We’re almost certain that the Earth and solar system were formed from a giant spinning cloud of gas and dust about 4.5 billion years ago. A lot of rigorous science has been done on this, so its probably true.
The science of planetary and stellar (star) formation is really interesting. We can’t test our theories directly but we can look out into our galaxy and see it happening.
Molly, I guess ultimately it all goes back to the Big Bang. Astronomers can measure that the universe is expanding so they can predict how long ago (nearly 14,000,000,000 years ago!) the universe began. Crazy stuff
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