Solar flares have lots of tasty (and *free*) antimatter in them, so why not fire a spare spaceprobe at a very high velocity through or past one to spoon up a bit so it doesn't go to waste on the kitchen floor of the solar system? Or have stationary satellites in solar orbit with powerful fields/scoops standing by for same purpose? Sure, the energy requirements to do this might be ridiculous, but, hey, so long as you've already got some antimatter to "ante up" with, why not? (The bootstrap principle being that you need anti to rake anti.-)
-- cloudface, Jan 18 2004

Meanwhile, elsewhere in the solar system... http://www.halfbake...ea/Mine_20the_20Sun
very similar idea about H3 [cloudface, Oct 04 2004]

Antimatter http://science.hows...com/antimatter1.htm
For [scout] [Worldgineer, Oct 04 2004, last modified Oct 21 2004]

Solar Flares Got Lots o' antimatter, NASA sez http://www.gsfc.nas...003/0903rhessi.html
Goomeister: Nope, solar flares do have antimatter. See link. [cloudface, Oct 04 2004, last modified Oct 21 2004]

Positron+electron = photon (singular) http://plus.maths.o...1/features/strings/
About 1/4 of the way down the page. What do I know? But if Feynman says it, I believe him. [MaxwellBuchanan, Feb 23 2007]

Positron+electron = photon (plural) http://en.wikipedia.org/wiki/Annihilation
[ldischler, Feb 23 2007]

There is no antimatter in solar flares. In fact, as far as we know, there's no antimatter anywhere in the universe, except when we make it in the laboratory.
-- goomeister, Feb 11 2004


//so it doesn't go to waste on the kitchen floor of the solar system?//

If the anti matter is only on the kitchen floor of the solar system for 5 seconds, can you still use it?
-- GenYus, Feb 11 2004


Anti matter is matter that is opposite (charge and/or spin) from regular matter. An example would be a positron (POSItive elecTRON). When it meets an electron, they both mutually annialate and create a gamma(?) ray.
-- GenYus, Feb 11 2004


2 equal and oppositely directed gamma rays (remember, conservation of momentum)
-- quantum_flux, Feb 23 2007


//2 equal and oppositely directed gamma rays// I could have sworn this was not the case.
-- MaxwellBuchanan, Feb 23 2007


Two or more, but never one.
-- ldischler, Feb 23 2007


That doesn't sound right, ldischler. I was trying to remember Feynman diagrams, which I thought I had seen showing an electron and a positron annhialating to form a single photon and, conversely, a single photon giving a positron/electron pair.

I found such a diagram (link); it's also in my Feynman books, but I can't link to those.
-- MaxwellBuchanan, Feb 23 2007


From Wikipedia: "The annihilation (or decay) of an electron-positron pair into a single photon...cannot occur because energy and momentum would not be conserved...However, in quantum field theory this process is allowed as an intermediate quantum state. Some authors justify this by saying that the photon exists for a time which is short enough that the violation of energy conservation can be accommodated by the uncertainty principle." Waving their hands like crazy, in other words, in order to justify a situation that is never observed.
-- ldischler, Feb 23 2007


Fair enough - I've learned something. Only two points of query/dispute: a) I don't see why momentum cannot be conserved by making a single photon (after all, the net momentum of the e- and e+ can, presumably, be anything before they collide?).

b) Likewise energy: a photon can have any amount of energy depending on its wavelength, so I don't understand why two photons are required to conserve energy, rather than one of shorter wavelength

c) I thought that the existence of virtual particles and photons was solidly established (Hawking radiation and all that), and not just hand-waving?
-- MaxwellBuchanan, Feb 23 2007


It seems to me that, without looking at it in detail, there may be some unique situation that would allow one photon and still satisfy both conservation laws simultaneously. But that might require such precise conditions that it would never occur. As for virtual particles being solidly established, they are, by definition, abstractions, and not real.
-- ldischler, Feb 23 2007


//might require such precise conditions that it would never occur// I still don't get it, sorry. Especially in terms of energy conservation, what is the difference between one photon of short wavelength and two of longer wavelength? (ie, why would you need two to conserve energy?)

As regards //they are, by definition, abstractions, and not real// I don't think that is correct. My understanding (bolstered by Mr. Wikipedia) is that the only fundamental difference between virtual and real particles is that the former arise through nature's sloppy book-keeping and are transient, whereas the latter are properly accounted for and more permanent.

Certainly there are many very tangible phenomena which are accounted for most simply by accepting the reality of virtual particles (van der Waal's forces, for instance). Exactly the same applies to "real" particles - they offer an explanation for observed phenomena.

I'm not claiming any great expertise here, so if you're a pukka physicist then I'll cede.
-- MaxwellBuchanan, Feb 23 2007


You have to conserve energy and momentum *simultaneously*. And the other difference between real and virtual particles is that virtual particles have never been detected. Nature didn't create them. We did, for our own sloppy bookkeeping.
-- ldischler, Feb 23 2007


//You have to conserve energy and momentum *simultaneously*// Well, I still don't see that you can't also conserve momentum with a single photon. However, I'm happy to accept that annhialation produces >1 photon, though I'd double-check if my life depended on it.

//And the other difference between real and virtual particles is that virtual particles have never been detected. // Nor have real particles; or both have. Without wanting to get into naive philosophical arguments, you only ever detect the effect of a particle. A proton curves this way in a magnetic field and leaves a trail in a cloud chamber; exchange of virtual photons produces attraction or repulsion between charges. What's the distinction?

//Nature didn't create them. We did, for our own sloppy bookkeeping.// That's silly. Heisenberg didn't invent his uncertainty - nature is just grainy and sloppy.
-- MaxwellBuchanan, Feb 23 2007


The difference is you can see the bubbles, but attributing forces to virtual particles is just a theory. With enough tweaking it gives the right answers, just as epicycles gave the right answers for planetary motion, but was totally wrong.

As for Heisenberg, he did indeed invent the uncertainty principle. But what his principle says about the underlying reality is subject to interpretation. (Eg, the Copenhagen interpretation, or the many worlds interpretation.)
-- ldischler, Feb 23 2007


//The difference is you can see the bubbles, but attributing forces to virtual particles is just a theory.// No, that's not a difference. Yes I can see bubbles; I can see electrostatic effects; I can see effects that depend on van der Waal's forces. In each case, the simplest way to account for the phenomenon is to postulate a particle (real in one case, virtual in the other).

Suppose I "see" (as trails in a bubble chamber) two protons repelling eachother. You're telling me that the bubbles-trails are "really" caused by protons, but that the repulsion between them is not "really" caused by photon exchange? One is as real as the other.
-- MaxwellBuchanan, Feb 23 2007



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