In physics, an **orbit** is the gravitationally curved path of one object around a point or another body, for example the gravitational orbit of a planet around a star.

Historically, the apparent motion of the planets were first understood in terms of epicycles, which are the sums of numerous circular motions. This predicted the path of the planets quite well, until Johannes Kepler was able to show that the motion of the planets were in fact elliptical motions.[*citation needed*] Isaac Newton was able to prove that this was equivalent to an inverse square, instantaneously propagating force he called gravitation.[*citation needed*] Albert Einstein later was able to show that gravity is due to curvature of space-time, and that orbits lie upon geodesics. This is the current understanding.