Assume we have two cities A and B both at the same longitude (say $45^{0}$ E) but at different latitudes say $8^{0}$N and $90^{0}$ N. Can we get a time difference between these two cities. I raised this question because the shape of the Earth is oblate spheroid,i.e., bulges out at the equator and constricts at the poles. In 24 hours the Earth rotates once. But the circle at the equator traversed by the sun is not equal to the high latitudes because of the shape of the Earth. This difference in circle traversed by the sun makes a difference in time between the two latitudes. Am I wrong to put it that way?

To elaborate a little bit, one day is 24 hours and is the period of time during which the Earth completes one rotation with respect to the Sun. We call it a solar day. One complete rotation around the equator gives big circle (longer circumference) and around the higher latitudes makes small circle (smaller circumference). So the time it takes to complete one complete circle around the equator is not equal to the time it takes in higher latitudes. Or are they equal?

  • 3
    $\begingroup$ Their angular velocity is the same so it takes an equal amount of time for them to make a full circle. $\endgroup$ – milancurcic Jan 28 '16 at 23:08

Earth's rotation has a fixed angular speed, therefore time is the same across the entire surface.

Even though the tangential speed (speed of the point in the surface) is different in each place of the surface, what counts here is the angular speed (the speed of rotation). Different tangential speed compensate the distance to the rotation axis by:

(angular speed) = (tangential speed)/(distance to axis)


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.