This probably has the wrong tag on it, for which I apologize. If I’m not mistaken, this is cosmology not just physics.
Anyways, how exactly does the background radiation suggest a universe with a beginning? Couldn’t the same kind of radiation exist in a more static one?
In: Physics
Imagine the universe was like a giant balloon, and a long time ago, it was really, really small and super hot. Then, it started to grow bigger, like when you blow up a balloon. As it grew, it cooled down.
Now, just like how when you bake cookies, the smell spreads out everywhere in the house, the heat from when the universe was tiny spread out everywhere. That heat is still around today, but it’s not hot anymore—it’s cooled down so much that we can’t feel it, but special tools can “see” it, like a kind of glowing light.
This glowing light is called cosmic background radiation, and it tells us the universe started from something small and hot, just like blowing up a balloon starts from something small. If the universe had always been the same size, we wouldn’t have this leftover heat spread everywhere. That’s why scientists think the universe started with a “Bang” and has been growing ever since!
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