How can we say there is no time before Big Bang? Matter i think i understand but how time cant exist before big bang?
In: Planetary Science
We don’t know.
All we know is that the universe, as in the space (and time) we exist in is expanding. That means if you go back in time, the universe used to be denser than what it is now.
Imagine you’re standing in a room that expands out to the horizon, infinitely. Your only reference point are the tiles on the ground inclufing the one you stand on. You can see other objects around you, very far away, and as time passes the tiles in which everything sits grow. Do it backwards now; despite the room being infinite, the objects in the room are now getting closer and closer to you as the tiles they rest on shrink. Eventually, they are within reach.
These tiles aren’t just space, but also time. So time itself was “smaller” in the early universe. Go far back enough, and both time and space are so small that the universe has infinite density, kind of like a black hole. It’s also infinitely hot, because everything is packed together so tightly there’s no room for particles to move without crashing with one another.
At this point, physics as we understand them no longer work, so no point in trying to go further to the past. It’s kind of like trying to divide by 0, you can get close to it by trying 0.01, then 0.0001, then 0.00001 and so on. Our physics can get very close to T=0, but not to the exact moment the universe “began” (if that’s even a thing)
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