The sun is heading south again

Have you checked your favorite south facing window recently, especially about high noon? If so you will notice sunlight streaming in to paint a bright spot on your floor.

That is one way you can verify the sun is indeed moving south toward its date with the equator on Sept. 22 for the autumnal equinox. I had forgotten to mention that Aug. 1 (often called Lammas Day, a cross quarter day), marks the halfway point between summer and fall and now we are almost all the way through August.

Remember from our previous discussions the reason for seasonal changes is the 23.5 degrees of Earth's axial tilt. That tilt exposes different parts of Earth's surface to direct sunlight at different times of the year.

I watched a televised public survey recently in which the question was, "What causes the seasons?" The most often wrong answer given was the distance of Earth from the sun. If that were true, then December would be hot and July cold because December is when Earth is closest to the sun and July is when it is farthest away.

Earth is closest to the sun in December but the Northern Hemisphere is tilted away from the sun, hence less sunlight and lower temperatures. Conversely, because of the 23.5 degree tilt, the southern hemisphere is angled toward the sun, thus warmer temperatures. Have you ever seen photographs in the newspaper of the good folks in Australia cavorting on the beach on Christmas Day? Another good reason for visiting Australia.

More about the coming seasonal change in coming columns.

At the time this column was written the launch of the next shuttle mission (SST-128) was scheduled for Aug. 25 at 11:36 pm MDT. If the launch occurred on time there will be more information about possible observations of overhead passes of the shuttle and the International Space Station (ISS) in future columns.

If you would like to watch current television coverage of the mission, like I do, point your favorite Web browser to: http://www.nasa.gov/multimedia/nasatv/ that is the official NASA television web page. Or you could pester your local cable-tv company to carry NASA TV on their broadcast schedule.

SKY WATCH: First quarter moon Aug. 27. The moon will visit Antares, the "Heart of the Scorpion" in the early evening hours of Aug. 27. Watch Mars pass the open star cluster M35 from this morning through Sept. 1. The red planet will pass just to the right of the cluster. Binoculars could do the job, but a telescope would be more interesting. Begin observing at about 4 a.m. looking due east. Also in the east starting at about 5 am from Aug. 30 to Sept. 3 look for very bright Venus to start a pass near M44, the Beehive Cluster, located in the constellation Cancer, the Crab. The star cluster will be slightly above and left of the planet.

If you have time, look in the southeast for winter's giant, Orion, the Hunter. I have always said, the changing of the constellations goes with the changing of the seasons. What you can see in the early morning indicates what is coming on the calendar.

The spring group has gone off to the west, the summer group is overhead, the autumn group is rising in the early evening and winter is rising in the early morning. Now is a good time to start checking your long johns.

NEXT TIME: More astronomical blathering.