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Physicists drive antihydrogen breakthrough at CERN

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Re: Physicists drive antihydrogen breakthrough at CERN

#91

Post by Symmetry »

jojobas wrote: post #89
Symmetry wrote: post #70

Earlier quoted context omitted.

It's way easier to make a fission bomb than a fission reactor. I reactor has to stay in the very narrow window where it's critical but not prompt critical. Even pure fission bombs can be marvels of engineering but the simplest gun-type bomb is easier to build than the simplest nuclear reactor.

Without a precisely timed neutron initiator you'll get a fizzle. Either way, gun-type bombs require highly enriched uranium. A simple reactor can be literally just brickwork of natural uranium and graphite. Reactors are much much simpler to pull off, which is why US had the first reactor whole 2.5 years before a nuclear bomb.

Something that explodes with the force of 100 tons of TNT is still a bomb, even if it isn't a bomb as impressive as the one you were hoping for. And getting the reactor you're thinking of to the point that it worked without exploding took a lot more effort than you're suggesting.

Re: Physicists drive antihydrogen breakthrough at CERN

#92

Post by jojobas »

Symmetry wrote: post #91
jojobas wrote: post #89

Earlier quoted context omitted.

Without a precisely timed neutron initiator you'll get a fizzle. Either way, gun-type bombs require highly enriched uranium. A simple reactor can be literally just brickwork of natural uranium and graphite. Reactors are much much simpler to pull off, which is why US had the first reactor whole 2.5 years before a nuclear bomb.

Something that explodes with the force of 100 tons of TNT is still a bomb, even if it isn't a bomb as impressive as the one you were hoping for. And getting the reactor you're thinking of to the point that it worked without exploding took a lot more effort than you're suggesting.

Introducing GoalpostMover-3000.

Re: Physicists drive antihydrogen breakthrough at CERN

#93

Post by antonvs »

fooker wrote: post #88
antonvs wrote: post #81

Earlier quoted context omitted.

We have an extremely good understanding of how gravity operates, both inside and outside of stars. There are no Nobel prizes waiting for things you describe, because that’s all well-established and settled science. Quantum physics tells us exactly why high temperatures and pressures are needed, and predicts numerically what values are needed. We have a great deal of confidence in its correctness, especially because c…

I'm amused at your confidence in stating that we have a good understanding of what's literally the most prominent open problem in physics, gravity at small/particle scales.

We do have an extremely good understanding of how gravity causes stellar fusion. We don't need quantum gravity to model that. The gravitationally-induced pressure due to the star’s total mass provide the conditions needed for fusion.

If you're thinking along the lines that if we knew how gravity worked at the quantum scale, we might find some sort of way to achieve fusion under much less extreme conditions, we probably can't entirely rule that out, but there's been many decades of work in that area, so it's seeming pretty unlikely. Also, that has nothing to do with what's happening inside a star.

We know about the need to overcome the electrostatic Coulomb barrier, we know what energies are required to overcome it and have models that predict those energies very accurately, we know how quantum tunneling allows this barrier to be penetrated, etc.

We can even do things like muon-catalyzed fusion, where we substitute muons for electrons in hydrogen atoms, which lowers the Coulomb barrier.

As such, the claims in the comment I originally replied to were just completely wrong.

Re: Physicists drive antihydrogen breakthrough at CERN

#94

Post by iNic »

adrian_b wrote: post #67
iNic wrote: post #61

Can't we argue for the low amount of anti-matter as a type of anthropic principle? The early universe was super dense meaning that areas with imbalance would quickly annihilate and leave only one type of matter. Then, due to rapid expansion, our observable universe is dominated by only one type of matter. If we imagine a universe with a more even mix it would be less welcoming to life, so we are less likely to observ…

Not only there is no evidence for the existence of antimatter in quantities comparable with matter, but there also is no logical necessity for this. People who entertain the idea of an initial state with equal amounts of matter and antimatter do this because thus the properties of the matter that are conserved, except the energy, would sum to zero in the initial state. However, such people forget that not only the pa…

This is very helpful thanks!

Re: Physicists drive antihydrogen breakthrough at CERN

#95

Post by antonvs »

IsTom wrote: post #75
antonvs wrote: post #51

Earlier quoted context omitted.

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.

This is a silly claim. Creating black holes is many orders of magnitude more difficult than creating antimatter.

Re: Physicists drive antihydrogen breakthrough at CERN

#96

Post by iNic »

adrian_b wrote: post #67
iNic wrote: post #61

Can't we argue for the low amount of anti-matter as a type of anthropic principle? The early universe was super dense meaning that areas with imbalance would quickly annihilate and leave only one type of matter. Then, due to rapid expansion, our observable universe is dominated by only one type of matter. If we imagine a universe with a more even mix it would be less welcoming to life, so we are less likely to observ…

Not only there is no evidence for the existence of antimatter in quantities comparable with matter, but there also is no logical necessity for this. People who entertain the idea of an initial state with equal amounts of matter and antimatter do this because thus the properties of the matter that are conserved, except the energy, would sum to zero in the initial state. However, such people forget that not only the pa…

Follow up question. How do we know that some distant galaxy we are observing isn't made up entirely of anti-particles? Wouldn't it behave identically?
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