John Davis wrote: >The info you want is in the BSS Glossary (plug, plug!) under "semidiameter". >The answers are 15.76 arcmins in July (aphelion) and 16.29 arcmins in >January (perihelion). For the purposes of looking at sunspots, I'd say this >was insignificant. If the differences were much larger, it would have a >noticeble affect on the seasonal temperatures!
It does have a noticeable, effect at current values. The following is an excerpt from p. 40 of Cecilia Payne-Gaposchkin's "Introduction to ASTRONOMY," 1961, University Paperbacks --- Methuen: London. " ... Because the earth's orbit is elliptical, and perihelion occurs near the winter solstice, the earth as a whole receives 6% more heat from the sun than at summer solstice. In the Northern Hemisphere this excess of heat is more than offset by the obliqueness of the sun's rays, but the December temperatures in the Southern Hemisphere are higher, on the average, than the June temperatures in the Northern because of the greater proximity of the sun. Although the Southern Hemisphere receives more heat from the sun at the winter solstice than the Northern Hemisphere does at the summer solstice, the earth moves faster at perihelion than at aphelion, and the total amount of heat received by the two hemispheres between alternate equinoxes is about the same. .... " Bill Maddux
