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	2022-11-23: How To See Black Holes By Catching Neutrinos 02:05: ... a low-energy neutrino with a wall of lead, the wall would need to be a light year thick to have even a 50-50 chance that the neutrino gets close enough to ... 08:08: It’s a beautiful spiral galaxy 47 million light years away.
	2022-10-26: Why Did Quantum Entanglement Win the Nobel Prize in Physics? 17:20: ... so I think the idea is that this works on the scales of hundreds of light years, but not many 1000s of  light years type scales. And  which ...
	2022-10-12: The REAL Possibility of Mapping Alien Planets! 01:25: ... many light years away. For example, to see a planet 100   light years away as anything more than a dot you’d need a telescope way bigger ...
	2022-09-21: Science of the James Webb Telescope Explained! 09:28: Those white blobby things are massive elliptical galaxies of the cluster, several billion light years away.
	2022-07-20: What If We Live in a Superdeterministic Universe? 13:12: The same team followed up with a cosmic Bell test using rather more distant objects - quasars several billion light years away.
	2022-06-22: Is Interstellar Travel Impossible? 02:01: The nearest star, Proxima centauri, is 4.2 light years away. 07:21: So both the gas and the dust are diffuse, but remember, we’re traveling 4 light years. 09:27: ... eroded by tiny impact craters down to around a millimeter depth every 4 light years. ... 13:32: ... interstellar trips further than a few light years, shielding against the interstellar medium, micrometeoroids and cosmic ...
	2022-06-01: What If Physics IS NOT Describing Reality? 15:25: ... a light-second across, while the   distance between them is light years. I’ve heard  an estimate for the number of stellar ...
	2022-05-25: The Evolution of the Modern Milky Way Galaxy 02:19: ... halo - also spheroidal, but twice the diameter of  the 100-thousand light year wide disk. This thing   is sprinkled with wayward stars and ... 08:29: ... guessed it - the thick disk,   which extends a few thousand light years  above and below its more slender counterpart.   Not all spiral ...
	2022-05-18: What If the Galactic Habitable Zone LIMITS Intelligent Life? 08:01: ... of   the atmosphere. For example, a supernova within  150 light years would obliterate our ozone layer.   On the other hand, some ... 10:48: ... starting out as a band between   around 20 and 30 thousand light years from the  center, it expanded inwards as the supernova ...
	2022-03-08: Is the Proxima System Our Best Hope For Another Earth? 01:38: That parallax revealed the system to be close - closer than any other - but still more than four light years distant.
	2022-01-19: How To Build The Universe in a Computer 10:28: It simulated 13-billion light years wide cube containing over 300 billion particles, each representing a billion-Suns worth of dark matter.
	2021-12-20: What Happens If A Black Hole Hits Earth? 00:29: ... very far. The nearest known is - the Cygnus X-1 black hole - at 1000 light years distant. It’s currently devouring its binary companion star, which is ...
	2021-11-17: Are Black Holes Actually Fuzzballs? 10:30: The normally Planck-length strings can therefore pile up into fuzzballs with sizes ranging from kilometers to light years.
	2021-09-07: First Detection of Light from Behind a Black Hole 02:23: ... that light reaches us - many, many millions of light years away - it’s still imprinted with a wealth of information about the ... 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.
	2021-08-18: How Vacuum Decay Would Destroy The Universe 11:34: ... safe. If the vacuum decay starts beyond several billion   light years, the accelerating expansion of the universe will throw us away from ...
	2021-07-21: How Magnetism Shapes The Universe 10:59: If you thought the 27 km ring of the large hadron collider was big, try the 300,000 light year ring around the Milky Way.
	2021-05-25: What If (Tiny) Black Holes Are Everywhere? 00:05: Happily for us, the nearest is probably many light years away.
	2021-05-19: Breaking The Heisenberg Uncertainty Principle 05:01: ... in the fabric of space caused by cataclysmic events up to billions of light years ...
	2021-02-17: Gravitational Wave Background Discovered? 00:00: ... in the fabric of space-time produced by colliding black holes a billion light years away since then ligo and its partner virgo have detected 50 similar ...
	2020-10-27: How The Penrose Singularity Theorem Predicts The End of Space Time 13:38: ... can   only see the universe of the past - e.g. a star 100 light years away being a century in the past.   Surely if we could ...
	2020-07-20: The Boundary Between Black Holes & Neutron Stars 00:29: ... of spacetime due to a cataclysmic collision of black holes billions of light years ...
	2020-06-30: Dissolving an Event Horizon 14:04: It has the same relative size compared to the universe whether that universe is trillions of light years across or a millimeter across. 14:31: That’s like another type of size, and it makes a big difference if you’re a millimeter from an electron versus a trillion light years. 14:40: ... of interacting over one second as do a pair of photons a billion light years apart over a billion ...
	2020-06-22: Building Black Holes in a Lab 00:16: ... this picture of the black hole at the heart of a galaxy over 50 million light years ...
	2020-06-15: What Happens After the Universe Ends? 02:17: It makes a big difference whether every atom in the universe is right next to each other or a billion light years apart. 02:42: Scale it up by around 30 quintillion times to describe a second universe that’s a billion light years across and lasts a billion years.
	2020-06-08: Can Viruses Travel Between Planets? 08:01: So yeah, stars sneeze, you might want to maintain 6 light years distance.
	2020-05-11: How Luminiferous Aether Led to Relativity 16:14: ... now 93 billion light years across - so the CMB sphere is around 85 million light years across. ...
	2020-05-04: How We Know The Universe is Ancient 01:35: ... to appear so faint in his telescope, they had to be many millions of light years ...
	2020-04-14: Was the Milky Way a Quasar? 03:18: ... gamma ray bubbles with sharp edges extending more than 25,000 light years in either direction above and below the plane of the Milky Way - that’ ... 11:25: ... however, is that these particular structures only extend 1400 light years above and below the plane of the Galaxy — leading astronomers to believe ...
	2020-04-07: How We Know The Earth Is Ancient 10:35: ... Kant’s Island Universes were indeed other galaxies, many millions of light years away. The world simultaneously got a lot older and the universe a lot ...
	2020-03-24: How Black Holes Spin Space Time 11:31: ... its brightness. We see these as gamma ray bursts from over 13 BIllion light years ...
	2020-02-03: Are there Infinite Versions of You? 09:40: For our 46-billion light year observable universe there are definitely no more than 2^10^123 possible unique configurations.
	2020-01-13: How To Capture Black Holes 00:59: ... of a second are what LIGO detects - sometimes from over a billion light years ... 04:50: ... those black holes are mostly random, so the swarm forms a spheroid a few light years across. The accretion disk is quite a bit smaller than the full swarm, ...
	2019-10-15: Loop Quantum Gravity Explained 13:02: This was tested in 2009 by looking for differences in the arrival time of light from a gamma ray burst nearly a billion light years away.
	2019-10-07: Black Hole Harmonics 08:09: ... the mass of the sun, spiraling into each other one and a half billion light years ...
	2019-09-30: How Many Universes Are There? 00:24: ... it: the observable part of our universe is 93 billion light years across, and that’s just a small fraction of the stuff created in our Big ...
	2019-07-25: Deciphering The Vast Scale of the Universe 04:27: He found that Andromeda is around 2 million light years away. 07:18: ... galaxies belong Laniakea, a cluster of superclusters some 500 million light years ...
	2019-06-06: The Alchemy of Neutron Star Collisions 02:47: ... it'll be detected by an as yet unborn civilization a hundred million light years away as will the explosion of electromagnetic radiation that immediately ... 13:02: ... it's enough to stop photons moving very far like only about a thousand light years now that sounds far but it's nothing compared to the size of the ...
	2019-05-16: The Cosmic Dark Ages 08:36: ... because the quasar has itself ionized a bubble spanning several million light years. By the time the quasar’s light reaches the edge of that bubble, the ...
	2019-05-01: The Real Science of the EHT Black Hole 01:09: ... is 53 million light years away, so resolving that black hole is equivalent to resolving a grain of ... 05:46: We see that jet extending 5000 light years outside the galaxy.
	2019-03-28: Could the Universe End by Tearing Apart Every Atom? 06:51: ... right now four patches of space very far apart - like, many billions of light years. ... 09:38: In fact, at this point the cosmic event horizon is still about 200 million light years away.
	2019-02-20: Secrets of the Cosmic Microwave Background 07:42: ... of the universe over that time that size should be about half a million light years at Recombination theoretically And that gives us our ruler Now when we ...
	2019-02-07: Sound Waves from the Beginning of Time 06:26: We call this the sound horizon. And at recombination, it was around five hundred thousand light years. 07:09: So those rings should be 150 mega parsecs across, 500 million light years.
	2019-01-24: The Crisis in Cosmology 00:39: ...by measuring the distances to the spiral nebulae They were many millions of light years from us,... 06:07: The SHOES project measures the recession of galaxies up to around 2 billion light years away.
	2018-10-10: Computing a Universe Simulation 12:40: Those gravitational waves and that light traveled a crazy long distance, 40 megaparsecs or around 150 million light years.
	2018-09-12: How Much Information is in the Universe? 03:31: Well, the radius of the universe is something like 47 billion light years, which is a few times 10 to the power of 61 Planck lengths.
	2018-07-04: Will A New Neutrino Change The Standard Model? 00:48: To have a 50/50 chance of stopping any given neutrino, you need a wall of lead 1 light year thick.
	2018-05-23: Why Quantum Information is Never Destroyed 11:49: Pepsi could extract some free energy if you could build a device that spans several million light years or, I don't know, install some solar panels.
	2018-05-02: The Star at the End of Time 09:41: ... matter exists in a puffy sphere some 200,000 light years in radius surrounding the Milky Way, compared to the 100,000 light years ...
	2018-04-25: Black Hole Swarms 00:43: We know these things because we see them, from our comfortable vantage 28,000 light years out in the galactic disk. 00:58: ... central few light years of the Milky Way is thought to contain a vast swarm of smaller black ... 03:33: Over a few billion years, we only expect the black holes from the central several light years to have made much progress inwards. 04:34: ... should lead to tens of thousands of black holes in the central few light years of the Milky Way's ... 06:11: They spotted 92 point-like X-ray sources within one parsec, or around three light years, of the galactic center. 07:25: ... to be at least hundreds of stellar-mass black holes in the central few light years in order to get these 13 X-ray ...
	2018-04-18: Using Stars to See Gravitational Waves 05:23: But much of this gravitational wave background will have wavelengths as long as many light years. 06:06: It monitors dozens of the fastest rotating pulsars, millisecond pulsars, spanning many thousands of light years.
	2018-04-11: The Physics of Life (ft. It's Okay to be Smart & PBS Eons!) 12:41: It's around 16 billion light years away.
	2018-03-28: The Andromeda-Milky Way Collision 06:20: When those black holes are around a light year apart, they'll start losing orbital energy to gravitational waves. 00:33: It's two and 1/2 million light years away and host to a trillion stars. 00:38: ... a beautiful spiral structure, spanning its gently rotating disk 220,000 light years in diameter, and a central bulge that hides a giant black hole that ...
	2018-02-14: What is Energy? 12:40: These star-forming clouds can vary in metallicity across their vast widths, which are often hundreds of light years.
	2018-01-10: What Do Stars Sound Like? 11:53: ... even if a super-focused 1-degree gamma ray burst hit us from a single light year away, that jet would have diverged to something like 10 times the size ... 11:12: A GRB within a few light years would be directly devastating to life. 11:24: Because there are no stars that could possibly explode that way for hundreds of light years.
	2017-12-20: Extinction by Gamma-Ray Burst 02:58: Any planet within a few tens of light years of a supernova is in trouble. 04:44: ... estimated that a typical gamma-ray burst within 10,000 light years could deplete ozone enough to cause up to a 30% increase in ultraviolet ... 06:50: ... finds itself in the path of between one and three GRBs within 10,000 light years. ... 07:10: The nearest potential GRB in the brewing is 8,000 light years away, so within the danger zone. 08:46: However, for a supernova to produce the same effects, it needs to be much closer, within 20 to 30 light years.
	2017-12-13: The Origin of 'Oumuamua, Our First Interstellar Visitor 05:25: PZ 17 performed more computer simulations to rewind the motion of both Oumuamua and the 3,700 stars within 100 light years of the sun.
	2017-10-25: The Missing Mass Mystery 07:56: And yet, those filaments are vast, tens of millions of light years long.
	2017-10-11: Absolute Cold 08:26: ... of a potential pair of binary supermassive black holes orbiting only one light year ... 09:53: ... Gamble points out that if this binary pair is a whole light year apart, then for us to see them orbiting each other, they need to be ...
	2017-09-28: Are the Fundamental Constants Changing? 06:44: These things can be seen out to billions of light years.
	2017-09-20: The Future of Space Telescopes 01:49: So how can we find a terrestrial planet around a star light years away? 07:41: ... outwards, it could spot a terrestrial planet at tens of light years distance and even map the cloud structure of a gas giant, especially if ...
	2017-09-13: Neutron Stars Collide in New LIGO Signal? 06:38: ... radiation-- so the highest energy light-- from a galaxy 130 million light years ...
	2017-08-02: Dark Flow 05:17: ... around 700 clusters in all directions on the sky and out to billions of light years. ... 06:02: When you look at scales larger than around a billion light years, you have basically the same amount of matter everywhere. 07:36: ... is a vast cluster of clusters that encompasses hundreds of millions of light years and several hundred entire galaxy ... 07:50: ... galaxies across the observable universe, or to two and a half billion light years at least, far beyond the gravitational reach of ...
	2017-04-19: The Oh My God Particle 07:52: In Now I'm talking close by on cosmic scales, so within 1 to 200 million light years.
	2017-03-22: Superluminal Time Travel + Time Warp Challenge Answer 05:23: You overtake the Annihilator at around the 67 light year mark and finish the race 150 years after the race began. 04:20: You're in a race to claim a newly discovered exoplanet 100 light years away. 04:57: The Annihilator races off towards the exoplanet, 100 light years this way.
	2017-03-15: Time Crystals! 12:03: ... who pointed out that we basically just learned all about a solar system light years away by studying how faint shadows make other faint shadows ...
	2017-03-08: The Race to a Habitable Exoplanet - Time Warp Challenge 02:04: A race to a newly found habitable planet 100 light years away.
	2017-03-01: The Treasures of Trappist-1 01:06: The TRAPPIST-1 system lies 39 and 1/2 light years away in the constellation of Aquarius.
	2017-02-22: The Eye of Sauron Reveals a Forming Solar System! 00:06: ... age, the Dark Lord Sauron fled Mordor into the sky and traveled about 25 light years towards the constellation Piscis ... 00:50: At only 25 light years away, it's the 18th brightest star in the sky.
	2017-01-25: Why Quasars are so Awesome 03:19: Its light must have been traveling from two billion light years away to acquire the observed redshift.
	2017-01-11: The EM Drive: Fact or Fantasy? 09:38: Joel, we're considering buying a lightly used EmDrive with your contribution, only 1,000 light years on the clock, apparently.
	2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer 01:36: The most famous and the closest is the Cygnus X-1 black hole, 6,000 light years away.
	2016-12-21: Have They Seen Us? 01:09: The outer edge of this bubble is now over a hundred light years away. 04:11: Our best-targeted search so far, the SETI Institute's Project Phoenix, scanned 800 stars within 200 light years. 04:27: ... from a civilization's internal broadcasts from within a couple of light years, if those broadcasts with the same strength as our ... 06:38: ... with the sensitivity to potentially see an alien TV bubble to many light years and that is large enough to filter out local ... 08:24: ... be sensitive enough to spot our own TV bubble from a hundred or more light years ... 09:44: That signal is now 50 light years away. 12:43: Any civilization within 40 to 50 light years could have sent a return signal that will reach us any day.
	2016-12-14: Escape The Kugelblitz Challenge 04:19: They're light years away.
	2016-11-16: Strange Stars 07:40: ... spot and found a young pulsar, a rapidly rotating neutron star 10,000 light years ...
	2016-11-02: Quantum Vortices and Superconductivity + Drake Equation Challenge Answers 07:36: Again, using the "solstation" website, we get that there are around 5,000 stars total per 100 light year radius sphere. 07:46: So you'd get 100,000 stars in a 270 light year sphere. 07:36: Again, using the "solstation" website, we get that there are around 5,000 stars total per 100 light year radius sphere. 07:46: So you'd get 100,000 stars in a 270 light year sphere. 03:00: ... is the only technological civilization to have ever arisen within 100 light years of Earth, what would that tell us about the chance of such a ... 03:58: So we're being pessimistic when we say that humanity is the only such civilization to have formed within 100 light years. 04:33: There are a few different ways to get the number of habitable planets within 100 light years. 04:46: For 100 light years, we have 512 G-Type stars: that's the same type as our sun. 05:05: So that means there are around 100 such planets orbiting stars like the sun within 100 light years. 07:13: The Kepler Observatory points only in one direction, so those stars are spread along a column a few thousand light years long.
	2016-10-05: Are We Alone? Galactic Civilization Challenge 01:23: And at the high end, there should be civilisations within 100 light years, which may have detected our own radio transmissions by now. 04:38: ... civilization to have arisen on any habitable planet within 100 light years, how low would that probability of technological emergence need to ... 05:08: ... consider Tabby's Star, an otherwise normal-looking F-type star, 1,500 light years away, which the Kepler mission revealed to be experiencing some weird ...
	2016-09-14: Self-Replicating Robots and Galactic Domination 06:21: Assume an average 10% light speed, 10 light year jumps for each probe, and up to 500 years for production of the first daughter probe at each jump.
	2016-08-03: Can We Survive the Destruction of the Earth? ft. Neal Stephenson 08:25: A supernova explosion within 30 light years would destroy the ozone layer, leading to a horrible hard ultraviolet bath and the worst sunburn ever. 08:58: ... enough to do the same damage as a nearby supernova, but from 6,500 light years ...
	2016-05-11: The Cosmic Conspiracy of Dark Energy Challenge Question 01:36: Say a cubic million light years, around 70% dark energy, 30% matter.
	2016-05-04: Will Starshot's Insterstellar Journey Succeed? 02:38: Alpha Centauri is 4.4 light years away and so even at a good fraction of the speed of light, it's a many year mission.
	2016-04-27: What Does Dark Energy Really Do? 02:53: ... in the time it took their light to reach us-- so billions of light years ... 06:03: ... years catching white dwarf supernovae exploding in galaxies billions of light years away to measure the past expansion history of the ... 02:53: ... in the time it took their light to reach us-- so billions of light years distant. ...
	2016-04-20: Why the Universe Needs Dark Energy 09:53: ... fact, you need to get millions of light years from the Milky Way for the gravitational field of the Milky Way and ...
	2016-04-13: Will the Universe Expand Forever? 04:13: ... do this and only possible because, on its largest scales, billions of light years, all of the galaxies and galaxy clusters are very evenly dusted across ...
	2016-04-06: We Are Star Stuff 12:35: It's happening right now in regions of the universe beyond what we call the Hubble Horizon, which is 13.7 billion light years away.
	2016-03-30: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners! 00:55: It was an elliptical galaxy 6 billion light years away. 02:42: The light traveled 13.7 billion light years. 05:57: 46.6 billion light years in radius now, translates to 42.3 million light years then, which is a volume of 2.7 times 10 to the 71 cubic meters. 07:50: Plug our numbers into this equation and we get a mean free path of around 7,500 light years. 08:08: But 7,500 light years is still very small compared to the size of the universe, even back then.
	2016-03-23: How Cosmic Inflation Flattened the Universe 04:03: ... within 0.4 of a percent of the center of the alley, and the alley is a light year ... 00:55: ... so huge, 93 billion light years from one edge to the other, that those most distant points should never ...
	2016-03-09: Cosmic Microwave Background Challenge 01:41: In fact, all of those blobs of plasma were a mere 43 million light years away from the patch of space that would later contain the Milky Way. 01:58: ... the light from the CMB had to travel a lot further than those 43 million light years to reach this patch of space because it was traveling through an ... 02:10: ... times further away, giving us an observable universe that's 93 billion light years ...
	2016-02-11: LIGO's First Detection of Gravitational Waves! 03:33: In the case of merging black holes, to five billion light years.
	2015-10-15: 5 REAL Possibilities for Interstellar Travel 01:19: It's only 4.4 light years away, but we have to get there before the Curbles and the impending K1 asteroid that's on its way.
	2015-09-30: What Happens At The Edge Of The Universe? 01:22: Let's start with that 46 billion light year number. 01:08: We even gave you a number, 93 billion light years in diameter, 46 billion in radius. 01:33: Now, it's not 46 billion light years to that actual blob. 01:37: ... is currently 46 billion light years to whatever galaxy or galaxy clusters that blob evolved into, racing ... 03:37: Given our best measurements of cosmological parameters, we think that the cosmic event horizon is around 16 billion light years away.
	2015-06-17: How to Signal Aliens 01:39: ... here minimum-- an array like this could be detected from a few thousand light years ... 02:45: You only get about 1,000 light years or so before it becomes too dim. 04:59: ... like the lasers, billboard transits could only be seen within a few light years of earth or maybe a couple thousand if the Kerbal Kepler instrument is ...
	2015-05-27: Habitable Exoplanets Debunked! 03:00: ... maybe it's nothing like Krypton, because at 500 light years from Earth, Kepler 186F is just too far away to determine its mass or ...
	2015-02-25: How Do You Measure the Size of the Universe? 00:16: It's common to put astronomical distances in light years. 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. 01:01: Well, it's a sphere with a radius of about 46 billion light years, or, rounding down to keep it simple, about 90 billion light years end to end. 01:33: Remember, that distance is not 13.8 billion light years. 05:10: Answer, about 46 billion light years away. 05:13: So that's how we know that the observable universe is about 90 billion light years in diameter.

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