Answers to Readers' Questions on General Topics - Astronomy. Also refer to physical science, telescopes, space, earth, moon, sun, galaxy, milky way, universe, black hole, big bang, mars, venus, jupiter, gravity, scientific instruments, Ron Kurtus, School for Champions. Copyright © Restrictions
Answers to Readers' Questions on General Topics
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Would someone ten light years away see a light?
Question
July 28, 2009
If i were to turn on a light on earth and turn it back off in theory that light goes of forever correct ? Because say someone ten light years away wont see it for ten light years and so on far any distance,so once lit it shines forever. Does this make since ?
Robert - USA
18076
Answer
A problem with most lights is that the wave spreads out as it travels away from its source. There is a distance where the energy is too small to see. Stars that are many light years away are so huge and bright that we can still see them. Astronomers estimate their distance by how much the light has dimmed.
A laser beam of light does not spread out, so that would be better to shine. Someone ten light years away could not see that beam until ten years from now.
So, when we look at distant stars, they probably aren't in the same position right now. In fact, some distant stars that we see right now may have even exploded and disappeared for all we know.
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Answers to Readers' Questions on General Topics