Thread: Cities on equator

Hi
On the Spring and autumnal equinoxes, the angle of the sun over the equator is 90 degrees, that is straight overhead, it casts no shadow. In Macapa, Brazil, on the equinox the angle of the sun is 90 degrees whereas Quito, Ecuador the angle is 89.9 degrees. Its the same for Libreville, Gabon also on the equator: 89.9 degrees. Why are they not at 90 degrees on the equinox like Macapa.

There would be no particular reason that I know of to locate a city directly on the equator.

Originally Posted by Harold14370

There would be no particular reason that I know of to locate a city directly on the equator.

Is equatorial location geometrically determined by distance, or is it taken as the "fattest" diameter existing, due to rotational affects? jocular

Originally Posted by jocular

Originally Posted by Harold14370

There would be no particular reason that I know of to locate a city directly on the equator.

Is equatorial location geometrically determined by distance, or is it taken as the "fattest" diameter existing, due to rotational affects? jocular

I don't quite know what you mean by this. If the sun is directly overhead on the equinox, you're on the equator.

Originally Posted by frejoh

Hi
On the Spring and autumnal equinoxes, the angle of the sun over the equator is 90 degrees, that is straight overhead, it casts no shadow. In Macapa, Brazil, on the equinox the angle of the sun is 90 degrees whereas Quito, Ecuador the angle is 89.9 degrees. Its the same for Libreville, Gabon also on the equator: 89.9 degrees. Why are they not at 90 degrees on the equinox like Macapa.

Because, unlike Macapa, the other two cities are not located exactly on the Equator. You only need to be ~11 km from the equator to account for that 1/10 of a degree difference.

Originally Posted by Harold14370

Originally Posted by jocular

Originally Posted by Harold14370

There would be no particular reason that I know of to locate a city directly on the equator.

Is equatorial location geometrically determined by distance, or is it taken as the "fattest" diameter existing, due to rotational affects? jocular

I don't quite know what you mean by this. If the sun is directly overhead on the equinox, you're on the equator.

I think I see what you are saying. I probably incorrectly have always thought that the equator was an imagiunary line about the Earth's circumference, equally distant everywhere from the two poles. However, as the rotation of the globe is thought to have "squished" the poles closer together than they would be given no rotation, the equator would locate itself based more on physical qualities of the mixed contents of the sphere. jocular

All those things are true, but measuring the distance to the poles, or diameter of earth would be hard. Driving a stake into the ground and measuring the length of the shadow is easy.

Small wonder that my wife constantly reminds me I am too complex...... jocular