Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: sudhir kumar on 06/12/2009 05:54:02
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Can photons collide? If so, what happens when they do?
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Sure.
Cosmic rays collide all the time, and most of the bosons (photons) will mostly miss each other and fall back into their collective quantum states, however, a small part of these photons will not miss each other, and they can create matter.
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No photons do not collide. They can't. "Two photons cannot ever collide. In fact light is quantized only when interacting with matter. If the transverse momentum transfer is large, one or both electrons can be deflected enough to be detected, this is called tagging. The other particles that are created in the interaction are tracked by large detectors to reconstruct the physics of the interaction."Two-photon_physics_1 (http://en.wikipedia.org/wiki/Two-photon_physics#Experiments)"
Here is a nice tutorial about two photon physics."Two-photon_physics_2 (http://www.hep.ucl.ac.uk/opal/gammagamma/gg-tutorial.html)"
What they can do is 'interfere', but only when treated as waves, meeting each other. What you can do to justify an idea of particles (Photons) interacting, is to use their wavelike properties in f ex. a beamsplitter to change their outcome/direction and then perhaps use a slot experiment to prove that they 'still' are particles.
But what you have done then is to mix two different properties, both intrinsic to photons but never the less totally different. The photon when behaving like a particle resembles 'restmass' (Matter) but when treated as a wave resembles radiation.
That is one of the strangest things there are with photons, that they have a 'dual identity'. You might call them the original schizophrenics :)
There are some really 'strange' laws defining what photons/waves can do and not do. And even though we can count on them, and know them very well in some ways, the real reasons behind their behavior is still open for questioning.
As for when photons fluctuate into a charged fermion-antifermion pair (matter/anti matter) then thats a 'spontaneous' fluctuation due to HUP (Heisenberg's Uncertainty Principle) and under that short period they exist other photons can become 'attached' to them.
At least how I understands it. For an example arguing that photons do 'collide' you can look here "Collisions (http://www.madsci.org/posts/archives/2004-02/1077201223.Ph.r.html)"
Remember though that this is his interpretation of the phenomena. And that no matter how long it's been since the idea of them 'not colliding' came to be the opposite is still not proved experimentally. Well, as I know it anyway..
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And, ah yes, this one was fun 'And Higgs Searches:' (http://www.hep.ucl.ac.uk/opal/higgs.html) from 'THE UCL-OPAL HOME PAGE' (http://www.hep.ucl.ac.uk/opal)