h a l f b a k e r yThe mutter of invention.
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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.-)
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]
[link]
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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. |
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//so it doesn't go to waste on the kitchen floor of the solar system?// |
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If the anti matter is only on the kitchen floor of the solar system for 5 seconds, can you still use it? |
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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. |
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2 equal and oppositely directed gamma rays (remember, conservation of momentum) |
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//2 equal and oppositely directed gamma
rays// I could have sworn this was not the
case. |
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Two or more, but never one. |
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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. |
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I found such a diagram (link); it's also in
my Feynman books, but I can't link to
those. |
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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. |
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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?). |
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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 |
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c) I thought that the existence of virtual
particles and photons was solidly
established (Hawking radiation and all
that), and not just hand-waving? |
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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. |
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//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?) |
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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. |
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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. |
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I'm not claiming any great expertise
here, so if you're a pukka physicist then
I'll cede. |
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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. |
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//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. |
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//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? |
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//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. |
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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.) |
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//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). |
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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. |
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