Some easy questions about space

[luke]

what is background radiation and is it everywhere?

[lemur]

what is background radiation and is it everywhere?

It is my understanding that all matter emits some level of radiation, no matter how cold. Also, radiation travels through a vacuum and gets re-emitted or conducted by matter it reaches. Thus if by "everywhere," you mean everywhere that matter is within visible range, then the answer would have to be yes unless it was somehow possible to shield some vacuum region from all distant radiation. Still, even if there was some reflective material that could be used to do this, it would still be impossible, as far as I know, to reduce the material of the container to absolute zero, so while it may be blocking outside radiation from entering, it would still be radiating its own heat into the interior of the container.

 

But what about black holes? Supposedly their gravity is strong enough to prevent any radiation from escaping; but they also supposedly emit Hawking radiation as a result of a complex processes that enables energy to be generated outside the event horizon. I can't think of any other possible situations in which absolutely no radiation would be present.

Edited February 25, 2011 by lemur

[Mr Skeptic]

http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

[Airbrush]

what is background radiation and is it everywhere?

 

In astronomy they refer to the "cosmic microwave background radiation" which is very uniform from every direction. It is so red-shifted that it is believed to originate from the moment the universe became transparent, less than 400,000 years after the big bang.