[davidk (OP)]

Hi,
What is the difference between astronomy and cosmology?

[chris]

Okay, I'll give this a go:

Astronomy is an observation-based discipline that looks at the Universe and uses various tools to make measurements which may, in turn, inform, support or refute predictions made by theoreticians including cosmologists. The latter are physicists who uses models, maths and observations to build an understanding of how the Universe behaves.

[evan_au]

Wikipedia has pages on both topics; It describes cosmology as a branch of astronomy, but that is rather subjective:
https://en.wikipedia.org/wiki/Astronomy
https://en.wikipedia.org/wiki/Cosmology

What surprised me is that the word "cosmology" was coined in 1656, before we knew about galaxies, the lifecycle of stars, expansion of the universe, Dark Matter, etc...

[tripathiankush]

Astronomy is "The science which treats of the constitution, relative positions, and movements of the sublime bodies; that is, of the considerable number of bodies in the material universe outside of the earth, just as of the earth itself in its relations to them

Cosmology is "The science or hypothesis of the universe as an arranged entire, and of the general laws which oversee it. Likewise, a specific record or arrangement of the universe and its laws. "

[Bill S]

 Astrology was a fanciful study of the “heavens”.
 
Astronomy developed from astrology and is a scientific study of the observable Universe.

Cosmology developed from astronomy, and is a fanciful study of what the universe might be like.

Nihil sub sole novum.