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2Physics Quote:
"Can photons in vacuum interact? The answer is not, since the vacuum is a linear medium where electromagnetic excitations and waves simply sum up, crossing themselves with no interaction. There exist a plenty of nonlinear media where the propagation features depend on the concentration of the waves or particles themselves. For example travelling photons in a nonlinear optical medium modify their structures during the propagation, attracting or repelling each other depending on the focusing or defocusing properties of the medium, and giving rise to self-sustained preserving profiles such as space and time solitons or rapidly rising fronts such as shock waves." -- Lorenzo Dominici, Mikhail Petrov, Michal Matuszewski, Dario Ballarini, Milena De Giorgi, David Colas, Emiliano Cancellieri, Blanca Silva Fernández, Alberto Bramati, Giuseppe Gigli, Alexei Kavokin, Fabrice Laussy, Daniele Sanvitto. (Read Full Article: "The Real-Space Collapse of a Two Dimensional Polariton Gas" )

Thursday, February 10, 2005

Physics: from Electron to Universe

... and what about your cellphone or the large TV in your living room?

In 1897 .. when J. J. Thompson conclusively discovered electrons,
many might have wondered what could be the use of learning about
such small particles ... a few millions of which can be accomodated
on the tip of a needle.
[Electron's 'classical' radius is about 2.8 X 10^(-15) meter
which means you need to divide 2.8 meters by 1 million billion.
Why 'classical?' - Be patient. We'll explain that later]

But within a few decades the world got revolutionized mainly with
the use of electricity (which is nothing but flow of electrons in wires)
and the great discovery of semiconductors in which energy of electron
is controlled in such a way that the device can be assigned to do
various kinds of logical operation and used to make wonderful
things ... like radio, T.V, telephone .... computer .... microwave oven..
Our modern day life is so much dependent on electrons that we
almost forget that these is being put to work day and night like slaves
by our technology experts for helping us to communicate and do
important jobs and provide us comfort!

Electron is a true revolution in mankind's history.
Alas! We never celebrate it!


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