The gravitational attraction between spheres of lead is strong enough to be measured in a high-school science lab (if you can remove the students and air curren

The gravitational attraction between spheres of lead is strong enough to be measured in a high-school science lab (if you can remove the students and air currents); this is the famous Cavendish experiment of 1798. I remember it blowing my mind to realize that although a lead sphere is tiny compared to the Earth, it's also right there: whereas the Earth acts like a point mass four thousand miles beneath your feet.