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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?

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    $\begingroup$ Their angular velocity is the same so it takes an equal amount of time for them to make a full circle. $\endgroup$
    – milancurcic
    Commented Jan 28, 2016 at 23:08
  • $\begingroup$ It might be better to use an example that isn't 90deg North : The concept of a day at a pole is going to be a bit more complex than elsewhere, so that might cause confusion. $\endgroup$
    – Semidiurnal Simon
    Commented Sep 2, 2019 at 4:22

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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)

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Only if you factor in relativistic differences! Someone standing on the equator is traveling at about 464 m/s whereas someone standing at 41° Latitude is only traveling at about 350 m/s. Hence the person at the equator would appear to be 4.6E-06 seconds per year slower in time than the person at 41° Latitude.

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  • $\begingroup$ grin assuming you're referring to Santiago's answer - no, it doesn't factor in relativistic differences :-) Welcome to Stackexchange. I've edited your answer to stand alone, rather than reading like a response to another answer. THat's because this isn't a discussion forum, and answers may appear in different orders in the future. If I've misunderstood your meaning, please let me know. $\endgroup$
    – Semidiurnal Simon
    Commented Sep 2, 2019 at 4:19

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