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2021-04-21: The NEW Warp Drive Possibilities

  • 04:59: ... people talk about the drive requiring negative mass - also called exotic matter - and yeah, that would do the trick too - ...

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

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

2020-05-18: Mapping the Multiverse

  • 07:34: For one thing, the ring singularity becomes entirely repulsive - as though it had negative mass.

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

  • 08:42: ... exotic matter is anything with negative energy density. Something with negative mass could produce the required negative gravity. But actually “exotic ...

2019-10-21: Is Time Travel Impossible?

  • 05:17: We need to counter gravity, and to do that we need another probably-non-existent form of mass – negative mass – also referred to as exotic matter.
  • 05:27: As far as we know, mass can only take on positive, real values, so a requirement of negative mass seems a non-starter.
  • 06:19: But is negative mass-energy as much of a non-starter as imaginary mass?

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

  • 12:11: ... violates the same energy conditions of general relativity that prohibit negative mass and time ...

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

  • 09:54: ... to come up with a perpetual motion machine based on the funky notion of negative mass. ...
  • 10:06: According to some interpretations, negative mass should be attracted to positive mass, but positive mass should be repelled by negative mass.
  • 10:15: The result is that a positive and negative mass should accelerate indefinitely, potentially powering an infinite energy device.

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

  • 13:19: Today, it's the 'Crisis in cosmology' and 'Negative mass perpetual motion' episodes.
  • 15:16: Ergo, time will prove negative mass' existence.
  • 16:03: flux_capacitor notes an alternate model for how negative mass might behave.
  • 16:08: In so-called bimetric gravity, you can have positive and negative masses, but each is described by its own set of Einstein field equations.
  • 16:18: That's kind of like having parallel spacetimes, one with positive and one with negative masses, which can still interact gravitationally.
  • 16:26: ... get the crazy runaway motion that occurs if you put both positive and negative masses in the same ...

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

  • 00:31: Matter with negative mass - has long been the pipedream of science fiction writers, futurists, and certain rather.
  • 00:59: And we also recently covered a very new use for negative mass: as “dark fluid”, a proposed explanation for both dark matter and dark energy.
  • 01:10: That episode really got me thinking about the subtleties of negative mass and how it should really behave gravitationally.
  • 03:19: OK, so how do negative masses work in Newtonian mechanics?
  • 04:45: A repulsive force on a negative mass becomes an attractive force and vice versa.
  • 04:51: ... this in the dark fluid episode, but to recap: this suggests that two negative masses produce an attractive force which actually drives them ...
  • 05:02: Even weirder, a positive mass should attract a negative mass while at the same time being repelled by it.
  • 05:08: A negative mass apple would still fall to the Earth, and you wouldn’t notice Earth’s infinitesimal repulsion from the apple.
  • 05:17: But put equal positive and negative masses next to each other and they should accelerate uniformly forever.
  • 07:13: That should mean that a negative mass behaves the same in a gravitational field as a positive mass.
  • 07:50: This suggests that a positive gravitational field attracts everything, including negative masses.
  • 08:01: Negative mass causes negative curvature, which in our sheet analogy looks like pulling the sheet up.
  • 08:13: That suggests that everything, regardless of mass, should be repelled from a negative mass.
  • 08:21: It suggests that positive masses attract everything and negative masses repel everything, including each other.
  • 08:29: A positive mass attracts and is repelled by a negative mass.
  • 08:51: So a positive and a negative mass apple placed side by side should chase each other across the cosmos, accelerating forever.
  • 09:06: ... mass apple gains positive momentum and energy as it speeds up, while the negative mass apple balances that with negative momentum and negative ...
  • 09:46: ... fact the mere existence of negative mass breaks certain energy conditions, but the prospect of a bottomless well ...
  • 10:26: Much less clear is the way a negative mass responds to an applied force.
  • 12:28: ... equivalence principle and the rest of physics, we need to conclude that negative mass of any type can’t ...
  • 12:55: Some say negative mass can’t exist, some say it can.
  • 12:59: ... say that, if they do, then positive mass always attracts while negative mass always repels, while others say that like mass signs always attract and ...
  • 13:18: ... it is: assuming that positive mass both attracts and is repelled by negative mass, come up with a way to use a pair of infinitely accelerating positive and ...
  • 13:59: Make the subject line negative mass challenge question.

2019-01-24: The Crisis in Cosmology

  • 13:26: ...about negative mass dark fluid...
  • 14:06: ...will give the exact opposite results if dark matter is due to this negative mass fluid...
  • 14:48: Marik Zilberman's distaste for negative masses...
  • 16:31: And a negative mass particle, moving backwards in time,...

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

  • 00:32: And it’s pretty wild: negative mass particles continuously popping into existence between the galaxies.
  • 00:58: Farnes 2018, “A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified Lambda-CDM framework”.
  • 03:58: He tried to do this in very different way: with negative mass.
  • 04:15: So what about negative masses?
  • 04:18: The answer is complicated - it’s not always obvious how weird stuff like negative masses translates from general relativity to Newton’s laws.
  • 04:45: Two negative masses should cancel each other’s signs so also give you an attractive force.
  • 05:29: For a negative mass, this equation suggests that acceleration is in the opposite direction to the applied force.
  • 05:36: Push a negative mass away from you it’ll move towards you, pull it and it’ll move away.
  • 05:45: So Farnes argues that the “attractive” gravitational force between two negative masses should actually drive them apart.
  • 05:56: At the same time, the repulsive force between a negative and positive mass should repel the positive and attract the negative mass.
  • 06:22: ... he programs a virtual universe into his computer with both positive and negative mass particles, along with his interpretations of Newton’s ...
  • 06:32: Those simulations showed that galaxies do indeed spin more quickly when surrounded by negative mass particles.
  • 06:39: ... is because the positive mass in the galaxy attracts a halo of negative mass, but at the same time that positive mass is repelled inwards by the ...
  • 06:59: To make the same negative mass stuff also emulate dark energy requires an extra gigantic assumption.
  • 07:07: The problem is that our negative masses will dilute away as the universe expands.
  • 07:12: To fix this, Farnes proposes that these negative masses are constantly created as the universe expands.
  • 07:20: That keeps the density of negative masses constant, even as the density of positive masses falls.
  • 07:26: The result is a very diffuse negative mass fluid that fills the universe and constantly replenishes itself.
  • 08:18: ... really the analog of Newton’s law of gravity for the whole cosmos, this negative mass fluid – as a negative cosmological constant – has the same competing ...
  • 09:55: Plugging negative masses into general relativity allows you to break causality.
  • 10:07: This is a strong indication that negative mass can’t exist.
  • 12:59: ... to get confused by the compounding negatives in what is probably not a negative mass, anti-gravitational, positive pressure, anti-deSitter space ...

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

  • 00:02: ... of pursuing fringe ideas even that new dark energy dark matter is a negative mass fluid thing reference to seem heavily and yeah we'll be covering that ...

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

  • 10:37: It's not negative mass despite this negative energy description.

2015-11-05: Why Haven't We Found Alien Life?

  • 10:55: ... bubble can traverse the walls in any direction besides forwards and our negative mass matter may also end up on the ...

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

  • 03:49: ... on macroscopic scales, you'd probably need some sort of exotic negative mass matter, like element zero, which is tricky, because there may be no such ...
  • 04:37: ... that you can even make negative mass matter, to make a warp field, some of it would need to go outside the ...
  • 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.
  • 05:46: ... Tardis style, which could get us down to needing only milligrams of negative mass. ...

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

  • 01:10: Or you need something exotic, like gravitationally repulsive negative mass, which doesn't exist.
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