4 ms·

My opinion is that we have not given anti-matter a serious enough thought. It certainly is expensive to create now, but it seems like the scientists are and wer

by jxcole 15y ago

My opinion is that we have not given anti-matter a serious enough thought. It certainly is expensive to create now, but it seems like the scientists are and were focused on creating antimatter to confirm it's existence and properties. Once they were able to confirm these things, they moved on to trying to use their devices to confirm the existence of other things, like the Higgs Boson (a noble effort). Has there actually been a concerted effort in the physics community to design a more efficient anti-matter creation/storage mechanism?

rubidium 15y ago
There was anti-hydrogen that was made and trapped for >1000 seconds in Dec 2010 (http://massen.web.cern.ch/massen/physics/andresen2010d.pdf http://massen.web.cern.ch/massen/physics/andresen2010d.pdf). Is that what you mean? There are certainly efforts in this direction.
- wcarss 15y ago
  That's storage, which is one possible component of practical anti-matter propulsion. You could generate a lot of it efficiently, store what you made, and send it as lightweight, high yield fuel. The other alternative is to somehow make it as you go: find some way to create pairs and annihilate them in the direction opposite to the direction of thrust you desire. If there were a cost-efficient, energy-efficient, weight-efficient way of generating even very small annihilating pairs, it would be a major propulsion technology. It would also be a major weapons technology, and the fact that we don't know about research being done on such a cool-sounding thing it means that it probably isn't being done, or is being done with surprising secrecy (kind of unlikely). Going out on a limb, I think that means we probably have solid theoretical grounding for believing it's infeasible. (obligatory disclaimer: I am (obviously) not a physicist)
  - wcarss 15y ago
    Actually, it may be a feasible driver of mass while not being a feasible weapon. If it takes something the size of 5-6 refrigerators to generate the particles, but they (+fuel) could generate the equivalent of >6ish refrigerators worth of our presently used fuel, it would be feasible for transportation. For weapons (I was thinking grenades and bombs) you would need to have smaller sizes, and it would have to be efficient to make the particle generators themselves. Spacecraft (at present) can be one-off designs. We could conceivably make a very expensive, reasonably lightweight, reasonably energy-efficient, reasonably large antimatter drive once while being unable to use that technology to make a reproducible superweapon.
  - blake8086 15y ago
    How do you give a direction to the annihilation?
    - Groxx 15y ago
      The same way you give a direction to the explosions we use to propel ourself now - contain it, and only let it escape in one direction.
      - blake8086 15y ago
        Contain it with what? The results of an explosion are gamma rays.
jerf 15y ago
Unless we can come up with some as-yet-entirely-unknown mechanism to convert matter directly into antimatter, the only known methods of producing antimatter require you to pour energy into subatomic particles, smash them together, and hope to collect antimatter from the wreckage, which means you are bounded by the energy you can put into those subatomic particles. This may be somewhat practical for a Kardeshev[1] type 2 civilization who, hypothetically, have the technology to fully automatically construct the relevant hardware and enough energy that if that was the only way to cross the stars, they might be able to put together enough antimatter to do it. But it's completely hopelessly infeasible within our (non-augmented) lifetimes. As far as I know, there's no known physics which "forbids" directly converting matter to antimatter with substantially less energy than going via energy (no conservations violated, etc), but to the best of my knowledge there aren't even any far-out fringe ideas on how to do it. That is, nobody even has any ideas on how to do it more efficiently than with rather large particle accelerators and with mind-bogglingly bad efficiencies. [1]: http://en.wikipedia.org/wiki/Kardashev_scale http://en.wikipedia.org/wiki/Kardashev_scale
- jordanb 15y ago
  > As far as I know, there's no known physics which "forbids" directly converting matter to antimatter with substantially less energy than going via energy (no conservations violated, etc) I think you'd have to put in at least as much energy as you get back out through annihilation of the antiparticle, which would be half the energy released (the other half coming from the destruction of the normal matter). And actually, we already have a working energy source that works by annihilation of matter: nuclear energy. Any future antimatter-based power plant would have to compete for full-cycle efficiency against future nuclear (possibly even fusion) designs.
  - TeMPOraL 15y ago
    > And actually, we already have a working energy source that works by annihilation of matter: nuclear energy. Releasing energy stored in nuclear bonds between particles is NOT annihilation. Nothing gets annihilated in nuclear reactions.
twp 15y ago
Do the back-of-the-envelope calculation on antimatter. I did it once, then mislaid the results. First question: make it or farm it? If you want to create antimatter then, at the very best, energy in = energy out. The energy required to accelerate a small mass of human seeds + associated robot farmers (say 100kg total) to a reasonable speed and to slow it down around the star at the other end is enormous, and a sizable fraction of the annual energy consumption of the entire human planet. It might not be impossible to realise, but it will require as much of a political effort as a scientific/engineering one. Of course, antimatter from space colides with our planet every second, so why not just harvest it? Imagine the entire planet covered with a web that captures every particle of antimatter arriving from space. Well, it would take hundreds of millions of years to harvest enough energy though antimatter to send that 100kg mass to a nearby star. Chemical rockets aren't going to get us there. Antimatter is currently the densest energy source known to man, and it's not enough. Barring the invention of warp drives, we're stuck here. Make the most of it.
- jxcole 15y ago
  I was mostly thinking of your first version, where antimatter is really more of a battery. We would create it from some energy source at the launch site and use it as the most efficient rocket fuel of all time. Most of my thoughts on anti-matter (though of course I am totally unqualified in every regard) is that the biggest problem with rockets these days is fuel efficiency. We are wasting most of the energy of putting something into space because most of the weight we put into space is actually the weight of the fuel and engine. A minority of the weight of the rocket on the ground is the actual payload intended for space. There are, to my mind, three competing emerging technologies that could solve the mass-weight ratio problem. They all involve kissing chemical rockets goodbye. 1) Nuclear 2) Anti-matter 3) Energy-beaming technology. I feel that number 1 gets too much attention. Obviously, if we ever want to get to other stars, we will have to get to other planets first. But I think once we get a solar-system wide economy our options will be much wider. I also feel that making predictions about what the human race is capable of in, say, 10,000 years of technological development is silly. Even if you look 200 years back at what people predicted about what we would be capable of now you see wild inaccuracies. I think that anti-matter could work for an interstellar rocket though. Consider what would happen if we built a factory that could convert 90% of the solar energy hitting the planet mercury into antimatter fuel. I bet that you could create an interstellar rocket from that. Maybe we'll never be able to do it. But I wouldn't count your chickens just yet.

by jxcole 15y ago

rubidium 15y ago

There was anti-hydrogen that was made and trapped for >1000 seconds in Dec 2010 (http://massen.web.cern.ch/massen/physics/andresen2010d.pdf http://massen.web.cern.ch/massen/physics/andresen2010d.pdf). Is that what you mean? There are certainly efforts in this direction.

wcarss 15y ago
That's storage, which is one possible component of practical anti-matter propulsion. You could generate a lot of it efficiently, store what you made, and send it as lightweight, high yield fuel. The other alternative is to somehow make it as you go: find some way to create pairs and annihilate them in the direction opposite to the direction of thrust you desire. If there were a cost-efficient, energy-efficient, weight-efficient way of generating even very small annihilating pairs, it would be a major propulsion technology. It would also be a major weapons technology, and the fact that we don't know about research being done on such a cool-sounding thing it means that it probably isn't being done, or is being done with surprising secrecy (kind of unlikely). Going out on a limb, I think that means we probably have solid theoretical grounding for believing it's infeasible. (obligatory disclaimer: I am (obviously) not a physicist)
- wcarss 15y ago
  Actually, it may be a feasible driver of mass while not being a feasible weapon. If it takes something the size of 5-6 refrigerators to generate the particles, but they (+fuel) could generate the equivalent of >6ish refrigerators worth of our presently used fuel, it would be feasible for transportation. For weapons (I was thinking grenades and bombs) you would need to have smaller sizes, and it would have to be efficient to make the particle generators themselves. Spacecraft (at present) can be one-off designs. We could conceivably make a very expensive, reasonably lightweight, reasonably energy-efficient, reasonably large antimatter drive once while being unable to use that technology to make a reproducible superweapon.
- blake8086 15y ago
  How do you give a direction to the annihilation?
  - Groxx 15y ago
    The same way you give a direction to the explosions we use to propel ourself now - contain it, and only let it escape in one direction.
    - blake8086 15y ago
      Contain it with what? The results of an explosion are gamma rays.

jerf 15y ago

Unless we can come up with some as-yet-entirely-unknown mechanism to convert matter directly into antimatter, the only known methods of producing antimatter require you to pour energy into subatomic particles, smash them together, and hope to collect antimatter from the wreckage, which means you are bounded by the energy you can put into those subatomic particles. This may be somewhat practical for a Kardeshev[1] type 2 civilization who, hypothetically, have the technology to fully automatically construct the relevant hardware and enough energy that if that was the only way to cross the stars, they might be able to put together enough antimatter to do it. But it's completely hopelessly infeasible within our (non-augmented) lifetimes. As far as I know, there's no known physics which "forbids" directly converting matter to antimatter with substantially less energy than going via energy (no conservations violated, etc), but to the best of my knowledge there aren't even any far-out fringe ideas on how to do it. That is, nobody even has any ideas on how to do it more efficiently than with rather large particle accelerators and with mind-bogglingly bad efficiencies. [1]: http://en.wikipedia.org/wiki/Kardashev_scale http://en.wikipedia.org/wiki/Kardashev_scale

jordanb 15y ago
> As far as I know, there's no known physics which "forbids" directly converting matter to antimatter with substantially less energy than going via energy (no conservations violated, etc) I think you'd have to put in at least as much energy as you get back out through annihilation of the antiparticle, which would be half the energy released (the other half coming from the destruction of the normal matter). And actually, we already have a working energy source that works by annihilation of matter: nuclear energy. Any future antimatter-based power plant would have to compete for full-cycle efficiency against future nuclear (possibly even fusion) designs.
- TeMPOraL 15y ago
  > And actually, we already have a working energy source that works by annihilation of matter: nuclear energy. Releasing energy stored in nuclear bonds between particles is NOT annihilation. Nothing gets annihilated in nuclear reactions.

twp 15y ago

Do the back-of-the-envelope calculation on antimatter. I did it once, then mislaid the results. First question: make it or farm it? If you want to create antimatter then, at the very best, energy in = energy out. The energy required to accelerate a small mass of human seeds + associated robot farmers (say 100kg total) to a reasonable speed and to slow it down around the star at the other end is enormous, and a sizable fraction of the annual energy consumption of the entire human planet. It might not be impossible to realise, but it will require as much of a political effort as a scientific/engineering one. Of course, antimatter from space colides with our planet every second, so why not just harvest it? Imagine the entire planet covered with a web that captures every particle of antimatter arriving from space. Well, it would take hundreds of millions of years to harvest enough energy though antimatter to send that 100kg mass to a nearby star. Chemical rockets aren't going to get us there. Antimatter is currently the densest energy source known to man, and it's not enough. Barring the invention of warp drives, we're stuck here. Make the most of it.

jxcole 15y ago
I was mostly thinking of your first version, where antimatter is really more of a battery. We would create it from some energy source at the launch site and use it as the most efficient rocket fuel of all time. Most of my thoughts on anti-matter (though of course I am totally unqualified in every regard) is that the biggest problem with rockets these days is fuel efficiency. We are wasting most of the energy of putting something into space because most of the weight we put into space is actually the weight of the fuel and engine. A minority of the weight of the rocket on the ground is the actual payload intended for space. There are, to my mind, three competing emerging technologies that could solve the mass-weight ratio problem. They all involve kissing chemical rockets goodbye. 1) Nuclear 2) Anti-matter 3) Energy-beaming technology. I feel that number 1 gets too much attention. Obviously, if we ever want to get to other stars, we will have to get to other planets first. But I think once we get a solar-system wide economy our options will be much wider. I also feel that making predictions about what the human race is capable of in, say, 10,000 years of technological development is silly. Even if you look 200 years back at what people predicted about what we would be capable of now you see wild inaccuracies. I think that anti-matter could work for an interstellar rocket though. Consider what would happen if we built a factory that could convert 90% of the solar energy hitting the planet mercury into antimatter fuel. I bet that you could create an interstellar rocket from that. Maybe we'll never be able to do it. But I wouldn't count your chickens just yet.