Calculating the circumference of the earth?

Question

The earth is not a perfect sphere so how would we go about doing this?

Answer 1

Parallax measurements. (simplified example) Mathmatics we know the distance to the Sun. We take an angle reading on the Sun at Sunrise (on an equinox at the equator) and again at sunset. We now have an angle with the Sun at the point of the angle, our observation points at sunrise and sunset as the other points. This gives us a triangel ABC as A is the sun, B is sunrise point, and C is sunset point. Simple Trig gives us either the sides or the angles or vice versa so our diameter is line BC. Line BC time pi gives us the circumference.

Answer 2

The Earth is composed of a large volume of mass. Due to iregularities,the Earth is not exactly a smooth surface. However ,viewed by the Astronauts the Earth appears as perfect sphere(no bulge).
The Calculation of the Earth's Circumference was achieved in Ancient Greece by Erasthotenes.(See historical description of Erasthotenes)
Today its very easy by using Satelite Globe positioning system and triangulation the diameter of the earth can be measured and the circumference calculated.

Answer 3

2200 years ago, they stuck two sticks in the ground and measured the angle of the sunlight to get the total circumference.

Since the earth bulges at the equator, and is tilted from the sun, this measures the local curvature. You could measure the curvature over the whole sphere to get the actual shape. The mountains are only local variation. You could measure down to each hill, but they average out anyway. If you measured every grain of sand the the circumference becomes infinite.

http://www.sciencebuddies.org/mentoring/project_ideas/Astro_p018.shtml

Answer 4

There are various ways of calculating it, but in terms of it not being a perfect sphere, it is customary to ignore hills etc, and it is also customary to specify which circumference you are talking about (eg the equator, north/south pole, etc).

Answer 5

the earth is changing"circumference alters ,erosion,mountains rising ,volcanos rising and lowering"any calculation to be accurate needs a day/time lat/long label on it,so the answer-with a lot of time and hard work.hope this helps.

Answer 6

distinction in altitude = distinction in selection = X° popular distance (d) corresponds to X° What distance could correspond to 360° d*360/X = circumference that's that easy (simply by fact of this it became finished 2000 years in the past).

Answer 7

With a big *** ruler

Answer 8

http://heasarc.gsfc.nasa.gov/docs/cosmic/earth_info.html

Answer 9

ask a scientist

Answer 10

use measuring tape