ANIMATION -- DOES NOT WORK WHEN PRINTED

Isaac Newton said that since gravity always pulls objects toward themselves, it is possible for one object to go into orbit around another. An object orbiting the Earth is constantly “falling” toward the Earth – it’s just that the Earth is curved so it never hits the surface!

http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/newt/newtmtn.html

Newton was able to show mathematically that the shape of these orbits were conic sections -- circles, ellipses, parabolas, and hyperbolas. Deriving the shape of orbits is beyond the level of this course -- subject matter for an advanced course in mechanics -- but we can learn a few basic things about orbits and how their shape relates to the energy of the orbiting object.