Nickle

Just walk south until you see people wearing hats on their feet.

SULPHUR

There was a reversal of the magnetic field at the same time.

Volker.Doormann

"Is it true that at the equator the length of day is always 12 hours of light and twelve hours of darkness?" ... "It is true that the relative lengths of day and night vary less at the equator .. http://newton.dep.anl.gov/newton/ask...ron/AST079.HTM

"For observers within a couple of degrees of the equator, the period from sunrise to sunset is always several minutes longer than the night."http://aa.usno.navy.mil/faq/docs/equinoxes.html

From this ('a couple of degress' 1° = 111 km) no one can know for clear, that he is standing ('a couple of inch') on the equator, counting the time of day and night.

Volker
(Astrologer)

Claudia

Another method based on the shadows length, but you have to observe the place a full year:
A place where a vertical stick always have a shadow is between the tropique an the pole of its hemisphere.
When there is just one day with no shadow, you are at one tropique.
When there are 2 days with no shadow, you are between the tropiquess.
When these 2 days with no shadows are separated by 6 months, you are on the equator.
Unfortunately, I do not think that the time beween both equinoxes is always exactly 6 monts. I seems to remember a slight variation, is it true?
With my method, you need no watch, just a way to count the number of days.

SULPHUR

You are right but I was pointing out one flaw with system. The variation is not always six months

Wiploc

How a bout a Foucault pendulum? That will rotate once a day at the poles, and not at all at the equator.

And how about the sunsets? In Alaska, they take forever, and the sun slants in at a big angle. Wouldn't an equitorial sunset be abrupt and vertical?

At the equator, the geosynchronous satelites are straight up. (There is a book called _Flight of the Old Dog_ which had a geosynchronous satelite over the north pole. This should be ignored.)

Assuming there's an equitorial bulge due to centrifical force during the formation of the earth, then the equator is where you would be heaviest. In order to prevent centrifical force from affecting that measurement, you only need to weigh yourself while you are running west fast enough to hold the sun at a fixed location in the sky.

And that suggests another experiment. At the equator, the angle of gravity should (theoretically, you know, if there are no mountains or subterainian densities around) should coincide with (or actually it would be the opposite of, pointing down instead of up) the angle of centrifugal force. That is, if you are near one of the poles, and you drive straight east or west at 500 miles an hour, then a plum bob would tend to hang out to the side. (Imagine your self 100 yards from the pole, going around and around it.) At the equator, you can be going east, west, or stopped, and a plum bob will always hang at the same angle.
crc

Asha'man

Was hanging out with some astrophotographers this weekend, and another version of this one came to mind:

A star that rises due East will climb straight up to the zenith, and then drop straight down to the West. If you are North or South of the equator, then the star will pass to the South or North of the zenith.

Bumble Bee Tuna

wait just a minute here...first everyone is claiming that the (imaginary) centrifugal force is stronger at the equator so you will weigh slightly less...but now wiploc says that the centrifugal force makes the Earth bulge at the equator, meaning there's a stronger gravitational force so you weigh more? Which is it?

-B

Mageth

Couldn't one just use a sextant, as navigators do, to determine latitude? I thought that was a relatively trivial operation.

I could propose some more radical methods of determining if one was at the equator. Tear 'em up if you wish; these are off the top of my head.

Is there some way to measure the rotational speed of the earth from the surface (e.g. by measuring the distance a star directly overhead travels in a given time, thus determining the angle rotated in the given time, etc.) If one knew the rotational speed at your location, one could (roughly) determine if one was at the equator.

Perhaps relativity could be used. For example, an atomic clock at the equator would run a calculable speed faster (IIRC) than equivalent clocks at other latitudes. So if one placed an atomic clock on the potential equator and two corresponding clocks equidistant north and south of the potential equator, one should be able to determine if the potential equator was the real equator from the differences in elapsed times on the clocks after a given period (adjusting for distances above mean sea level).

You could also launch a rocket to orbit directly east. It takes less fuel to get a rocket into retrograde orbit from the equator than from other latitudes. If the amount of fuel consumed to reach the orbit was known (e.g. downlinked from sensors), one could roughly determine if the launch was from the equator. Further, if a satellite launched in the due east orbit passed directly overhead in future orbits on line with the launch, one would know the launch was from the equator (due east launches from other latitudes acquire sinusoidal orbits).

Edited to add: I noticed Yggdrasill suggested a sextant on the first page.

SULPHUR

because of bulge at the equator you weigh less than at the poles which are closer to the center of earth. F=1/d^2