Parallax is the observed displacement of an object caused by the change of the observer's point of view. In astronomy, it is an irreplaceable tool for calculating distances of far away stars. When you ...

A wide open space (It could be your backyard or a park.) Two Hula-Hoops (Alternatively, you could use two flat rocks or bricks that you can sit on.) A yardstick or meterstick (Use one that has clear ...