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Does light have mass?

  1. Sep 20, 2013 #1
    Einstein said it would take an infinite amount of energy to move something at the speed of light. Photons move at the speed of light every day, so we can infer that photons have no mass. However, a black hole has so much gravity (gravity only affects matter) even light is sucked in. Because light is sucked into a black hole, we can infer that photons have mass. WHAT?!?!? how can this be?
    I assume either some how photons can be propelled without an infinite amount of energy (very unlikely). Or light is sucked into a black hole for another reason besides gravity.
  2. jcsd
  3. Sep 20, 2013 #2


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    This is not true. Gravity affects light too.

    Nope, it's just gravity.
  4. Sep 20, 2013 #3
    It's because gravity isn't just a field force; it's the curvature of space-time, according to Einstein. When light is traveling across space-time, it must follow this curvature whether or not it has mass, and the curvature is caused by objects with mass/a gravitational force.
    At least, that's how I interpret it.
  5. Sep 20, 2013 #4


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  6. Sep 21, 2013 #5
    depends on question also
    what i know is that light is made of photons and mass less electric and magnetic fields.

    photons have zero rest mass and its masswhile moving = h/λc (by the de brogle)
    mind me to saying it may be wrong
  7. Sep 21, 2013 #6
    Last edited: Sep 21, 2013
  8. Sep 21, 2013 #7
    Do photons have mass?
    https://www.physicsforums.com/showthread.php?t=511175 [Broken]
    Last edited: May 6, 2017
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