[deleted] t1_j4kkfuq wrote
[removed]
BrooklynVariety t1_j4lvzg4 wrote
> Stuff farther away moves faster away than stuff closer to us. So we know relative distances to us.
I blame this on poor science communication, but I see people talking about redshift being used to measure distances in all the wrong contexts.
Redshift ONLY works when measuring the distances to GALAXIES outside our local group. So relative velocities are meaningless even when talking about andromeda, much less stars in the milkyway.
Puppy-Zwolle t1_j4mxv09 wrote
I was not talking red shift. This is just one of the methods. Not for our neighborhood but does paint a picture we can apply to our neck of the woods.
BrooklynVariety t1_j4n0tdd wrote
Not really, the whole “things moving faster further away from us” only applies to the things furthest away from us, not at all our neck of the woods. The physics that governs that phenomenon is irrelevant within the local group and certainly within our galaxy, so it doesn’t really tell us anything about how we map our own galaxy.
Oknight t1_j4mpblo wrote
Problem is, what do you mean by the "size" of the galaxy? Where is the edge of a cloud?
Puppy-Zwolle t1_j4myljc wrote
You mention one of the issues. This one is among the rather fluid definitions like; ''How big is a planet ''and ''How small is a moon''.
Size is a relative as big and small. The moon is smaller than the sun and bigger than a tomato. In galactic perspective that's already pretty close.
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