> Rather it's that the rate of expansion of the universe is accelerating, so that we're moving away from parts of it faster than its light can cover the distance to us. It will never reach us.
It's actually even worse than that. Because of the accelerating expansion of the universe, over time the part of the universe that we can observe will get smaller, allowing us to see less and less of it. Eventually, all that we'll be able to see is our own local group of galaxies, where gravitational attraction will win out over the universe's expansion. However, this won't really be a problem for a few billion years.
I know it is considered increasingly unlikely, but: What a parallel to flat Earth ideas people had (...) hundreds of years ago, until they realized we are on a sphere. Maybe in a few hundred years people will laugh about our limited ideas of the universe as well.
This is wrong by an order of magnitude. It was already known thousands of years ago that the Earth is more-or-less spherical. The idea that people in recent history believed in a flat Earth is a myth.[0]
>The idea that people in recent history believed in a flat Earth is a myth.
The way you've worded this, you're incorrect. There are people today who believe in a flat Earth, crazily enough.
Of course, the idea that most of society (namely educated people) believed in a flat Earth is a myth. From your link:
"The myth of the flat Earth, or the flat earth error, is a modern historical misconception that European scholars and educated people during the Middle Ages believed the Earth to be flat."
What the typical serf working in the fields thought about the shape of the Earth is probably unknown.
If we had to guess (of course not good research to be guessing): The typical person working on a field probably believed what the church told them the world looks like. If they ever heard about being on a sphere, they would probably laugh and point to the horizon, saying: "How can Earth be a sphere? Don't you have eyes to see? Look into the distance, all is flat!" and any kind of argumentation, that it is simply so huge, that one cannot see it, would seem to them like a made up story, a lie to further some hidden agenda the explaining person has.
That does not really detract from my comment though. Thousands of years are also hundreds of years. Just more hundreds. So if we are getting technical about that, I don't think it is wrong what I wrote. Still, thanks for putting the time frame a bit clearer.
It's actually even worse than that. Because of the accelerating expansion of the universe, over time the part of the universe that we can observe will get smaller, allowing us to see less and less of it. Eventually, all that we'll be able to see is our own local group of galaxies, where gravitational attraction will win out over the universe's expansion. However, this won't really be a problem for a few billion years.
Relevant Kurzgesagt video: https://www.youtube.com/watch?v=uzkD5SeuwzM