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Is Cosmology a Branch of Physics or Astronomy?

  1. Feb 23, 2015 #1
    I have always considered cosmologists to be physicists because I noticed that cosmologists usually apply (Correct me if I'm wrong) general relativity. They seem to take approaches similar to those of physicists. Astronomy is the study of celestial objects, while cosmology is the study of the universe as a whole. While many achievements and studies in cosmology have been aquired through observations done with telescopes, that doesn't exactly imply astronomy, does it?

    So is it a branch of physics or is it a branch of astronomy?

    Oh, by the way, I'm not a cosmologist or physicist; I'm just a prospective physics major.

  2. jcsd
  3. Feb 23, 2015 #2


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    Astronomy is usually considered a branch of physics as well. Granted, you don't have to know very much (if any) physics to do amateur astronomy. But people who work as astronomers are usually involved in investigating the physical properties of objects in the universe, such as planets, stars, galaxies, and galaxy clusters. There's quite a lot of overlap between astronomy, astrophysics, and cosmology.
  4. Feb 23, 2015 #3
    They are all branches of physics, physics 100 years ago was a simple distinction to make in relation to the other sciences but with the exponential increase in the amount of knowledge on these subjects physics is broken down into many overlapping fields. Theories and concepts have applications in a wide variety of these sub-fields.

    With the evolution of knowledge, especially owing to Quantum mechanics, came the evolution of highly specialized fields that pretty much occupy the knife edges between disciplines.

    Take for example how development of the Pauli Exclusion principle lead to Quantum chemistry (an understanding of the reason for the structure and properties of the elements of the periodic table). There is also an emerging field referred to as Quantum biology in which the quantum mechanics of biological processes (such a photosynthesis and brownian motors) are analyzed.

    As science progresses i would expect that, just as the distinctions between the sub-fields of physics are seemingly forming a continuum of knowledge, the fields considered distinct from each other (such as chemistry and biology) may become increasingly interrelated by new theories.

    As a prospective physics major i would suggest you also keep in mind the fact that mathematics is the all important back bone to the sciences. You can no longer separate mathematics as a distinct discipline from physics as well as history allowed. Modern discoveries owe their actualization increasingly to a sort of conglomeration known as mathematical physics.

    However tangential that last point may seem to the question, i just wanted to instill in you the importance of a mathematical skill set when considering physics as a subject choice. Since majority basic education tends to try and make a clear distinction between them.
  5. Feb 23, 2015 #4
    Can you still become an astronomer today? Or is everything related to astronomy now under "astrophysics"?

    I'm currently taking calculus as a senior in high school. I love mathematics; it's like a puzzle. However, this thread is not the place to discuss this; otherwise, it will go off-topic.
  6. Feb 23, 2015 #5

    The point i was making was that it is semantic. Looking at courses entitled Astronomy or Astrophysics, you'll find they have almost exactly the same content. Amateur astronomy is highly accessible these days. Also, the basics of any physics course will teach you what you need to know to understand basic astronomy (e.g. optics, basic cosmology, basic EM for understanding imaging)
  7. Feb 23, 2015 #6


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    Certainly. It just means you focus more on the observational side of things.

    Good! A good foundation in calculus is an excellent foundation for probably 90% of the math in physics, if you're interested in going that route.
  8. Feb 23, 2015 #7
    Oh no, I'm not planning on astrophysics. I'm looking towards either medical physics or experimental particle physics.
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