Question: Where did scientists get the info from the big bang

Remsha Afzal answered on 13 Nov 2018:

Great question! So basically when we look at the night sky with our eyes, the stars we see are the ones in our own galaxy. But scientists can use powerful telescopes to see other galaxies like our own- they are much, much further away than the stars.They looked closer at those galaxies, and realized that almost all of those galaxies are moving away from us – some at very high speeds!
So if the galaxies are moving away from us, that means that the Universe is expanding right? Think of a cake in an oven that’s baking, it slowly expands from just the batter till its big and fluffy.

So that’s the same concept with big bang. if we know the universe is expanding, that means ages ago it was closer than it is now. And if you go back far enough, then there was a moment in the past when all the matter in the Universe was packed into a point and expanded outwards. That moment was the Big Bang. Astrophysicists can even work out when it happened, from the current size of the Universe and the speed at which it is moving – about 14 billion years ago!