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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Refraction. was: Bubble Horizon Altitude Corrections
From: Robert Gainer
Date: 2004 Jul 7, 20:05 +0000
From: Robert Gainer
Date: 2004 Jul 7, 20:05 +0000
Temperature inversion in the San Fernando Valley, California. Bob >From: "Trevor J. Kenchington">Reply-To: Navigation Mailing List >To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM >Subject: Re: Refraction. was: Bubble Horizon Altitude Corrections >Date: Tue, 6 Jul 2004 23:31:37 +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 > http://home.istar.ca/~gadus _________________________________________________________________ Get fast, reliable Internet access with MSN 9 Dial-up � now 2 months FREE! http://join.msn.click-url.com/go/onm00200361ave/direct/01/