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Particle Creation and Spin
Name: James
Status: student
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
A buddy and I got into a debate late one night while on
guard duty here in Iraq. I know I have heard this somewhere but I
can't seem to find the proof I need to show that I am right. The
question is, do two particles created at the same moment have
similar spins and do they maintain that similarity despite the
distance between them? So if one were to have a spin of one
"direction" and suddenly changed by an outside force its brother
would respond and change its own spin even if it were on the other
side of the galaxy. Now I might be mixing star trek with real
science but I could swear I heard something about that back in high
school physics. Thanks for any light you an shed on this.
Replies:
I think you are thinking of the concept of 'entangled' particles. Quantum
physics predicts that certain particle decay events will create 'entangled
particles' whereby two mirror-image particles are created, with opposite
properties (e.g. momentum, spin, etc.). A weird feature of quantum physics
is that the particles are identical until you observe them (they do not
instantly acquire their ultimate spin state). When observe the spin of one,
it coalesces into its spin state, and the other into the opposite spin
state. Before the observation though, they're an equal mix of both states.
Here's some more detailed info:
http://en.wikipedia.org/wiki/Quantum_entanglement
So, by observing one, you 'force' the other into one state instead of its
previous 'mixed' state.
Related is the EPR Paradox (named for its 'inventors', Einstein, Podolski,
and Rosen). Einstein hated this 'action at a distance'. EPR came up with a
thought experiment to try to 'disprove' this crazy quantum physics. If you
separate these entangled particles by a large enough distance, and then
observing one causes a change in another very far away, then you have
information being transmitted faster than light, they reasoned. The paradox
it turns out is not one at all -- but I will let you read about that
yourself...
http://scienceworld.wolfram.com/physics/Einstein-Podolsky-RosenParadox.html
,among many other sites.
Hope this helps, and THANK YOU for your service to our country.
Burr Zimmerman
James,
What you might be referring to is quantum entanglement. You can find a
icely detailed article here:
http://en.wikipedia.org/wiki/Quantum_entanglement
Matt Voss
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Update: June 2012
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