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Location: UFOUpDatesList.Com > 2007 > Feb > Feb 26

Re: Natural Phenomenon? - Shough

From: Martin Shough <parcellular.nul>
Date: Mon, 26 Feb 2007 15:12:25 -0000
Fwd Date: Mon, 26 Feb 2007 10:28:10 -0500
Subject: Re: Natural Phenomenon? - Shough


>From: Brian Callaghan <bjcallaghan.nul>
>To: ufoupdates.nul
>Date: Sun, 25 Feb 2007 12:16:52 -0500
>Subject: Natural Phenomenon?

>Does anyone have an explanation for stars that appear to flash
>or rotate green and red colours?

This is "scintillation" - otherwise known as "twinkling". White
light being refracted into its spectral colours, as in a prism,
is called dispersion. The refractive index of the air varies
with the temperature, and because the path of the light through
the atmosphere to your eye is very long (and the nearer the star
to the horizon, the longer the path) lots of temperature
fluctuations are encountered along the way. So, by the time the
light reaches your eye it has minutely changed direction many
times and this history of dispersion causes the changing colours
you see. The effect can be very noticeable with stars because
the angular size of the "point source" - effectively zero - is
small compared to the image wander caused by these random
refractions. Planets show images that are not so small in
comparisn to the refractions, which is why they tend not to
twinkle.


Martin Shough




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