Please enable it or navigate using this table. The Topics Navigator requires JavaScript 1.1 or higher. We usually disregard the attraction of object at the earth's surface by other celestial bodies in the universe. Within the limits of this approximation, the weight of an object at the earth's surface is determined only by the force of attraction applied on it by the mass of the earth. Ask a Question page.
All planets move in elliptical orbits, with the sun at one focus.
A line that connects a planet to the sun sweeps out equal areas in equal times. The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit. You are guest number since Sept. 15, 1999. Div. of Sci. Search Send comments and questions to Irina Nelson, Ph.D. , Physics Professor.