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    Re: Refraction. was: Bubble Horizon Altitude Corrections
    From: Trevor Kenchington
    Date: 2004 Jul 6, 23:31 +0000

    I always hesitate to find fault with George's postings because it
    usually turns out that the error is mine. However, when he writes:
    > If there was a temperature
    > gradient in the air, the temperature falling fast enough as height
    > increased, that could in theory be enough to counteract the effects of the
    > falling pressure. In that case the air-density would conceivably increase,
    > not decrease, as height increased, which could cause light to be curved
    > upwards, not downwards; the effect that I think Fred is looking for.
    I have to ask: George, if the density of the air increased with
    altitude, what would stop the dense air from descending and displacing
    the lower-density air upwards?
    Sure, air masses can be unstable and we do see down draughts and rapidly
    rising air (as in cumulus clouds). But can enough high-density air
    really sit on top of low-density air for the usual direction of
    refraction to be reversed?
    Trevor Kenchington
    Trevor J. Kenchington PhD                         Gadus@iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
                         Science Serving the Fisheries

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