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Homework Help: Does light lose energy (frequency decrease) with time?

  1. Nov 8, 2012 #1
    This isn't a direct homework question but it pertains to a little presentation I'm working on. I was curious because answers, to some extent, seem to be all over the place. Wanted to get the opinion of physicsforums. Does light traveling through space (assuming no interactions with other matter), lose energy and thereby experience a decrease in frequency...say, going from visible light to infrared or radio, just by the passage of time?

  2. jcsd
  3. Nov 8, 2012 #2
    Then energy wouldn't be conserved, would it?
  4. Nov 8, 2012 #3
    Of course not. (completely embarrassed I didn't think of that)

    Guess that settles it. Thanks.
  5. Nov 8, 2012 #4


    Staff: Mentor

  6. Nov 8, 2012 #5


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    Think about this: the universe was 3000 K when it became transparent to light. Today, the temperature is below 3 K. The blackbody spectrum shifted to lower energies over time. How did that happen?
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