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

What is the cause of gravity?

  1. Sep 17, 2008 #1
    I am a bit of Physics noob and I am reading some of Newton's stuff. But I am trying to figure why gravity exists.
    There is the theory of gravitons,but aren't they impossible using Stranded Model?
  2. jcsd
  3. Sep 17, 2008 #2


    User Avatar
    Homework Helper

    If I was stranded on a desert island that's the model I would use--the Stranded Model! Yup, no gravitons for me in the ol' Stranded Model.

    Good luck and cheers.
  4. Sep 18, 2008 #3
    Physics is not really concerned with explanation of Why things exist. We simply try to understand it, describe it mathematically, design a model, and be able to predict future behavior. Your question is more philosophy then physics.

    Simple answer as far as I am aware is that we simply don't know. I mean... why do electrons exist? They just kinda do.
  5. Sep 18, 2008 #4
    I mean why does gravitational forces exist. For example the Sun has a gravitational pull on the Earth....Why?

    I mean Standard Model...
    Last edited: Sep 18, 2008
  6. Sep 18, 2008 #5
    maybe everything is just a simulation on some cosmic supercomputer and therefore everything everywhere can be explained by transistor logic. but is that really the sort of answer you want? ultimately explaining the universe as we know it will require some minimum number of axioms. there is a limit to how far one can simplify things.
  7. Sep 18, 2008 #6


    User Avatar

    that's not correct. whenever a new and better theory supercedes and older one, you can say that the effects described by the old theory happen because of the law or descriptions contained in the new. that is answering a "why" question. it's not much different than the "how" question.

    philosophy is about everything. the discipline of physics is contained in that set. not all of philosophy is about physics. if the "why" question is answered with "because God made it so", that is clearly not about physics.

    how about why do protons exist? are you leaving the answer as "they just kinda do"?

    gravity exists because spacetime is curved by the presence of matter (and the equivalent of energy). why spacetime is curved by the presence of matter is a question to be addressed by later generations. (or maybe the present regarding string theory, but i know so little about string theory, i dunno how it would explain it. and, of course, it might be that string theory is no good, but it's worth exploring.)
  8. Sep 18, 2008 #7


    User Avatar
    Science Advisor

    If you're reading Newton, it won't be long before you come across his quote, "...I leave it to the reader to speculate as to the mechanism by which this force is propogated...", (or words to that effect; I'm pretty sure I messed up the wording there).

    It was Einstein who later took him up on that statement, and tried to figure out what gravity is "made of." He's the one who proposed that gravity is not, in fact, a force, but rather a condition of the geometry of spacetime. That's where we get the picture of curved space that we all know and love today. This model, which envisions space as something that can be curved or dented by the presence of mass, works pretty well, and makes accurate predictions in the exact areas where Newton's "force" model does not.

    Of course, this begs the question, "why does space curve or dent in the presence of mass?". That's one for which we don't yet have even a decent geuss, but then we don't exeactly know why mater has mass, to begin with. Maybe if the LHC produces the Higgs Boson, we can get some ideas by observing it. Mass and gravity seem to be directly linked, so if we egt a better udnerstanding of the partical responsible for mass, it stands to reason we might get a better understanding of gravity.
  9. Sep 18, 2008 #8
    Supporting upstairs.
    Einstein's general relativity theory will give you much help. I don't also believe in action at a distance.
  10. Sep 19, 2008 #9
    A scientist named Weber had a theory about gravity waves. In the Smithsonian museum of science his apparatus was on display in the '80's and might still be. It consisted of a 3000 lb. cylindrical aluminum block on bearings. I saw it in the '80's. One of my profs in the '70's was fascinated w/ gravity waves and I took a limited interest in it at the time. But I don't think Dr. Weber's aluminum ylinder resulted in any breakthroughs.

    I'd suggest googling using key words " Weber gravity waves ".

    It might turn up something. Also, general relativity is a good source of info regarding gravity.

    What causes anything is a tough question. If we knew what caused gravity, say a graviton, then the next question to immediately follow is "what gives a graviton its properties?"

    There is always a smallest wave/particle/energy that can be detected due to the limited resolution of our instruments. When our ability to observe is more refined, we will know more. I don't think anyone has actually determined what causes gravity, as well as the other forces. BR.

  11. Sep 19, 2008 #10
    What I find interesting about gravity is that without it, our sun, the other stars, planets, black holes, etc... could not exist in their present form.

    It's as if gravity, whether or not some type of fundamental force, seems to be a fundamentally required characteristic of many important aspects of our universe.
  12. Sep 19, 2008 #11
    Yes, but without the strong force, no element besides hydrogen would exist; without that, our sun, the other starts, planets, black holes, etc... could not exist in their present form. o:)

    You could the same about much of physics. I think the only thing special about gravity is how magnificently difficult it has been to truly understand it.
  13. Sep 21, 2008 #12
    I just find it odd, that we have a good atomic explanation of nuclear and basic electromagnetic forces...but not gravity.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook