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What is light?

  1. Mar 30, 2008 #1
    Time-gravity relativity is based on the fact that the anything that can effect the speed of light can also effect time. Blackholes have enough mass to suck light, so light must traval in the form of matter( and matter has to have mass) not radiation/energy, so what is light?

    P.S. Sorry if this has been posted, but I couldn't find a "search" button.
    Last edited: Mar 30, 2008
  2. jcsd
  3. Mar 31, 2008 #2
    Light is just a propagation of changing magnetic and electric fields. Or you could view it as a massless particle whose momentum is related to it's frequency.

    It is true that black holes suck light it, but that does not mean light has mass. According it General Relativity space-time is flat with things travelling in straight lines on it. But it can become curved when we place massive objects into it. THen the light that is traveling in a straight line through such a curvature will become bent and "get sucked into" the black hole.
  4. Apr 1, 2008 #3
    I always thought of it this way:

    Start imagining:

    There is a cloth floating in air, just a thin piece of paper cloth. Think of this as the fabric of space and time. This cloth exists around many others like it, there are an infinite amount floating nearby.These are other nows, pasts, futures, and possibilities.

    Several specks of sand lie on the cloth. These are suns. Nearby, some pebbles(Giant stars), about 2.5 mm in diameter exist.

    Then, suddenly, a large stone appears(Black hole). This stone tears through the cloth. It rips and falls into all the other cloths around it.

    Light comes into this as the size of an atom. It's so small, but it still falls through the hole.

    I think this theory is accurate. Any mistakes?
  5. Apr 1, 2008 #4


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    Light doesn't need to have mass to be affected by a black hole, since in general relativity you can explain the motion of light in terms of the the black hole curving spacetime, and light following a geodesic path in this curved spacetime.
  6. Apr 2, 2008 #5
    as matter is sucked into a black hole the matter will begin to emanate light. This light will not be travelling in a geodeisic path how does it get sucked in?

    Also how do you consturct a 3 dimensional curve so that light entering from any angle will travell in a geodeisic path? For this to be true the light would have to take a geodesic oath regardless of the angle of attack!

    You say massive objects bend space but any object no matter how tiny, as long as it has mass, has gravity so even tiny objects ie an electron must bend space, just less, yes ?
  7. Apr 2, 2008 #6
    the light emanated from matter being sucked into a black hole may go in any direction even opposite to a vector pointing to the centre of the black hole. What phenomenon turns that photon around so that it heads back to the black hole ?
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