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How do black holes attract light with no mass?

  1. Jul 13, 2004 #1
    Isn't light supposed to have no mass? If gravitational pull equals (G * m1 * m2) / (d^2), then it wouldn't matter how great the mass of the black hole is, because the mass of light is 0 and thus the gravitational pull is 0.

    Am I missing something here?
  2. jcsd
  3. Jul 13, 2004 #2
    Light has energy associated with it, and energy is equivalent to mass relativistically, so gravity can act upon it.
  4. Jul 13, 2004 #3
    That thing can not be explained with classical physics as Newton's law. As pnaj said, mass is also a kind of energy and viceversa, so the light can be attracted.
  5. Jul 13, 2004 #4
    You need general relativity to explain that.
  6. Jul 13, 2004 #5
    I see, thanks.
  7. Jul 13, 2004 #6
    Light does have mass, just no rest mass.
  8. Jul 13, 2004 #7
    Has anyone the math equation for this?
  9. Jul 13, 2004 #8
    mass and energy

    [tex]E=mc^2[/tex]? is that it i think that shows that mass is equivalent to energy and vice versa
  10. Jul 14, 2004 #9


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    Black holes do not attract any more light then any other body. To the best of my knowledge no massive body "attracts" light. It is more approbate to say that a body intercepts light.

    It is possible for light to be following a geodesic which essentially ends in a black hole, thus the energy of the light would contribute to the mass of the Black Hole. It is not clear to me that this is really a form of "attraction".
  11. Jul 14, 2004 #10
    that shows that mass is equivalent to energy
    Has anyone the math equation for this?

    According to Barut
    The measured mass of the particle is a result of the motion of the initially massless “particle” in an external field. Although this idea appears to be very attractive it is not possible, at the present time, to build a complete theory on this basis. Certainly the quantum effects must be taken into account. But even within the framework of quantum theories the nature of the mass of the particles remains unexplained.

    On my webpage you will find a table that shows that by using the sum of the line force it is possible to argue that mass is the maximum force reading within a Newtonian force field. I have used this method to show that all isotopes of each element also have the same sum of line force, I am waiting for data that will comfirm this before adding it to my webpage.

    As far as I am aware this is the first time that mass and energy have been linked mathematically to (particle and atomic) radius, and charge. that, of course, is not to say that I am correct, but merely to point out the possibility.

    I get a lot of criticism for publishing ongoing work, but what else is expected in a theory developement forum? but so far, this latest work has not recieved any detrimental comment.

    If, and I know it is a big 'if'; I am right; then the whole of particle physics can be greatly simplified and most of the questions raised on particle and atomic forums can be answered.
  12. Jul 14, 2004 #11
    I've actually heard an instersting theory about what mass actually is. It seemes way out there, but it can be interesting from the way it's consistent with major theories. I dont know much about it, but here goes...basicly, there this thing called the Higgs field, and it's ALL over the universe. Particles have a resistance when in the Higgs field, and this resistance is what mass is. I'm guessing that a particle going through the field causes more resistance, and therefore will have more mass (relativity). And very small particles, like photons and neutrinos are too small to be affected by the Higgs field, i guess they pass through it. I'm not sure if what i say is correct about the theory, because it was only briefly talked about at a lecture at Brookhaven National Laboratory. I was there with the Mariachi program with the help of QuarkNet. Anyways, I just wanted to see what people think of that theory, honestly I though it was absurd when i heard it. :D
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