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Visualizing photon spread

  1. Mar 10, 2010 #1


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    Gold Member

    Just for fun I wondered about how many photons hit the hubble telescope from a single star 13 billion LY away during a one day time exposure and came up with about 40 billion photons. Considering that a single star radiates light in all directions to a radius of 13 billion LY, it puts a perspective on just how many photons are out there. I'm not going to reveal how I came up with this number as I'll get laughed out of the forum :wink:. Anyone else care to come up with a number?
  2. jcsd
  3. Mar 10, 2010 #2


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    Science Advisor

    2000 for a star 13 million LY away. With billions, ~1 photon/year.
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