> scott wrote:
>> Lasers?
> 
> I don't actually know how those work. I was under the impression that it 
> works by exciting atoms so that they emit photons - much the same way a 
> lump of iron glows if you put it in a hot fire. (But with some mirrors 
> in there to ensure the light only travels in one direction...)

It's not the same thing at all. Laser light is very coherent, i.e. all 
the photons in it have almost the same wavelength. When you just heat 
iron you don't get that at all... And what makes it work is that the 
mirrors build a resonant optical cavity, they are not there just to give 
the direction.

-- 
Vincent

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