Quote:
Originally Posted by rcglinsk
[snip]
Anyway, I think most people who say observation would not mean an estimation of how things were 13 billion years ago. Especially because arriving at those numbers requires applying a lot of other theories. For example the theories of how galaxies formed or how stars produce heavy elements.
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Correct me if I'm wrong but all we can readily measure is rotational velocities of visible objects. That can tell us about a centripetal force, but it cannot tell us if that force is 100% gravity allowing a conversion to mass.
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rcglinsk, you're wrong, big time ... and we covered this in an earlier exchange.
The "
rotational velocities of visible objects" are only estimated by "
applying a lot of other theories"!
It seems that, for you, some theories are quite "the real thing" (rotational velocities, visible objects, centripetal force, mass, ...), but others are not.
Or do you not realise just how inextricably intertwined these are, with theories? If I may recommend something: please re-read
Ken G's post, very, very carefully.
Quote:
[...]
Also, you mentioned the hubble deep field and how the movement of those galaxies on the horizon is nearly imperceptible. Is that not true for any stellar object a sufficient distance away? Doesn't that only set a minimum distance and not say much about the particular distance?
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Did you read the links provided, re "distance"?
Do you have any questions concerning the disconnect between your (apparent) intuitive understanding of "distance" and what the term means in astrophysics?