WHAT IS THE ARCTIC CIRCLE?
If you are going to ride to the Circle, you better at least know what it is! The following explains the general principle of Latitude and the Arctic Circle.
In order to understand what the Arctic Circle is, you must first have a basic idea of latitude. Latitude lines are marked east and west around the Earth, starting from 0 degrees latitude at the Equator and ending at 90 degrees at the North and South Poles. These lines are imaginary, so don't start walking around looking for them.
So where do the degrees come from? Imaging you are standing at the center of the Earth and are able to see the surface of the Earth. If you look straight in front of you, you see the Equator forming a complete circle around you at eye level. For the purpose of this argument, lets say that this is 0-degrees, which is true since the Equator is 0-degrees latitude. Now tilt your head back 10-degrees, as if you were looking up into the sky. In our example, you are now looking at another imaginary ring on the surface of the earth (like the Equator), only at an angle of 10-degrees above the Equator. This would be the 10-degrees latitude line. Now still standing at the center of the earth, look straight up from your position. You are now looking at the North Pole. You had to tilt your head back 90-degrees, thus the North Pole is at 90-degrees latitude.
In this example, we assumed that we were looking up (or North) from the Equator, thus these are "North" latitude lines. If we had repeated the example, only looking down towards the South Pole, we would be looking at the "South" latitude lines from 0-degrees at the Equator to 90-degrees South latitude at the South Pole. The North Pole is at 90° North Latitude and the South Pole is at 90° South Latitude. Latitude lines are parallel to each other so they are also called parallels.
Unless you are a pretty badass earthworm, it is impossible to stand at the center of the Earth (if I have to explain this to you, you need serious help, and understanding latitude should be the least of your worries). In the old days, sailors could figure their latitude by using an instrument such as a quadrant or sextant, and measuring the angle of a constellation above the horizon, and then comparing that angle to a chart. The Polar Star or Polaris (the North Star), can be used to determine latitude in the northern hemisphere. It's a bit more difficult in the southern hemisphere but the Southern Cross, a constellation, could be used in the same manner. With modern GPS units, latitude is extremely easy to measure, provided you can find the power button.
There are several identified latitude lines. The Tropic of Cancer (23 1/2°N) and the Tropic of Capricorn (23 1/2°S) mark the farthest points north and south of the equator where the sun's rays fall vertically. The Arctic Circle (66 1/2°N) and the Antarctic Circle (66 1/2°S), mark the farthest points north and south of the equator where the sun never sets on June 21st (summer solstice) and the spot where the sun never rises on December 21st (winter solstice) (with respect to the Arctic Circle, these events are reversed at the Antarctic Circle).
So that is a basic description of Latitude. A position on the Earth can be determined more accurately by further dividing the fractional degrees (e.g. 0.50) into minutes and seconds. Each degree can be divided into sixty minutes. Each minute can be divided into sixty seconds. So the Arctic Circle's latitude (66.5°N) is equivalent to 66 degrees 30 minutes 0 seconds North Latitude (written as 66° 30' 00" N ).
Got it?... That's what you think. Nothing is that simple.
Although lines of latitude are considered relatively constant, the location (latitude) of the Arctic Circle is determined by the tilt of the Earth on its axis, relative to the plane of its orbit around the sun. This tilt is also responsible for the seasons on Earth. The tilt is not constant, however, and varies with time. This variation of tilt determines how far north and south the sun can be seen (or not seen) on the winter and summer solstices, thus changing the actual latitude of the Arctic and Antarctic Circles. The Arctic Circle location varies by 2.5 degrees of latitude on a 41,000 year cycle (approximately). The movement of the Arctic Circle, due to changes in the Earth's axial tilt, is called the Milankovitch Cycle, which was named for Serbian climatologist Milutan Milankovitch.
Milankovitch recognized that the tilt of Earth's axis shifted from about 22 to 24.5 degrees over the course of 20,500 years. The axis shifts back during the course of another 20,500 years (41,000 year cycle). The Earth is sort of like a spinning top that has a little bit of wobble. That wobble is what happens during the Milankovitch Cycle.
How does the wobble affect the Arctic Circle? The 2.5 degrees of axis shift every 41,000 years equals roughly 200 miles of movement in that time, or about 25 feet each year. However, the wobble of the Earth is not constant, thus the actual movement of the Arctic Circle is not constant either. The Arctic Circle has been recorded moving up to 50 feet in a single year.
Currently, the Earth's tilt measures approximately 23°27' (23 degrees 27 minutes). This puts the current location of the Arctic Circle at approximately 66°33' North Latitude (3 minutes Latitude north of its "standard" location of 66°30' N). Three minutes latitude doesn't sound like much, but when calculated based on the diameter of the Earth, this puts the current location of the Arctic Circle approximately 3.45 miles north of 66°30' North Latitude.
At the very least this should give you a basic understanding of what the Arctic Circle is. Why ride there on motorcycles?... Those who would ask such a question probably wouldn't understand, but take a look at the pictures for this epic motorcycle tour, and you may begin to fathom it.