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Astronomy and Cosmology

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: the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties



1 a : a branch of metaphysics that deals with the nature of the universe b : a theory or doctrine describing the natural order of the universe

2 : a branch of astronomy that deals with the origin, structure, and space-time relationships of the universe; also : a theory dealing with these matters


According to these definitions cosmology is a branch of astronomy, but as I read the second definition of cosmology I think to myself, "I thought that was the defintion of astronomy too." Can someone please explain what the difference is exactly. What more does astronomy include that makes cosmology just a branch of it? :assimilated:

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Well, Fenriz, Cosmology is what is the Universe. Not what is in it? What is the universe's shape? What are the building blocks of the stuff inside the universe? What is the nature of the universe? Are there other universes? What is our link to the universe? What is our existance copared to the existance of the universe?


Astronomy is what is inside the universe. Planets, stars, comets, and shaped concrete things that we can detect. Cosmology is the abstraction of Astronomy.


Astronomy is to Cosmology as Biological existance is to philosophical existance.

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I don't know too much about cosmology (I've only a couple published papers in that field compared to the plethora of nuclear physics papers). However, in general, the goal of many cosmologists (NOT cosmetologists, which is what you will find at the beauty parlor) is to measure the macroscopic quantities of the universe and relate them to the matter in it. Some of the key arguments, problems, or observations in cosmology in the past decade have been. The list is by no means comprehensive:

- Age of the universe. This is starting to fizzle out a bit, but still comes


- Cosmic Microwave Background Radiation (CMBR). A big study that

also bleeds heavily into astrophysics and astronomy. Studying this

may help us learn a bit about what we refer to as Inhomogeneous

Big Bang Models.

- Gravity. The unification of this force with the other three fundamental

natural forces, its relationship to the dimension of the universe,

and it's metric (i.e., how we measure it). Deals slightly with what

we call the "decoupling phase."


Astronomy is a very observational science. The astronomers spend a lot of time doing spectrosopy - essentially looking at emission and absorption spectra to see what the stuff in space is made of. It's a very broad field. Some of the hot topics include spectroscopy (especially the very old "metal poor halo stars"), the search for extra-solar planets, and the study of our own sun (especially interactions with the magnetic field) to name but a few.


The fields are not mutually exclusive. They trade information back and forth heavily, and the physicists also rely on astronomical observations for their theories and experiments.


A couple of books on cosmology:

Principles of Physical Cosmology -- by Phillip James Edwin Peebles: not a bad book for someone scientifically oriented.

Gravitation -- by Misner, Thorne, and Wheeler: A great book on (what else?) gravity. Referred to as "the telephone book" by students in the field for its shear size.

The Red Limit -- by Timothy Ferris. A layman's book. I don't like it, but the history is not too bad. Tim Ferris is pretty much a self-absorbed, money-mongerer, but this particular book isn't too bad.

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If you like a simple explanation of theoretical physics and cosmology check out books of stephen Hawking.

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