Astronomy

[ydoaPs]

What is the difference between astronomy and cosmology?

[Sayonara]

Literaly speaking, astronomy is 'of the stars' and cosmology is 'of the cosmos'.

[ydoaPs]

i know etymology, i just want to know wat the difference is because this thread is in "Astronomy and Cosmology". so wat is the difference?

[Sayonara]

Astronomy deals with the universe in terms of stars and their movement etc.

 

Cosmology deals with everything else that's out there.

[ydoaPs]

Astronomy = stars, cosmology = planets, nebulea, asteroids, etc. ?

[Martin]

yourda,

 

there is a conventional distinction---but we are free to use the words however we want

 

the conventional distinction goes like this:

cosmologists study the parameters of the universe

 

like the Hubble parameter (a kind of "expansion rate")

like the estimated age: 13.7 billion years

like the energy density needed for spatial flatness, the so-called

"critical density" which is now estimated at around 0.83 joules per cubic km

 

they want to estimate the density of dark energy

and the density of ordinary (baryonic) matter

 

they want to see how close to spatially flat the universe is, or to see if they can detect spatial curvature (so far it looks flat to them, but there is uncertainty in the measurements and it may have some slight positive curvature)

 

they want to see if it is possible to detect evidence of inflation---there are many different ideas or "scenarios" of inflation and they would like to

be able to distinguish

 

they model conditions at very early times (near big bang) to see which chemical elements formed then and which only formed later in stars

 

here is a mainstream survey article about Cosmology by a prominent cosmologist named michael turner. It is online

 

Turner

"Making Sense of the New Cosmology"

http://arxiv.org/abs/astro-ph/0202008

 

---------------

 

Cosmologists study global parameters which describe the whole universe

(age, temperature and density at certain time, energy density, expansion rate, acceleration of expansion, abundance of various chemical elements)

 

Astronomers study specific objects: galaxies, clusters of galaxies, quasars, neutron stars, black holes seen in centers of galaxies, planets, comets, asteroids, young stars, old stars, big stars, little stars, variable stars, gas clouds, jets, large scale magnetic fields,

 

they study the details. they leave the overall study of the universe and its beginnings and its history and future destiny to be studied by the cosmologists

[swansont]

Astronomy deals with the universe in terms of stars and their movement etc.

 

Cosmology deals with everything else that's out there.

 

There's also Astrometry, which is the measurement of the positions of stars (and everything else) and is important for navigation.