

Ask HN: How can you be sure the world is moving? - z3bra


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justintocci
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.

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

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

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z3bra
Thanks for your answers

