Who determined that the equator is the exact "half" of the Earth and what points of reference did they use?

Question

Why can't the "half" be in England or the north pole?

Answer 1

There are two or three parts to this answer. So far, from the answers I've seen, nobody has gotten it.

Let's answer the last part first. "great circle" (i.e., a circle that goes all the way around the world) cuts the world in half. Any meridian (a line through the poles), or an oblique great circle line through England or anywhere else will do the job.

But the equator is a special line. It's the great circle whose plane (the "equatorial plane") is perpendicular to the earth's axis of rotation.

Now we'll get to the other part of the question -- who figured it out, and how did they do it?

I don't know who figured it out, but I can tell you that the ancients certainly knew about it. There's the well-known story of Eratosthenes -- the Greek astronomer who calculated the circumference of the earth to within 5% accuracy in about 200 B.C.E.

He noticed that the sun was directly overhead at noon on the summer solstice in Syene (now Aswan), Egypt. From that, he calculated the earth's circumference quite accurately.

Now, Syene/Aswan is on the Tropic of Cancer at 23.5 degrees north latitude. This 23.5 degrees is the same as the earth's tilt with respect to the sun (the ecliptic plane). This also means that on the winter solstice, the sun at noon will be 47 degrees from the vertical. (You can get that by measuring the shadow of a pole.)

If Eratosthenes was smart enough to calculate the circumference of the earth based on these measurements, then he certainly knew that the earth's tilt relative to the ecliptic was 23.5 degrees, and he also knew that the equator was 23.5 degrees south of Syene/Aswan.

That's the best I can do on your question.

Answer 2

The word "equator" comes from Latin and means something like even or equal. I can find no record of who used the word first referring to the globe, but it must have been shortly after the western world discovered that the earth was a globe.

If it did not divide the globe in half, you would use a different word.

The reason equator does not cross England or the North Pole, has to do with the rotation of the earth. It spins on an imaginary axis going through the Nort and South Pole. Equator is half way between the 2 poles. This makes sense for many reason, such as climate, navigation and astronomy.

Answer 3

The equator isn't exactly half,

I seem to remember from my physics lessons that the shpae of the earth fluctuates with the time of year and distance it is from the sun.

There is a line through London from the North pole, it is called the Greenwich meridian, if you count the international date line on the other side, this makes the equivelant of the equator. During Winter it will be considerabbly longer than in the Summer.

but it has been a LONG time since I stdied physics.

Answer 4

Some say that Archimedes conceived the idea, and thus coined the word.

The equator can't pass through England or the North Pole because it is, by definition, equidistant from the North and South poles.

Answer 5

because of the angle of the axis. The equator runs directly perpendicular to the axis and curves around the earth at its widest point. England actually has the most important line of longitude in it anyway, the prime meridian.

Answer 6

The Earth was measured by using triangulation during a transit of Venus across the sun's surface.

Answer 7

the poles are the top and bottom or the planet, the earths magnetic polarity eminates from there, thats why we call it the "polar regions". the equator is at the equal meeting points from north and south.

Answer 8

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Answer 9

the euquator was detrimed by the nation of ecudaor in 1906, they won political support for this idea by planted an informant in Europe in assinate Arch Duke Francis Ferdinand

Answer 10

half way between the axis points