Patch South Whitehall, PA --By Gary A. Becker
*StarWatch** 875 for the week of May 26, 2013*
One of the two coordinates that allows you to find your position on the Earth’s surface is latitude, the angular measure north or south of the equator.
Polaris, the North Star, can easily allow you to observe your change in latitude if your summer travel plans take you in a northerly or southerly direction, like the Caribbean or northern Europe. This is because Polaris lies in the same line of sight as the extension of the Earth’s axis into space.
At the North Pole, 90^o north latitude, the North Star is essentially overhead, while at the equator, 0^o latitude, Polaris lies along the horizon. Its altitude or angular height above the horizon gives an observer a good approximation of his or her latitude position.
Follow the Pointer Stars of the Big Dipper downward to Polaris.
Presently, they are farthest to the left in the cup and are cresting in the north after darkness. For a good swath of the US, the North Star’s elevation is approximately 40^o. That’s equivalent to four clenched fists held at arm’s length (thumb on top), stacked one on top of the other.
Let’s say that you’re traveling to Disney World this summer. You’re out by the pool after dark, and the kids are swimming before bed. Polaris will be about three fists high, 28^o above the horizon.
Traveling to southern Europe? The change will be negligible. Rome (42^o N) and Athens (38^o N) are too close to our latitude to note any differences by using your fist. However, London is about 52^o N, five fists high for Polaris, and southern Alaska is about 60^o N. That’s six fists.
In Alaska measurements are impossible to make until later in the summer because you are too far north, and the sun never makes it far enough below the horizon for complete darkness to occur.
Finally, if Hawaii or a Caribbean cruise is in the offing, Polaris will hug the horizon at two fists or less. To see the change, make sure that you first take a measurement from where you live. Reported by Patch 1 hour ago.