Whoops. Bill's right - I reversed the seasons. The northern summer is the longer. Very sorry. Regards to all.
Chris Lusby Taylor Email: [EMAIL PROTECTED] Date: 30 Jul 1999 11:01:40 From: "Wm. S. Maddux" <[EMAIL PROTECTED]> To: "Chris Lusby-Taylor" <[EMAIL PROTECTED]> Subject: Re: Question about annual amount of sunlight Cc: SUNDIAL <[email protected]> Return-Path: <[EMAIL PROTECTED]> Received: from mail-gw3.uk.oracle.com by uksn71 (SMI-8.6/SMI-SVR4) id LAA20897; Fri, 30 Jul 1999 11:03:05 +0100 Received: from mail-gw2.uk.oracle.com (uksn98.uk.oracle.com [138.3.208.67]) by mail-gw3.uk.oracle.com (8.9.3/8.9.3) with ESMTP id LAA06662 for <[EMAIL PROTECTED]>; Fri, 30 Jul 1999 11:03:05 +0100 (BST) Received: from hpamgaab.compuserve.com (ah-img-2.compuserve.com [149.174.217.153]) by mail-gw2.uk.oracle.com (8.9.3/8.9.3) with ESMTP id LAA11920 for <[EMAIL PROTECTED]>; Fri, 30 Jul 1999 11:03:03 +0100 (BST) Received: (from [EMAIL PROTECTED]) by hpamgaab.compuserve.com (8.8.8/8.8.8/HP-1.7) id GAA15502; Fri, 30 Jul 1999 06:02:00 -0400 (EDT) Sender: "Wm. S. Maddux" <[EMAIL PROTECTED]> Message-ID: <[EMAIL PROTECTED]> MIME-Version: 1.0 Content-Type: text/plain Content-Disposition: inline Chris Lusby-Taylor wrote: >I find the quarter day argument rather nit-picking, and irrelevant over a >span of, say, four years. But the eccentricity of the earth's orbit, with >perihelion very close to a solstice, makes the northern winter / southern >summer significantly shorter than half a year. A quick calculation >suggests that the north pole gets about 11 3/4 hours sunshine per day on >average and the south pole 12 1/4. Chris, Since, because of the elliptical orbit, the northern summer interval, vernal equinox to autumnal equinox, is 186 days, while from autumnal to vernal is only 179 days, I believe you have reversed the case. At the North Pole it would be about: 186/365 * 24 = 12.2hrs., and for the South Pole it would be about: 179/365*24 = 11.8hrs. Because of the reduced distance at perihelion, the earth AS A WHOLE receives about 6% more heat from the sun at winter solstice than it does at summer solstice. December temperatures in the Southern Hemisphere are, on average, higher than June temperatures in the Northern Hemisphere. However, because of the faster motion near perihelion, the total heat received by the two hemispheres between alternate equinoxes is about the same. Paradoxically, a square mile at the South Pole at winter solstice, in 24 hrs., receives 25% more light than does a square mile at the equator in the same interval. Only the accumulated ice from its long, dark winter, keeps it from then being the earth's hottest place! Sciagraphically, Bill.
