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

Where does the photon live

  1. Aug 29, 2012 #1
    Where does the photon "live"

    What happens to space-time when you remove the time?

    Its said that the photon experiences no time, it seems to be generally accepted that a photon is emitted by one atom and then instantly absorbed by another in its reference frame but this seems paradoxical. If it was emitted by an atom and then never experienced time it would exist forever. The very fact it is created and then destroyed suggests it must experience time. Is it that the distance between the atom that emits it and the atom that absorbs it is zero or does it occupy all of "space?" until its absorbed?

    How is it waving in our reference frame?

    We observe an electric field that creates a magnetic field and so it propagates as a wave, but in its frame there is no time and without time an electric field cannot create a magnetic field!! change requires time. Does this mean its both waves at once until we observe it?

    When photons are created they radiate outwards as a wave but it can only be detected at one point in space, this is also crazy because it would suggest that if you were in a room with a light bulb and you put a photon detector at any point in the room it should absorbed all the photons leaving the rest of the room dark.

    If the laws of nature have courts then the photon should stand trial for giving me headaches.
  2. jcsd
  3. Aug 29, 2012 #2


    User Avatar

    Staff: Mentor

    Re: Where does the photon "live"

    There is no such frame. There is no inertial reference frame in which a photon or electromagnetic wave is at rest. It's a self-contradictory concept.

    Last edited: Aug 29, 2012
  4. Aug 29, 2012 #3
    Re: Where does the photon "live"

    Thanks for the link, I'm sure the answer to my question is in there but I still don't get it.
    If its still moving at speed c in its reference frame then how come its not experiencing time? how can it be in motion and yet not experience time when motion requires time.
  5. Aug 29, 2012 #4


    User Avatar
    Gold Member

    Re: Where does the photon "live"

    I don't think there's anything to support this view. The two fields are in phase but perpendicular. You might just as easily say that the magnetic component creates the electric field.

    See the Wiki article http://en.wikipedia.org/wiki/Electromagnetic_radiation
  6. Aug 29, 2012 #5
    Re: Where does the photon "live"

    I hear ya,

    perhaps the photon asks the same for something that doesn't have to move at c. It's equally odd isn't? The photon wonders how we include time in our observations of it.

    The last paragraph is ignoring quanta of EM isn't?
  7. Aug 29, 2012 #6
    Re: Where does the photon "live"

    A universe without time is mere speculation. - it isn't realistic at all.
  8. Aug 29, 2012 #7


    User Avatar
    Science Advisor
    Gold Member

    Re: Where does the photon "live"

    Why, after jtbell told you, there is no reference frame for a photon, do you quote him and then ignore him by repeating the same self-contradictory question?

    Before you can ask meaningful questions about a reference frame, you need to learn and understand what it is and how it is defined. Part of that definition requires clocks at rest at different locations in that reference frame. You cannot build a clock out of just photons, you need massive particles which cannot travel at c. Therefore, the definition of a reference frame is meaningless for a photon.

    The definition of a reference frame also requires the use of a rigid ruler which also requires massive particles. You cannot build a ruler out of just photons. Therefore, your first question, "What happens to space-time when you remove the time?", when applied to a photon should more appropriately be "What happens to space-time when you remove the space and the time?" Do you see how meaningless it gets?

    It's not that "the photon experiences no time", it's that the photon has no experience. You need to learn what a reference frame is and how it is used in Special Relativity before this will make sense to you.
  9. Aug 29, 2012 #8


    Staff: Mentor

    Re: Where does the photon "live"

    It is NOT moving at c in "its reference frame", there is simply no such frame which can be called "its reference frame".
  10. Aug 29, 2012 #9
    Re: Where does the photon "live"

    Particles and light don't experience time. When an electron absorbs a photon, it's always the first time, i.e. it has no memory. People have memories, they track time.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook