Ask HN: How can you be sure the world is moving?

You can't. All movement is relative. First, you pick a point of reference and call that not moving, then everything else is moving in reference to that. There is no point in the universe that is not moving independent of choosing a point of reference.

This is actually related to Galileo. What he said is irrelevant. What he did was pick a point of reference without a reason, the sun, and that was of course immediately denied by both the church and all science to this day.

Speaking practically, when calculating satellite orbits one uses a two body universe, Earth and Moon. To include the Sun, other planets, the Milky Way or distant galaxies would be inefficient and not yield a result different enough to bother. So many people legitimately treat the Earth as the center of the universe every day and to do otherwise would be inappropriate.

Science of course, pretty much since G went out on a limb, says that planets don't orbit. All heavenly bodies are affected by all others based on formulas that we've got figured out pretty accurately. But we teach orbits because the additional forces are tiny enough that orbits work very well.

If "moving" includes "rotating": We can tell the Earth is rotating because its shape approximates an oblate spheroid, not a sphere.

I think the sun's gravity is going a good job of that.

Thanks for your answers