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2022-12-14: How Can Matter Be BOTH Liquid AND Gas?

  • 01:00: For example, it’s not just temperature that determines the state of matter, it's also pressure.
  • 01:14: But high pressure helps to keep particles together so that it takes more heat energy to break bonds.
  • 01:29: The relationship between temperature, pressure, and phase is mapped on a phase diagram.
  • 02:02: For example, at low pressures there’s a boundary where increasing temperature takes you directly from solid to gas - we call that sublimation.
  • 02:11: ... From the triple point, if we increase both temperature and pressure in the right proportions we follow the phase transition boundary between ...
  • 02:37: It's almost like the map gives out - as though our explorer experimentalists haven’t traveled that far across the realms of pressure and temperature.
  • 04:03: Liquids, for example, are remarkably difficult to compress in volume by the application of external pressure.
  • 04:08: That enables their use in things like hydraulic presses, where they can be used to exert enormous outward pressures.
  • 04:15: ... And the volume of liquid doesn’t change even in the absence of external pressure. ...
  • 04:46: While pressure doesn’t influence liquid volume, temperature does.
  • 04:53: Gases on the other hand will always expand to occupy the entirety of their container, and are also relatively easy to compress by exerting pressure.
  • 05:09: Those impacts exert a pressure on the container.
  • 05:13: ... but it’ll take longer for each particle to travel between walls, so pressure drops; vice versa if you shrink the ...
  • 05:23: Increase temperature and the gas particles move faster, hit harder, again increasing the pressure.
  • 05:29: ... forces, its behavior can be described by a simple relationship between pressure, temperature and volume given by the Ideal Gas Law: ...
  • 05:43: OK, that’s about enough blah pressure temperature blah blah.
  • 06:15: This is a pressure chamber containing dry ice - carbon dioxide in solid form.
  • 06:21: That ice was presumably created below the 194.7 Kelvin freezing point of CO2 at atmospheric pressure.
  • 06:36: ... atmospheric pressure, liquid CO2 can’t exist, but in the small volume of the chamber, ...
  • 06:57: To reach supercriticality, we need to get to this part of the diagram, so both pressure and temperature need to increase.
  • 07:12: ... the temperature rises the pressure of the gas increases a proportional amount, but this temperature is also ...
  • 07:27: ... first we might think this pressure has no effect because liquids are incompressible, but look at the phase ...
  • 07:54: We remain stuck following the transition boundary, upwards in temperature and pressure, trapped in our state by thermodynamics.
  • 09:53: On the other hand, if the chamber is opened then pressure drops, and the supercritical fluid transforms straight into a gas.
  • 13:03: ... ground in geothermally active areas can reach the high temperatures and pressures needed for a supercritical state, and even, albeit rarely, emerge in ...
  • 13:25: ... the surface to more than 700 K. Combined with the extreme atmospheric pressure, this puts CO2 within a few kilometers of the surface well beyond the ...

2022-12-08: How Are Quasiparticles Different From Particles?

  • 05:28: ... of the covalent bonds as springs, so when an atom receives pressure it will move, pressing on the springs, and causing other nearby atoms to ...

2022-08-17: What If Dark Energy is a New Quantum Field?

  • 01:41: ... anti-gravitational effect of dark energy is due to it having negative pressure. That’s counter-intuitive because negative pressure is an inward pulling ...
  • 02:31: ... energy is that, on top of the anti-gravitational effect of its negative pressure, it also produces regular attractive gravity due to its positive energy ...
  • 12:31: ... omega is between -⅓ and -1 then the outward-pushing negative pressure still dominates over the inward pull of regular gravity, so expansion ...

2022-07-27: How Many States Of Matter Are There?

  • 02:26: Transition temperatures depend on the material, but they also depend on pressure.
  • 02:32: For example, water boils and freezes at a lower temperature on a mountain top where the air pressure is low.
  • 02:38: Instead of a 1-dimensional relationship between phase and temperature, think of a 2-dimensional relationship with both temperature and pressure.
  • 02:59: ... example, at temperatures and pressures above the critical point, the line between gas and liquid blurs and we ...
  • 03:12: The two numbers related on the phase diagram - temperature and pressure - are statistical properties of a large collection of particles.
  • 03:37: For example in an ideal gas, pressure is proportional to temperature and inversely proportional to density.
  • 07:16: Here it's temperature versus baryonic potential instead of pressure, which is basically how much energy quarks can absorb or emit.
  • 11:54: ... analogs of temperature, pressure, etc. are informational parameters like memory, computation, and ...

2022-06-30: Could We Decode Alien Physics?

  • 01:25: ... incorrect electronic circuitry.   The President exerts some pressure  to switch it on already because   an election is coming up. ...

2022-04-20: Does the Universe Create Itself?

  • 15:24: ... it’s a positive energy density, just like matter. But it’s negative pressure can allow even a closed universe to expand forever. Thanks, dark ...

2022-03-30: Could The Universe Be Inside A Black Hole?

  • 08:15: ... spherical cloud of matter with a perfectly homogeneous density and zero pressure. ...
  • 08:53: They get denser towards the center and have plenty of pressure.
  • 09:06: ... assumption of homogeneity and zero pressure was the same that Alexander Friedmann made when he first solved the ...

2021-12-20: What Happens If A Black Hole Hits Earth?

  • 06:35: ... a black hole can produce. That same radiation causes an outward pressure that partly counters the black hole’s intense gravity. Try to feed a ...
  • 06:56: ... that the material around a black hole can radiate before radiation pressure cuts off the ...
  • 11:02: ... when a black hole hits, it doesn’t stop- it goes straight through. The pressure from the superheated plasma around it creates a shockwave that pushes ...

2021-12-10: 2021 End of Year AMA!

  • 00:02: ... up okay the energy builds up and as it does so the star expands the pressure increases the star expands and at some point the other regions become ...

2021-11-17: Are Black Holes Actually Fuzzballs?

  • 02:18: We can describe the behavior of the air in this room with very few numbers: its bulk motion, its temperature, pressure, etc.

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

  • 10:44: Regular matter was kept from collapsing into  any structures by the pressure of the intense radiation of that era.

2021-10-20: Will Constructor Theory REWRITE Physics?

  • 00:32: describe some aspect of the universe with numbers - like the temperature, pressure, etc of a gas or the position, velocity, etc. of a particle Step 2.

2021-10-05: Why Magnetic Monopoles SHOULD Exist

  • 16:22: ... Lyons asks what happens when the degeneracy pressure - the structural support against collapse produced by the Pauli ...
  • 16:32: ... stellar core is massive enough it smashes through the degeneracy pressure that supports white dwarf stars and instead produces a black hole or ...
  • 16:51: When degeneracy pressure is broken it’s because new space in quantum states opens up.
  • 17:05: So the loss of electrons reduces the degeneracy pressure, allowing gravitational collapse to continue.

2021-09-15: Neutron Stars: The Most Extreme Objects in the Universe

  • 01:02: ... fiction. An indestructium  craft to withstand the radiation and pressure,   and an anti-gravitational field to resist  the ridiculous ...
  • 02:35: ... Earth’s atmosphere is mostly oxygen and nitrogen in molecular form. Pressure increases as you go   down, so that at Earth’s surface the ...
  • 04:04: ... become what we call degenerate, and electron   degeneracy pressure stops further collapse and ultimately holds the atmosphere ...
  • 06:38: ... to  protons are only stabilized by the incredible   pressures and extreme electron  energies in the neutron ...
  • 07:43: ... star is now increasingly supported by   neutron degeneracy pressure. But neutrons  can get much closer to each other before   ...
  • 12:23: ... is all highly theoretical,   but it may be that these extreme pressures and energies we find ‘hyperon’ particles containing   ...

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

  • 15:46: ... actually makes this less likely because losing mass reduces the internal pressure, the fusion rate, etc. You can actually defuse a potential future ...

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

  • 07:24: ... star. The matter inside is crushed closer together until there’s enough pressure to resist the extra gravity - so the original matter contains a smaller ...

2021-07-21: How Magnetism Shapes The Universe

  • 04:29: ... the pressure gets too high, these field lines snap and then reconnect, and in the ...

2021-05-19: Breaking The Heisenberg Uncertainty Principle

  • 09:34: And that introduces its own type of noise - radiation pressure noise as these photons transfer energy to the mirrors in the interferometer.

2020-12-15: The Supernova At The End of Time

  • 01:39: ... weirdness has supported itself against gravitational collapse by the pressure exerted by its electrons ...
  • 04:07: Unable to get any closer, the electrons in degenerate matter exert a powerful outward pressure - electron degeneracy pressure.
  • 04:32: ... they could be composed of his degenerate matter, and that degeneracy pressure alone would be enough to stop them from collapsing under their own ...
  • 04:55: Its core would collapse until halted by electron degeneracy pressure.
  • 05:49: ... this degeneracy pressure could support a dead star up to a point - if that stellar remnant’s mass ...
  • 06:06: ... fewer electrons means less electron degeneracy pressure, which means the star begins to collapse, which means more electrons ...
  • 09:56: Remember that the Chandresekhar limit gives the largest mass possible for a stellar remnant to be supported by this pressure.

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

  • 05:01: ... produce this convergence. It would take negative mass or negative pressure   to cause light rays to diverge. This focusing property of ...

2020-10-05: Venus May Have Life!

  • 01:33: This traps so much heat that the surface of Venus reaches a temperature hot enough to melt lead, and with a pressure that would crush most submarines.
  • 02:43: ... is completely hellish, at around 50km altitude both the temperature and pressure are close to those at Earth’s surface, with the only problem being that ...
  • 08:11: ... would have to remain in the regions with survivable temperature and pressure, and the critters need to somehow survive the crazy ...
  • 09:44: ... - including the vacuum of space and the extreme temperatures and pressures of meteor impact or atmospheric ...

2020-09-01: How Do We Know What Stars Are Made Of?

  • 07:10: ... get if you have a cloud of some element at a given temperature and pressure. ...
  • 07:38: ... within the sun traverses a large distance, over which temperature and pressure drop ...

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

  • 15:59: ... - it’s the maximum mass of a white dwarf before crushing gravitational pressure causes electrons to be pounded into protons to form neutrons, causing ...
  • 16:32: In order to get a neutron star, you need a very symmetrical, clean application of pressure.

2020-08-17: How Stars Destroy Each Other

  • 01:17: At a critical point, that surface reached the temperature and pressure of a stellar core.
  • 04:02: ... sputtering and flaring as they do so, until a critical temperature and pressure sends them over the ...

2020-07-28: What is a Theory of Everything: Livestream

  • 00:00: ... to be discussing such esoteric topics yeah so uh i'm feeling a lot of pressure piled on me already here especially by you stephanie counting on me ...

2020-06-30: Dissolving an Event Horizon

  • 04:10: ... singularity - which point-like in this case - results in a negative pressure that again resists the inward pull of ...

2020-05-27: Does Gravity Require Extra Dimensions?

  • 11:58: This is the negative pressure due to the exclusion of quantum vacuum modes, or virtual particles, between two very closely separated plates.

2020-05-18: Mapping the Multiverse

  • 02:16: Well, in a Kerr black hole that rotation results in an outward pressure that partially counteracts the inward flow due to gravity.
  • 04:06: But now as we fall the outward pressure due to the black hole’s rotation starts to win against that inward flow.
  • 12:16: When they meet they don’t cancel out - instead they stream past each other producing enormous pressure.
  • 12:23: That pressure produces its own gravitational effect on par with the black hole itself, accelerating the streams further.
  • 13:13: ... the electromagnetic field within causes massive tension, or negative pressure that produces an antigravitational ...

2020-04-22: Will Wormholes Allow Fast Interstellar Travel?

  • 08:42: ... that. Thorne and Morris describe a type of matter exerting an outward pressure capable of holding open the wormhole, but without the enormous mass or ...

2020-03-16: How Do Quantum States Manifest In The Classical World?

  • 17:40: ... of air in the room lead to the same measurement of temperature and pressure - so we'll almost always observe those macroscopic ...

2019-09-16: Could We Terraform Mars?

  • 00:44: But those settlements will need to be cocooned - shielded against the deadly cold, the intense radiation and the fatal lack of atmospheric pressure.
  • 01:34: Mars’ current atmospheric pressure is 0.6% that of Earth – and that means circulatory shutdown within a minute for an unprotected humans.
  • 04:47: They assess whether release of the accessible CO2 reserves could get Mars anywhere near Earth’s atmospheric pressure.
  • 06:10: At any rate, even if we managed to heat the entire regolith across the entire Martian surface we’d only get 4% of the Earth’s atmospheric pressure.
  • 07:12: We need about 10,000 kg of material per square meter to duplicate Earth’s atmospheric pressure.
  • 09:27: Nonetheless, our descendants could see a Mars with sufficient air pressure and greenhouse effect to allow liquid water to persist on the surface.
  • 11:00: But that still doesn’t give us the needed atmospheric pressure.

2019-09-03: Is Earth's Magnetic Field Reversing?

  • 04:18: It’s solid because of the pressure at that depth – at around 5500 Kelvin temperature, it would instantly melt at lower pressures.

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

  • 02:49: ... at much higher temperatures which increases efficiency and at much lower pressure than water the high pressures required for water-cooled reactors add a ...

2019-06-17: How Black Holes Kill Galaxies

  • 13:30: ... the thing is, strange matter is probably only stable under extreme pressure Release it from the embrace of the neutron star and all the strange ...

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

  • 02:47: ... prior to collision the stars neutrons were stabilized by extreme pressure but once released this nuclear group expands and destabilizers it breaks ...

2019-03-28: Could the Universe End by Tearing Apart Every Atom?

  • 03:05: ... Newton's, gravity is influenced by mass and energy density but also by pressure. Both mass energy density and any positive pressure act to decelerate the ...
  • 04:32: ... can express our lambda as a sort of equivalent mass and pressure in fact, let's make it an emo party and get rid of regular massive ...

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

  • 07:51: ... In addition, an air-launch craft can be optimized for the low pressure of that altitude, rather than have to operate at a range of ...

2019-02-20: Secrets of the Cosmic Microwave Background

  • 02:05: ... condensed into over-dense regions this led to a massive buildup of pressure Collapsing baryons rebounded producing an expanding sound wave That ...

2019-02-07: Sound Waves from the Beginning of Time

  • 02:54: Second: Light was able to exert an enormous pressure on this plasma, as we'll see that it'd lead to the production of colossal sound waves.
  • 03:35: Light exerts no pressure on dark matter.
  • 04:24: But also at that density peak, the imprisoned photons exerted an enormous outward pressure.
  • 04:30: To equalise this pressure, radiation pushed outwards and carried the baryons with it.
  • 06:37: Immune to the radiation pressure, the central dark matter overdensity had continued to grow It pulled on the expanding shell, and was pulled by it.
  • 07:44: Gravity pitted against radiation pressure.

2019-01-30: Perpetual Motion From Negative Mass?

  • 06:36: ... presence of active gravitational mass, and of energy, momentum, pressure, and more, change the geometry of spacetime and that new geometry defines ...

2019-01-24: The Crisis in Cosmology

  • 08:09: ...while light generated a powerful pressure to resist that collapse.

2019-01-09: Are Dark Matter And Dark Energy The Same?

  • 02:53: But here’s the punchline: if empty space has a constant, positive energy density then it also has a negative pressure.
  • 03:02: For obscure reasons that we delve into those episodes, negative pressure produces an anti-gravitational effect.
  • 03:10: ... energy density gives it a positive gravitational effect but its negative pressure is ...
  • 04:06: Forgetting that pressure stuff for a moment, positive masses and energies always have a positive gravitational effect.
  • 07:57: And that a positive Lambda results in an antigravitational negative pressure?
  • 08:10: That gives a positive pressure, and in general relativity positive pressure adds an attractive gravitational force, no matter what causes it.
  • 08:42: But that effect is overwhelmed by the effect of the pressure, which in this case is attractive – it works to recollapse the universe.
  • 12:59: ... in what is probably not a negative mass, anti-gravitational, positive pressure, anti-deSitter space ...

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

  • 00:37: ... thousands of GS and hundreds of thousands of Earth atmospheres in shock pressure similar forces apply when it smacks down at the other end of the journey ...

2018-11-21: 'Oumuamua Is Not Aliens

  • 04:26: With no visible coma or tail, it doesn't look like outgassing, so maybe it's radiation pressure.
  • 04:45: Now that's exactly what you'd expect for solar radiation pressure.
  • 04:58: ... the radiation pressure thing would only work if Oumuamua is incredibly thin and light, thinner ...

2018-11-07: Why String Theory is Right

  • 15:59: That leads to a net pressure pushing the plates together.

2018-09-05: The Black Hole Entropy Enigma

  • 04:03: ... particles based on the global properties like temperature, volume, pressure, et ...

2018-07-25: Reversing Entropy with Maxwell's Demon

  • 01:44: ... if we only know the thermodynamic properties of a system-- temperature, pressure, volume, et cetera-- how much extra information would we need to ...

2018-07-18: The Misunderstood Nature of Entropy

  • 04:37: Macrostates are entirely defined by thermodynamic properties, temperature, pressure, volume, and number of particles.
  • 07:20: ... equilibrium, in which energy is maximally spread out and temperature, pressure, density, volume, et cetera have the values we expect from classical ...

2018-06-20: The Black Hole Information Paradox

  • 13:20: ... electric charge within the black hole produces a negative pressure that actually halts the cascade of space within the black hole and ...

2018-05-02: The Star at the End of Time

  • 06:00: ... helium white dwarf, supported by quantum mechanical electron degeneracy pressure. ...

2018-03-07: Should Space be Privatized?

  • 11:42: When fusion switches off, the star contracts, until electron degeneracy pressure stops the collapse.

2018-02-21: The Death of the Sun

  • 02:51: That burning shell is so thin that radiation escapes outwards without providing pressure to resist collapse.

2018-02-14: What is Energy?

  • 07:42: ... energy of the fluid and also of the internal energy due to fluid pressure. ...

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

  • 01:53: But as soon as that starts to happen, the drop in energy production disrupts the delicate balance between outward pressure and gravity.
  • 02:17: But with the same mass packed into a smaller volume, the core is under more gravitational pressure than before.
  • 07:12: But we may delay the inevitable by offsetting that greenhouse rise with the loss of CO2 or the decrease in atmospheric pressure due to nitrogen loss.

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

  • 02:34: ... by earthquakes and can travel around the planet as longitudinal pressure, or p-waves; transverse shear, or s-waves; and surface waves, which are a ...
  • 03:24: However, it's the pressure waves-- the p-waves-- that really dominate in stars like the sun.
  • 03:45: ... bell ringing, a single traveling wave feeds its energy into standing pressure waves that cause the entire star to ...

2017-11-22: Suicide Space Robots

  • 01:38: It fought against the blistering 445 Celsius heat and crushing 90 atmosphere pressure for 23 minutes before going quiet.
  • 01:48: ... from the surface of another planet-- accurate temperature and pressure readings of the atmosphere that killed ...

2017-11-08: Zero-Point Energy Demystified

  • 04:36: The result is a pressure differential that produces a measurable force, pulling the plates together.

2017-10-19: The Nature of Nothing

  • 09:11: The higher vacuum energy outside, compared to the inside of the plates, should result in a pressure differential that pushes the plates together.
  • 12:43: Actually, yes, helium is unfreezable at atmospheric pressure.
  • 12:48: But increase the pressure to around 24 atmospheres, and you can make helium ice at around 1.5 kelvin.
  • 12:56: The point at which a substance changes phase depends on both temperature and pressure.
  • 13:02: The higher the pressure, the higher the temperature of these phase changes.
  • 13:06: ... the fact that the temperatures there are way higher than the atmospheric pressure evaporation point of ...

2017-09-20: The Future of Space Telescopes

  • 08:46: ... colorful arcs across the sky, scientists have proposed we use photon pressure to suspend a cloud of tiny reflective particles in Earth's ...
  • 12:04: The final phase of the core of such a star is a giant ball of nickel and iron, held up briefly by electron degeneracy pressure.
  • 12:18: That support gives way when pressure rams electrons into protons in the nuclei to turn them into neutrons.
  • 12:42: ... a neutron star holds this collapse, when they hit neutron degeneracy pressure, the most massive stars don't manage to stop before the core is smaller ...

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

  • 02:22: They are mostly composed of neutrons at the density of an atomic nucleus and are held up by a quantum mechanical force called degeneracy pressure.
  • 13:31: ... a large enough bomb could be brought to bear, it wouldn't reduce the pressure in the eye for longer than it takes the shock front to leave the ...
  • 13:41: Pressure depends on the actual amount of air present relative to the surroundings.
  • 13:50: If anything, it'll reduce air pressure and add heat to the ocean, making things worse.

2017-08-16: Extraterrestrial Superstorms

  • 03:25: See, a low pressure core draws inwards, replenishing the water supply.
  • 04:50: ... the gas giants' atmospheres span such a wide range of temperature and pressure that all sorts of molecular species ...
  • 05:29: But on the gas giants, it can extend 100 miles into the planet's murky depths, where pressure forces the gas into a metallic liquid state.

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

  • 04:20: OK, physics time-- the cores of stars are under extreme pressure due to the gravitational crush of their great mass.
  • 04:28: The more mass, the greater the pressure.
  • 04:30: And by the ideal gas law, temperature increases with pressure.
  • 05:58: Now, for that collapse to proceed, the pull of gravity needs to overcome the cloud's own internal thermal pressure.
  • 06:58: Unimpeded by pesky thermal pressure, the cloud collapses quickly.
  • 07:11: This occurs until whatever weak thermal pressure remains can halt the free falling gas.
  • 07:31: Thermal pressure kicks in much earlier to slow the collapse, before much of the fragmentation happens.
  • 07:37: Pressure and temperature have time to equalize across the cloud before it breaks apart.
  • 12:44: At the very least, with the removal of environmental pressures, the passive evolution that has maintained certain traits is impacted.

2017-05-17: Martian Evolution

  • 04:17: A mother's pelvis needs to be able to withstand significant pressure that has nothing to do with the gravitational field.
  • 04:29: That would be a huge selection pressure in any population without very consistent access to safe c-sections.
  • 05:46: We'll always need some degree of technology both for a survivable air pressure and oxygen level and to protect us from space radiation.
  • 08:16: This results in a massive selection pressure to keep our immune system up to date.

2017-05-03: Are We Living in an Ancestor Simulation? ft. Neil deGrasse Tyson

  • 14:47: Pressure builds up as density increases, and that resists this convergence.
  • 15:26: Now it's those same particle interactions that gives rise to pressure.
  • 15:30: But pressure is statistical in nature.
  • 15:45: As a result, the net pressure is positive, outward pushing.
  • 15:49: The pressure is as much a statistical emergent phenomenon as entropy.
  • 15:54: You can have spontaneous increases in pressure.
  • 15:57: ... that the subsequent series of interactions leads to a large increase in pressure. ...

2017-04-26: Are You a Boltzmann Brain?

  • 01:31: ... with the gas outside the piston-- everything the same temperature and pressure, perfectly ...

2017-04-05: Telescopes on the Moon

  • 07:20: ... mercury is expensive, heavy, and likely to evaporate in the moon's low pressure Atmosphere Pete Worden, Director of NASA's Ames Research Center and ...
  • 11:33: ... is expected to produce an antigravitational effect through negative pressure, in a way that's mathematically similar to dark ...

2017-03-15: Time Crystals!

  • 05:43: This is sort of like the phase diagram of regular matter in which you plot pressure versus temperature.

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

  • 10:48: ... it fragments, because local gravitational collapse happens faster than pressure can equalize across the ...
  • 11:12: As you suggest, it's when inward gravitational forces and outward gas pressure are in equilibrium.

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

  • 02:26: As the gas collapses, it builds up heat and density until the pressure of the gas dramatically slows collapse.

2017-01-11: The EM Drive: Fact or Fantasy?

  • 02:36: Roger Shawyer explains the EmDrive's alleged thrust as resulting from differential radiation pressure between the two ends.
  • 03:33: Eagle Works itself had previously tested the device in air at atmospheric pressure and found a positive thrust.
  • 03:55: But the latest test was in a vacuum chamber at 1/10 billionth of sea level atmospheric pressure, so no convection is possible.

2016-11-30: Pilot Wave Theory and Quantum Realism

  • 15:53: ... at atmospheric pressure-- or even inside Wolverine pressure-- it would expand into a gas ...

2016-11-16: Strange Stars

  • 03:42: And we certainly can't test what happens to it when subjected to the insane pressures at a neutron star's core.
  • 04:38: ... the quark matter in a neutron star is forged by insane pressures, not by the greater-than-a-trillion-Kelvin temperatures of the Quark ...
  • 05:10: Quark matter made of these quark types would need to be confined by incredible pressures to maintain stability outside the atomic nucleus.
  • 05:27: It may be that when neutrons disintegrate under high pressure, half of the down quarks are converted to strange quarks.
  • 07:08: And those may provide the final pressure that halts the collapse of some stars into a black hole, at least for another million years or so.

2016-11-09: Did Dark Energy Just Disappear?

  • 01:11: ... outward pressure that has come to be known as "dark energy." The finding led to a shared ...

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

  • 11:29: Turcan Fred asks about what sort of insane pressures you'd expect to find at 100 kilometers deep in Europa's ocean.
  • 11:43: So even at 100 kilometers depth, the pressure is only about 20% higher than at the deepest point of the Earth's ocean.

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

  • 12:01: Last week, we wrapped up our conversation on dark energy, talking about anti-gravity, negative pressure, and conservation of energy.

2016-05-18: Anti-gravity and the True Nature of Dark Energy

  • 04:14: That's the pressure due to fast-moving particles and radiation.
  • 04:18: In general relativity, energy slash mass and pressure both curve space time.
  • 04:25: The way pressure does this is pretty weird.
  • 04:36: ... if fast-moving particles produce an outward push in pressure, then is this how dark energy is causing expansion to accelerate, by ...
  • 04:50: Because pressure only produces a direct force if there's a difference in pressure between two regions, a pressure gradient.
  • 05:00: In order for the pressure of fast-moving particles to create an outward push, the region beyond them has to be an area of lower pressure.
  • 05:15: And so the pressure is the same everywhere.
  • 05:17: Instead, the overall effect of pressure on the curvature of space time is a purely relativistic effect.
  • 05:25: See, high pressure from regular matter and energy means very fast-moving particles.
  • 05:39: ... even if the overall energy density of those regions is the same Positive pressure pulls the universe ...
  • 07:08: The effect of the cosmological constant is the combined effect of dark energy's own density and pressure.
  • 07:17: ... regular matter will have diluted away and will only have the density and pressure due to dark energy, rho lambda and p ...
  • 07:56: That leaves us with pressure.
  • 07:58: But we just discussed how positive pressure can't cause expansion to accelerate outwards.
  • 08:03: It turns out that dark energy does produce an enormous pressure.
  • 08:09: That pressure isn't a positive.
  • 08:24: It's negative pressure.
  • 08:26: What does negative pressure even mean?
  • 08:28: Well, positive pressure pushes outwards, like in our pressurized tank.
  • 08:33: So negative pressure would pull inwards.
  • 08:47: But positive pressure pushes out.
  • 08:49: Negative pressure pulls in.
  • 08:54: Weirdly, the inward pulling pressure of dark energy ultimately drives expansion outwards.
  • 09:05: The direct effect of dark energy's negative pressure doesn't do anything, because that negative pressure is the same everywhere in the universe.
  • 09:14: But even though the negative pressure has no direct effect, it has its relativistic effect.
  • 09:19: Relativistically, negative pressure has to do the opposite of positive pressure and results in anti-gravity, because math.
  • 09:29: The relativistic effective of negative pressure is actually really, really hard to describe intuitively.
  • 09:38: Part of the problem is that negative pressure doesn't come from the motion of dark energy particles, whatever they might be.
  • 10:09: That's exactly how we define negative pressure.
  • 10:12: A volume has negative pressure if it takes work to expand, just like a volume with positive pressure takes work to compress.
  • 10:22: Negative pressure means energy is gained on expansion.
  • 10:35: That looks like negative pressure, and yet this abstract-sounding negative pressure has a very real physical effect.
  • 10:44: It's the opposite effect to positive pressure.
  • 11:01: But both agree that a constant energy density and the resulting negative pressure leads to accelerating expansion.

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

  • 01:57: And it describes all of the energy, the pressure, the momentum, and more-- all of the stuff within that spacetime.

2016-04-06: We Are Star Stuff

  • 06:23: ... energy, and kept the core hot and puffed up, outflowing radiation pressure, resisting gravitational ...

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

  • 00:53: ... and every brick, cable, and bolt has to perfectly balance the tension, pressure, and torque resulting from the downward gravitational pull on all other ...
  • 03:49: They're under a lot of pressure.
  • 03:51: And the resulting pressure gradient force balances gravity in the up-down direction.
  • 03:57: See, pressure acts outwards.
  • 04:00: A block around halfway to the center of the Earth has to push up with the pressure needed to support the weight of 3,000 blocks above it.
  • 04:08: The one below it exerts more pressure.
  • 04:56: See, pressure shares that same symmetry as gravity.
  • 05:15: ... equal force to each other because they're all at the same depth and same pressure. ...
  • 05:31: Any two neighboring blocks are actually at different depths below the surface compared to each other, and so are at different pressures.
  • 05:46: A block closer to the Equator is further below the surface and so will exert more pressure than its neighbor that's closer to the pole.
  • 06:20: See, rock is really, really good at not being crushed by direct pressure.
  • 07:11: Here the pressure comes from the upward flow of energy from the nuclear fusion engine in the core.
  • 07:26: But wait, gravity and pressure are not the only things at work here.
  • 09:58: Spheres happen when pressure is the dominant effect resisting gravity.
  • 10:02: Pressure is spherically symmetric.

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

  • 08:18: In fact, a giant balloon filled with atmospheric pressure air would float nicely at around 50 kilometers.
  • 08:24: So think a huge dome filled with a breathable atmospheric pressure air, or an even larger balloon base.
  • 08:32: It could be tethered to the surface with heat and pressure-resistant cables, carbon inner tube cables perhaps.
  • 08:56: The atmospheric pressure is so thin that it doesn't generate enough force to move big stuff.

2016-02-03: Will Mars or Venus Kill You First?

  • 01:52: The atmospheric pressure on the surface of Mars is now around 0.5% of that of Earth.
  • 02:39: See, this extremely low pressure is going to do horrible things to your body.
  • 02:55: The most dangerous thing about the drop in pressure is that the boiling point of liquids also drops dramatically.
  • 03:08: Your blood stays mostly liquid though, because it's kept under some pressure.
  • 06:26: Now, the pressure and temperature on the surface, 90 atmospheres and 450 degrees Celsius, will implode and roast you instantly.
  • 06:56: It's a pleasant 0.9 times Earth's gravity, and the atmospheric pressure is around that of Earth's surface.

2016-01-13: When Time Breaks Down

  • 09:07: In the compressed spring, there's increased pressure throughout the material.
  • 09:12: That pressure increases the resistance to further compression in all directions.

2016-01-06: The True Nature of Matter and Mass

  • 01:52: All the walls of the box will feel the same pressure, so there's no overall force on the box.
  • 02:05: It feels a little more pressure from their impact than before.
  • 02:08: In the meantime, the front of the box, moving away from the incoming photons, feels less pressure.
  • 02:40: But as long as acceleration continues, the pressure differential persists.
  • 04:03: And then a pressure wave communications the force to the front until the whole spring is moving.
  • 07:23: The presence in the flow of energy and momentum as well as pressure all have their quite different effects on the curvature of space-time.

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

  • 04:32: ... the degeneracy pressure, resulting from particles not having anywhere else to collapse into, is ...
  • 07:01: So Heisenberg lets us circumvent that pesky degeneracy pressure.

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

  • 05:30: The pressure of the nuke, and of the ejected asteroid bits, will push the NEO off target.

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

  • 03:44: We can create something like it, a negative pressure, on quantum scales via Casimir effect.

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

  • 13:33: ... masked by the much more dominant effect of temperature variations and pressure variations on the atmospheric distribution around the ...

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

  • 05:33: ... the surface of the planet can produce a pretty decent increase in water pressure. ...
  • 06:26: Lakes just don't have enough area for the tiny pushes on it to build up enough pressure to change the water level.
  • 06:31: ... big lakes, like Lake Michigan in North America, can generate enough pressure to produce mini tides, maybe with a couple of centimeters difference ...
  • 08:06: But mostly, it's that nooks and crannies in the continents affect the details of how pressure gets distributed through the ocean in non-uniform ways.

2015-06-17: How to Signal Aliens

  • 04:45: Now, we would need to tweak the orbit occasionally due to solar wind and radiation pressure.
  • 10:22: So all the air pressure equalizes and the balloon doesn't go anywhere.
  • 10:26: Now, technically, it will take a few milliseconds for the pressure to equalize, during which there will be some slight bobbing of the balloon.

2015-05-27: Habitable Exoplanets Debunked!

  • 01:04: ... planet actually has a surface and provided there's enough atmospheric pressure. ...
  • 01:25: For instance, Venus has a solid surface and it has plenty of atmospheric pressure.

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

  • 03:40: ... to give support, but also have enough give that it wouldn't apply weird pressure ...

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

  • 09:52: ... in a rotating ship like "Babylon 5," assuming that you had atmospheric pressure at the rim and that atmospheric pressure dropped with altitude, would ...
  • 10:10: You might be able to have something on the axis to sort of inject more air out and artificially increase the air pressure there.

2015-04-01: Is the Moon in Majora’s Mask a Black Hole?

  • 07:57: No, but not because of temperature or pressure issues.

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

  • 03:28: But the bigger problem is the barometric pressure on the surface.
  • 04:29: The pressure at that altitude also dropped to almost exactly one Earth atmosphere.
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