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Light continuum?

  1. Oct 22, 2003 #1
    light as a continuum

    We have an iron rod and it is connected to a power supply.

    One meter away there is a sheet of white paper hanging on a wall.
    Both the rod and the paper are unlit.

    Very slowly we increase the voltage passing through the iron rod.

    Very slowly the rod starts to glow a dull red and then as we increase the voltage the rod gets brighter and brighter.

    Simultaneously the sheet of white paper reflects the red glow of the rod and also gets brighter and brighter,

    The rod eventually glows a bright white and so the paper also reflects this light.

    The question is:

    At what moment did the light start to travel to the paper one meter away?
  2. jcsd
  3. Oct 22, 2003 #2
    The light started to travel the moment it left the rod.
  4. Oct 22, 2003 #3
    ha ha...good answer....but when was that?
  5. Oct 22, 2003 #4


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    Not simultaneously, but 1/300000000 of a sec later. Any change in the emission of light by the rod won't reach the paper until that much later.
  6. Oct 22, 2003 #5


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    It did not "start" radiating EM. Every body is continuously radiating EM according to its tempeature. In a warm room your body adsorps more energy then it radiates, there for you begin to sweat, this increases your rate of heat loss to help maintain a balance.

    In a cold room you radiate more then you gain, therefore you feel cold.

    Your steel bar is always radiating heat, it does not become visible until the temperature is such that its blackbody wavelength is in the visible spectrum.
  7. Oct 22, 2003 #6
    so we can agree that the rod never started to radiate light (whether visible or not) or heat.?

    We can go on to say that the rod will never cease to radiate light and heat. (it's temperature always being above absolute zero)


    WE have a continuum relationship with the paper on the wall and the rod. (and everything else)

    So correct me if I'm wrong:

    The rod is never on and the rod is never off.(same for the paper) So the obvious question is how can we determine that it's emmissions are travelling when in fact because it is never off or on it is never out of it's relationship with the paper.

    Could it be we are just witnessing a change in intensity in this continuum relationship? And that change in intensity is measured as "c" even though the emmisions haven't travelled as they are already there.


    If "Matter" never stops emitting whether visible or not then it is in a continuous relationship with everything else. There for the concept of travelling seems to be proved wrong. All we are
    witnessing is a delay in the increase or decrease in intensity.

    If we are unable to determine a start or stop to the emmission then how can we determine it's speed.?

    If there is no start and no stop then how do we know that it is travelling at all?
    Last edited by a moderator: Oct 22, 2003
  8. Oct 22, 2003 #7


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    Well, the relationship ends when you crumple up the paper and throw it away.
    First part yes, second part yes and no. Emissions are already there? How exactly? If they are there, why can't they be detected? That doesn't make a whole lot of sense.

    By blocking (unblocking) or otherwise changing emissions you can measure the speed at which they propagate.
  9. Oct 22, 2003 #8
    at what moment does a 200 billion year old particle start to emit?
  10. Oct 22, 2003 #9
    along time a ao according to theory there was an explosion and in time stars where formed. They weren't to far apart at this stage and so their light could be seen everywhere. AS the universe expanded the stars got further and further apart. And their light that they were shining slowly ceased to be able to be seen because they lacked the intensity to be visible. Soon they were so far away and their light was so dim that very few instruments could even detect that they existed at all.

    Later....the instruments could not detect them at all and as far as we were concerned they didn't even exist.

    So, the light started to exist with the big bang and has never gone out since.......just to dim to see.

    So, to look up at the sky and say that we can't see a star because the light hasn't got here yet because of it's "C" is just ludicrous.
    Last edited by a moderator: Oct 22, 2003
  11. Oct 22, 2003 #10
    How come?
  12. Oct 22, 2003 #11


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    I've never heard of a theory that says that. It sounds like a misunderstanding of the Big Bang Theory: the first stars not form until quite a while after the Big Bang.
  13. Oct 23, 2003 #12
    Wow! Your hypothetical particle is older then the universe
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