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

  • 15:32: ... Exoplanets," “Planet Hunting with the James Webb Telescope, or “Killer Asteroid: Defending Earth,” which looks at how new space missions are being ...

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

  • 14:53: We told you that an asteroid-mass, atom-sized black hole would pass straight through the earth if it impacted.

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

  • 03:25: ... contentious window of possible masses, comparable to the masses of large asteroids. Black holes this big don’t devour stars like Cygnus X-1, and they don’t ...
  • 04:01: ... thousands, of them to be in the solar system right now. And, just like asteroids, given enough time some of them will quite literally cross paths with the ...
  • 04:26: ... question. So let’s figure it out. First to allay your concerns - if an asteroid-mass primordial black hole hit the Earth we wouldn’t be destroyed - which is ...
  • 05:13: ... hole has the mass of the Martian moon phobos - 10^16 kg like a large asteroid. That gives it an event horizon the size of a hydrogen atom. At ...
  • 07:05: ... for matter trying to flow in. Its Eddington limit is very low. For an asteroid-mass black hole at the absolute top end of our mass range, the cloud of ...
  • 08:16: ... These days standard narrative is that the Tunguska resulted from an asteroid or comet exploding in the ...
  • 10:44: ... the shape of a black hole’s crater would be different from that of an asteroid. ...
  • 11:02: ... an asteroid hits the moon, it stops very quickly, making something of a big round ...
  • 12:01: ... of quartz and pyrite that otherwise couldn’t be produced by regular asteroid impacts, and a line of that fancy quartz should point from one crater to ...

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

  • 06:20: ... matter to be made of black holes with masses around that of a larger asteroid or small moon, we’d need truly ridiculous numbers of them to get all the ...

2020-12-08: Why Do You Remember The Past But Not The Future?

  • 02:16: Actually I’m an astrophysicist, so we’ll think of the brain as a very small asteroid.
  • 02:37: So what does an asteroid remember?
  • 03:10: Any good geologist could read the asteroid’s memory and deduce a rough formation history.
  • 03:15: ... the exact positions and velocities of every particle comprising the asteroid and calculate their paths backwards to recover its exact formation ...
  • 03:59: NONE of that appears to be recorded in the asteroid of the present day.
  • 04:02: ... fast forward many, many times the current age of the universe and the asteroid will decay into a mist of subatomic ...
  • 06:02: ... “Feynman diagram” of our asteroid looks like countless particles coming together in many different ways - ...
  • 06:28: The time-reversed view of the asteroid looks nothing like the time-forward view.
  • 06:34: ... asteroid just assembles from subatomic particles with all of its detailed ...
  • 07:04: The reverse time direction seems unnatural, but what’s different in terms of the asteroid’s record, or memory of its formation?
  • 07:14: Let’s look at the asteroid after its very last interaction with the outside universe.
  • 07:50: But in the case of the asteroid, time symmetry is much more easily broken.
  • 07:56: Just rewind the clock to the moment before the asteroid’s very last interaction with the outside universe.
  • 08:06: ... predict that future cosmic ray strike with the internal structure of the asteroid ...
  • 08:18: Before the cosmic ray strikes, the asteroid has no knowledge of the incoming impact.
  • 08:36: ... the time-reversed case we have an asteroid formed from an incredibly improbable coalescence of particles - but the ...
  • 08:56: That means that before the cosmic ray hit, the asteroid was correlated with its environment.
  • 09:14: ... then the asteroid will loses those correlations one by one. This reversed time scenario ...
  • 10:17: ... is increasing universe-wide, but the smallest chunks of the universe - asteroids, brains for example - also tend to build correlations with their ...

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

  • 17:44: ... Stark realizes we can have an asteroid impact and alien virus wrapped up in one convenient single apocalypse, ...

2020-06-08: Can Viruses Travel Between Planets?

  • 08:06: Viruses can also be launched into space embedded in rocks that are ejected in asteroid or comet impacts.

2019-12-09: The Doomsday Argument

  • 15:47: Now the non-brain-breaking analogy is a 2-torus like in the game Asteroids, or PacMan where opposite walls connect to each other.

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

  • 09:48: It no doubt sucked up many comets and asteroids would otherwise have hit the Earth.
  • 11:08: ... development - what if the Cambrian explosion had never happened, or the asteroid never wiped out the dinosaurs, or an extra asteroid wiped out our ...

2019-09-23: Is Pluto a Planet?

  • 04:01: So the class of asteroids came into being.
  • 04:18: How many asteroids should we then classify as planets?
  • 07:34: Pluto became to the Kuiper belt what Ceres was to the asteroid belt.
  • 15:56: ... than a planet and so presumably easier to protect from radiation and asteroids than the entire surface of ...

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

  • 09:41: ... could be an asteroid or comet impact, an interaction between the core and mantle – for ...

2019-08-12: Exploring Arecibo in VR 180

  • 01:02: ... is also a space radar that can bounce rate of pulses off planets and asteroids as far as Jupiter Or send messages to the stars. Let's check out the ...

2018-12-12: Quantum Physics in a Mirror Universe

  • 00:02: ... better numbers than randomly scattering with the philic bacteria from asteroid impacts with a non technological planet even if non-tech planets are ...

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

  • 00:37: ... that debris from planetary surfaces can be ejected into space during asteroid or comet impacts hundreds of meteorites have been found on earth that ...

2018-11-21: 'Oumuamua Is Not Aliens

  • 00:41: Nothing unusual about such asteroids and comets.
  • 02:05: ... produce a cometary tail, so it was assumed it must be more rocky or asteroid-like, at least on the ...
  • 02:17: The geometry is very unusual for an asteroid or comet.

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

  • 09:35: But smaller stellar remnants, ancient planets, asteroids, et cetera, could persist.

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

  • 11:01: In the last two episodes we covered the black-hole-information paradox and asteroid mining.
  • 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.
  • 12:22: So Earth is around 2,000 times more massive than the entire asteroid belt.
  • 12:38: Some of you also wondered whether mining the Moon could be more efficient than mining the asteroid belt.
  • 12:43: Well, the moon is definitely an option for mining, and it's going to have some useful heavy elements from crashed asteroids.
  • 12:49: It's not clear that it's better than near-earth asteroids.
  • 12:53: ... gravitational field compared to essentially no such field in the case of asteroids. ...
  • 13:01: Also, mining the moon is going to have a lot of political complications compared to asteroids.
  • 13:14: Asteroids, however, are fair game.

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

  • 00:26: ... the banner of a new company, Planetary Resources, they would mine asteroids for their precious resources and perhaps save the world along the ...
  • 01:11: That resource-- asteroids and the precious materials they contain.
  • 01:16: Astrophysicist Neil deGrasse Tyson predicts that the world's first trillionaire will be an asteroid miner.
  • 01:32: But asteroid mining isn't the same as drilling a hole and hoping black gold spurts out.
  • 01:38: ... and billions of dollars to extract the first dollar's worth of useful asteroid ...
  • 01:50: To answer this question, we need to learn a bit about asteroids.
  • 01:55: Asteroids, along with comets, are leftover material from the formation of the solar system.
  • 02:01: They range from a meter or so to hundreds of kilometers in diameter, and they live primarily in the asteroid belt between Mars and Jupiter.
  • 02:09: ... are also a few smaller groups of asteroids inhabiting different regions and orbits in the inner solar system, ...
  • 02:20: Unlike the more-icy comets of the outer solar system, asteroids are rocky or metallic.
  • 02:33: The most abundant asteroids are C-type or carbonaceous asteroids, constituting 3/4 of all known asteroids.
  • 02:46: C-type asteroids do contain some valuable heavy elements, but not as much as some of the other asteroid types.
  • 02:52: For example, S-type, or silicaceous asteroids, they make up roughly 17% of the asteroids and contain, you guessed it, silicates.
  • 03:11: Third-most abundant are M-type asteroids.
  • 03:18: These are the leftover cores of larger asteroids that were destroyed by collisions.
  • 03:24: If an asteroid is massive enough, it will undergo a process called differentiation.
  • 03:29: During its formation when it's still a giant bowl of molten space rock, heavier iron and nickel will sink to the asteroid's center.
  • 03:37: Smash that asteroid hard enough and you shatter it, exposing a juicy, rich metallic core.
  • 03:43: All asteroid types have the potential to be profitable.
  • 03:55: What loot do asteroids drop-- well, definitely gold and platinum and other precious metals.
  • 04:01: It's not that there's more of this stuff in asteroids than on Earth, it's just that it's more accessible.
  • 04:07: See, the same differentiation process that led to M-type asteroids long ago sucked Earth's crust dry of many of these elements.
  • 04:30: These elements are just more accessible in all but the largest asteroids.
  • 04:34: In fact, much of the precious-metal content of Earth's crust came from old asteroid impacts.
  • 04:40: ... Planetary Resources company estimates that a single 30-meter asteroid may contain $30 billion in platinum alone, and that a 500-meter rock ...
  • 04:54: Kilometer-scale asteroids would be worth many trillions.
  • 05:04: Asteroid miners are going to have to be careful not to crash the value of these materials with oversupply.
  • 05:10: Perhaps the most lucrative asteroid loot will be the stuff that's useful to industry.
  • 05:56: Asteroids are literal gold mines for stuff we want to bring back to Earth, but they also contain materials useful for the mining process itself.
  • 06:04: ... but they can go towards building infrastructure in space, including more asteroid-mining ...
  • 06:27: ... cut back on the amount of mining equipment, and you also limit what asteroids you can ...
  • 06:37: The perfect asteroid has a decent amount of water but also a high abundance of valuable materials.
  • 06:49: ... eventually we'll probably see mining operations in the actual asteroid belt where useful rocks are plentiful, but to start with, it's much ...
  • 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: ... of these near-Earth asteroids can be accessed with relatively little fuel expenditure from Earth ...
  • 07:24: This asteroid prospecting is the current focus of effort for Planetary Resources and its competitors.
  • 07:31: ... know of over 17,000 near-Earth asteroids, but only a small fraction are likely to be cheaply accessible, large ...
  • 07:40: To be short of a profitable composition, robotic prospectors are going to have to visit asteroids.
  • 08:12: So, let's say we find the right asteroid.
  • 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 to the Earth, ...
  • 08:26: This can be done with a gravitational tractor, which we talked about before, or with rockets fueled by the asteroid's own water supply.
  • 08:34: ... a near-Earth asteroid into lunar orbit was the goal of NASA's Asteroid Redirect Mission, but ...
  • 08:45: It was one of the few missions that had a clear track to massive potential profits and saving the planet from asteroid impact.
  • 08:52: Because if we learned how to land on and push an asteroid to a different course, we could potentially push an Earth-killing asteroid off course.
  • 08:59: OK, we found our asteroid and sent our mining facility.
  • 09:08: Smaller asteroids are expected to be loosely bound rubble piles, so breaking them apart will be relatively easy.
  • 09:15: There are also proposals to scrape regolith, asteroid dust, from the surface, or to magnetically harvest loose surface metals.
  • 09:39: For larger solid asteroids, it may make sense to actually tunnel into their interiors, but that's a way down the track.
  • 09:46: The first asteroid-mining missions are slated for the 2020s, but the timetable is very loose.
  • 09:59: Money talks, and tens of billions or even trillions of dollars per asteroid speaks very loudly.
  • 10:06: Perhaps in just a few decades we'll have mining outposts in the asteroid belt.
  • 10:15: But as the industry scales up in the asteroid belt, real-life human operators may be needed.

2018-05-09: How Gaia Changed Astronomy Forever

  • 07:38: It's tracked over 14,000 asteroids and other solar system objects, and found many new ones.
  • 07:44: This is useful for future asteroid mining missions, and to identify potentially, Earth-threatening objects.

2018-03-07: Should Space be Privatized?

  • 04:28: Asteroid mining seems likely to drive the next wave of private enterprise, because the potential profits are astronomical.
  • 10:23: We'll start small, maybe a skateboard tied to a weather balloon and work up to launching sportscast to the asteroid belt. Baby steps, right?

2018-02-21: The Death of the Sun

  • 07:28: ... is now a lonely desolate world orbiting out in the old location of the asteroid belt, or perhaps it didn't quite make ...

2018-01-31: Kronos: Devourer Of Worlds

  • 08:59: It should be possible to deflect an asteroid into an elliptical orbit that takes it near both the Earth and Jupiter.
  • 09:10: The asteroid loses angular momentum in the process, but it regains it as it flies by Jupiter.
  • 09:15: Essentially, we steal angular momentum from Jupiter via the asteroid, which increases our orbit.
  • 09:22: ... a big enough asteroid, one encounter per several thousand years should be enough to maintain ...

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

  • 00:35: ... a good chance we can prevent the most imminent, like asteroid strikes, or at least deal with their effects, like the damage caused by ...
  • 01:41: Some of these mass extinctions were due to giant asteroid impact, including the most recent, which wiped out the dinosaurs 65 million years ago.
  • 01:53: In fact, we've already talked about asteroid impacts and how to deflect them.
  • 11:06: A typical asteroidal density is 2,000 kilograms per cubic meter.

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

  • 00:12: This is the first time we've ever seen an asteroid like object that came to us from interstellar space.
  • 00:36: ... that constantly monitors the sky for moving or variable objects like asteroids or ...
  • 02:39: That suggests the surface to at least one meter depth is rocky like an asteroid rather than icy like a comet.
  • 03:00: ... previously observed asteroid-- indeed, every previously observed everything in our solar system-- moves ...
  • 06:38: Given how many stars there are, there should be a ton of asteroidal objects floating around in interstellar space.

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

  • 01:38: Shoemaker, in particular, was incredibly active, discovering or co-discovering 32 comets, 377 minor planets, and over 800 asteroids.

2017-02-15: Telescopes of Tomorrow

  • 08:49: We'll spot countless fast-moving objects in our own solar system, including potentially hazardous asteroids that could one day impact the Earth.

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

  • 04:10: First of all, we aren't going to find primordial black holes less than around a billion tons, or the mass of a small asteroid.
  • 06:17: ... we're left with are either lots of PBHs with masses similar to a large asteroid like Ceres, so around 10 to the power of 21 kilograms, or a much smaller ...
  • 08:40: If PBHs are closer to the mass of a large asteroid, then they're too low in mass and probably moving too fast to do any gravitational damage.
  • 09:11: ... around a billion tons-- these would be much more abundant than asteroid mass ...

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

  • 04:40: ... applications, like asteroid mining, Dyson swarm construction, and terraforming-- really any ...
  • 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.

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

  • 05:16: ... the sun, we'd probably need to devour Venus, Mars, and a good number of asteroids and outer solar system moons, too, assuming we want to leave Earth ...
  • 05:50: Real companies are gearing up to do autonomous asteroid mining, perhaps within a couple of decades.

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

  • 13:11: ... 404, Hoder Not Found had a great idea in which you collect asteroids and put them in orbit around the Earth, ready to sling at any oncoming ...

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

  • 00:35: In that case, we're pretty sure that a giant asteroid or comet was the culprit, slamming into the Chicxulub peninsula in modern Mexico.
  • 01:47: Some may not be so easy to deal with as an asteroid impact.
  • 03:01: ... the most obvious example would be just a big asteroid coming in and striking the Earth on short notice, which would be-- could ...
  • 03:28: But in the case of a big asteroid impact or a nearby supernova, it could come with so little warning that we might not have time to do much about it.
  • 06:02: Any asteroid or comet bigger than a few kilometers diameter has the potential to cause extreme climate change and mass extinction.
  • 06:42: ... us at least some warning and are somewhat easier to see coming than an asteroid. ...
  • 07:37: It only takes a couple of lazy generations to miss that big asteroid.

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

  • 03:32: ... worrying comets that cross its orbit, it also perturbs the orbits of asteroids in the asteroid belt and can send them plummeting towards the ...
  • 03:58: At first, there was the gassy, dusty protoplanetary disk, and then a mess of asteroids and planetesimals left over from the formation of the planets.
  • 07:09: The asteroid belt is also an interesting clue.
  • 09:13: ... have a tiny Mars, no super Earths, a weird, mixed up asteroid belt, and an early obliteration of Earth's surface, and, perhaps, a ...

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

  • 06:56: For example, the 578-kilometer-diameter asteroid Vesta is lumpy, but the 1,000-kilometer Ceres is spherical.

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

  • 11:20: Now, in the last full episode, we talked about how to stop a killer asteroid from hitting the earth.
  • 11:27: ... of the gravitational tractor, you could just land a spacecraft on the asteroid and push it with its ...
  • 11:35: ... amount of fuel to pull by a gravitational tractor as it would to push an asteroid by landing a rocket on it, assuming that the rocket can push with ...
  • 11:47: Now, that's tricky because the asteroid will certainly be rotating.
  • 12:08: Max Shifter asked about the plausibility of directing a killer asteroid into the sun.
  • 12:13: So even the largest asteroid hitting the sun would barely make a splash.
  • 12:57: A lot of people point out that One-Punch Man could easily destroy a killer asteroid.

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

  • 00:03: Today we have a solution to our killer asteroid challenge episode, but before we get to that there's something very special about today.
  • 01:39: In our recent challenge episode, I asked whether you could save the Earth from a killer asteroid.
  • 01:43: In a hypothetical scenario, the asteroid Apophis will buzz by the Earth in 2029 but then hit the Earth in 2036.
  • 01:57: ... pulsed fusion drive spacecraft is to intercept the asteroid in the 2029 pass and pull Apophis 25,000 kilometers ahead of its would ...
  • 02:35: That way we don't need to worry about the asteroid's initial 30 kilometer per second velocity at all.
  • 02:39: In the asteroid's frame, its starting velocity is zero.
  • 02:45: The x-axis is the orbital path of the asteroid.
  • 05:16: We're trying to pull the entire asteroid, so we have to include its mass as part of the spacecraft mass.
  • 05:40: Rearranging all of this, we get this equation for the ratio of fuel mass to asteroid mass.
  • 05:54: However, remember that the thrusters have to be angled to miss the asteroid, otherwise we'll just push the extra backwards.
  • 06:21: ... have thrusters pointing in at least two directions on either side of the asteroid to cancel the sideways component ...
  • 06:34: Putting this together, we get a ratio of fuel mass to asteroid mass of 5.3 by 10 to the minus 7.

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

  • 00:03: It's a scientific fact that the planet Earth will be hit by cataclysmic asteroids in the future.
  • 00:52: And the Chelyabinsk asteroid came in at a shallow angle, so it had lots of atmosphere to burn up in.
  • 01:16: So when can we expect the next killer asteroid?
  • 02:30: ... asteroid of this magnitude probably killed the dinosaurs 65 million years ago, ...
  • 02:58: ... to find and track most of the biggest, one kilometer plus, comets or asteroids that cross Earth's ...
  • 05:30: The pressure of the nuke, and of the ejected asteroid bits, will push the NEO off target.
  • 05:36: A regular nuke would be fine for smaller asteroids.
  • 05:47: Seriously, arm a spacecraft with a cosmic-sized can of spray paint, and color one side of the asteroid white.
  • 06:44: The asteroid or comet is heading straight for us.
  • 07:04: My favorite idea so far is the Hypervelocity Asteroid Intercept Vehicle.
  • 07:20: This uses the nuke's energy much more efficiently, sending shockwaves through the asteroid, that will break it into much smaller pieces.
  • 07:27: ... of HAIV team, a one megaton H-bomb should break up a 500 meter asteroid nicely, although it depends on the structure of the ...
  • 07:44: For a giant asteroid, you're going to need a gigaton blast.
  • 08:31: ... assuming no giant asteroids hit in the meantime, I'll see you on the next episode of "Space Time." ...

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

  • 00:06: This question is going to draw on two episodes-- our interstellar travel episode from a few weeks ago and next week's episode on killer asteroids.
  • 00:18: The near-Earth asteroid, Apophis, is set to buzz by Earth on April 13, 2029 and then again exactly seven years later on April 13, 2036.
  • 00:40: This 325-meter-diameter asteroid weights around 30 billion kilograms, and it's traveling at 30 kilometers per second.
  • 01:03: ... spacecraft will hover just in front of the asteroid and act as a gravitational tractor, slowly increasing the asteroid speed ...
  • 02:15: ... at by November 20 and use the subject line, Spacetime Killer Asteroid ...

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

  • 05:25: Thicken the walls of the warp field, and you get the negative mass/energy requirement down to the equivalent of maybe the moon or even an asteroid.

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

  • 09:40: Large bodies like asteroids are rare enough in interstellar space that hitting one is very unlikely.

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

  • 01:19: It's only 4.4 light years away, but we have to get there before the Curbles and the impending K1 asteroid that's on its way.

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

  • 06:58: ... also estimated that each halo has as much mass as the entire asteroid belt. So new question, do any sci-fi franchises get all the physics ...

2015-03-18: Can A Starfox Barrel Roll Work In Space?

  • 08:56: Culwin brought up that Ceres is actually the largest asteroid.
  • 09:00: I thought that a dwarf planet and an asteroid designation were mutually exclusive, they appear not to be.
  • 09:05: But even if Ceres is an asteroid, it's only about three and a half times as massive as 4 Vesta, still not enough energy to destroy the Earth.

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

  • 00:00: Lots of unpleasant things from nuclear war to asteroid impacts could destroy life on Earth.
  • 01:43: So let's move on to the next obvious suspect-- asteroids.
  • 01:58: Even 4-Vesta, the biggest object that's still classified as an asteroid, would only care about half a percent of the required energy.
  • 02:15: But asteroids orbit the sun about 35 times slower than that.
  • 02:27: Now with those speeds, an object could only carry enough energy to destroy Earth if it had a huge mass, which asteroids don't.
  • 02:44: Well, Earth and Mars' field gravitational pulls not just from the sun, but also from the other plants-- and from big asteroids too.
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