PDA

View Full Version : Winter/Summer And Precession.



interstellaryeller
2008-Dec-29, 08:24 PM
Right now Polaris is our north polar star. In 12,000 years Alpha lyrae will be, correct? How will this effect the summer in the northern hemisphere. Will are days be even longer than they are now and the Suns cross the meridan higher in the sky? A interesting speculation. And will contellations like Sagittarius ride higher in our night sky?

Romanus
2008-Dec-29, 11:40 PM
Though I'm shaky in this area, my understanding is that if we could take a time machine, say, 12,000 years in the future, and use the same Gregorian Calendar, that events like the summer solstice would still take place on June 21, and so it would still be hot summer weather in the Northern Hemisphere (precluding an ice age, of course)...however, the night sky would show current winter constellations like Orion and Canis Major instead of Scorpius and Sagittarius. Orion would indeed ride low in the sky like the summer ecliptic constellations do now, while Scorpius and friends would be high overhead during the winter.

grant hutchison
2008-Dec-29, 11:51 PM
Precession of the equinoxes won't, on its own, alter the seasonal range of day lengths, or the altitude of the sun at the meridian, since the inclination of the Earth's axis to its orbit remains the same under precession.
However, there is a superimposed 40,000-year cycle in axial tilt (between 22 and 24.5 degrees) that will make a slight difference to seasonal day lengths.

Grant Hutchison