What Was It Like When Planet Earth Took Shape?
“There was almost certainly a high-energy collision with a foreign, out-of-orbit object that struck our young Earth in the early stages of the Solar System, and that collision was required to give rise to our Moon. But it was very likely much smaller than Mars-sized, and it was almost certainly a sturdy strike, rather than a glancing collision. Instead of a cloud of rock fragments, the structure that formed was a new type of extended, vaporized disk known as a synestia. And over time, it settled down to form our Earth and Moon as we know them today.
At the end of the early stages of our Solar System, it was as promising as it could be for life. With a central star, three atmosphere-rich rocky worlds, the raw ingredients for life, and with gas giants only existing much further beyond, all the pieces were in place. We know we got lucky for humans to arise. But with this new understanding, we also think the possibility for life like us has happened millions of times before all throughout the Milky Way.”
One of the deepest existential questions we can ask about the Universe is how, after more than 9 billion years, all the phenomena in our cosmic history led to the creation of planet Earth. Going from an environment where stars were actively forming to one where the Sun, Earth, and all the other planets were in place is a daunting task for people who create scientific simulations of our early environment, and involves gravitational interactions, planetary migrations and ejections, and even enormously energetic collisions between planets and proto-planets.