What are you standing on? What’s it standing on? What’s that thing standing on. Eventually you get to the earth. How did that get here? How did we get on it? How long will it be here? How long will it be hospitable to human life?
These are the questions of astronomy. Whether fortunately or unfortunately, our lives are not long enough to notice what is really going on in the universe. In the scale of the universe we almost don’t exist. There is something really big going on over an extremely long period of time but in the blur of our lives the universe appears to be virtually static. Astronomers are working on a lot of really “boring stuff” but it is all ultimately related to this same question that all of us have wondered about. Where is here?
To the best of my knowledge, the answer is this:
The Big Bang happened and spacetime started expanding and matter began condensing and (ultimately) clumping together. Some of the clumps condensed to the point that they started nuclear fusion and became stars. Before our Sun there was at least one other star that made us — the one that went supernova. We suspect we are born of supernova because of all the heavy elements around us, like the earth, the moon, pancakes, Mars, bowling pins, etc., are not produced in quantity by any other processes we know of. There was no mud in the Big Bang. Stars turn Hydrogen into Helium and Helium into Carbon but heavier elements are fairly scarce in stars. Anyway, so the Big Bang happened, a star was formed (among trillions of others), it went supernova and created a bunch of junk. Our solar system condensed out of this junk. The planets, including earth, condensed out of a big accretion disk that sort of swirled around the newborn Sun. This was roughly 4 billion years ago. The universe they say is roughly 13 billion years old. So the earth has been around for roughly 1/3 of the age of the universe.
Sometime I’ll talk about how the earth is ultimately doomed.