15 December, 1996

After coming back from the South Pole somebody asked me if there were any geographical features there. I told them no, it looked the same in every direction for as far as I could see, very white and very flat. That led them to the question, how did Amundsen know when he had reached the Pole. As I mentioned in an earlier journal entry, using a compass isn't very helpful because the geographic pole and the magnetic pole are not at the same location. In 1911 the magnetic pole was 1200 nautical miles to the north, at about 70 degrees South latitude. Using stars as a navigational tool wasn't possible either because all expeditions were during the perpetual daylight of the Austral Summer. There was one star that was available to them, the sun.

The earth's axis of rotation is tipped toward the sun by about 23 degrees in late December. At McMurdo Station we are 12 degrees north of the pole. That means at midnight the sun is still above the horizon by 11 degrees, (23-12) and at noon it is 35 degrees above (23+12). At the geographical pole, you would be 0 degrees north and the sun would be 23 degrees above the horizon at both noon and midnight. You wouldn't have to watch it for a full day, just observe that in the course of the day, the sun never got higher or lower with respect to the horizon.

When Amundsen reached his goal he sent three men out in different directions for 20 kilometers to make sure they had encircled the actual pole. When I was there yesterday it was a mild day, minus 30 degrees, I wouldn't have looked forward to a 20 km hike. I have to admire the early explorers of this continent.