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Real time effects of light, light speed, and the sun?

  1. Jan 5, 2006 #1
    If I am to understand correctly, light speed is the speed at which light travels through space. As I also am led to believe, our sun is some four lightyears away. I recall hearing that since it takes roughly four years for light to travel from the sun to us, the light we see during the day actually originated from the sun from four lightyears ago. That being said, in theory if the sun were destroyed (and we could ignore the gravitational effects that would create) would we continue to have light and heat for four years?

    Also, if any of what I heard/described above is accurate, is the sun we see from sunrise to sunset the actual, physical sun, or is it just an image? i.e. if the sun theoretically exploded and we were still intact, would we see the results immediately, or would it take some four years till we see a change?
  2. jcsd
  3. Jan 5, 2006 #2


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    Hi rolandov00!
    The Sun is about 8 lightminutes from the earth.
    (But our next nearest star is about 4 lightyears away.)
    So if the sun suddenly dissapeared it would take 8 minutes before we noticed it (including gravitational effects).
    Last edited: Jan 5, 2006
  4. Jan 5, 2006 #3
    Thanks for the answer.
  5. Feb 6, 2009 #4
    Actually, although it is known what gravity does, how it does it is not known. No "gravitons" have been found so if the sun were to suddenly vanish, it is not known whether gravity would instantly disappear, or like light, continue for some minutes.
  6. Feb 6, 2009 #5


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    No, we are fairly confident that gravity propagates at or close to the speed of light. Certainly not instantaneously.

    See: http://en.wikipedia.org/wiki/Speed_of_gravity
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