| Re: Have Scientist ever seen Anti Matter? |
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Group: alt.philosophy · Group Profile
Author: Michael MoroneyMichael Moroney Date: Sep 12, 2008 09:27
funkenstein gmail.com> writes:
>Assume a sun-like stellar wind with 10^31 particles/second. Assume
>isotropy, and that all the energy goes to gamma rays, none to heat,
>other particles, or other electromagnetic channels (unlikely but an
>upper limit on gamma flux). Take alpha cen as 4 light years away, so
>the sphere with alpha cen at the center and us on the edge has a
>surface area of 6*10^33 meters. This would give us an expected flux
>of 511keV gamma photons from alpha cen of ~0.002 ph/m^2/s. That's
>2*10^-7 ph/cm^2/s, well under galactic background.
This reminds me of a puzzle I heard once. We get in communication with a
civilization from a distant stellar system. They want to send a visitor
to earth. We reply "Wait - we want to be sure that you aren't made of
what we call antimatter - and vice versa. You'll have to perform an
experiment and tell us the results first." What experiment can they (and
we) do to tell if they're made of the same matter as us? Remember, it
can't be something like "what is the charge on one of your protons?"
because they have their _own_ definitions of "positive" and "negative",
we have no idea whether their "positive" charge is the same or different
from our "positive" charge. No interchanging of samples or something like
whether there are lots of 511 keV gammas when they approach our solar wind
(this is also really interchanging samples) Also ignore the lags in
communication time, as if they had a Star Trek type communicator.
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