Big bang

We are told that radiation from the beginning of time is being detected by Hubble and that gives us an insight into the time of creation of the universe. Please could you explain how if we are indeed picking up ancient radiation from the big bang or creation of the universe era, how we (the earth) got here in the first place to be in advance of the radiation. Surely all radiation that was emitted at the creation must be long gone and we must follow it to our present position in the universe. I’m sure I’m missing some vital aspect of this but I am constantly confused by this reasoning.

Re : Big bang

No, it doesn't follow that traces of something that happened in the past must have disappeared by now.

For instance as a very simple example, take sound that echoes around a cave. It has already left our mouths but we can hear it several times long after it has gone out of our mouths in 'the future'. Or think of a photograph that shows us now how something was in the past.

In terms of the background radiation, this is present throughout space and time, and the radiation has cooled a lot over time. Let's say in year one the temperature was x kelvin, and each year from then the temperature of space from that radiation falls by y degrees, then after n years the radiation is simply x-yn.

You would expect that after billions of years the radiation is almost zero, and indeed the temperature has fallen to only just above absolute zero due to the cooling. So the earth isn't "in advance" of the radiation, whichever way we looked in the night sky we would pick up the background radiation and it would look pretty similar in each direction.