If this doesn't make a featured question I don't know what will. Oh, and before anybody says it, I dont think they use a really really long piece of string...................... do they?
2006-08-21 09:34:28 · 14 answers · asked by Anonymous in Science & Mathematics ➔ Geography
Here is a detailed answer on how the first guy did it (in 240 BC)
http://www.juliantrubin.com/bigten/eratosthenes.html
Summary: it used sunlight, geometry, and astornomy.
Nowadays you could figure it with any satellite by determining the size of the Earth from the satellite's view and the distance above the surface that it was orbiting.
2006-08-21 09:43:09 · answer #1 · answered by Shofix 4 · 2⤊ 0⤋
I think this is a very good question. The truth, as far as I can tell, is that no one has actually measured the circumference of the Earth. Astonishingly precise measurements are available, but the source is never quoted.
Personally, I've never ventured out of sight of land, on account of the fact that I might fall off the edge. I've heard that some people got as far as America, but looking at the nonsene on this web site, that's obviously nothing more than a silly rumour.
2006-08-22 14:24:22 · answer #2 · answered by Trust Me 4 · 1⤊ 0⤋
The circumference of the earth at the equator is 24,902.4 mi. (40,076.5 km). The earth is not exactly a round ball, but bulges at the equator due to it's rotation. to measure the circumference at different latitudes use
As you go from 0 degrees latitude (the equator) to 90 degrees (north or south poles), the circumference of the circle defined by that latitude line will decrease in direct proportion to the cosine of the angle of latitude.
Thus, the circumference of the circle is
C = 2 pi r cos(x),
where pi = 3.14159..., r = the earth's equatorial radius = 6378 km, and x is the angle of latitude.
Now to the original question, it's a little complicated but go to this site listed below will help you out, if you know trig and some math you can also figure it our like our great historians
2006-08-21 16:59:45 · answer #3 · answered by Juggernaut 3 · 0⤊ 0⤋
They take a sample of elevations around the earth and average a section of them depending on where they want to measure. Using this data they can easily calculate the distance mathematically.
But the circumference is never the same, depending on where you want to measure, and when. The earths crust is always moving around too, especially underwater. You might as well include the atmosphere in your calculations.
But they can get a pretty good idea.
2006-08-21 16:53:44 · answer #4 · answered by Anonymous · 0⤊ 0⤋
This was done 1000's of years ago in Egypt. You find a point were the sun is exactly overhead at noon on June 21st. Then walk south and measure the distance. See how many degrees the sun is off vertical at this new point. As you have the angle and the distance this gives the size of the world
2006-08-22 03:59:19 · answer #5 · answered by bwadsp 5 · 0⤊ 0⤋
no, it's not a really big string. it's actually a really big cable that they lay out using a gigantic ship with a cable coil operating on large muffler bearings to relay the cord out. when that's done, and the wire is all the way around the earth, they send an electrical signal and time how long it takes to go around the earth.
2006-08-21 16:42:50 · answer #6 · answered by promethius9594 6 · 0⤊ 0⤋
The same as a referee measures 10 yards for a free kick in football.
2006-08-21 16:43:33 · answer #7 · answered by Anonymous · 0⤊ 0⤋
Oh come on we all know the earth is really flat and stands on four elephants who in turn stand on a giant turtle.
2006-08-21 18:59:30 · answer #8 · answered by bo nidle 4 · 2⤊ 0⤋
No a really long tape measure
2006-08-21 16:40:57 · answer #9 · answered by voluptuous 3 · 1⤊ 0⤋
Well from every source I have found The estimations were calculated by a man, therefore it must be exagerated.
You know how men and their " inches" can be.
2006-08-22 16:04:51 · answer #10 · answered by ? 6 · 1⤊ 1⤋