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The Question

(Submitted February 20, 1997)

In light of your answer regarding light life, would it be theoretically possible to construct a container that would contain and preserve light energy for use later? As a follow-up to the question regarding the big bang, if the energy that was emitted in the form of light at the time of the big bang has a direction away from the center, how is it possible to observe it? Are we observing the cosmic energy that it leaves behind as it passes each point in space or is that energy emitted by the expanding sphere in a direction opposite to its expansion?

The Answer

Yes, it would be theoretically possible to construct a container to preserve light energy. It would have to be made of a material that was perfectly reflecting so that when the light hit the walls, it would bounce off without losing any energy.

In reference to the Cosmic Microwave Background (CMB), when we called it a gas, it was not just an analogy. The air in a room has no "direction" or "source", and the same is true for the photons that make up CMB. The cooling of the CMB since the Big Bang is determined from essentially the same equations that you would use to figure out how much any other gas cools when it expands.

No, the cosmic background should not be thought of as emanating from a single central location in space. Remember to think of it as "gas" of photons that has no "direction" or "source", just as the air in a room. Hence, the cosmic background permeates the entire Universe uniformly In essence, the radiation expanded outward with the Universe as the Universe expanded. The background radiation observable to infrared detectors by looking at any empty region of space (i.e. a region without a star or a galaxy).

Jim Lochner
for Imagine the Universe!

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