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$\begingroup$ Upvoted, but: The stars in our galaxy do not orbit the center of mass of the galaxy; while they do move around the center of the galaxy, they move way too fast, and the observed rotation speed curve does not match what would be expected from Kepler's laws. This is the problem to which cosmologists have assigned the name dark matter. $\endgroup$

AlexP
– AlexP

2025-10-05 23:38:13 +00:00
Commented yesterday
3

$\begingroup$ @AlexP a little strong to say stars don't orbit the CoM of the galaxy when it is, in fact, the belief that they do which motivates talk of dark matter. Better to say that at a galactic scale we don't really have a good understanding/accounting of matter and energy. $\endgroup$

nitsua60
– nitsua60

2025-10-06 12:42:56 +00:00
Commented 13 hours ago
$\begingroup$ While all this is true, these relative changes happen on epochal scales. Not only do biological beings not live that long, but nothing they create lasts that long either. For reference a Galactic Year is about 225 Million earth years, making life on Earth only 17 galactic years old. 22 Galactic years from now the Milky Way will collide with Andromeda, screwing up all maps anyway. $\endgroup$

T.E.D.
– T.E.D.

2025-10-06 22:07:40 +00:00
Commented 3 hours ago

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