Re: Not quite magic physics

John Clark (
Mon, 23 Aug 1999 10:15:15 -0400

Hash: SHA1

Spike Jones <> Wrote:

>I had two lasers. I wondered how the two beams would effect each
>other. Would they interact like two streams from water hoses?
>I had two lasers intersect and watched the targets. The one beam
>didnt seem to know or care that it had passed thru another beam.
>I never could make the two beams mess each other up.

That's true. A stream of photons from a laser acts differently from a stream of atoms from a water hose because photons have an integer spin and atoms don't. The Pauli Exclusion Principle explains why you can put many particles with integer spin, like photons in the same quantum state but no two particles with half integer spin, like electrons, can be. If photons had half integer spin and thus 2 photons could not be in the same place at the same time then you couldn't see the moon or the stars or even the man sitting next to you. Photons from an object you wanted to look at would collide and be hopelessly scrambled by photons moving at right angles to them. You'd be blind as a bat. Even worse, if electrons and protons had integer spin then there would be nothing to prevent even the earth's weak gravity from collapsing matter into a mathematical point turning the planet into a black hole.

John K Clark

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