Posted July 20, 2009
If you were standing inside a hollow sphere with a mirrored internal surface, and if you had a light source, what would you see on the walls?
It is a question that is hard to answer because there are several plausible answers.
Much depends on the location of the light source. Let's say it's dead center in the sphere. Then, in an ideal setting, the beam will hit the exact orthogonal and just be reflected back to the center - and further on to the opposite side. In this case you would probably only see two "dots" opposite eachother in the sphere.
If you move the light source off center and off symmetry, any variety of paths is possible. You can split them into two groups though; closed and open paths. A closed path will eventually repeat itself, leading to you seeing any number of illuminated spots like in the first example. An open path will just continue bouncing ad infinitum, illuminating the entire sphere.
If you tried this in practice though, due to everything not being ideal, you'd probably always end up just illuminating the whole sphere, possibly turning yourself blind in the process.
Also, the illumation effect would dissipate over time as more and more energy escape the sphere - no material is in practice able to contain 100% of this energy. If such a material existed - what would happen is another question entirely. You'd probably build up an energy singularity and rip the universe apart, or something.
Now take that answer back to your physics teacher. :D
Post edited July 20, 2009 by stonebro
