: And galaxy clusters do this all the time, turning the background universe into a funhouse mirror of stretched out and duplicated galaxies. 01:52: Gravity just behaves differently on the vast scales of galaxies and clusters. 02:19: ... this is dark matter, the galaxy would need to be swarming with baryonic things as massive as stars, but ... 03:23: Well, the problem is that the stars on the edge of the galaxy are moving just as fast as the stars near the center. 03:41: But what about the entire galaxy? 04:29: Modified versions of GR can actually do pretty well, especially predicting orbits within galaxies. 05:21: Map the mass based on the warping of light from more distant galaxies. 05:45: It has to be pretty slow moving, or cold, because we know that dark matter clumps together gravitationally to build galaxies and clusters. 05:59: ... of orange plasma to today's highly structured universe of clusters and galaxies, something had to act with enough gravity to pull stuff ... 06:13: Dark matter, as well as binding the galaxy together, is also the main force in forming galaxies in the first place. 06:20: No dark matter, no galaxies. 06:23: And even then, galaxies could only have formed if dark matter particles are cold, massive, and weakly interacting. 01:09: And galaxy clusters do this all the time, turning the background universe into a funhouse mirror of stretched out and duplicated galaxies.
	2015-04-01: Is the Moon in Majora’s Mask a Black Hole? 09:00: The Earth has superimposed an individual motion through the galaxy.
	2015-03-25: Cosmic Microwave Background Explained 00:12: Stars and galaxies notwithstanding, space is pitch black. 03:06: At this temperature, it's too hot for electrons and protons to even coalesce into atoms, let alone stars, planets or galaxies. 05:03: Well, they managed to clump, become stars, galaxies, and through a complicated process of cosmic recycling, us.
	2015-03-18: Can A Starfox Barrel Roll Work In Space? 08:18: Lots of you asked whether Earth could suffer a collision when the Andromeda and Milky Way galaxies merge in about 4 billion years. 08:28: ... so much empty space between star systems and galaxies that the probability of any two of them colliding would be similar to ...
	2015-03-11: What Will Destroy Planet Earth? 05:14: ... useful to think of that process-- the expansion-- not as galaxies flying apart through space, but instead as the space between distant ... 05:22: Note that the Earth and you and I stay in one piece because the space inside galaxies is not stretching-- at least not yet. 05:54: ... galaxies, then inside planetary systems, inside planets themselves until ...
	2015-02-25: How Do You Measure the Size of the Universe? 00:30: The Milky Way, our galaxy, that's about 100,000 light years across or close to 1 quintillion kilometers. 00:37: And the next closest major galaxy, Andromeda, that's 2 and 1/2 million light years away, which is just silly to talk about in kilometers. 01:47: Each raisin represents a cluster of galaxies in the dough space. 02:01: Galaxy clusters aren't expanding and neither are individual galaxies, or the Earth, or people, or trees. 02:05: It's just the relatively empty space between those large clusters of galaxies. 03:07: ... space were not expanding, then light from a distant galaxy would be the same color when it arrived on Earth as it was when it first ... 03:31: The light from more distant galaxies is redshifted more than light from nearby ones. 04:01: Just find a bunch of faraway galaxies, much further than Andromeda. 05:21: Aren't there galaxies even further away, whose light hasn't reached us yet? 00:37: And the next closest major galaxy, Andromeda, that's 2 and 1/2 million light years away, which is just silly to talk about in kilometers. 02:01: Galaxy clusters aren't expanding and neither are individual galaxies, or the Earth, or people, or trees.
	2015-02-18: Is It Irrational to Believe in Aliens? 00:40: Well, the Milky Way galaxy has about 200 billion stars. 02:35: You would still expect over 1,000 alien civilizations in our galaxy by now. 02:39: If the chances of intelligent life evolving are even lower, well, 200 billion is just the number of habitable planets in our galaxy. 02:45: If we sweep nearby galaxies into our planet account, we can add trillions more planets to compensate. 03:07: ... is rooted in the democratic notion that our planet, our Sun, our galaxy, none of them are ... 03:29: One prominent no aliens argument begins by pointing out that our galaxy is not just very big, but also very old, about 10 billion years old. 03:40: ... but also enough time for at some of that life to spread around the galaxy. ... 03:59: In fact, with current propulsion technologies and no fancy sci-fi stuff, we could send probes or robots across the whole galaxy. 04:08: The galaxy is 10 billion years old. 04:17: ... given how old the galaxy is, shouldn't there be evidence of at least one other such species ... 05:10: It only takes one, one Klingon Richard Branson to hop around the galaxy and leave some kind of a trace. 05:19: The galaxy is 10 billion years old and humanity, right now, would only need 20 million years to spread all over. 05:28: So someone should have left something, even in our little corner of the galaxy, huh? 05:39: ... spread out in any observable way in the 10-billion-year history of the galaxy. ... 06:07: But the odds of intelligent life going extinct before it can spread into the galaxy are also high. 05:28: So someone should have left something, even in our little corner of the galaxy, huh?

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