Thursday, June 14, 2007

Summit Camp, Greenland

Talk at the Quonset Hut, and at lunch while dominated by science, also had the first glimmer of returning home. Mostly, it was logistics-finishing, packing, and deadlines, but there was talk of family, and what will happen after time on the ice. Many of us are leaving on Tuesday, June 19, 2007 to make way for a group of teachers and students, as well as some Distinguished Visitors (DVs). If you weren't sure, I am not a DV, but I appreciate your uncertainty. Typically, DVs are NSF officials, politicians, and representatives of non-governmental agencies. Often, DVs have some direct or indirect influence on funding.

Thursday, June 21, 2007 is Summer (Northern Hemisphere) Solstice or June Solstice. It is on this day, the Northern Hemisphere is most tilted towards the sun. Therefore, for any one day of the year, the length of daylight in a twenty-four hour period is greatest. Also, it is on this day the rays of the sun are most directly pointing on the Northern Hemisphere. The more direct the rays of the sun, the greater the heating. Following the 21st, in the Northern Hemisphere, the time of daylight per day will decrease until December 22, 2007 termed the Winter or December Solstice. From the standpoint of Northern Hemisphere observers, September 23, 2007 will be the Autumnal (Fall) Equinox, and Vernal (Spring) Equinox will occur on March 20, 2008. Equinox means that that the sun is observed directly over the earth's equator. Then, for a twenty-four hour period, the length of daylight and nighttime are approximately equal.

For earth, the repetitive, predictable progression of seasons, solstices, and equinoxes are due to the tilt of the earth (approximately 23.5 degrees), and the earth's revolution or movement around the sun. Let's distinguish between the terms rotation and revolution. For our purposes, rotation means spinning about one's own axis. For a visual, think of a basketball spinning on a basketball player's finger. As sunlight falls on earth's surface, earth's rotation causes daytime and nighttime. Revolution means repetitive, somewhat circular movement around another object. Excluding any processional events, etc., the earth's axis is permanently pointed in one direction at 23.5 degrees. As earth revolves about the sun, this means that in progression the Northern Hemisphere receives the most direct rays of the sun (June Solstice), Northern and Southern Hemispheres receive equal amounts of sunlight (Autumnal Equinox), the Southern Hemisphere receives the most direct rays of the sun (December Solstice), and to complete the cycle the Northern and Southern Hemispheres receive equal amounts of sunlight (Spring Equinox). Remember, the Northern Hemisphere's summer is the Southern Hemisphere's winter, etc. The more direct the sunlight is striking the surface, generally, the greater amount of daylight/day, and the greater warming. Notice, the distance from the earth to the sun does NOT cause the seasons.

I have never been "above" the Arctic Circle, or "below" the Antarctic Circle on solstice before. However, this is about to change, and I will be above the Arctic Circle for the first time next week on solstice! So, when I fly home on June 23rd, I will not only be returning to hotter temperatures and family (happily), but I will be returning to a place that has nighttime. Last time this happened, I was flying home from Antarctica to Atlanta, GA. I had a couple of days layover in Christchurch, NZ. I remember standing in Christchurch's central square looking at the night sky over a church's spire. It was a beautiful, warm, clear, star-filled night. One should appreciate nighttime; Stars are out, temperatures decrease, and the sounds of nighttime are different. I encourage you to take a few minutes and experience the tapestry of the night sky. Use binoculars and a simple star chart to help yourself navigate the celestial dome. It will not be difficult to imagine the ancients generating myth to deal with the infinity before them.
Graphics courtesy of Wikipedia. The specific sites are, and

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