Search PBS Space Time


2022-11-09: What If Humanity Is Among The First Spacefaring Civilizations?

  • 01:30: We are in fact on a typical planet, orbiting a typical star in a typical galaxy.
  • 08:16: Since they’re very dim, orbiting planets need to be very close to the star in order to have liquid water, which may be necessary for life.

2022-10-12: The REAL Possibility of Mapping Alien Planets!

  • 00:33: ... images will never reveal anything more   than a single dot in orbit around a star. If we find evidence for life, we’re going to want ...
  • 06:05: ... distance  of Pluto, or well over 500 times the Earth’s   orbital radius. Around 550 “astronomical  units” or “AUs” in ...
  • 09:31: ... spacecraft starts out by launching  backwards compared to Earth’s orbital direction,   using sails to slow down and sort of tack ...

2022-09-28: Why Is 1/137 One of the Greatest Unsolved Problems In Physics?

  • 02:36: ... spins are separated slightly by their interaction with their own orbital magnetic ...
  • 04:17: And the orbital speed of an electron in the ground state of the Bohr model of the hydrogen atom is 137 slower than the speed of light.

2022-08-24: What Makes The Strong Force Strong?

  • 00:28: ... electrons are held in their orbitals by the electromagnetic force - opposite charges attract, so the ...
  • 03:38: Well, slight correction: electron orbitals can contain two electrons, but that’s because those electrons can have a different spin state.
  • 06:20: So an electron bound to an atomic nucleus will feel less force from the nucleus at larger orbitals.

2022-06-22: Is Interstellar Travel Impossible?

  • 08:26: ... onto our ship by the ISM is around a billion times lower compared to orbital ...

2022-06-01: What If Physics IS NOT Describing Reality?

  • 13:41: ... black hole, that black hole will end up in some  orbit within our galaxy’s gravitational well.   It’ll interact with ...
  • 14:22: ... that a star will move through many different   regions as it orbits the galaxy. It’ll be born in  a spiral arm probably, and then move ...

2022-05-25: The Evolution of the Modern Milky Way Galaxy

  • 02:19: ... on a minor outcropping of one of the spiral  arms. It orbits in the same direction as all the   disk stars once every 230 ...
  • 05:58: ... from the   same merger, they should also have similar  orbits. If their orbital speeds are even   slightly different, they ...
  • 06:57: ... which in turn allows astronomers to reconstruct   detailed orbits of Milky Way stars. The stars from  Gaia-Enceladus move in highly ...
  • 08:29: ... Way to create it. It’s made of stars, not gas,  and these stars orbit just a little faster   on orbits that are more inclined than ...
  • 09:11: ... of the two galaxies slamming into each other  kicked up the orbits of many of the stars in   the Milky Way’s original thin disk ...

2022-05-18: What If the Galactic Habitable Zone LIMITS Intelligent Life?

  • 13:03: ... about this planetary system, even with our personal bias that we orbit   most important and yet mundane star in the  apparently uninhabited ...

2022-05-04: Space DOES NOT Expand Everywhere

  • 01:24: ... tend to move around due to nearby gravitational influences - planets orbit stars, stars orbit in the mutual gravity of their galaxies, galaxies ...
  • 16:38: ... - only electrons whose wavefunction peaks and valleys line up on each orbit can exist. Maybe the universal wavefunction is the just that ...

2022-03-23: Where Is The Center of The Universe?

  • 00:25: ... Copernicus shoved us from our pedestal onto a random rocky planet orbiting an ordinary star in the outskirts of an unremarkable ...

2022-03-08: Is the Proxima System Our Best Hope For Another Earth?

  • 01:28: ... to watch alpha-cen sway relative to the background stars as Earth orbited the ...
  • 02:33: A faint red star crawled on a vast, half-million year orbit around its brighter siblings.
  • 02:39: For the entire history of humanity that orbit has placed this red dwarf closer to the earth than its companions.
  • 04:05: Planets don’t really orbit stars.
  • 04:08: A planet-star pair mutually orbits its shared center of mass - its barycenter - which is usually deep inside the star.
  • 04:58: But the more edge-on the orbits, the more motion there is in the radial direction, and so the more chance of spotting the wiggling spectrum.
  • 06:18: Such a short orbital period, combined with the star’s mass, gave them an orbital radius for the exoplanet of around 20 times smaller than the Earth’s.
  • 07:18: The nearest habitable exoplanet orbited the nearest star.
  • 07:52: It’s also way further out, with 5-year orbit at the same distance as Mars.
  • 08:02: ... prospective Proxima D is just a quarter of Earth mass and orbits once every 5 days, well inside the orbit of Proxima B. That’s interior ...
  • 08:36: ... Rigel Kentaurus and an Earth-sized body may have transited Toliman on an orbit that would fry it to a ...
  • 09:17: ... have forced the planet’s rotation period to be in resonance with its orbital ...
  • 10:26: Other orbital resonances can occur - for example, 2 days per year, 3 days per 2 years, etc.
  • 14:56: But there’s another white star on the horizon,  but it’s slowly slipping away on its own orbit around the Milky Way.

2022-01-27: How Does Gravity Escape A Black Hole?

  • 02:36: It would take 8 minutes for us to notice the sudden darkness, and the Earth would continue to orbit the now-empty patch of space for the same time.

2022-01-12: How To Simulate The Universe With DFT

  • 15:14: The minimum velocity it could have on reaching the Earth is the solar system’s escape velocity at Earth’s orbit, or around 42 km/s.
  • 15:37: Most likely the black hole was moving faster than 42 km/s - that would only be the case if it had exactly the same galactic orbit as the sun.

2021-12-29: How to Find ALIEN Dyson Spheres

  • 01:00: ... cover the entire sphere surrounding the Sun with the radius of Earth’s orbit, we’d collect all of the Sun’s light - a billion times more than what ...
  • 02:01: ... pretty reasonable actually as a swarm of independent craft, either in orbit around the star or kiting in place on the solar ...
  • 04:21: Anything capable of producing that much power at that low a temperature must be huge - the size of a planetary orbit.
  • 10:56: ... in brightness and colour over time, as might be expected if a giant orbiting structure partially eclipses the star in an irregular ...

2021-11-10: What If Our Understanding of Gravity Is Wrong?

  • 02:18: That means the orbital velocities of stars out there should be lower in order to keep them in orbit.
  • 02:25: The so-called rotation curve should drop - orbital  speed should diminish with distance from center.

2021-11-02: Is ACTION The Most Fundamental Property in Physics?

  • 05:52: ... was the fact that Newtonian mechanics failed to correctly predict the orbit of Mercury. If you calculate that orbit using the Einstein equations in ...
  • 06:47: ... equation, you get equations of motion correctly describing the orbit of Mercury around the ...

2021-09-21: How Electron Spin Makes Matter Possible

  • 16:12: ... from a bit further out - the photosphere where light can actually orbit the black ...

2021-09-07: First Detection of Light from Behind a Black Hole

2021-08-10: How to Communicate Across the Quantum Multiverse

  • 14:53: ... share an envelope - you can also describe that as saying he white dwarf orbits inside the other star. Now V471 is a post-common-envelope system, ...

2021-08-03: How An Extreme New Star Could Change All Cosmology

  • 03:19: ... it gives us spectral lines. When electrons in an atom move between orbitals, they emit or absorb light with very specific wavelengths. That tells us ...
  • 09:18: ... could be the result of a white dwarf collision. If two white dwarfs are orbiting each other, we expect them to slowly spiral together because they emit ...
  • 09:51: ... from its spinning parent stars - it has the angular momentum from the orbits of the parent stars. This process also explains the intense magnetic ...
  • 15:55: ... asks whether magnetic fields have any measurable effect on the orbits of stars around the galaxy. Not directly. The galactic magnetic field is ...
  • 16:19: So the locations that stars formed may be influenced by magnetic fields, which in turn affects their orbits. So the answer is yes, sort of.

2021-07-21: How Magnetism Shapes The Universe

  • 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.
  • 08:39: And that plasma in turn drags the magnetic fields in orbit around the galaxy.

2021-07-07: Electrons DO NOT Spin

  • 02:25: ... magnetic field like a tiny bar magnet. The different alignments of that orbital magnetic field relative to the external field turns one energy level ...
  • 03:20: ... it acts like a tiny bar magnet. So you have the alignment of both the orbital magnetic moment and the electron’s  internal moment contributing ...

2021-06-23: How Quantum Entanglement Creates Entropy

  • 13:44: ... later. But that was 40 years ago,   and the number of tracked orbital debris has increased from around 4500 to more like ...
  • 15:02: ... presumably our future AI overlords will be better at managing our orbital space,   which will further reduce the Kessler ...

2021-06-09: Are We Running Out of Space Above Earth?

  • 00:30: While the litter seems a little inconsiderate, this is probably far safer than the alternative: leaving junk in orbit.
  • 01:22: ... orbit in the midst of a giant cloud of debris - rocket boosters, protective ...
  • 01:36: The quickest low-altitude orbits circle the Earth 16 times a day.
  • 01:45: ... while a loose screw or paint chip may not be all that scary on earth, at orbital speeds of 7 km/s they can carry as much energy as a ...
  • 03:34: In the case of satellite collisions, exponential increase is inevitable unless debris is removed from orbit or the risk of collision is mitigated.
  • 04:05: A functional satellite in harm's way can then steer itself into a safe orbit.
  • 04:24: It produces a drag that causes orbits to slowly decay.
  • 05:37: The only way this stuff gets cleaned up is if its orbit decays.
  • 05:41: I already mentioned that orbits decay due to interaction with the upper reaches of Earth’s atmosphere.
  • 05:47: Below around 1000 km, that drag slows satellites, causing them to fall into lower orbits where the drag is even greater.
  • 05:53: This is another positive feedback loop - orbital decay accelerates until the satellite finally burns in a glorious blaze of re-entry.
  • 06:03: Satellites in low earth orbit may need to be boosted a few times a year to prevent this inspiral.
  • 06:18: That’s annoying, but orbital decay is the most important process for cleaning low-earth orbit of defunct satellites and debris.
  • 06:26: Ultimately, the Kessler Syndrome can be avoided if orbital decay cleans up low-earth orbit faster than new launches and new collisions fill it.
  • 08:02: The issue with destroying satellites is that the fragments don’t stay in the same orbit as the progenitor satellite.
  • 08:23: This increases the altitude range of the risk, and can also mean that collisions in fast-decaying orbits can still generate long-lasting debris.
  • 08:33: So bringing this all together we can paint a picture of our trashed orbital space.
  • 08:43: That debris then decays in orbit.
  • 08:45: Very slowly for the highest orbits, quite quickly for the lowest.
  • 08:49: But those lowest orbits are continuously repopulated as debris rains down from higher up.
  • 08:54: ... example, even though the International Space Station orbits several hundred kilometers below where the Iridium-Kosmos collision ...
  • 09:10: As long as the self-cleaning of the lowest orbits outpaces the introduction of new debris, we avoid exponential buildup.
  • 09:18: But these lowest orbits are the most useful and cheapest to launch to - and so are the most densely populated.
  • 10:29: This will increase the number of satellites in orbit by a factor of more than 10.
  • 10:53: I should add that StarLink will be in very low orbit, and so has a fast decay time - under 5 years.
  • 11:21: The Kessler syndrome accelerates, churning up low earth orbit into a cloud of shrapnel.
  • 11:54: Higher orbits, like medium earth orbit where the GPS satellites live, will probably also be okay due to the relative low density up there.
  • 12:02: ... high altitudes- maybe they could be destroyed in collisions in low earth orbit, creating a train of debris that wreaks havoc higher ...
  • 12:13: But the real risk is for anything trying to stay in low earth orbit.
  • 12:42: After about a decade, very low earth orbit - up to 400km - will become usable again.
  • 12:51: It’s possible to plan to deorbit booster rockets and old satellites, or send them up into safer graveyard orbits.
  • 13:14: ... to maintain our cosmic front yard, and continue our safe use of Earth’s orbital space ...

2021-05-11: How To Know If It's Aliens

  • 00:19: 45 years ago, a pair of small Earth spacecraft inserted themselves into orbit around Mars.

2021-04-13: What If Dark Matter Is Just Black Holes?

  • 10:01: ... center by now, and in the process flung less massive stars into higher orbits. ...

2021-03-16: The NEW Crisis in Cosmology

  • 07:28: ... use this same trick to measure the distance to stars. As the earth orbits the   sun over the course of the year, nearby ...
  • 08:03: ... And that’s what ESA’s Gaia mission has given us. Parked in an orbit just past the moon,   Gaia scans the sky year after year, ...

2021-02-17: Gravitational Wave Background Discovered?

  • 00:00: ... in the cores of most galaxies these super massive black holes can end up orbiting each other when galaxies collide and that slow fatal in spiral produces ...

2021-02-10: How Does Gravity Warp the Flow of Time?

  • 10:17: ... note of caution: be aware that circular orbital motion in a gravitational field is very different from our rotating ...

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, ...
  • 03:45: ... found by how it affects the rotation of galaxies, and how it drives the orbits of galaxies inside galaxy clusters, and by the way it bends light around ...

2021-01-12: What Happens During a Quantum Jump?

  • 00:36: ... idea that electrons in atoms jump randomly and instantaneously from one orbit or energy level to another, without ever occupying the intervening ...

2020-12-22: Navigating with Quantum Entanglement

  • 15:10: ... familiar Russell’s teapot is a hypothetical piece of chinaware that orbits the sun between the earth and mars, and which science has yet to prove ...

2020-10-27: How The Penrose Singularity Theorem Predicts The End of Space Time

  • 12:11: ... supermassive black hole by monitoring the   crazy orbits of stars in the galactic core. The work of Ghez and Genzel and ...

2020-10-05: Venus May Have Life!

  • 02:05: Our landers and orbiters - Venera, Pioneer, and Magellan - caught hints of unusual atmospheric chemistry.

2020-09-28: Solving Quantum Cryptography

  • 17:05: ... of light and energy and are at the center of the universe, and we're orbited by specks of dust infested with some sort of mud-based ...

2020-09-21: Could Life Evolve Inside Stars?

  • 14:19: ... any arbitrarily complex orbital motion can be represented with enough sine wave pairs in a fourier ...

2020-09-08: The Truth About Beauty in Physics

  • 01:12: ... the first effort, by Claudius Ptolemy, the planets orbited the Earth in complicated systems of circles embedded within circles - ...
  • 01:26: Nicholaus Copernicus found more beauty of simplicity by placing the Earth along with all planets in simple circular orbits around the Sun.
  • 03:48: ... more beautiful or perfect than others - in their case circular orbits - and so surely nature must preferentially choose these for its ...
  • 04:03: Even Kepler fell for that one - he tried to relate his “messy” elliptical orbits to the more perfect Platonic solids.

2020-08-24: Can Future Colliders Break the Standard Model?

  • 13:35: Without you we’d probably have to film in, like, low-earth orbit rather than deep space.

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.
  • 02:07: ... more than half of all stars existing in binary orbits, it’s inevitable that many stellar remnants will end up in these ...
  • 07:58: ... it turns out this object is a pulsar, and it’s in orbit around a companion star - in this case a brown dwarf, which is a star ...
  • 08:18: That brown dwarf orbits perilously close to the neutron star.

2020-08-10: Theory of Everything Controversies: Livestream

  • 00:00: ... a graviton detector the size of the planet jupiter and put it in orbit around the neutron stars stuff like this so you can make a lot of fun ...

2020-07-20: The Boundary Between Black Holes & Neutron Stars

  • 09:40: We see those in X-ray binaries - when a black hole is orbiting and cannibalizing another star.

2020-07-08: Does Antimatter Explain Why There's Something Rather Than Nothing?

  • 09:19: ... measure the difference in energies between the various positron orbitals in the anti-atoms using laser spectroscopy. The exact energy of one of ...
  • 12:37: ... keep working on the cake, but in the meantime have a wonderful next orbital revolution - from me and all the space time ...

2020-06-30: Dissolving an Event Horizon

  • 07:15: Stuff doesn’t normally fall straight into a black hole - it spirals in as its orbit decays.
  • 07:20: It’s that orbital angular momentum that is fed to the black hole.
  • 07:24: But in order for an object orbiting a black hole to fall into it, it actually has to lose at least some of that angular momentum.
  • 07:29: Otherwise it would just keep orbiting forever.
  • 07:55: ... the rotating black hole, giving the gas a sort of boost so it can still orbit even with very little of its own angular ...
  • 08:06: ... fast enough to lose its event horizon - the gas near the event horizon orbits entirely riding on the carousel of frame-dragged state, and has no ...
  • 08:30: More generally, there is no trajectory into an extremal black hole that can add angular momentum from the trajectory or the “orbit” itself.

2020-06-22: Building Black Holes in a Lab

  • 00:16: ... one. Nonetheless, the evidence for their reality is overwhelming. Stars orbiting in crazy slingshot orbits around a patch of nothingness in the center of ...

2020-06-15: What Happens After the Universe Ends?

  • 14:49: ... patreon supporters will have their names encoded in the orbital frequencies of colliding suppermassive black holes at the end of time to ...

2020-03-24: How Black Holes Spin Space Time

  • 05:49: ... as long as you don’t get too close to the event horizon it’s possible to orbit a black hole in a perfectly stable way. For a non-rotating black hole ...
  • 06:48: ... name for the size of these innermost stable circular orbits is ... innermost stable circular orbit. Or ISCO. For a black hole that ...
  • 07:27: So yeah, you can orbit “safely” pretty close to the Kerr black hole’s event horizon.
  • 07:50: ... the angular coordinate becomes time-like - it’s as difficult to resist orbiting the black hole than it is to travel backwards in time - which is to say ...

2020-02-03: Are there Infinite Versions of You?

  • 12:45: ... relativity gives no perfect analytical solutions for TWO bodies in orbit around each ...
  • 12:56: That's because objects in orbit are all moving, so the curvature of the background spacetime is constantly changing.
  • 13:09: ... the other then the Schwarzschild solution gives simple equations for orbits which work pretty well as long as the bodies aren't too close ...
  • 13:41: In any 2-body system, there are these 5 places that a third body can be placed and will stay in stable orbit.
  • 14:14: These would no longer be called "Lagrange points", but they are true stable or metastable 3-body orbits.

2020-01-27: Hacking the Nature of Reality

  • 00:14: The year is 1925 and the young Werner Heisenberg is striving to understand the mechanics of the newly-discovered electron orbitals of hydrogen.
  • 00:43: ... the mysterious frequencies of light produced as electrons jump between orbitals. ...
  • 03:14: At the beginning of the 1960s the atom was understood as fuzzy, quantum electron orbits surrounding a nucleus of protons and neutrons.
  • 14:29: ... some places it gives up angular momentum - it's orbital energy - to the gas, causing it to migrate inwards, while in other ...

2020-01-20: Solving the Three Body Problem

  • 00:20: ... for planetary motion in only one case - when two and only two bodies orbit each other sans any other gravitational influence in the ...
  • 02:06: ... it the parabola of a thrown ball, the circle or ellipse of a planetary orbit, or the hyperbola of an interstellar comet - in general, conic sections - ...
  • 03:18: ... states are highly dependent on small changes in the initial conditions. Orbits tend towards wild and unpredictable patterns, and almost inevitably one ...
  • 04:12: ... system with the Sun. That gives you a series of simple elliptical orbits, like those predicted by ...
  • 04:24: But those orbits eventually shift due to the interactions between the planets.
  • 04:29: ... body and assume that it moves within the completely solvable two-body orbits of its larger companions. We call this the reduced three-body problem. ...
  • 06:43: ... was Leonhard Euler, who found a family of solutions for three bodies orbiting around a mutual center of mass, where all bodies remain in a straight ...
  • 07:56: ... three-body solutions, we had to search the vast space of possible orbits using computers. The key was to find three-body systems that had ...
  • 09:25: ... poles are equilateral triangles - so, Lagrange’s solutions. All other orbits move on this sphere as the triangle defined by the orbits evolves. It ...
  • 10:05: ... hundreds of stable 3-body orbits are known - although it should be noted that besides the Euler and ...
  • 11:21: ... were likely - and by doing so they could map the range of likely orbital properties for the two objects left behind after the ejection. This ...
  • 12:21: ... series that added together an endless chain of terms to solve the orbital calculation. Because the series converged, which successive terms ...
  • 12:55: ... is perfectly solved uselessly, or for seemingly useless and bizarre orbits. And it can be approximately solved for all useful and practical purposes ...

2020-01-13: How To Capture Black Holes

  • 00:59: ... predicted black hole mergers. When two very massive stars are in binary orbit with each other, they may end their lives to leave a pair of binary ...
  • 02:16: ... most awesome possibility: what if black hole mergers actually occur in orbit around supermassive black holes, embedded deep in the whirlpools of ...
  • 04:50: ... of an accretion disk mean for the swarm of stellar mass black holes? The orbits of those black holes are mostly random, so the swarm forms a spheroid a ...
  • 05:58: ... hole pair gets captured by the disk, the surrounding gas saps their orbital energy much more quickly than by gravitational radiation alone. This ...
  • 06:15: ... or lose angular momentum. If it gains angular momentum the size of its orbit increases, so it moves further out in the disk - or “migrates outward”. ...
  • 09:31: ... that was orbiting the binary suddenly finds itself moving too quickly for the reduced ...

2019-11-18: Can You Observe a Typical Universe?

  • 00:34: ... position at the center of the universe into just one of several planets orbiting the ...

2019-11-11: Does Life Need a Multiverse to Exist?

  • 13:40: ... into early earth, causing a lot of Earth's rocky crust to be thrown into orbit before congealing into the ...

2019-11-04: Why We Might Be Alone in the Universe

  • 04:31: ... by Earth-like I mean rocky planets about the size of the Earth in orbit around stars very similar to the Sun at the right distance to sustain ...
  • 07:19: Its size and also its composition and orbit suggest that it formed when a Mars-ish sized planet collided with the Earth right after its formation.

2019-10-07: Black Hole Harmonics

  • 04:24: For a black hole, another way to think of its quasinormal modes is as a set of gravitational waves trapped in orbit around the black hole.
  • 09:05: .69 means this is a rapidly rotating black hole, which is unsurprising seeing as it just absorbed the orbital angular momentum of two black holes.

2019-09-30: How Many Universes Are There?

  • 16:01: Here the IAU definition again: "A planet is a sun-orbiting body massive enough to be round and to have cleared it's orbit of debris".
  • 16:13: It's that last bit - cleared its orbit - that excludes Pluto.
  • 16:16: ... might be considered arbitrary because "clearing the orbit" doesn't necessarily reflect a fundamental difference in the physical ...
  • 16:30: ... fact, whether or not a body clears its orbit depends strongly on where in the solar system it forms - the further ...
  • 16:42: If Earth formed at 100 times its current distance from the sun it wouldn't have cleared its orbit either, and so wouldn't be considered a planet.
  • 17:22: That brings us to the first part of the IAU definition - a planet has to be orbiting our Sun.

2019-09-23: Is Pluto a Planet?

  • 00:02: A big round thing that orbits a star.
  • 02:34: The solar system finally made observational and theoretical sense: there were now 6 planets orbiting the sun in perfect mathematical harmony.
  • 03:27: ... deviations in Uranus's orbit betrayed the existence of Neptune, which was discovered first in the ...
  • 03:43: At the beginning of the 1800s Vesta, Juno, Ceres and Pallas were all spotted between the orbits of Mars and Jupiter and classified as planets.
  • 04:47: Even with the discovery of Neptune, the orbit of Uranus still appeared a bit off - at least in some calculations.
  • 05:37: ... Orbital calculations put the object beyond the orbit of Neptune, and it appeared ...
  • 06:02: The orbit of this new object was far more elliptical - stretched out - than any other planet.
  • 06:07: It also seemed too faint to possibly have the mass required to explain Uranus’s orbital discrepancies.
  • 06:15: By 1931, astronomers had figured out that there didn’t need to be a ninth planet to account for Uranus’s strange orbit.
  • 07:04: And yet some brown dwarfs orbit other, more massive stars just like planets do.
  • 07:15: Also through the 1990s more and more moving specks were discovered within our solar system, beyond Neptune’s orbit.
  • 07:22: ... - what we now call the Kuiper belt - and that encompasses Pluto’s orbit. ...
  • 09:02: A planet must: One - be in its own orbit around the Sun, not around another planet like a moon.
  • 09:18: And Three - Have "cleared the neighborhood" around its orbit.
  • 09:27: Were it a proper planet, it would have collected or scattered all Kuiper belt objects in its orbit.
  • 09:38: ... entire new class of object - dwarf planet - an object which has its own orbit and is spherical-ish, but not massive enough to clear its ...
  • 11:04: Look, Pluto - I’m afraid you haven’t cleared your orbit of debris this quarter.
  • 14:58: Dwarf planet David is a frigid, lifeless ball of ice and rock half the mass of Pluto and orbiting at the outer rim of the Kuiper belt.

2019-09-16: Could We Terraform Mars?

  • 02:47: I mean, that's conclusive – our rovers and orbiters have found incontrovertible evidence of an ancient watery surface.
  • 04:23: ... Martian atmosphere, based on observations of NASA’s Mars Reconnaissance Orbiter and Mars Odyssey ...
  • 05:21: ... of CO2 ice – discovered by radar soundings with the Mars Reconnaissance Orbiter. ...
  • 13:19: The easiest would be to do that in space – an orbiting field generator placed between Mars and the Sun, like a giant space umbrella.

2019-07-01: Thorium and the Future of Nuclear Energy

  • 16:59: ... it's most obvious effect is that it changes how closely an objects can orbit the black hole in a stable ...
  • 17:49: ... objects orbit in the same direction as a black hole's rotation that can be stable much ...

2019-06-20: The Quasar from The Beginning of Time

  • 06:39: If it replaced our Sun, it would easily swallow Saturn's orbit.

2019-06-17: How Black Holes Kill Galaxies

  • 00:08: ... the Black Hole mass and the speed that stars are moving in their random orbits within galactic bulge the so called, Stellar Velocity ...
  • 01:35: ... they definitely aren't directly responsible for the speed of stellar orbits outside their local region Sure, Galaxies and their Black Holes probably ...

2019-06-06: The Alchemy of Neutron Star Collisions

  • 02:47: ... collapse into black holes so take a pair of neutron stars in binary orbit perhaps twin remnants of a once binary pair of massive stars they slowly ...

2019-05-16: The Cosmic Dark Ages

  • 08:11: ... or emitted when an electron jumps between the ground and second electron orbitals of ...

2019-05-01: The Real Science of the EHT Black Hole

  • 06:24: The photon sphere is where gravity is so strong that light itself can orbit the black hole.
  • 06:29: That orbiting light will eventually leave the photon sphere– either falling into the black hole or escaping outwards.
  • 06:47: If the black hole is rotating then you can get photon orbits over a range of distances.
  • 07:10: That’s the innermost stable circular orbit – the ISCO – and it’s the closest you can get to the black hole and still orbit in a stable way.

2019-04-24: No Dark Matter = Proof of Dark Matter?

  • 00:03: ... to explore another possibility what if the discrepancies in the orbits within galaxies and clusters is not due to an unknown source of gravity ...

2019-03-20: Is Dark Energy Getting Stronger?

  • 15:54: A few of you dispute the use of the term spaceship for a craft that doesn't reach orbit.
  • 16:10: But neither entered orbit.
  • 16:28: That said, Virgin Orbit - a spin-off of Virgin Galactic has air-launch rocket that is expected to put satellites in orbit this year.
  • 16:55: ... plane - MUCH bigger than the SpaceShipTwo launcher and designed for orbital rocket launches as well as space ...

2019-03-13: Will You Travel to Space?

  • 06:32: ... a few minutes in space the craft re-enters and lands. It never reaches orbital velocity so it's low speed reentry is less fraught than say the space ...
  • 08:09: ... launch can beat out reusable rockets for actually putting things into orbit remains to be seen. But the technique is looking great for sub-orbital ...
  • 12:23: ... first private spacecraft designed to carry humans to make it into true orbit. Now Dragon 2 didn't have passengers on this test, but in July it will. ...
  • 13:51: Electrons escape their orbits by quantum tunneling, and protons themselves may eventually decay.

2019-03-06: The Impossibility of Perpetual Motion Machines

  • 06:36: Like a perfect Carnot engine, or a frictionless wheel – with or without magnets and mercury tubes – or a planet orbiting a star.

2019-01-24: The Crisis in Cosmology

  • 03:53: ...whose distances can be figured using stellar parallax Tracking their tiny motions on the sky, as Earth orbits the Sun.

2018-12-06: Did Life on Earth Come from Space?

  • 00:37: ... cyanobacteria and lichens can also survive direct sunlight in low Earth orbit briefly mortality is still high in all of these like and seem to do the ...

2018-11-21: 'Oumuamua Is Not Aliens

  • 00:29: ... remnants of the formation of our solar system drifting on their endless orbits around the sun, and faintly glimmering with its reflected ...
  • 00:48: It was not in orbit around the sun at all.
  • 09:22: ... at all, but rather comes from our own Oort cloud and was socked from its orbit by impact and or gravitational interaction into a trajectory that will ...
  • 10:24: And that's a pretty typical speed for a random object orbiting in the Milky Way.

2018-10-31: Are Virtual Particles A New Layer of Reality?

  • 16:52: They were apparently orbiting a center of mass that wasn't even between the stars.

2018-10-25: Will We Ever Find Alien Life?

  • 02:14: The Transiting Planet Survey Satellite is now in orbit and taking over from Kepler.

2018-10-18: What are the Strings in String Theory?

  • 06:48: Niels Bohr came up with the first quantum model for electron orbits by thinking of them as ring-like standing waves around the hydrogen atom.
  • 06:57: But quantum strings are much more ambitious than boring electron orbits.

2018-08-30: Is There Life on Mars?

  • 08:20: A series of orbiters, landers, and rovers found increasing evidence of past and present activity of water on Mars.
  • 08:26: ... Mars "Odyssey" orbiter detected atmospheric hydrogen that told us of enormous quantities of ...
  • 11:42: ... using radar reflections from the MARSIS instrument on the "Mars Express" orbiter. ...

2018-08-23: How Will the Universe End?

  • 05:13: As dark star remnants rotate through countless galactic orbits, they interact with each other gravitationally.

2018-08-15: Quantum Theory's Most Incredible Prediction

  • 04:27: Electrons in atoms feel the magnetic fields produced by their own orbits around the atom.

2018-08-01: How Close To The Sun Can Humanity Get?

  • 03:12: We already monitor it constantly with ground-based telescopes and spacecraft orbiting the earth or orbiting the sun at a safe distance.
  • 05:54: ... need to withstand continuous exposure over many orbits to solar radiation and intense temperatures, upwards of 1,650 Kelvin, ...
  • 06:33: To escape Earth's orbit in the outward direction, you first, need to escape Earth's gravitational pull and then, accelerate to achieve a larger orbit.
  • 07:06: ... its velocity, causing it to fall into a more stretched out elliptical orbit that will take it closer to the ...
  • 07:17: Venus will end up traveling infinitesimally faster as it absorbs Parker's orbital energy.
  • 07:38: ... its orbital period will be the same as Mercury's-- 88 days-- because of its ...
  • 07:54: ... spin roughly, 11 days doing science during each orbital cycle, while spending the other 77 days in the outer parts of its ...

2018-07-04: Will A New Neutrino Change The Standard Model?

  • 12:14: A few of you wonder whether adding extra mass to Earth from asteroid mining could lead to problems like with our orbit or Earth's gravitational pull.

2018-06-27: How Asteroid Mining Will Save Earth

  • 02:09: ... also a few smaller groups of asteroids inhabiting different regions and orbits in the inner solar system, including some that cross Earth's ...
  • 06:59: Fortunately for asteroid miners, though less fortunately for the dinosaurs, many asteroids do cross Earth's orbit in their passage around the Sun.
  • 07:08: ... can be accessed with relatively little fuel expenditure from Earth orbit, and these will be the target of the first ...
  • 08:15: ... we can attempt to mine it on location, so with the orbit of the asteroid, or we can nudge it into a more accessible orbit close ...
  • 08:34: ... a near-Earth asteroid into lunar orbit was the goal of NASA's Asteroid Redirect Mission, but it was canceled in ...

2018-06-20: The Black Hole Information Paradox

  • 14:58: HebaruSan noticed that, in our graphic, the Earth completed 1.75 orbits in the supposed 8 minutes it took the Sun's gravitational field to vanish.

2018-06-13: What Survives Inside A Black Hole?

  • 03:54: The Earth orbits the Sun, but more directly it orbits the Sun's gravitational field.
  • 04:00: You could change anything about the Sun other than its mass and the Earth would continue in the same orbit.
  • 04:06: If the Sun were to suddenly vanish, Earth would continue to orbit the existing gravitational field for 8 minutes.
  • 04:12: The spacetime at the location of Earth's orbit would remain curved until the elastic fabric straightened itself out at the speed of light.
  • 09:14: It dramatically changes the shape of the event horizon and the orbit of anything nearby.

2018-05-16: Noether's Theorem and The Symmetries of Reality

  • 04:07: ... the spherically-symmetric gravitational field experienced by a satellite orbiting the earth-- then, Noether's theorem predicts another conserved quantity, ...

2018-05-09: How Gaia Changed Astronomy Forever

  • 01:37: The spacecraft orbits the sun at Lagrange point two, tracking the Earth's orbit, but 1.5 million kilometers further from the sun.
  • 01:47: As it traverses its orbit, Gaia detects the tiny shifts in the positions of stars due to this motion, a phenomenon called stellar parallax.
  • 02:04: Gaia's winks are the size of its entire orbit.
  • 04:28: The stars all move in their own orbits around the galactic core.
  • 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

  • 09:54: ... center is in itself a dense swarm of smaller black holes in a shared orbit amounting to the same total ...
  • 10:06: Well, the answer is that we can constrain the size of the Milky Way central black hole, Sagittarius A*, because we can see stars in orbit around it.

2018-04-25: Black Hole Swarms

  • 00:35: It flings nearby stars into extreme slingshot orbits.
  • 02:51: As a black hole orbits the galaxy, it tugs on its neighboring stars.
  • 03:18: The ultimate result is that the black hole slows down and no longer has the velocity it needs to maintain its circular orbit.
  • 04:49: Black holes are effectively invisible, but things can be different if a black hole and a companion star are in a binary orbit around each other.
  • 06:04: Hailey and team used the orbiting Chandra X-ray Observatory to hunt for these, and surprise, surprise, they found them.

2018-04-18: Using Stars to See Gravitational Waves

  • 02:54: Observatories across the planet and in orbit around the planet swiveled to watch the afterglow of this collision.
  • 03:35: ... roughly corresponds to the frequency of the binary orbits just before merger, which for black holes and neutron stars clocks in at ...
  • 04:17: The three components of this craft will trail behind the earth in an orbit around the sun.
  • 08:03: A similar effect may cause white dwarf stars in binary orbits to explode as they absorb gravitational radiation from their own orbits.

2018-03-28: The Andromeda-Milky Way Collision

  • 06:09: Gravitational interactions with stars slingshots those stars into larger orbits or even completely out of the galaxy.
  • 06:20: When those black holes are around a light year apart, they'll start losing orbital energy to gravitational waves.
  • 07:03: There's a higher chance of another star passing inside Neptune's orbit, which might cause some gravitational disruption.
  • 07:22: ... follows several candidate suns, simulation particles with similar orbits and masses to our sun, and they track their final ...
  • 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.

2018-03-07: Should Space be Privatized?

  • 01:57: ... encouraged to take over the day to day business of transport to Earth orbit. ...
  • 02:09: To spur private competition, NASA implemented its Commercial Orbital Transport Services Program in 2011.
  • 02:32: Orbital ATK followed closely.
  • 04:09: And as a result, there are many private companies in the business of slinging satellites into orbit.

2018-02-21: The Death of the Sun

  • 03:21: ... process accelerates, and the sun inflates to around the size of Venus' orbit, shining with a few thousand times its current ...
  • 05:31: This time it's outer layers will reach Earth's orbit, and probably then some.
  • 05:54: ... it loses mass, its gravitational hold weakens and so the Earth's orbit expands, perhaps eventually taking it out beyond Mars' orbit, if the sun ...
  • 06:16: On the one hand, these diminish the sun's hold on us, expanding our orbit.
  • 06:44: It may well end up in orbit inside the sun.
  • 07:28: ... managed to escape the expanding sun and is now a lonely desolate world orbiting out in the old location of the asteroid belt, or perhaps it didn't quite ...
  • 07:46: It's also possible that the iron core survives and will continue to orbit the white dwarf sun until the end of everything.
  • 08:22: The habitable zone, the region with the right solar flux liquid water, will expand beyond Neptune's orbit in the first red giant phase.
  • 08:30: And that's Neptune's current orbit.
  • 08:32: All the planet's orbits will have expanded, and to the moons of Neptune, Uranus, and even Saturn, may provide brief refuge.

2018-02-14: What is Energy?

  • 13:38: The grand tack hypothesis suggests that Jupiter may have migrated to Mars' orbit before moving back out again.

2018-01-31: Kronos: Devourer Of Worlds

  • 02:38: ... primary tool is Gaia, an orbiting telescope launched by the European Space Agency in 2013 on a five-year ...
  • 03:34: That means they're almost certainly a wide binary pair with an orbital period of around 10,000 years.
  • 07:08: ... or if the gas giant is perturbed by a passing star into an elliptical orbit. ...
  • 08:28: Andrew Milo recommends we block out some of the sun's light with orbiting solar farms.
  • 08:59: It should be possible to deflect an asteroid into an elliptical orbit that takes it near both the Earth and Jupiter.
  • 09:15: Essentially, we steal angular momentum from Jupiter via the asteroid, which increases our orbit.
  • 09:22: ... enough to maintain the current solar flux by increasing the size of our orbit. ...

2018-01-24: The End of the Habitable Zone

  • 06:28: The Goldilocks zone will expand beyond Earth's orbit.

2018-01-17: Horizon Radiation

  • 03:14: ... observers, be they floating in empty space or accelerating or orbiting a black hole, should agree on the basic result of that interaction-- two ...

2018-01-10: What Do Stars Sound Like?

  • 11:37: Dmitry also asks whether being in a different spot in our orbit can save us from a gamma ray burst.

2017-12-20: Extinction by Gamma-Ray Burst

  • 07:34: This star is part of a binary system, and it's this binary orbit that produces the spiraling nebula.
  • 08:16: Also, further observations with the Keck telescopes indicate that the system's orbital axis isn't pointed directly at the Earth.
  • 08:30: But the orbital axis of a binary system and the rotational axis of its stars are often correlated, so we may have dodged a bullet in this case.
  • 09:00: It orbits the Milky Way, and its galactic neighbors come and go.
  • 09:04: Maybe in a few 250-million-year orbits, a stellar time bomb will wander into our vicinity.

2017-12-13: The Origin of 'Oumuamua, Our First Interstellar Visitor

  • 00:51: ... after 34 days of follow up observations, and a bit of orbital mechanics, it became abundantly clear that we were looking at the first ...
  • 03:00: ... previously observed everything in our solar system-- moves in elliptical orbits as governed by Kepler's ...
  • 03:11: The eccentricity of the orbit measures how stretched out the ellipse is.
  • 03:19: And eccentricity is less than one, our elliptical orbits.
  • 03:25: The earth, for example, has an eccentricity of 0.0167, giving us a nearly circular orbit.
  • 03:47: And they never actually orbit the sun.
  • 04:07: Oumuamua had a maximum speed of 87.7 kilometers per second at its closest approach to the sun, which is well inside Mercury's orbit.
  • 07:39: And based on this, PZ 17 predicts that two to 12 of these interstellar objects should pass through our solar system inside Earth's orbit every year.

2017-11-29: Citizen Science + Zero-Point Challenge Answer

  • 03:08: JunoCam is a camera mounted to the Juno Jupiter Orbiter.

2017-11-22: Suicide Space Robots

  • 02:23: ... Mars landers-- more like crash landers-- to the notorious Mars climate orbiter, which accidentally entered the Martian atmosphere due to a unit ...
  • 04:47: This orbiter studied Saturn and its moons and rings for 13 years.

2017-10-19: The Nature of Nothing

  • 02:41: In each quantum state, so each combination of particle properties, there is a ladder of energy levels, a bit like electron orbitals in an atom.
  • 07:10: ... Rutherford noticed a tiny energy difference between the two electron orbitals that comprise the second energy level of the hydrogen ...
  • 07:26: According to the best existing theory of the time, those orbitals should have had exactly the same energy.
  • 07:50: Virtual particle-antiparticle pairs in the space between the orbitals and the nucleus align themselves with the electric field.
  • 07:58: ... partially shields the orbiting electrons from the positive charge of the nucleus, with the amount of ...
  • 09:57: They just measure its relative effect, inside versus outside Casimir plates, or between electrons in neighboring orbits.

2017-10-11: Absolute Cold

  • 02:07: They can only occupy certain energy levels of vibration or motion, much like the discrete electron orbitals in an atom.
  • 08:26: ... new observation of a potential pair of binary supermassive black holes orbiting only one light year ...
  • 09:53: ... if this binary pair is a whole light year apart, then for us to see them orbiting each other, they need to be traveling insanely ...
  • 10:06: But, actually, we haven't seen them orbiting each other.
  • 10:09: We just know they must be in orbit because their probable masses are large enough that they must be gravitationally bound.
  • 10:16: They would actually take a few thousand years to complete one orbit.

2017-10-04: When Quasars Collide STJC

  • 00:29: We may be about to find out, because astronomers report spotting a pair of them in a close binary orbit for the very first time.
  • 00:38: ... a paper that reports the detection of a pair of supermassive black holes orbiting only one light-year apart from each ...
  • 07:35: Each time they do that they lose a bit of orbital energy or angular momentum, causing them to fall deeper into the gravitational well.
  • 07:58: That means they stall and fall into a stable binary orbits around each other.

2017-09-28: Are the Fundamental Constants Changing?

  • 04:34: Electron energy levels-- or orbitals in atoms-- are quantized, meaning only certain levels are allowed.
  • 05:31: These same electrons are also orbiting the atomic nucleus, and that motion generates its own magnetic field.
  • 05:38: ... magnetic fields produced by an electron's spin and by its orbital motion actually interact with each other in an effect called spin orbit ...
  • 05:48: There are two stable configurations for this interaction-- the little bar magnet may be aligned with the orbital field, or opposite to it.
  • 06:02: So when electrons jump between orbitals, the energy they absorb or emit depends on their spin alignment.
  • 13:10: It would send a spacecraft to at least 550 times the Earth's orbital radius, out beyond the edge of the solar system.

2017-09-20: The Future of Space Telescopes

  • 01:14: ... that is, rocky planets like our Earth-- are extremely common and may orbit most stars in the Milky ...
  • 03:46: The main motivation for building starshades is to suppress the glare of stars enough to see the planets that orbit them.
  • 04:01: So one of these things would allow us to see Earth in orbit around the sun from 60-light years away.
  • 07:35: An aragoscope in geosynchronous orbit could resolve a hamster on the surface of the Earth.
  • 08:40: The future could lie in orbiting rainbows, an idea as creative as it sounds.
  • 08:46: ... pressure to suspend a cloud of tiny reflective particles in Earth's orbit. ...
  • 09:49: Results probably won't top those of the magnificent starshade and aragoscope, but the orbiting rainbow is cheap.
  • 10:47: ... when the first orbiting rainbow is launched and that sparkling glitter cloud is thrown into the ...

2017-09-13: Neutron Stars Collide in New LIGO Signal?

  • 03:01: This was the Hulse-Taylor binary, two neutron stars in orbit around each other, one of which is visible to us as a pulsar.
  • 03:17: And that gravitational radiation sucks energy from the orbiting system, causing the neutron stars to spiral inwards.
  • 03:30: The rate of loss of orbital energy exactly matches the expected rate of emission of gravitational radiation.
  • 03:38: Any neutron stars or black holes in close orbit with each other will eventually collide as they leave gravitational radiation.
  • 03:46: We now know of plenty of neutron star pairs in binary orbits.

2017-08-24: First Detection of Life

  • 00:25: Now, a quarter of a century later, we're on the verge of conducting that same experiment on a world orbiting another star.
  • 07:55: ... is a so-called hot Jupiter, a gas giant, even larger than Jupiter, that orbits its star closer than the orbit of ...

2017-08-16: Extraterrestrial Superstorms

  • 08:28: ... spends most of its orbit millions of miles away from Jupiter's harsh radiation, but every 53 days ...

2017-08-02: Dark Flow

  • 00:26: Planets orbit stars.
  • 00:28: Stars orbit within galaxies.
  • 02:05: This motion is due to the sun's orbit around the Milky Way and the Milky Way falling to the Great Attractor-- more on that last one soon.

2017-07-26: The Secrets of Feynman Diagrams

  • 13:05: Surely, it would retain the same orbit as its satellite.
  • 13:16: But that nudge is far less powerful than whatever you need to launch to orbit.
  • 13:24: Lewinham asks what the real problem is with filling low earth orbit with debris.
  • 13:28: So the issue is that stuff in low earth orbit is moving it around 8 kilometers per second.

2017-07-19: The Real Star Wars

  • 01:30: It also inspired a race to win the military advantage of low-Earth orbit.
  • 01:51: ... they don't actually into orbit, they exceed the altitudes of most low-Earth orbit satellites, hitting ...
  • 02:01: Despite definitely being in space, these are called suborbital trajectories because they don't actually reach orbital velocity.
  • 02:33: ... Soviet program, the Fractional Orbital Bombardment System, actually did enter true orbit, and it would allow ...
  • 06:45: ... things would need to live in Molniya orbits, highly elliptical orbits that allowed them to spend most of their time ...
  • 07:09: ... signatories from placing nukes or other weapons of mass destruction in orbit or on a celestial ...
  • 07:26: ICBMs are still allowed because they don't actually enter orbit, but the nuke-powered Excalibur was a definite no-no.
  • 07:53: ... fast-moving, non-explosive chunks of matter Brilliant Pebbles propose an orbiting weapons platform that delivered non-explosive missiles to destroy ...
  • 08:39: But the idea was to drop nine-ton, six-meter long tungsten cylinders from orbit.
  • 09:47: ... literally "satellite fighter," was a missile designed to actually enter orbit and maneuver up close to its target satellite before ...
  • 10:24: ... there was the Polyus spacecraft, a full-fledged orbiting the battle station that would have had a megawatt laser designed to take ...
  • 11:00: One, the resulting debris massively increased the amount of space junk in low-Earth orbit.
  • 11:27: ... official line is that the satellite was decaying from orbit, and the purpose of its destruction was to avoid the unlikely event of ...
  • 11:39: ... debris wasn't as dangerous as the Chinese explosion because that debris' orbit will decay much more ...
  • 12:02: ... hits and destroys more satellites in increasingly crowded low-Earth orbit. ...
  • 12:23: The Cold War arms race was on track to fill Earth's orbit with satellite-destroying weaponry and nuclear warheads.

2017-06-21: Anti-Matter and Quantum Relativity

  • 03:24: In the case of electrons in atoms, it suggests that we should only find one electron per atomic orbital, if we count each orbital as a quantum state.
  • 03:34: However, we actually observe two electrons per orbital.
  • 10:47: A penny of anti-matter could be used to launch a good-sized rocket into orbit.

2017-05-31: The Fate of the First Stars

  • 02:18: Today, they're found in the galactic bulge or in globular clusters, which are ancient, dense islands of stars that orbit far out in the galactic halo.

2017-05-17: Martian Evolution

  • 03:36: We know that the zero-G experienced in orbital or interplanetary space leads to decreased bone density and muscle mass in astronauts.
  • 14:15: In fact, it's the moon's orbit around the Earth that results in the shadow's movement.
  • 14:20: The moon orbits the Earth once a month, which means it moves about 0.5 degrees per hour.

2017-05-10: The Great American Eclipse

  • 01:26: The moon's orbit about the Earth and the Earth's orbit about the sun, the ecliptic plane, are misaligned by about 5 degrees.
  • 04:12: The moon's orbit is elliptical, and so sometimes it eclipses the sun when it's a bit further away from the Earth.
  • 06:41: Mercury orbits so close to the sun that it's hard to catch in a dark enough sky.

2017-04-05: Telescopes on the Moon

  • 00:41: ... five days of travel and another week of lunar orbit, it descended onto the surface and became the first soft landing on the ...
  • 12:39: The sideways components, angular or orbital components in spherical coordinates, stay space-like.

2017-03-29: How Time Becomes Space Inside a Black Hole

  • 03:06: This equation assumes no orbital motion, only motion towards or away from the center of the black hole, which is a distance r away.

2017-03-15: Time Crystals!

  • 02:49: Cups of coffee cool down, planets orbit the sun, the universe expands.
  • 10:45: Solano Felicio asks about the possibility of stable orbits when planets are so close together.
  • 10:52: Well, that's where orbital resonance comes in.
  • 10:55: The planet's orbital periods have evolved so that each pair of planets lines up at regular intervals.
  • 11:02: That actually stabilizes the orbits rather than makes them more chaotic.
  • 11:07: ... configuration, and that probably drove the planets from much larger orbits to their current locations very close to the ...
  • 11:54: Yet it's estimated that a system with an Earth-like planet orbiting a Sun-like star has around a 1% chance of transiting from our perspective.

2017-03-01: The Treasures of Trappist-1

  • 01:26: The seven planets huddle extremely close to this star-- all within one fifth of Mercury's orbit.
  • 02:13: ... planets have now settled into stable orbital resonances with each other, and that's a hint that they may have formed ...
  • 03:08: Our solar system's habitable zone extends from roughly 1 astronomical unit-- so Earth's orbit-- to 1 and 1/2 AU, covering Earth and Mars.
  • 03:43: The outermost planet, which orbits past the snow line, should be icy.
  • 08:29: Remember also that a potentially habitable Earth-like planet was recently found orbiting the very nearby Proxima Centauri.

2017-02-22: The Eye of Sauron Reveals a Forming Solar System!

  • 03:57: By the time it's at least 10% of the Earth's mass, it will have cleared its orbit of other planetesimals, and will have rounded out into a planet.
  • 05:07: Every grain of dust in the Fomalhaut system is in orbit around the star.
  • 05:11: The closer an object orbits to a given star, the faster it moves through space.
  • 05:17: The farther out it orbits, the slower it moves.
  • 05:31: Infused with extra energy, that dust orbit shifts outwards.
  • 06:13: Fomalhaut B shows up as a bright orbital body in Hubble images.
  • 07:28: Dagon's highly eccentric 1,700 earth year orbit is larger than Neptune's.

2017-02-02: The Geometry of Causality

  • 12:58: Joan Eunice asks whether there's a spot near a quasar where a stable orbit could be created, and what would time dilation be like there?
  • 13:06: Well, the smallest stable orbit around a black hole is the so-called innermost stable circular orbit.
  • 13:30: ... atoms, orbiting at around 10 times the Schwarzschild shield radius, undergo an extremely ...

2017-01-19: The Phantom Singularity

  • 16:50: The state owned China Academy of Space Technology announced in December that it's testing the device in orbit.
  • 17:09: But honestly, orbital tests don't eliminate most of the issues of vacuum chamber ground tests.

2017-01-04: How to See Black Holes + Kugelblitz Challenge Answer

  • 01:18: ... the motion of a visible star reveals it to be in orbit around a companion that is dark invisible light but bright in ...
  • 02:20: They show crazy slingshot orbits around an empty patch of space.
  • 02:24: These orbits tell us that a dark something of around four million solar masses lurks in the center.
  • 05:12: It has enough energy to produce a black hole with a mass of 100,000 suns and an event horizon that almost reaches the moon's orbit.
  • 05:25: One-- Project Phoenix Egg is to build a giant Dyson sphere just outside the moon's orbit to absorb the incoming radiation.
  • 05:34: ... two, Project Disco Ball, proposes a satellite network orbiting the Earth at half the moon's orbit radius, capable of generating a ...
  • 08:24: The light shell passes the moon's orbit, and a true event horizon forms.
  • 09:11: Our other plan was to build a Dyson sphere just outside the moon's orbit.

2016-12-21: Have They Seen Us?

  • 09:02: These emission spikes may also shift back and forth in frequency due to Doppler shift, as the distant technologically advanced planet orbits its star.
  • 10:04: ... and equivalent to a dish around three times the radius of the Moon's orbit. ...

2016-12-14: Escape The Kugelblitz Challenge

  • 05:55: Plan A is to build an infinitely-strong Dyson sphere surrounding the earth just outside the moon's orbital radius.

2016-11-16: Strange Stars

  • 07:40: ... technological advancements, we pointed our radio telescopes and then the orbiting Chandra X-ray Observatory to that spot and found a young pulsar, a ...

2016-11-02: Quantum Vortices and Superconductivity + Drake Equation Challenge Answers

  • 05:05: So that means there are around 100 such planets orbiting stars like the sun within 100 light years.

2016-10-19: The First Humans on Mars

  • 00:24: NASA's new budget mandates a 25-year timescale for putting astronauts in orbit around Mars.
  • 01:05: First step-- a spaceship is launched into orbit by a rocket booster.
  • 01:14: It relaunches and delivers to the orbiting spaceship enough fuel for the four-month journey to Mars.

2016-10-12: Black Holes from the Dawn of Time

  • 08:14: If it passed anywhere near the planetary system, the gravitational tug would disrupt the planet's orbits.

2016-09-14: Self-Replicating Robots and Galactic Domination

  • 05:25: After several decades, it decelerates into a neighboring star system, and parks in orbit, or lands on a nice, big asteroid or gas giant moon.
  • 05:49: It builds fuel collectors-- maybe orbiters to harvest deuterium or tritium from gas giant atmospheres.
  • 11:01: Well, a full Dyson swarm interior to Earth's orbit would, indeed, block sunlight and freeze our planet.

2016-08-24: Should We Build a Dyson Sphere?

  • 01:38: The plausibility of a solid sphere the size of a planetary orbit is not really in question.
  • 02:49: ... kilometers or less in diameter and each with its own independent stable orbit around the ...
  • 04:33: We start with limited mining, space launch, and orbital construction facilities, all of it autonomous.
  • 09:13: Then use that partial Dyson swarm's energy to build Kugelblitzes, in orbit, say, around Jupiter.

2016-08-10: How the Quantum Eraser Rewrites the Past

  • 11:10: ... system, even if nowhere near the Earth, would probably disrupt planetary orbits and either rearrange or scatter our planetary ...
  • 13:11: ... Found had a great idea in which you collect asteroids and put them in orbit around the Earth, ready to sling at any oncoming impactors before they ...

2016-08-03: Can We Survive the Destruction of the Earth? ft. Neal Stephenson

  • 06:13: ... of objects larger than one kilometer in diameter that crossed Earth's orbit. ...

2016-07-27: The Quantum Experiment that Broke Reality

  • 12:35: My pleasure-- a resonant frequency is when two orbiting bodies have orbital periods that form a neat ratio of small integers.
  • 12:43: For example, for every one orbit of Jupiter's moon Io, its moon Europa orbits twice and Ganymede four times.
  • 12:52: For every eight Earth orbits, Venus does 13.

2016-07-06: Juno to Reveal Jupiter's Violent Past

  • 00:02: Two days ago on the 4th of July, 2016, the Juno spacecraft entered orbit around the planet, Jupiter after a five-year journey from Earth.
  • 00:45: Jupiter's enormous gravity influences the orbit of all the planets in the solar system.
  • 00:50: In fact, its effect during the first billion years of the solar system's formation defines the positions of all planetary orbits.
  • 02:19: Its ponderous orbit takes around 12 years.
  • 02:39: ... own Milankovitch cycles, periodic changes in Earth's orbit and spin, are largely driven by Jupiter's influence and give us our ...
  • 03:10: I'm talking about the rare long period comets that orbit the sun with periods of hundreds to many thousands of years.
  • 03:32: ... it probably intercepts some of the most worrying comets that cross its orbit, it also perturbs the orbits of asteroids in the asteroid belt and can ...
  • 03:50: Jupiter probably didn't form in its current orbital location.
  • 04:09: There were no stable orbits in this sort of environment.
  • 04:12: A planet can lose angular momentum to the debris, causing its orbit to shrink.
  • 04:45: ... through the protoplanetary disk before settling into its current orbit or driving other planets to do the ...
  • 05:37: Saturn would have quickly followed until it fell into orbital resonance with Jupiter, three of Saturn's orbits to every two of Jupiter's.
  • 07:53: However, the Nice Model posits that the orbits of the four gas giants were much more tightly clustered back then.
  • 08:21: At some point, Saturn's orbit once again fell into resonance with Jupiter's, but now two Saturnian orbits to every one Jovian.
  • 09:52: The key to finding Jupiter's birth orbit is in its internal composition, and that is one of the things the Juno spacecraft was sent to discover.

2016-06-22: Planck's Constant and The Origin of Quantum Mechanics

  • 02:12: ... but also the Schrodinger equation, the energy levels of electron orbits, and importantly, the relationship between the energy and frequency of a ...

2016-06-15: The Strange Universe of Gravitational Lensing

  • 08:29: This is a region where light paths are so strongly curved that photons can actually orbit the black hole, forming a shell of light.
  • 08:38: There are no stable orbits this close to a black hole.

2016-06-08: New Fundamental Particle Discovered?? + Challenge Winners!

  • 07:17: In the paleoclimate record, we see that an increase in temperature due to Earth's changing orbit proceeds an increase in CO2.
  • 12:47: ... your address, US T-shirt size, and let us know if you want a black hole orbit or an I'll sign to anything I want ...

2016-05-25: Is an Ice Age Coming?

  • 02:33: ... the elongation or the eccentricity of Earth's elliptical orbit shifts from almost completely circular to somewhat more elliptical in ...
  • 03:41: In addition, the long axis of Earth's elliptical orbit also precesses.
  • 03:47: Together, these two effects define where in the orbit the seasons occur.
  • 04:11: Our spin axis is now tilted at 23 1/2 degrees relative to the axis of our orbit.
  • 06:26: Every time Earth's orbit becomes more circular, the planet warms and the glaciers go away.
  • 07:55: Now, by themselves, shifts in Earth's orbit aren't enough to radically change climate.
  • 08:37: There is an unfortunate combination of orbital properties that kickstarts this process.
  • 10:07: See, the recent eccentricity maximum was a sad little pig, and our orbit remains pretty circular.

2016-05-04: Will Starshot's Insterstellar Journey Succeed?

  • 02:19: This solar sail has buzzed past Venus and now explores the interplanetary space in an orbit between Earth and Venus.
  • 05:51: ... with camera tech capable of resolving continents and oceans on planets orbiting Alpha Cen, assuming they have ...

2016-04-13: Will the Universe Expand Forever?

  • 11:54: However, stars don't all orbit at exactly the same rate.
  • 11:58: Orbits aren't perfectly circular, and stars drift apart as they move in and out of the spiral arms and above and below the galactic disc.
  • 12:06: The Sun has orbited the Milky Way around 18 times since it formed.

2016-04-06: We Are Star Stuff

  • 09:27: ... two very massive stars in binary orbit leave behind neutron star corpses, those remnants will eventually spiral ...

2016-03-30: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners!

  • 08:46: And also let us know whether you'd prefer a I'll Science Anything I Want t-shirt or a Black Hole Orbits T-shirt?

2016-03-23: How Cosmic Inflation Flattened the Universe

  • 10:54: So the orbits of any bit of dark matter can be in any orientation or direction.
  • 10:59: And random orientation orbits give you a spheroid.
  • 11:08: Stars a small enough, compared to the distances between them, that they can be in these random orbits.
  • 11:52: ... or centripetal force-- in this case, that's gravity-- acting on the orbiting ...
  • 12:08: The orbiting object is subject to the full acceleration caused by gravity, which is what causes it to move in an orbit.

2016-03-16: Why is the Earth Round and the Milky Way Flat?

  • 09:14: The gas can't fall any closer to the axis of rotation because it's orbiting that axis.
  • 10:05: Disks happen when orbital motion dominates the resistance to gravity.

2016-02-17: Planet X Discovered?? + Challenge Winners!

  • 00:48: And presumably is just one of many such rocks orbiting the Sun in the vast Kuiper Belt, out beyond Neptune.
  • 00:55: You see, Brown also found Sedna, a minor planet, whose elongated orbit takes it out way beyond the Kuiper Belt.
  • 01:10: ... who first noticed that several Kuiper Belt objects had these elongated orbits, orbits that are roughly aligned with each other in the axis of their ...
  • 01:31: ... mass well over 10 times that of the Earth, and a stretched out eccentric orbit with a period, a year-length, of 15,000 Earth years, and an average ...
  • 02:20: Now, the alignment of those weird Kuiper Belt orbits is pretty unlikely to have happened randomly, a 0.007% chance, to be precise.
  • 02:39: ... discrepancies in Uranus' and Neptune's orbits, which have now been debunked, nonetheless led to the original discovery ...
  • 08:02: Also, let us know if you prefer an I'll Science Any Question I Want t-shirt or a Black Hole Orbits t-shirt.

2016-02-11: LIGO's First Detection of Gravitational Waves!

  • 01:53: Any orbiting pair of massive objects generates gravitational waves.
  • 01:57: ... only extremely massive objects, through orbiting extremely close together, produce gravitational waves strong enough for ...
  • 02:18: Now these stellar remnants are sometimes found in pairs, typically when the original stars were also a binary pair in orbit around each other.
  • 02:30: But gravitational waves carry energy, which is sapped from the orbital energy of the system.
  • 02:40: Now we've seen this slow orbital decay in binary neutron stars.
  • 04:31: ... squeezes per second, that matches the rate at which the black holes were orbiting each other just before ...
  • 04:41: And we're talking up to 1,000 orbits per second.

2016-01-13: When Time Breaks Down

  • 01:11: ... vibrating in metal lattices, bound by electrons flickering in their orbits, themselves held in place by protons that are comprised of quarks in ...

2015-12-09: How to Build a Black Hole

  • 04:02: Now, this rule is what keeps electrons in their separate stable orbits and, in turn, is part of what allows solid matter to have its structure.
  • 12:18: ... its velocity enough to hit the sun, or even to fall into Earth's orbit-- which was another suggestion-- would take vastly more energy than just ...

2015-11-25: 100 Years of Relativity + Challenge Winners!

  • 02:28: First, let's do the calculation in the frame of reference of Apophis' 2029 orbital velocity.
  • 02:45: The x-axis is the orbital path of the asteroid.

2015-11-18: 5 Ways to Stop a Killer Asteroid

  • 02:58: ... the biggest, one kilometer plus, comets or asteroids that cross Earth's orbit. ...
  • 03:14: ... the late 2100s, and the 300 meter Apophis, who will buzz us inside the orbit of the geosynchronous satellites in 2029 and 2036, but will almost ...
  • 03:50: ... is fund raising to launch the Sentinel infrared telescope, that will orbit the sun and look outwards, tracking hundreds of thousands of ...

2015-11-11: Challenge: Can you save Earth from a Killer Asteroid?

  • 00:31: Something like a passing comet has perturbed it's orbit.

2015-10-28: Is The Alcubierre Warp Drive Possible?

  • 07:31: It'll be an orbiting gravitational wave observatory designed to detect much higher frequency gravitational waves than advanced LIGO.

2015-10-22: Have Gravitational Waves Been Discovered?!?

  • 02:03: But two objects orbiting each other, or an asymmetrically spinning or exploding thing, does.
  • 04:22: ... so when, say, two massive objects orbit each other close enough to produce a lot of this gravitational ...

2015-10-15: 5 REAL Possibilities for Interstellar Travel

  • 06:55: ... built on the moon and powered by massive Helium 3 reactors or in orbit around the sun powered by vast solar ...

2015-09-30: What Happens At The Edge Of The Universe?

  • 08:03: For example, the predictions GR makes for planetary orbits can give us a mass for the Sun.
  • 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?

  • 00:24: ... see, we can only account for 10% of the mass needed to hold its stars in orbit. ...
  • 04:29: Modified versions of GR can actually do pretty well, especially predicting orbits within galaxies.

2015-08-27: Watch THIS! (New Host + Challenge Winners)

  • 00:03: Which of two particles, one orbiting around the outside of a planet and one going straight through the middle, reaches the other side first?
  • 01:09: ... from what I just said, you can also work out an expression for the orbital period of a particle moving under the planet's gravity in a circular ...

2015-08-19: Do Events Inside Black Holes Happen?

  • 01:06: Suppose that I'm very far from a black hole and there's a pony orbiting the black hole.
  • 01:29: ... clocks in high-altitude orbit will get ahead of clocks on the ground by a few microseconds each day, ...
  • 04:56: ... resulting geodesics of which correspond to things like radial freefall, orbits, et ...
  • 05:16: Earth will freeze, of course, but its orbit won't be any different.
  • 06:16: You can orbit them just fine.
  • 06:29: For example, that is an allowed planetary orbit in that region.

2015-08-12: Challenge: Which Particle Wins This Race?

  • 00:36: That sphere is not rotating, and it's not orbiting any other larger bodies.
  • 00:46: Suppose that a particle is orbiting the planet right at the surface.
  • 00:49: And I know, technically it's not orbiting if it's on the surface.
  • 00:52: So fine, if it makes you feel better, say that it's orbiting a billionth of a nanometer above the surface.
  • 00:59: ... Newtonian gravity, you can work out an expression for the orbital speed of this particle in terms of the mass and radius of the planet, or ...
  • 01:37: At the same time that the orbiting particle passes this point, let's release the second particle from rest from exactly the same height.

2015-08-05: What Physics Teachers Get Wrong About Tides!

  • 08:03: Well, location relative to the plane of the Moon's orbit is certainly part of it.
  • 12:04: A lot of you wanted clarification on how curvature of time is what's responsible for, say, circular orbits around the Earth being geodesics.

2015-07-29: General Relativity & Curved Spacetime Explained!

  • 07:07: ... though it's hard to visualize, it's curved time that makes the free fall orbits of satellites looks spatially circular in frames of reference that cover ...
  • 07:50: ... geodesics into 3D spatial and temporal terms, what you find is planetary orbits or spatially straight, radially inward trajectories along which you ...

2015-07-15: Can You Trust Your Eyes in Spacetime?

  • 01:34: The moon doesn't orbit Earth.

2015-07-08: Curvature Demonstrated + Comments

  • 05:18: ... Earth, and we were taking a vector and moving along a circle in orbit around the ...

2015-07-02: Can a Circle Be a Straight Line?

  • 00:16: ... general relativity, objects that fall or orbit aren't being pulled by a gravitational force, they're simply following ...
  • 08:12: ... to discuss the calendar, the seasons, and their connection to Earth's orbit. ...
  • 09:18: ... understood, but since magnetic pole reversal wouldn't affect Earth's orbit or the tilt, any effects on the seasons would be ...

2015-06-24: The Calendar, Australia & White Christmas

  • 00:16: ... Earth's equator is tilted from the plane of its orbit by approximately 23 and 1/2 degrees, so that different parts of the ...
  • 01:29: ... the fact is that Earth's axis precesses in the opposite sense of Earth's orbit around the sun, so that the equinoxes and solstices backtrack along ...
  • 02:22: But it doesn't track Earth's 360-degree orbit in space the way you might think.
  • 02:26: Instead, it's locked to the solar year, to the seasons, so that it backtracks along Earth's orbit right along with the equinoxes and the solstices.
  • 02:59: So the location of Earth on successive New Year's Eves backtracks along the orbit.
  • 03:08: So every four years, we add February 29 to re-sync with Earth's orbit and undo that backtracking.
  • 03:13: But the calendar isn't trying to sync to Earth's orbit.
  • 03:24: We also need a little bit of extra slippage, because the annual discrepancy between the calendar and Earth's orbit also isn't precisely six hours.
  • 04:17: If you look on time scales of tens of thousands or hundreds of thousands of years, Earth's orbit is a lot crazier than you would expect.
  • 04:23: The shape of the orbit flexes.
  • 04:27: The orbital plane wobbles.
  • 04:33: Now, one effect of all this orbital craziness is that the mean tropical year is actually getting shorter by about a half second every 100 years.
  • 05:58: Also, if you'd like to see an episode on what Earth's orbit and rotation really look like in space and why, let us know that, too.
  • 06:04: ... signal aliens, including maybe putting planet-sized geometric objects in orbit around the ...
  • 06:45: ... thruster situation, because these things are going to get blown out of orbit by the solar wind without some kind of ...
  • 06:58: ... a few tens though, going in different orbital planes, you could actually probably see them from most places, because ...

2015-06-17: How to Signal Aliens

  • 02:48: But at those distances, a laser's spot size would only grow to around the size of Jupiter's orbit.
  • 04:35: So I'm picturing an ultra-thin, ultra-lightweight, opaque material that we could launch into solar orbit and then unroll like a sail.
  • 04:45: Now, we would need to tweak the orbit occasionally due to solar wind and radiation pressure.
  • 05:55: ... does now, should SETI also be looking for geometric alien billboards orbiting nearby ...

2015-06-03: Is Gravity An Illusion?

  • 08:27: Second, by your criterion, Einstein, orbiting frames of reference-- like on the space station-- should also be considered inertial.
  • 09:30: And in that curved spacetime, the orbit of the ISS is a constant-speed straight line.
  • 10:42: Earth analogs in Earth-like orbits around Sun-like stars are not going to be visible.

2015-05-27: Habitable Exoplanets Debunked!

  • 01:04: ... the habitable zone, in turn, is defined as the sweet spot of orbital distances from that star at which the energy from starlight would ...
  • 01:29: Plus, if you expand its orbit just a teensy bit, it would be in the sun's habitable zone.
  • 01:39: A planet with a super-thick atmosphere, for example, could have surface water in a larger orbit than you'd ordinarily expect.
  • 02:39: ... were able to infer the radius of the planet and some features of its orbit, like its approximate distance from that ...
  • 02:49: Turns out Kepler 186F is about 10% larger in radius than Earth in an orbit around the size of Mercury around a fairly dim red dwarf star.
  • 03:11: All we know are its radius and the approximate size of its orbit.
  • 04:32: But this only works for planet that are in very large orbits outside the habitable zone, because closer in, the contrast is still too low.
  • 05:34: ... could have analyzed the atmospheres of Earth-sized planets in Earth-like orbits around Sun-like like ...

2015-05-20: The Real Meaning of E=mc²

  • 03:57: Don't worry, Earth's orbit is going to be fine.

2015-05-13: 9 NASA Technologies Shaping YOUR Future

  • 00:56: Next problem-- the space station orbits Earth so fast that each new sunrise happens every 90 minutes.
  • 04:08: So, how do you keep astronauts from falling apart in orbit?

2015-05-06: Should the First Mars Mission Be All Women?

  • 01:29: ... of them were in orbit six months or less, which is a lot less time than the eight months of ...
  • 05:35: ... need to work out how much fuel it would take to get that food from Earth orbit to Mars orbit and back, and then estimate the cost of getting the food ...
  • 06:03: ... descent to Mars, that you'd leave all the food for the return trip in orbit around Mars, and that you'd leave all your waste down on the Martian ...

2015-04-29: What's the Most Realistic Artificial Gravity in Sci-Fi?

  • 05:17: ... The ring habitat in that novel has the same radius as Earth's entire orbit around the sun, around 93 million ...
  • 05:51: To sustain 1 g, the ring would need to complete the equivalent of one Earth orbit around the sun in only nine days.

2015-04-22: Are Space and Time An Illusion?

  • 07:59: Joey Broda and McKnowledge1000 both asked why human gene expression isn't altered in orbit if bacterial gene expression is.

2015-04-15: Could NASA Start the Zombie Apocalypse?

  • 02:18: ... mono-- all of which suggests that viruses also are more virulent in orbit. ...
  • 02:57: NASA also has thorough quarantine sterilization procedures to minimize germs hitchhiking into orbit.
  • 03:28: ... or space hotels where ordinary people are taking vacations to low-earth orbit. ...
  • 03:46: And dealing with that fact is one of the biggest challenges in establishing a larger human presence in Earth orbit and beyond.

2015-04-08: Could You Fart Your Way to the Moon?

  • 07:44: ... seem to need the moon to orbit around the planet at the same rate that the planet spins on its axis, ...

2015-03-11: What Will Destroy Planet Earth?

  • 02:15: But asteroids orbit the sun about 35 times slower than that.
  • 02:40: Mars orbit outside Earth's orbit, so how could they collide?
  • 02:52: But if everything lines up just right, then over billions of years, they could have a sizable cumulative effect and distort those orbits.
  • 03:19: But in 1%, the inner planet orbits stretch out after about three billion years and Earth starts doing drive-bys of Venus and Mars.
  • 03:56: ... inflating until it becomes slightly larger than Earth's entire current orbit. ...
  • 04:27: In the process, the sun will lose a lot of mass and a lot of gravitational pull, causing Earth's orbit to actually grow.

2015-03-04: Should We Colonize Venus Instead of Mars?

  • 02:15: In Earth orbit, astronauts lose bone mass at about 10 times the rate of someone with advanced osteoporosis.
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