Shouldn't any radiation from the Big Bang just have radiated away ahead of us?

Question

Why can we still "see" this background radiation? We took a lot longer to get here than any radiation would, right? I can't wrap my head around this.

Answer 1

Scientists have accepted the Big Bang theory. As they discover more and more things, the tendency is to identify them as something that proves their theory.

Answer 2

the cosmic background radiation is in the microwave wavelength range of the electromagnetic spectrum (ers). Now, microwave wavelenths are long waves (near 30cm) which therefore hold less energy than shorter waves such as gamma rays. Also, because of the first law of thermodynamics - energy cannot be created nor destroyed, only changed in form - then that means that all of the energy in the universe also had to exist in a much smaller volume near the beginning of the universe. This would have been a much hotter and more dense universe (think gas law - PV=nRT) which would have meant higher wavelengths of radiation exisiting. Now, as the universe expanded, the amount of energy remained the same, but began to congeal into matter, and the very small radiation wavelengths began to expand uniformly. Now, the key here is to realize that there is NO absolute center of the universe. That is, there is no single location I can point to and say "That is the center of the universe." But rather everywhere expanded equally from everything else. That is, every single point in space is the "center", therefore, if everything expands equally from each other, then there is no radiating ahead, because everything is ahead of everything else. So rather, there is just more space for the waves to expand in.

Yes, we did take longer to get here than radiation, but as hopefully you now see, that it is in the microwave range uniformly at this point in time, but will eventually expand into extra-long radio waves, but that should take hundreds of billions of years.

Answer 3

Well - first you have to realize that the "big bang" is a theory of earth's origins, so the background radiation is also an assumption. So one reason you can't "see" the background raditation is because it's not there! Another reason is that if it really happend billions of years ago (all supposing here), then the radiation has dissapated and there is nothing to see. Just don't forget, in the issue of earth's origins, there are like a thousand theories of how it got started - none are proven, it's a mystery. I know, scientists don't like mysteries. I'm a scientist and I don't like the unknown and the thought that there are some questions that can't be answered. That's life.

Answer 4

1. How can you radiate away from yourself? Presumably we are part of the radiation from the Big Bang, just coalesced into matter.
2. Which direction is ahead? The reference link has a really good explanation of why every point in the universe observes itself as being the center.

http://www.exploratorium.edu/origins/hubble/tools/center.html

Answer 5

The cosmic background microwave radiation actually comes to us from the far boundary of the observable universe. This is the "surface of last scattering" where matter and energy become separate entities, 13.7 billion years ago, and now located at an apparent distance of 13.7 billion light years. So the radiation happened incredibly long ago, incredibly far away, and is only just now reaching us. (Of course, it's been reaching Earth for as long as Earth has existed. 4 billion years ago, it was radiation from 4 billion light years closer and 4 billion years more recent.)