The first one "220" has a nice discussion, in particular a comment by pfdietz:
> It increases the rate of production of neutral antihydrogen from antiprotons and positrons by a factor of 8. It doesn't increase the efficiency of production of antiprotons, which is the extremely inefficient, energy intensive part.
As a side note, it's mind boggling that overwhelming majority (more than 98%) of the visible universe's mass are only from two most lightweight of chemical elements namely Hydrogen and Helium.
There is a theory that primordial black holes formed in the very early universe. I'm not sure when this process would happen relative to the formation of atoms. But, if it actually happened, it would have been long before stars started forming.
Yes, it's a little mind boggling because the typical human context is this rocky ball of what is ultimately a very uncommon distribution of heavy elements. It's a strange feeling to know that almost everything is utterly unlike the everyday human experience. If you turn down the uhm acksshuwlly a few notches I think parent post's point is quite obvious.
As I learned it long ago in school, elements up to the mass of iron are formed by stellar fusion. That's the point where fusion is no longer exothermic. Any element on earth that is heavier than iron is the product of a supernova. So we live on a ball of supernova debris.
You can skip the first 42 minutes that are about how bad is an article titled "how antimatter space craft will work". This part is absolutely boring as hell !
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.
Before we get too excited, this current "breakthrough" is making less than 1 antihydrogen atom per second. This corresponds to a delivered annihilation power of less than 1 nanowatt.
Neutrons were first definitively observed in 1932.
First nuclear reactor was 1942, and bomb was 1945.
Once the science is established, we have smart engineers to make a short work out of it.
Fusion energy is really the only counterexample in history, which makes me think we are still missing some crucial physics about how it works, for example in stars. Specifically the particle physics view of how it's reliably triggered with minimal energy.
What's the key point regarding how we would get a bajillion times more anti-matter than we can now generate, and without expending all the energy we now expend on getting it?
His point seems to be that we haven't yet seriously tried optimizing for energy efficiency of producing antimatter. It's a call to action. If we actually tried it's plausible that we could get to a level that, while still fantastically inefficient in an absolute sense, would still be worthwhile for spaceflight propulsion, where energy density is vitally important. As far as I know, antimatter is the most energy dense fuel possible in known physics by many orders of magnitude.
Also he proposes a few ways that antimatter could be practically used for propulsion, including as a catalyst for fission which seems interesting.
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 observe it. Has someone modeled something like this?
The anthropic principle doesn't imply that our entire observable universe has to contain only matter.
Why shouldn't we observe clouds of anti matter and matter annihilating millions or billions of light years away? Why does the annihilation have to have happened so early on that we can't see any evidence anywhere?
I think there does need to be an explanation and it can't be an anthropic principle cop out.
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 particle-antiparticle pairs that can be generated or annihilated through electromagnetic interactions have this property that the conserved quantities except the energy sum to zero.
The particle-antiparticle symmetry is important only for the electromagnetic interactions, while other interactions have more complex symmetries.
All the so-called weak interactions are equivalent with the generation or annihilation of groups of 4 particles, for which all the conserved properties except energy sum to zero. Such a group of 4 particles typically consists of a quark, an antiquark, a charged lepton or anti-lepton and a neutrino or antineutrino.
For instance the beta decay of a neutron into a proton is equivalent with the generation of 4 particles, an u quark, an anti-d quark, an electron and an antineutrino. The electron and the antineutrino fly away, while the anti-d quark annihilates a d quark, so the net effect for the nucleus is a change of a d quark into an u quark, which transforms a neutron into a proton.
The generation and annihilation of groups of 4 particles in the weak interactions are mediated by the W bosons, but this is a detail of the mechanism of the interactions, which is necessary for computations of numeric values, but not for the explanation of the global effect of the weak interactions, for which the transient existence of the W intermediate bosons can be ignored.
So besides the symmetry between a particle and an anti-particle, we have a symmetry that binds certain groups of 4 quarks and leptons.
There is a third symmetry, which binds groups of 8 particles. For instance, there are 3 kinds of u quarks, 3 kinds of d quarks, electrons and neutrinos, a total of 8 particles that belong to the so-called first generation of matter particles (i.e. the lightest such particles).
All the conserved quantities except energy sum to zero for this group of 8 particles. The neutrino is necessary in this group so that the spin will also sum to zero, not only the electric charge and the hadronic charge.
These 8 kinds of particles are exactly those that are supposed to compose in equal quantities the matter of the Universe at the Big Bang.
So all the conserved quantities except energy sum to zero for the Universe at the Big Bang, when it is composed entirely of ordinary matter, without any antimatter.
Therefore there is no need for antimatter in the initial state.
There is no known reason for this symmetry between the 8 particles of a generation of quarks and leptons, except that this allows for the initial state at the Big Bang to have a zero sum for the conserved properties.
It can be speculated that this symmetry might be associated with a supplementary hyper-weak interaction, in the same way as the symmetry between certain groups of 4 quarks and leptons is associated with the weak interaction. Such an interaction would allow the generation and annihilation of ordinary matter, without antimatter, but with an extraordinarily low probability.
Can't wait for the day we can trap more antimatter so that governments that right now pretend this is for science weaponize it into a bomb way larger and harder to detect than nukes
I think the same subject was addressed in both of these...
https://news.ycombinator.com/item?id=46011889
The first one "220" has a nice discussion, in particular a comment by pfdietz:
> It increases the rate of production of neutral antihydrogen from antiprotons and positrons by a factor of 8. It doesn't increase the efficiency of production of antiprotons, which is the extremely inefficient, energy intensive part.
As a side note, it's mind boggling that overwhelming majority (more than 98%) of the visible universe's mass are only from two most lightweight of chemical elements namely Hydrogen and Helium.
> it's mind boggling that overwhelming majority
is it though? I mean literally everything has to start there and the only way get to heavier elements is via stars and many-many iterations.
it's not like heavier things popped into existence.... or did they...
There is a theory that primordial black holes formed in the very early universe. I'm not sure when this process would happen relative to the formation of atoms. But, if it actually happened, it would have been long before stars started forming.
Yes, it's a little mind boggling because the typical human context is this rocky ball of what is ultimately a very uncommon distribution of heavy elements. It's a strange feeling to know that almost everything is utterly unlike the everyday human experience. If you turn down the uhm acksshuwlly a few notches I think parent post's point is quite obvious.
3 replies →
Feels like most resources on the map aren’t mined yet.
And earth contains so much of heavier elements.
As I learned it long ago in school, elements up to the mass of iron are formed by stellar fusion. That's the point where fusion is no longer exothermic. Any element on earth that is heavier than iron is the product of a supernova. So we live on a ball of supernova debris.
4 replies →
This piece argues that antimatter could be feasible for space propulsion and we could start developing it now: https://news.ycombinator.com/item?id=46073414
For those who are time-rich and knowledge-poor:
https://youtube.com/watch?v=i6jMnz6nlkw
(Angela is genuinely a great science communicator and that video is time well spent if you are interested in this topic.)
You can skip the first 42 minutes that are about how bad is an article titled "how antimatter space craft will work". This part is absolutely boring as hell !
1 reply →
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.
21 replies →
Depends. Do we know how to obtain a miniature black hole?
5 replies →
We know how to make antimatter and have actually done it. We have no realistic way to obtain a black hole of any size.
1 reply →
They made a movie about this. It didn’t end so well for the crew.
2 replies →
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?
4 replies →
Before we get too excited, this current "breakthrough" is making less than 1 antihydrogen atom per second. This corresponds to a delivered annihilation power of less than 1 nanowatt.
Neutrons were first definitively observed in 1932.
First nuclear reactor was 1942, and bomb was 1945.
Once the science is established, we have smart engineers to make a short work out of it.
Fusion energy is really the only counterexample in history, which makes me think we are still missing some crucial physics about how it works, for example in stars. Specifically the particle physics view of how it's reliably triggered with minimal energy.
6 replies →
There was also a great episode on antimatter engines recently by PBS Space Time.
https://www.youtube.com/watch?v=eA4X9P98ess
What's the key point regarding how we would get a bajillion times more anti-matter than we can now generate, and without expending all the energy we now expend on getting it?
His point seems to be that we haven't yet seriously tried optimizing for energy efficiency of producing antimatter. It's a call to action. If we actually tried it's plausible that we could get to a level that, while still fantastically inefficient in an absolute sense, would still be worthwhile for spaceflight propulsion, where energy density is vitally important. As far as I know, antimatter is the most energy dense fuel possible in known physics by many orders of magnitude.
Also he proposes a few ways that antimatter could be practically used for propulsion, including as a catalyst for fission which seems interesting.
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 observe it. Has someone modeled something like this?
The anthropic principle doesn't imply that our entire observable universe has to contain only matter.
Why shouldn't we observe clouds of anti matter and matter annihilating millions or billions of light years away? Why does the annihilation have to have happened so early on that we can't see any evidence anywhere?
I think there does need to be an explanation and it can't be an anthropic principle cop out.
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 particle-antiparticle pairs that can be generated or annihilated through electromagnetic interactions have this property that the conserved quantities except the energy sum to zero.
The particle-antiparticle symmetry is important only for the electromagnetic interactions, while other interactions have more complex symmetries.
All the so-called weak interactions are equivalent with the generation or annihilation of groups of 4 particles, for which all the conserved properties except energy sum to zero. Such a group of 4 particles typically consists of a quark, an antiquark, a charged lepton or anti-lepton and a neutrino or antineutrino.
For instance the beta decay of a neutron into a proton is equivalent with the generation of 4 particles, an u quark, an anti-d quark, an electron and an antineutrino. The electron and the antineutrino fly away, while the anti-d quark annihilates a d quark, so the net effect for the nucleus is a change of a d quark into an u quark, which transforms a neutron into a proton.
The generation and annihilation of groups of 4 particles in the weak interactions are mediated by the W bosons, but this is a detail of the mechanism of the interactions, which is necessary for computations of numeric values, but not for the explanation of the global effect of the weak interactions, for which the transient existence of the W intermediate bosons can be ignored.
So besides the symmetry between a particle and an anti-particle, we have a symmetry that binds certain groups of 4 quarks and leptons.
There is a third symmetry, which binds groups of 8 particles. For instance, there are 3 kinds of u quarks, 3 kinds of d quarks, electrons and neutrinos, a total of 8 particles that belong to the so-called first generation of matter particles (i.e. the lightest such particles).
All the conserved quantities except energy sum to zero for this group of 8 particles. The neutrino is necessary in this group so that the spin will also sum to zero, not only the electric charge and the hadronic charge.
These 8 kinds of particles are exactly those that are supposed to compose in equal quantities the matter of the Universe at the Big Bang.
So all the conserved quantities except energy sum to zero for the Universe at the Big Bang, when it is composed entirely of ordinary matter, without any antimatter.
Therefore there is no need for antimatter in the initial state.
There is no known reason for this symmetry between the 8 particles of a generation of quarks and leptons, except that this allows for the initial state at the Big Bang to have a zero sum for the conserved properties.
It can be speculated that this symmetry might be associated with a supplementary hyper-weak interaction, in the same way as the symmetry between certain groups of 4 quarks and leptons is associated with the weak interaction. Such an interaction would allow the generation and annihilation of ordinary matter, without antimatter, but with an extraordinarily low probability.
How many times does the rate need to be increased 10x before it's a problem?
If I remember correctly, 6.023x10^23 protons (with electrons) is one gram of hydrogen.
Can't wait for the day we can trap more antimatter so that governments that right now pretend this is for science weaponize it into a bomb way larger and harder to detect than nukes
https://www.youtube.com/watch?v=-hYNl1hnwUc&t=115s