is distant starlite coherant?


by brianhurren
Tags: coherant, distant, starlite
brianhurren
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#1
May7-13, 10:00 AM
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by the time light from a distant star reaches us, lets say from Canopus, does the light become coherent?

and if it is coherent, can you make an astrohologram?
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Simon Bridge
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May7-13, 10:20 AM
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How do you mean "coherent"?
http://en.wikipedia.org/wiki/Coherence_(physics)
... like a laser you mean?
Short answer: no.
Chronos
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May9-13, 04:18 PM
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Perhaps you meant polarized instead of coherent. That too is essentially untrue. You can test this yourself by viewing stars through a polarized lens, then rotate the lens 90 degrees and see if the stars changes in brightness. Star light can be mildly polarized due to scattering by dust particles over vast distances and also by strong magnetic fields on the star.

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May9-13, 07:10 PM
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is distant starlite coherant?


... possibly just thinking of the light being parallel?
@brianhurren: any of this useful?
Varadha
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#5
May9-13, 09:31 PM
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If two observers are near, the light rays from such a distance source may be considered as coherent because, the angle between the light rays is too small and negligible. Theoretically, this assumption is valid
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May9-13, 11:09 PM
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Like this?
http://skullsinthestars.com/2008/09/...ics-coherence/
... OP has yet to logon since that post - but it's early days yet.
HallsofIvy
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May10-13, 07:19 PM
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Quote Quote by Varadha View Post
If two observers are near, the light rays from such a distance source may be considered as coherent because, the angle between the light rays is too small and negligible. Theoretically, this assumption is valid
Saying that light rays are parallel does not mean they are coherent.
Varadha
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May10-13, 10:09 PM
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Quote Quote by HallsofIvy View Post
Saying that light rays are parallel does not mean they are coherent.
Oh. Sorry. I thought any parallel rays in phase are coherent
davenn
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May10-13, 10:17 PM
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Quote Quote by Varadha View Post
Oh. Sorry. I thought any parallel rays in phase are coherent
yes they are, but that wasnt in your statement earlier, you didnt mention anything about them being in phase

Dave


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