22 December, 2000

Solstice

This morning at 2:30AM local time (GMT +13) was the solstice- or, noon at the pole, since the sun rises and sets once a year. Today the sun is the highest it ever gets here, 23 degrees above the horizon.

Just to make sure that the sun actually is 23 degrees above the horizon, we have a solar locator that will help us measure the angle of the sun. It has been set up in AST/RO since October, and Chris Martin has been marking the angle of the sun periodically for the last few months. Other groups around the world are taking similar measurements, and the results collected in one central place: topweb.gsfc.nasa.gov/antarctica_imagegal/solar_project.html. At that site, you can also download the solar locater that we used and measure the angle of the sun where you are.

The sun began at 13 degrees in late October and has been steadily climbing since then, slowing down as it reaches its peak. Beginning today, the sun will start to reverse its path, slowly heading for sunset in March, on the equinox. It is interesting to note that a second sheet of paper needed to be added to the locator for most of the season. It was only in the last week that the suns angle was great enough to cast a shadow on the single sheet of paper that was folded for the locator.