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2022-06-22: Is Interstellar Travel Impossible?

  • 06:08: ... gas is around 90% hydrogen, and most of the rest is helium with traces of heavier elements The average gas density through the ...
  • 08:59: They figure that the light hydrogen and helium don’t do lasting damage - they just deposit heat.

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

  • 03:22: ... from very slight  over-dense regions in the hot hydrogen and helium   gas that filled the universe after the Big Bang.  It’s hard to see ...
  • 14:38: ... enough rocky or icy core forms to start  holding on to hydrogen and helium atmospheres.   That needs to happen before the star ...

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

  • 03:40: ... Earth, while the larger collected  vast atmospheres of hydrogen and helium and became   the gas giants. At the same time, the core  ...
  • 05:52: ... are mostly made out of hydrogen  and helium, with trace amounts of heavier   elements. But those elements ...

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

  • 08:50: ... are in the primes of their lives - those powered by fusing hydrogen into helium in their cores - lie on this tight band called the main ...

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

  • 00:02: ... giant stars um and uh the the core has undergone what we call the helium flash so they're now fusing helium into carbon uh in their core um but ...

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

  • 03:07: ... a young neutron star. Those nuclei   are mostly hydrogen and helium, captured from the nearly-empty space surrounding the ...

2020-11-04: Electroweak Theory and the Origin of the Fundamental Forces

  • 01:24: It’s one of the main ways radioactive nuclei decay - the other being alpha decay, where the emitted “alpha particle” is really a helium-4 nucleus.

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

  • 00:28: ... that the sun and the other stars are giant balls of fiery hydrogen and helium, powered by raging nuclear furnaces in their ...
  • 08:56: On Earth, hydrogen is the third most abundant element after oxygen and silicon, while helium is extremely rare.
  • 09:05: Her results suggested that hydrogen was by far the most common atom in the sun, followed closely by helium.
  • 09:29: ... likely the result of not understanding the atomic theory of hydrogen and helium well ...
  • 09:39: ... the fact of the sun being made mostly of hydrogen and helium was confirmed only a few years later, and Cecilia Payne is widely ...

2019-12-17: Do Black Holes Create New Universes?

  • 06:30: That cooling is extremely slow if the gas only contains the hydrogen and helium produced in the big bang.

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

  • 06:01: ... to bind to each other to form a diproton - a neutron-free version of helium which is unstable in our ...

2019-07-18: Did Time Start at the Big Bang?

  • 01:56: ... There's also the relative abundance of simple elements hydrogen and helium in particular Whose ratio is exactly what we expect if the entire ...

2019-07-15: The Quantum Internet

  • 13:16: It's cool because it's passively cooled by gas flow - for example, helium.

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

  • 00:33: ... a mere 0.4 percent of the mass of hydrogen nuclei as it fuses them into helium But that's enough to power the Sun for 10 billion years Practical fusion ...

2019-05-16: The Cosmic Dark Ages

  • 01:34: ... right? Prior to recombination, the universe was filled with hydrogen and helium atoms stripped of their electrons - in other words, ionized - in the ...
  • 02:19: ... of new sources of light and the fog of atomic and molecular hydrogen and helium that filled the ...

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

  • 01:37: For the first few hundred thousand years in the life of our universe, All of the space was filled with hydrogen and helium in plasma form.
  • 05:57: But the plasma, now hydrogen and helium gas, stalled.
  • 06:46: ... Once more in the gravitational grip of dark matter, hydrogen and helium could begin the long work of collapsing into stars and galaxies work of ...

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

  • 04:27: The most common types are electrons, helium ions, AKA alpha particles, and protons.

2018-05-09: How Gaia Changed Astronomy Forever

  • 02:58: For example, stars on this diagonal band-- the so-called, main sequence-- are in the primes of their lives, fusing hydrogen into helium.
  • 04:04: These are stars near the ends of their lives, now burning helium in their.

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

  • 01:51: Stars generate energy, fusing hydrogen into helium in their cores.
  • 03:40: Rivers of plasma flow from the core to the surface, carrying both energy and the helium produced in the fusion reactions.
  • 03:48: That helium gets mixed through the star, while new hydrogen is brought to the core for fusion.
  • 03:53: Over the course of its long life, a red dwarf will convert all of its hydrogen to helium.
  • 06:00: ... the last hydrogen fuel spent, the entire star will become composed of helium and will quietly contract into a helium white dwarf, supported by ...

2018-03-07: Should Space be Privatized?

  • 10:45: As the hydrogen fuel in the sun's core gets diluted by helium, the fusion rate does decrease and the core shrink.
  • 11:12: That means new hydrogen flows down to the core, while the helium produced in core fusion is mixed through the star.
  • 11:36: But by the time a red dwarf finishes using its fuel, the entire star is made of helium.

2018-02-21: The Death of the Sun

  • 00:49: They live their lives fusing hydrogen to helium in their cores, shining bright and stable for as long as that hydrogen lasts.
  • 02:07: As the last traces of hydrogen are slammed together into helium 4 nuclei, fusion will cease.
  • 02:14: That helium is useless as a fuel, at least for now, because helium fusion requires temperatures of around 100 million Kelvin.
  • 02:58: Instead, the helium produced in the shell is deposited on the dead core, causing the inner regions to collapse further.
  • 04:31: It heats up to that critical 100 million Kelvin temperature, then in an instant, it ignites in the helium flash.
  • 04:40: The once inert helium fuses into carbon via the triple alpha process.
  • 04:50: It expands again, and the corresponding lower density allows helium fusion to slow down.
  • 05:06: The helium burning will convert that core into carbon and oxygen in only 100 million years or so, after which the final dance with death begins.
  • 05:16: Finally, surrounding an inert carbon oxygen core are two fusing shells, helium fusion inside hydrogen fusion.
  • 08:41: During the helium burning phase, the habitable zone contracts again for 100 million years.

2018-02-14: What is Energy?

  • 14:02: ... out the ridiculousness of astronomers calling all elements heavier than helium a metal, because technically, lithium is grunge, not ...

2018-01-31: Kronos: Devourer Of Worlds

  • 03:57: And the strength of these lines can tell us the relative abundance of non-hydrogen and helium elements within the star.
  • 04:04: In astro-speak, they tell us the star's metallicity, although for an astronomer, anything heavier than helium is called a metal.

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

  • 00:27: Hydrogen is fused into helium in the sun's core, producing energy that keeps it shining and keeps the earth warm and hospitable to life.
  • 01:22: The rate of fusion of hydrogen into helium increases with the temperature and density of the core.

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

  • 06:21: ... how much of the sun's hydrogen fuel source has already been burned into helium. ...

2017-10-25: The Missing Mass Mystery

  • 03:07: For example, in the first several minutes after the Big Bang, hydrogen fused into deuterium and helium.
  • 03:23: ... the relative abundance of helium and deuterium today tells us that there should have been 10 times as ...

2017-10-19: The Nature of Nothing

  • 12:36: Man from Nantucket asks whether helium can be frozen if pressurized.
  • 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.
  • 13:19: Laxmi Papney asks whether I said that helium-4 is a boson.
  • 13:53: But in a helium-4 nucleus, the protons pair up and have opposite spins, so they cancel out, same with the neutrons and the electrons.
  • 14:06: And so helium-4 gets to behave like a boson.

2017-10-11: Absolute Cold

  • 03:51: Only one substance is known to produce a superfluid for conditions possible in a lab, and that's helium, in particular, helium 4.
  • 04:00: Helium 4 has a total spin of 0, which makes it a boson so a particle with integer spin.
  • 04:15: The other unique property of helium is that it can't be frozen.
  • 04:30: The unfreezability of helium reveals an even deeper quantum mystery.

2017-08-24: First Detection of Life

  • 08:37: We've even started to look at super-Earths, like in 55 Cancri e, detecting hydrogen and helium.

2017-08-02: Dark Flow

  • 03:39: ... and are bathed in a diffuse but searing hot plasma-- hydrogen and helium, with temperatures up to 100 million ...

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

  • 00:45: See, the sun and all stars are made of the raw material forged in the heat of the Big Bang itself-- hydrogen and helium, mostly.
  • 01:25: By the way, astronomers call any element heavier than helium a metal.
  • 01:30: And the relative quantity of metals versus hydrogen and helium is a star's metalicity.
  • 02:32: ... in the first ever proto galaxies, born of the pristine hydrogen and helium gas that filled the universe soon after the Big ...
  • 07:22: But without materials to help cooling, a giant cloud of pristine hydrogen helium gas can't shed its heat quickly enough.

2017-04-19: The Oh My God Particle

  • 05:10: And a fair number are helium nuclei.

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

  • 06:50: ... Telescope has confirmed that the a, b, and h planets don't have hydrogen helium atmospheres, which means they aren't gassy planets like ...

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

  • 01:55: ... impossibly large quantities, much more than there is non-hydrogen or helium matter in all of the planets in the solar ...

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

  • 01:22: ... gravity to start holding on to the 300-ish Earth masses of hydrogen and helium that make up most of the planet ...

2016-06-01: Is Quantum Tunneling Faster than Light?

  • 03:06: On its own, this would be a helium nucleus.

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

  • 10:27: Some of the most common involve either adding helium-- that's helium capture-- or losing helium after another fusion reaction.

2016-04-06: We Are Star Stuff

  • 03:28: ... to overcome the electrostatic repulsion between them, fusing them into helium-4 ...
  • 04:08: ... fact, that helium-4 nucleus weighs less than the sum of the protons that went into it, and ...
  • 04:18: In those 20 minutes, 25% of the original protons were forged into helium with a touch of deuterium, lithium and beryllium.
  • 04:31: And all of that hydrogen and helium would later become the fuel for the later formation of stars.
  • 04:55: Our sun, and in fact every star in the prime of its life on what we call the main sequence, shines by forging hydrogen into helium.
  • 05:05: ... to become a red giant while its core shrinks and heats up to convert its helium into carbon and ...

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

  • 04:21: ... and helium nuclei, the other common charged particles hanging around the universe ...

2016-03-09: Cosmic Microwave Background Challenge

  • 02:42: ... filled with this plasma that consisted mostly of protons, electrons, and helium ...

2016-02-24: Why the Big Bang Definitely Happened

  • 07:15: ... and at what temperature, and so predicts the proportions of deuterium, helium, and lithium that should have been ...

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

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

2015-06-17: How to Signal Aliens

  • 06:13: We followed it up last week with a challenge about a helium balloon in free fall.
  • 09:13: ... I take a van that has a balloon in it filled with helium that's attached to the floor by a string and I simultaneously drop the ...
  • 09:35: Now, if you put a helium balloon, even in a van filled with air in intergalactic space, how would it know which way to go?
  • 09:51: Now, how do you reconcile this with the fact that helium is still less dense than air?

2015-06-10: What Happens to a Helium Balloon in Freefall?

  • 00:26: Now, in that balloon video, there's a helium-filled balloon attached by a string to the floor of a minivan.
  • 00:32: Let's take Dustin and his kids out of the minivan but leave the helium balloon in.
  • 00:39: And at the same moment that I let go, I want to cut the string that holds the helium balloon to the floor.

2015-06-03: Is Gravity An Illusion?

  • 04:04: Destin at "Smarter Every Day" has a pretty famous video of a helium balloon in an accelerating car that happens to illustrate this point really well.

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

  • 08:22: Gareth Dean pointed out that the early universe contains not just hydrogen but also helium, and asks whether CMB analysis takes this into account.

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

  • 04:45: ... dense enough for lots of stuff to floae-- like balloons filled with helium or maybe filled even with just regular Earth ...
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