Oh, and is it possible that for some unknown reason all the antimatter is outside the observable universe? Thus making the fact that we only see matter a bit of a fluke? It seems not, since (depending on the size of the whole universe) that would make the universe not seem particularly homogeneous. But I’m not sure if this has been officially rejected as a hypothesis.
That depends on the particles in question. If it’s just electrons and positrons, then it all goes directly to photons. If you’ve got most of your mass in protons and neutrons, though, you’ll get a whole mess of particles at first (mostly pions), and then those pions will decay to photons or to yet other unstable particles. Eventually, everything would end up in some mixture of photons and neutrinos, with probably about 2/3 of the initial energy in neutrinos, and 1/3 in photons.
If you actually had a large chunk of each, then it’s likely that the energy released when the surfaces first contacted would be enough to blow the rest of the chunks apart from each other. Near the surface of the Earth, though, this would just mean that the antimatter chunk would end up being knocked into something else (the air, at least), and continue reacting.
How devastating would an annihilation explosion be?
Would it kill a person in close proximity, a person some distance away, destroy a city block or a whole city or … whatever.
I assume it would also depend on the amount of matter/antimatter involved.
Would any kind of deadly radiation be produced. Any long term residual effects like nuclear explosions fallout.
If you were making an antimatter weapon, you’d probably choose the amount of devastation you want, and then choose the amount of antimatter accordingly. Annihilate a single positron with a single electron, and there’s a very small chance that you might give someone standing right next to the event a cancer that takes decades to kill them. Annihilate a gram or so of antimatter with an equal amount of matter, and you’ll level a city. Annihilate a trillion tons or so, and you’d blow the entire planet to smithereens.
According to Wiki, a gram of matter will convert to 21.5 kilotons of TNT equivalent energy. This is almost exactly the same yield as the “Fat Man” bomb that was dropped on Nagasaki.
Let’s say our chunks are cubes of width 10 cm. Let’s arrange for these to slowly drift toward each other in deep space, aligned so that they strike face-on.
The lattice spacing in the lead is around 0.3 nm, so the surface layer alone contains 10[sup]16[/sup] atoms. Let’s say that you only get 0.1% burn of that first atomic layer. And, let’s say that only 5% of the released energy gets absorbed by each chunk. This is still enough to instantly vaporize the lead blocks, as their temperatures would reach about 16,000 K.
(And this only used 3x10[sup]-11[/sup] of the available lead atoms/anti-atoms.)
Strange, I always assumed that no matter the size and shape of the antimatter that it would always react pretty much instantaneously.
I guess when they start to build antimatter bombs they should have many different subcompartments (most likely several thin tubes of antiplasma) rather than a single chunk of antimatter so the antimatter would all react at once and you wouldn’t have a chunk of antimatter jetting off into the atmosphere and reacting over a second or so.
An anti-matter bomb would be almost indistinguishable from a standard nuclear warhead. You’d start with a burst of very high energy photons - gamma rays, mostly - that would interact with the atmosphere. As they move down to lower levels, they heat the atmosphere, creating a whole spectrum of radiation and the classic fireball.
The difference is that a classic nuclear weapon is only converting about 0.1% of the matter into energy. A well-designed anti-matter weapon would convert 100% to energy. So a much smaller explosive mass would be required, though that might be offset by the need to carefully contain the anti-matter in magnetic fields or something of the sort. In fact, one major drawback to anti-matter weapons is that their default state is to explode. If a traditional nuke is damaged or destroyed, it just reverts to a mostly harmless lump of metal. Anything that damages the containment of an anti-matter weapon sets it off.
I think anti-matter weapons would be relatively clean in terms of radioactive fallout, but you’re still talking about nuclear reactions with very high energies. Some radio-isotopes will be produced.
Right. So long as we’re imagining the magical tech (;)) required to produce large quantities of antimatter, we might as well imagine that this technology can be miniaturized to fit within a warhead. (Perhaps you’d use a hydrogen bomb to power your antimatter-creating device in the instants before it, too, would be destroyed.) That would be pretty much the only way to safely field an antimatter weapon - design it in such a way that you only create the antimatter a tiny fraction of a second before you want an Earth-shaking kaboom.
Realistically, it’s hard to imagine much of an advantage to antimatter weapons - we already have the capability to make and field nukes that are more powerful than anything we care to bother with. (The US, for example, prefers its strategic nukes to produce yield in the hundreds-of-kilotons range, not megatons).
Anyone who is really interested in the question should list to the segment titled Apprehending anti-atoms. It is an interview with the guy who made the anti-hydrogen. Aside from discussing the difficulty of confining it, he speculates a bit on what its properties might be. E.g. does it have the same spectral lines as hydrogen? The standard model predicts it will but he would love to make enough of them to test it. Imagine if they were different? Again the standard model predicts they will fall down, but suppose they didn’t? Nobel prizes in his future. But essentially he doesn’t know for sure and would love to find out.
Every time I think back to that “crap”, I just remember that my high school teachers wanted to be there as much as I did.
~ ~ ~
By the way, they don’t look the same. Anti-Spock had a goatee.
FWIW (IANAQP), I think that that is an excellent theory, for a variety of Flatland-type reasons.