Ask A Scientist© Astronomy Archive

Author:      dewayne
How fast do the Earth and Moon rotate?  

Response #:  1 of 1
Author:      rcwinther
The Moon rotates once in about 27.32 days, and its radius is 1080 miles or
1738 km.  The rotational speed starts at zero at either geographic pole (the
two places where the axis of rotation intersects the surface) and increases
(but not at a constant rate) as you head toward the lunar equator, where it
reaches its maximum of about 10.3 mi/hr (or 16.7 km/hr).  Pretty slow!  By
contrast, the Earth rotates once in 24 hours, and its (equatorial) radius is
3963 miles (6378 km).  As with the Moon, the rotational speed starts at 
zero at either geographic pole and increases as you head toward the equator,
where it reaches its maximum of about 1038 mi/hr (1669 km/hr).  At 45
degrees north or south latitude, the rotational speed is about 0.7 of this
maximum speed.