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## Halfway between the Equator and the North Pole?

A cache by Northwoods Explorer Message this owner
Hidden : 11/5/2007
In Maine, United States
Difficulty:
Terrain:

Size:  (other)

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### Geocache Description:

Welcome to the 45th parallel and Perry Maine. Here you are half way between the equator and the north pole or are you?

This location has been commemorated since 1896 by pink granite marker at this state roadside rest area on US Route 1 just north of Perry. It states, “THIS STONE MARKS LATITUDE 45 NORTH HALFWAY FROM THE EQUATOR TO THE POLE.” But is it really half way if you had to travel to both the pole and then to the equator?

While it is commonly believed that the 45th Parallel is halfway between the equator and the pole, this is not precisely true. Since the earth is not a perfect sphere but bulges near the equator, the 45th parallel is a 45° angle drawn from the center of the earth that does not quite match the halfway point of a line drawn along its surface. Instead, the halfway point lies almost 10 miles north of the 45th Parallel in the area of Whitlocks Mill at another rest area.

When the metric system was set up, the meter was defined so that the distance from the equator to the pole so that it would be exactly ten million meters or 10,000 kilometers, making the circumference 40,000 kilometers. That is why the little experiment that you will do will work for you. In an ideal world halfway between the equator and pole would be 5000 km. But the earth spins causing it to bulge around the center which when coupled with the fact that the original calculations were done over 200 years ago leaves some room for error. So while the 45th parallel is the halfway mark by angle it is not the halfway mark by distance. Either way it is really cool to think that if you can step over the line. Travel up the road and you will be closer to the pole while traveling south you are headed for the equator.

Remember this is an earthcache so there is no container just an earth science lesson in an amazing area. To log this cache, you must then travel to a second set of coordinates where you will use the information collected to calculate the diameter of the earth. Then Email me through my profile the calculated diameter of the earth. Below are the instructions for calculating the earth’s diameter. It also would be nice if you would post a photo so others would know what they have to look forward to at this earth cache.

Drive your car to N44 57.198 W67 05.325 and find a location on the side of the road. Where ever you are make sure that the latitude is the only thing that changes. Now change you GPS in your setup to read metric with the coordinates in decimal degrees (it should read DD.DDDD.) Now read the distance in kilometers to the first location using the find feature on your GPS and then determine the difference between the two latitudes. To find the circumference of the earth you must divide 360 by the difference of latitude in degrees and then multiply that number by the distance (in km) between the two locations. The number you get in your little experiment is the distance in kilometers around the earth or its circumference. If you divide this by 3.14 you will have the diameter. Don’t forget to return your setting to what ever you generally use for your GPS.

If you enjoy this earthcache you may want to check the Maine Geological Survey located at (visit link)
They have developed a number of information sheets or field localities giving a great deal of information about geologic features. They also have a number of books and maps about Maine’s natural history/ geology that you might find interesting.

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