Comets necessarily obey the same physical laws as every other object. ... If one considers only two bodies -- either the Sun and a planet, or the Sun and a comet -- the smaller body appears to follow an elliptical path or orbit about the Sun, which is at one focus of the ellipse. ... Another quantity that is conserved is called angular momentum. ... Comets simply are bodies which in general have more angular momentum per unit mass than do planets and therefore move in more elongated orbits. ...