Expert: Tom Whiting - 1/30/2007

Question
What is the axis pointing towards in the Northern Hemisphere during spring and fall?

Answer
Hi jj,
The Earth's axis in the N. Hemisphere always points to
the star Polaris, as far as laymen are concerned....day and night, 24 hours, 7 days a week, and 365 days a year.  But if you really want to be more specific, the
Earth's polar axis points to a spot in the sky at exactly
90 degrees Declination, which is about 3/4 of a degree from
Polaris, but you only have to be this super-accurate IF you're
using your telescope to photograph the night sky.
For simply visual purposes, alignment on Polaris is close
enough.
Of course, this close alignment is not permanent.....the star
Thuban (Alpha Draconis) was the "pole star" when the
Pyramids were being built some 4000 years ago.  Due to
precession, our axis does a slow "wobble" with a period
of nearly 26,000 years.  13000 years from now, the bright
star Vega will be the Pole Star, and 26000 years from now
Polaris will once again be the Pole Star.
But this will change very little during a normal lifespan of
say, 100 years.
Oh, closest approach of our pole to Polaris?  It will occur In 2105 AD, about 98 years from now,  when our pole location will be only 1/2 degree from the star Polaris.

Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA

FOLLOW UP:
Oh, by the way, the seasons have nothing to do with the
pointing direction of our axis, which is tilted 23.5 degrees
from the vertical.  The seasons, spring, summer, fall, and winter, are caused by... whether or not we are tilted toward, or away from, the sun. In the summer, our axis is tilted toward the sun, so the sun's strongest rays are striking the N. Hemisphere.
In winter, we are on the opposite side of the sun, thus our
axis (which doesn't not change spacial orientation, just like
a spinning gyroscope) is then pointing away from the sun
so it's winter in the N. Hemisphere, because the direct rays
of the sun are striking the S. Hemisphere.
Just thought I'd better clear that up, so you know what causes our seasonal changes.
Clear Skies,
Tom Whiting