View Full Version : light in the universe

2009-Mar-03, 01:46 AM
Here is my question. If all the matter in the universe was created at the big bang, was all the light in the universe created at that same moment.

2009-Mar-03, 02:06 AM
Light would have been created, destroyed, created, destroyed, ... very much so. Continue like so to 380 000 years after the big bang, and now whatever light is being constantly produced stops being destroyed. I wonder how much light was being produced per second after the 'last scattering' compared to before.

So the short answer is no. The long answer is yes, since all the light was basically set free at the same time.

2009-Mar-03, 05:04 AM
Light is pure energy. You can get light from matter by having electrons drop from higher shells to lower ones and in the process releasing a photon of a given energy level.

So...Yes all the light was created at the big bang indirectly.

But better answer is No. New photons are always being created and destroyed. When a photon of a particular energy level hits an appropriate atom that has an electron that can just up to a free spot on a higher shell using that amount of energy, or the amount of energy is enough to completely kick the electron out of the atom, then the photon is absorbed and the electron gains that amount of energy. Eventually the electron will try to get to its ground state and in doing so release one or more "new" photons.

2009-Mar-03, 01:42 PM
Are you thinking of the Olbers Paradox?

The universe is infinite, so there is a star in every possible direction.
Every star shines brightly.
So the night sky should shine as brightly as a star.

Obviously it doesn't - why?
Lots to read up on this; suggest you start with the Wiki: http://en.wikipedia.org/wiki/Olbers'_paradox