system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do we continually observe background radiation that was created very soon after the big bang. I would assume that the light from that period would be limited in quantity and it would eventually have all passed us so it would stop being visible.
gpt
The idea that light from the big bang could have "passed" us implies that the Big Bang happened somewhere else and came towards us. In fact, the Big Bang happened everywhere that existed, ie the tiny point at the start. That everywhere has got bigger but it is still all the universe that has ever existed and ever will, just more spread out. So we are still inside the expansion from that point, as is all the radiation. The spreading out has just cooled it to the temperature we now measure.