Comment by IsTom
1 day ago
If you can electromagnetically trap enough antimatter to use it as fuel you could as well trap a miniature charged black hole that can be fed regular matter to produce power, which skips the whole inefficient part of making antimatter.
Miniature black holes would just evaporate. Antimatter wouldn't.
That's the point, evaporation turns matter into energy. You can tune power by chosing mass of the black hole and then feed it regular matter at a steady rate.
Minor nit-pick but Hawking Radiation hasn't been observed and remains a theoretical prediction.
It's pretty widely accepted though. He himself hated the idea so you can expect he did the calculations thoroughly.
1 reply →
It's a pretty fundamental prediction though, and it's been derived in many different ways, all of which give the same prediction.
It's closely related to the Unruh effect, which is a direct consequence of pure QFT. The Unruh effect describes how an accelerated observer sees a different vacuum from an inertial observer - they see radiation that the inertial observer doesn't.
Hawking radiation is essentially this same effect, except that "acceleration" is replaced by "gravity" (Einstein's equivalence principle.) There's a bit more to it, but that's the basic intuition.
For Hawking radiation to be wrong would require some fundamental changes to GR, QFT, or both.
2 replies →
Not before efficiently converting a large amount of mass into usable energy.
But you want that to happen in space and to control the output of energy.
Otherwise you just have a bomb.
4 replies →
In the same way that atomic weapons and radioisotope generators both convert mass into energy. It's just a matter of slightly different timescales.
How could we harness this energy and make it usable?
6 replies →
Depends. Do we know how to obtain a miniature black hole?
There have been several proposals. This paper proposes a feasable mechanism[1]:
-"a SBH could be artificially created by firing a huge number of gamma rays from a spherically converging laser. The idea is to pack so much energy into such a small space that a BH will form."
1. https://arxiv.org/abs/0908.1803
The biggest problem is that if you're creating it with lasers, you're only going to get the energy out that you put in. You really want to be able to feed it matter, which would effectively make it an anything-to-gamma-radiation converter, which means you have to feed it quite a lot of matter, against the radiation pressure of all that energy coming out. The paper mentioned assumes a worst case of not being able to feed the black hole at all, but doesn't (in my skim) address the fact that this means you have to put in all the energy you'll be using for the lifetime of the black hole at the creation of it, which seems significantly more outrageously infeasible than the bare necessity of creating a black hole at all.
2 replies →
There’s a recent paper on the formation of such a “kugelblitz”; it’s argued to be unfeasible.
https://arxiv.org/abs/2405.02389
We know how to make antimatter and have actually done it. We have no realistic way to obtain a black hole of any size.
If you can create enough AM to last a space voyage you certainly know how to build big enough particle accelerators.
They made a movie about this. It didn’t end so well for the crew.
I admit to invoking the phrase “Where we’re going, we won’t need eyes to see” at least once a year when something feels like it’s going horribly wrong.
But it was one hell of a ride! ;-)
The romulan empire does this.
> a miniature charged black hole that can be fed regular matter to produce power,
What form of power and through what principle?
Hawking radiation, I think. Yes, this is at best speculatively feasible.
Probably more like a water wheel - matter spinning around the hole can be accelerated.
2 replies →