Home >> Science & Nature >> Nature

How Are Latitude & the Angle of Polaris Related?

Earth revolves on its axis, so to an observer the stars appear to turn. Polaris is directly above the north pole so it remains fixed in the sky while all the other stars revolve around Polaris -- counterclockwise, once every 24 hours. An observer in the northern hemisphere can always orientate toward north by heading toward the north star. You can also deduce your distance from the equator by noting the angle of Polaris above the horizon.

Longitude
- Over two thousand years ago, Eratosthenes proposed the system of longitude and latitude. The lines of longitude run from pole to pole. They are all the same size and they all meet at the poles. The lines of latitude run around the earth parallel to the equator. They get progressively smaller as they approach the poles. Lines of latitude are approximately 69 miles apart. Lines of longitude are 69 miles apart at the equator but the distance shrinks to zero the nearer you get to the poles. The equator is considered to be latitude zero. The lines north of the equator are called degrees north, and the lines south of the equator are called degrees south. For example. the boundary between North Korea and South Korea is 38 degrees north of the equator or approximately 2600 miles (69 X 38 = 2622) north of the equator. Lines of latitude are often called "parallels" so this border is called the 38th parallel.
Polaris
- The Earth spins on an axis so an observer on the north pole would see the stars spinning around a point directly overhead. The star nearest this point of rotation is Polaris -- the pole star. This star is also known as the north star, because it is an easy star to find and a good way to orientate during the night -- especially at sea when there no landmarks. To find Polaris, find the Big Dipper (one of the most obvious constellations in the Northern hemisphere). From the two end stars of the dipper, go about six times the distance between these two stars in the direction that the dipper would spill. You will find a star that is the end star in the handle of a smaller dipper -- this is Polaris.
Longitude and Polaris
- The angle between Polaris and the horizon corresponds to the degrees north latitude -- you can not see Polaris from the southern hemisphere. If you are on the equator, Polaris will be on the horizon -- the elevation of Polaris is zero and your location is zero degrees north latitude. If you are on the north pole, your location is ninety degrees north latitude. If you are on the Korean border, Polaris will be 38 degrees above the horizon.
Compass Deviation
- Observation of Polaris actually gives a more accurate picture of true north than the compass does. A compass indicates magnetic north -- not geographic north. The difference is called the magnetic deviation and it differs for every area. You can find out the magnetic deviation for your area from the public library of by calling the United States Geological Survey (USGS).

Nature