Turn on thread page Beta
    • Thread Starter
    Offline

    13
    ReputationRep:
    (Original post by mik1a)
    Are you sure about the part that gluons don't contribute to gravity though? If I could find it, I'd quote Brian Greene when he said something along the lines of "since gluons are very energetic, they contribute to the gravitational pull of a nucleus".

    Roger Penrose's new book is out now and apparently it says how he is skeptical about string theory, and he puts forward some other unifying theories. Unfortunately if you want to read only that part, you have to buy the whole 1100 page book!

    Technically gluons do cause gravitation, but this is not what keeps the atomic nucleus together. Gluons are, correctly, heavy particles, but it is the strong force ( the colour force) that causes the atraction between quarks within the nuclei and thus holds the protons and neutrons together.
    • Thread Starter
    Offline

    13
    ReputationRep:
    (Original post by PhillRamsden)
    if a photon has mass, as there is squillions (or more) of them (if you disagree, see zero point mass) the universe would collapse.

    Phill
    Eaven if you had a trillion photons it would not contribute very much to gravity since they all have much less than 0.00000[insert a trillion zeroes]here ....000001 kilograms of mass. A feather contains an enourmous ammount of atoms, yet its not heavy enough to cause the universe to collapse because each atom is very very light. Thsi should be pretty obvious, really...
    Offline

    14
    ReputationRep:
    (Original post by Jonatan)
    Technically gluons do cause gravitation, but this is not what keeps the atomic nucleus together. Gluons are, correctly, heavy particles, but it is the strong force ( the colour force) that causes the atraction between quarks within the nuclei and thus holds the protons and neutrons together.
    that's what I meant. yes they are strong force people but they contribute to gravity
    Offline

    1
    ReputationRep:
    (Original post by mik1a)
    that's what I meant. yes they are strong force people but they contribute to gravity
    Surely the gravitational force contributed by gluons is negligible?


    I have a question though I am perhaps not as good as physics as I wish I was! Energy induces a gravitational field? By energy what do you mean? For example in an EM wave clearly we're aware of the two perpendicular E&M fields there, but since it has energy as well, there is a gravitational field also? How would this look? Or have I gone far off tangent already?

    A lot of this QM talk gets me confused, worse than some GR concepts!

    On a separate note I'm interested to hear if anyone has any views on loop quantum gravity and how it might be a more solid contribution than superstring theory? There does seem to be a complete lack of experimental proof available from these theories. I heard a lecture by Edward Witten on this and all I could gather was that they had calculated the gravitational constant to a high degree of accuracy, perhaps that is a positive outcome in such an extremely theoretical area of research
    Offline

    15
    ReputationRep:
    (Original post by LifeWired)
    For example in an EM wave clearly we're aware of the two perpendicular E&M fields there, but since it has energy as well, there is a gravitational field also?
    This thread has been discussing whether photons cause gravitation. We came to the conclusion that they did. You've asked whether EM waves cause gravitation. I can answer your question by telling you that EM waves are photons .
    Offline

    1
    ReputationRep:
    (Original post by AntiMagicMan)
    This thread has been discussing whether photons cause gravitation. We came to the conclusion that they did. You've asked whether EM waves cause gravitation. I can answer your question by telling you that EM waves are photons .
    I'm beginning to hate wave-particle duality...! (Well, not that I didn't already :rolleyes: )

    I still remain uncertain on one point, which was that energy causes a gravitational field? Is there a precise form that this is relevant to? (And thank you for your precise answer!)
    Offline

    15
    ReputationRep:
    (Original post by LifeWired)
    I'm beginning to hate wave-particle duality...! (Well, not that I didn't already :rolleyes: )

    I still remain uncertain on one point, which was that energy causes a gravitational field? Is there a precise form that this is relevant to? (And thank you for your precise answer!)
    I'm sorry I don't understand the question. If you are asking "does energy cause a gravitational field?" then my answer is yes.

    But the question "Is there a precise form that this is relevant to?" confuses me. Are you asking if only certain types of energy cause gravitation?
    Offline

    1
    ReputationRep:
    (Original post by AntiMagicMan)
    I'm sorry I don't understand the question. If you are asking "does energy cause a gravitational field?" then my answer is yes.

    But the question "Is there a precise form that this is relevant to?" confuses me. Are you asking if only certain types of energy cause gravitation?
    Yes
    Offline

    15
    ReputationRep:
    No. In other words, all energy causes gravitation according to general relativity.
    Offline

    1
    ReputationRep:
    (Original post by AntiMagicMan)
    No. In other words, all energy causes gravitation according to general relativity.
    Okay, thanks
    I will need to think over this much more it seems.
 
 
 

University open days

  • University of Roehampton
    All departments Undergraduate
    Sat, 17 Nov '18
  • Edge Hill University
    Faculty of Health and Social Care Undergraduate
    Sat, 17 Nov '18
  • Bournemouth University
    Undergraduate Open Day Undergraduate
    Sat, 17 Nov '18
Poll
Black Friday: Yay or Nay?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.