“The distinction between mass and weight is always a little tricky, since they are exactly proportional to each other. Monteith made it easy. Out in space, you can lift a barbell off the floor of the shuttle much more easily than you can on Earth, because its attraction to Earth is diminished at that distance. But you can’t roll it on the floor any faster than you can on Earth, because the mass does not change with distance from Earth. The barbell’s weight is due to a certain attraction to Earth (the nearest significantly large body), but mass is a resistance to acceleration that belongs to the barbell in itself, independently of the barbell’s location, and regardless of the direction in which you attempt to accelerate it. “Weight is attraction; mass is shove resistance”, he would say. (I could rattle off a bunch of those pithy one-liners that have helped me through my subsequent courses in physics.) When a fellow student of mine said he was still confused about the difference, Monteith’s eyes bulged as he strode over to my neighbor’s desk. “Would you rather lift my car or push it if you had to do one or the other?” “Pushing it is easier.” “Then mass isn’t weight, is it? The mass of my car resists your push. The weight resists your lift.”