kek@hoxna.UUCP ( K. E. Kepple) (06/26/85)
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* This brings to mind a question that's been on my mind for a number
* of years:
*
* Given that the twinkling effect is caused by tthe atmosphere as
* stated above, why is it that the stars twinkle but the planets don't.
*
* The explanation I've always heard is that it's because the planets are
* closer--but I don't see what that has to do with it; after all, they aren't
* closer than the atmosphere. (Are they? :-)
*
* In other words, why does the atmosphere have that effect on
* starlight but not on the light reflected from the planets?
*
The twinkling effect on light from stars and not from planets is because the
stars are so distant that they are a point-source of light. That is, due to
the stars great distance from us, the straight narrow beams of light emitted
outwardly in all directions from their surfaces are so sparse by the time
they reach us that our eyes receive a beam of light one photon wide. Any
interference that even slightly deflects this extremely narrow beam of light
(such as what happens as the light travels through various layers of the
atmosphere) causes the star to momentarily disappear from our view. Planets,
even though they seem very far away, are much closer than the stars. Close
enough so that we receive a far wider beam of light (many of these narrow
one-photon beams). Even if a few of the light photons become deflected
momentarily, there are so many being received from a planet that we do not
perceive the loss. Hence, stars twinkle and planets do not.
Ken Kepple
hoxna!kek datakit: ho/bedrock/fred!kek
AT&T-Bell Labs - Holmdel NJ 07733 201-949-6525 Cornet 8-233-6525
...!{hocda, ihnp4, floyd!vax135!ariel!houti!hogpc}!houxm!houxf!hoxna!kekclaus@inuxd.UUCP (David Claus) (06/28/85)
> The twinkling effect on light from stars and not from planets is because the > stars are so distant that they are a point-source of light. That is, due to > the stars great distance from us, the straight narrow beams of light emitted > outwardly in all directions from their surfaces are so sparse by the time > they reach us that our eyes receive a beam of light one photon wide. I have a question about this. If the beams are so sparse by the time they reach us how are we able to see the star at all. I guess what I'm saying is that even if we build a telescope the size of the Earth, there will still be stars that we cannot see because the photon ouptut in our direction is not dense enough by the time it reaches us. Is this correct? Dave Claus AT&T/Indy