I can’t get my head around how we measured the radiation from the Big Bang in order to discover how old the universe really is. How does that specific radiation differ from many other types of radiation? Newest findings suggest that the age of the universe has been mistaken not because of an error in calculations, but because of some kind of error in the understanding of the nature of cosmos itself. While I will probably not think up anything remotely usefull to anybody, I’d like to understand this part – please help a humble redditor.
The CMB is detected by its light just like other things we detect with telescopes, it’s just not visible light. When you look in-between stars and galaxies with an optical telescope space appears completely dark but if you have a sensitive enough radio telescope you can pick up a faint background noise, or glow, coming from all directions. That glow is the CMB.
Imagine the big bang less like a bomb, spitting out debris into empty space, more like a balloon being blown up.
Now mark two points on a balloon as you blow it up, as the balloon expands the marks stay where they are (as in they’re on the same atoms that make up the balloons skin) but they appear further apart.
Now imagine you’re an ant trying to travel between those two marks as the balloon expands. This is what light is.
Now imagine a whole colony of ants swarming around the balloon as you blow it up, even though your balloon is getting bigger there are still ants moving around everywhere.
The balloon represents space, the ants represent the photons.
The cosmic microwave background radiation is what we think is a remnant of the Big Bang because it’s generally uniform – i.e. it’s coming from everywhere, and not one particular source. This suggests that it happened as a result of the Big Bang’s expansion, and as the universe expanded, this radiation became thinner, less dense and colder and allowed other elements to form and bind. But that’s how it’s different from other sources as far as I can tell – other radiation comes from specific sources we can identify, like a star or a black hole, etc. CMB is generally everywhere and mostly uniform, and consistent with the expansion of the universe.