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Alive or already dead

  1. May 22, 2004 #1
    "Alive" or already "dead"

    Would you please tell me how people can check out if a star is still active or already dead ? Since the lights we can see are unable to guarantee for its 'living'_ness, this is why i make this question...So please help..

    Thank you very much,
     
  2. jcsd
  3. May 22, 2004 #2

    selfAdjoint

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    You mean because the light takes so long to reach us we don't know the state of the star "right now". And we don't, and can't. Information can only reach us at the speed of light, and causes can only effect us from sources whose light can have reached us.
     
  4. May 22, 2004 #3
    You mean basing on causes and effects to know what we want to know or am i missing your points ?
     
  5. May 22, 2004 #4

    selfAdjoint

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    I think you are getting there. Yes, causes and effects, due to relativity, must be connected by the ability of a light beam to get from the point of space and time of the cause to the pint of space and time of the effect. For instance, light moves at about one foot per nanosecond. Say something happens a yard (3 feet) away from me. I won't be affected by it until 3 nanoseconds have passed, the time for light to get from the something that happened to me. This isn't just about seeing, nothing about that event a yard away from me can affect me until those 3 nanoseconds have passed.
     
  6. May 23, 2004 #5
    Thank you,
     
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