00:00When you think of the big bang, what do you picture? A huge explosion with light and matter
00:05flying outward from a single point? That's not quite right. The big bang was more like a hot
00:11dense ball of everything suddenly getting a lot bigger, stretching and expanding until it's much
00:18cooler and far less dense. So here's what we actually think happened in those first few minutes
00:25after the universe began. For starters, the big bang wasn't really a bang at all. It wasn't even
00:31really an explosion. It was more like a rapid inflation that brought our universe into existence
00:38from an extremely hot, dense state. But where did this idea come from? How do we know that's what
00:45happened? Well, it helps to take a step back and look at some of the evidence for how the big
00:50bang
00:51came to be the big bang, the prevailing model of the universe today. Known unsurprisingly as the
00:57big bang theory suggests that our universe started off small and incredibly hot and dense before
01:03rapidly inflating to the size we see today. This idea has been fleshed out over decades thanks to
01:09observations by astronomers, physicists, and cosmologists, as well as mathematical modeling.
01:16As an example, one observation that helped scientists formulate their model was the redshift
01:23of distant galaxies. When you hear a siren approaching you and then passing by, the sound
01:29waves get compressed as it comes toward you and then expand once it's passed, shifting the pitch
01:35up and down. Light waves behave similarly when they move through space. As distant galaxies move away
01:42from us, their light gets stretched, shifting the waves to longer, redder wavelengths, just like that
01:50a slight-at-ambulance siren, andbros of those of you have tuned totally more.
01:51How soon did you see the amplified ambient siren when they come out with them?
01:51And the sound of the reflected
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