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

Graviton Properties, best guesses?

  1. Mar 19, 2006 #1

    Do physicists have any idea about any of the theorized 'graviton's' properties?

    rest mass
    wave length

    As far I know (which is very little) the only thing we know is Gravity's strength relative to the other 3 forces.

    P.S. Why was LISA's three arms set at 5 million km apart? Surely this must have been based on some expected value for probability of detection? Otherwise, why not set them 1 million km apart.
    Last edited: Mar 19, 2006
  2. jcsd
  3. Mar 19, 2006 #2


    User Avatar
    Gold Member

    spin 2. It can be argued from tensorial properties, and also because odd spin forces are repulsive between equal charges.

    Also it can be argued that a closed string has spin two because two open strings have spin one each :rofl:
  4. Mar 19, 2006 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Spin: As mentioned, 2
    Charge : 0
    Rest mass: 0
    Wavelength: dependent on its frequency.
  5. Mar 19, 2006 #4
    1) So gravity is theorized to be a sinusoidal wave like EM then?

    2) Why charge = 0, because we observe that it doesn't interact with electrons, protons and other charged particle?

    3) How was spin = 2 derived, any papers you know of that I can read?

    Thanks a bunch.
  6. Mar 19, 2006 #5
    The distance is to optimize detection of GW frequencies below 1 millihertz (.001 hertz).


    -Lottery: The government"s way of taxing the mathematically challenged.-
  7. Mar 19, 2006 #6
    Not exactly, Chaos.
    EM wave is dipolar. GR predicts the lowest order radiation of GW's to be quadrupolar based on the necessity of a changing quadrupole mass source. (Gravity itself is not a wave, but a changing quadrupole mass moment is expected to produce a gravity wave).

    Last edited: Mar 19, 2006
  8. Mar 20, 2006 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Gravitational radiation is, but not gravity itself.

    The graviton serves the same role for gravitation as the photon does for electromagnetism.

    In electromagnetism you have a field which manifests itself as an attraction/repulsion between charges, and a radiation which manifests itself as radio waves/light( which can also be thought of as "ripples" in the field).

    The photon is a unit of that radiation which, due to QM, has some particle-like properties).

    Also in QM, you can have virtual particles, these are particles that appear out of nowhere by virtue of "borrowed" energy and then vanish giving up this energy before they can be detected.

    The electromagnetic field is maintained by these virtual particles, in this case, virtual photons. It is these virtual photons that are the method by which the field exchanges force between the attracting/repeling charges.

    For gravity, just insert gravitational field, gravitational radiation and graviton into the appropiate spots above.

    Gravitons are the units of gravitational raditation and virtual gravitons are the exchange particle for gravity.

    Of course there are differences between the two interactions, as noted by Creator.
  9. Mar 24, 2006 #8
    But the ripples through this field, i.e. EM waves, are made of real photons.
    Real photons are no force carriers.
    But they (of course) transmit energy between matter.
    They are created when charges accelerate and if bound systems decay.

    Are these four remarks correct? Would someone like to add something?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook