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Photon radiation, how does it work?

  1. Dec 21, 2007 #1
    When photons are emitted, they radiate outwards from the point of radiation at all angles, so much so that clear pictures can be observed from vast distances. How is it that you can radiate photons in so many strait lines that the gaps between the lines don't become to far apart to make a clear picture.
     
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  3. Dec 21, 2007 #2

    malawi_glenn

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    Before going further, have you studied Rayleighs criterion?
     
  4. Dec 21, 2007 #3
    I havn't
     
  5. Dec 21, 2007 #4

    russ_watters

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    Basically, photons are small packets of energy, so a lot of them are emitted. But for really, really distant objects, when people take pictures of them, they capture only a handful of photons a second.
     
  6. Dec 21, 2007 #5
    W3pcq, great question!! Now I am really wondering! Think of a quasar 12 billion light years away, and two telescopes recording images simultaneously a few meters apart. !!

    Separate photon streams? A single photon stream that is "blurred" over a large "footprint" (by diffraction in the vacuum of space?) ?
     
  7. Dec 21, 2007 #6

    russ_watters

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    You basically have that backwards. Having separate telescopes record the same image (using interferometry) increases the resolution. Basically, it allows distinguishing between light rays that aren't quite parallel.
     
  8. Dec 21, 2007 #7
    Well I may have gone off track a little there.....
    Let me rephrase the original question. If observers on the entire night side planet of earth can observe a 12 Gly quasar at the same time, then there are photons from the quasar colliding with observers on every point on the planet WITH NO GAPS. Is it even theoretically possible us to be so distant from a luminous object that the photons strike our planet piecemeal with gaps between the arriving photons? Even in another 100 billion years? 100 trillion years? (Hypothetically speaking, ignoring the eventual decay of all matter, big crunches, bounces, etc.).
     
  9. Dec 21, 2007 #8

    DaveC426913

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    Why do you think photographs of very dim objects require such long exposures? Only a relatively few photons from those distant quasars reach Earth every second. But hold hte exposure for a minute or so and you collect enough to get a decent pic.

    I don't know how many people can see light from a quasar 12Gly distant with their naked eye, so the conclusion is that, yes, there ARE gaps. But note that the gaps are spread across both space AND time. The photograph I mention above can't maximize the space to capture more photons, but it can maximize the time over which it collects them.
     
  10. Dec 22, 2007 #9

    russ_watters

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    YES! I said this already. For extremely dim objects, telescopes may record only a few photons every second, but by recording them for hours or even days, they get a bright picture of the object.
     
  11. Dec 22, 2007 #10
    Thanks Russ I get it now... photons are emitted radially at ALL angles, it's just as you get down to really tiny angles you just have to wait longer and longer to see the object, because your photon detection equipment always has a radius. It is therefore theoretically possible to be so far from an object that you get over one hundred years between photons, necessitating really long exposures to see the object.
     
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