Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

2 questions

  1. Mar 16, 2007 #1
    i have 2 questions:
    1. what is the difference between astronomy, astrophysics and cosmology?
    2. what did Alan Guth mean when he said, "The universe is the ultimate free lunch"?
  2. jcsd
  3. Mar 16, 2007 #2
    If you ask me, the term astronomy refers anything to do with "heavenly objects" in general. It includes you or me looking at a fuzzy patch of a nebula through a small refractor to people publishing papers in Nature.

    Astrophysics:Understand the dynamics of stars, galaxies, inter-stellar/galactic medium. This probably includes planetary dynamics/geology, as well.

    Cosmology: Studying the structure and evolution of the (visible) universe as a whole.

    Of course, these days, the terms are more or less used synonymously. How many times have you heard Hawking being described as the "the world's foremost astrophysicists."

    I really don't know. I've managed to erase most of the stuff I have read from popular-science books, so I think you should read his book 'The Inflationary Universe'.
  4. Mar 16, 2007 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    (1) Neutrino defined it well. I'll just note that astrophysics and cosmology can be considered subsets of the general topic 'astronomy' (but I agree with neutrino that 'astronomy' often refers to mapping/charting of astronomical objects whereas astrophysics gets into the more in-depth dynamics of it). And as for the 'evolution' (cosmology), that can refer to the origin, changes to, and ultimate fate of the universe.
    (2) I too don't recall the exact context in which Guth used that phrase...and I don't see 'free lunch' in the index of the book either :)...but I suspect it was along the lines of how the entire universe (thus, 'ultimate') seems to have originated from next to nothing.
  5. Mar 17, 2007 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

  6. Mar 18, 2007 #5
    Astronomy: The Universe in a nutshell
    Astrophysics: The comical attempt of Physicists to apply Physics to Astronomy to describe phenomenon in the universe.
    Cosmology: Like archeology, but you get to use a radio telescope and your subject is the Universe.

    Mmmm.... Free food!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook