The Stars in their Courses Author:Isaac Asimov Seventeen essays that originally appeared in The Magazine of Fantasy and Science Fiction in 1969 and 1970. — How Much Does the Earth Weigh? The answer is simple. The Earth is in free fall and, like any object in free fall, it is responding in full to the gravitational fields to which it is subject. It is not "attempting" to make any further respo... more »nse and therefore it is weightless. The weight of the Earth, then is zero. -- from The Man Who Massed the Earth.
Asimov's writing isn't stuffy and he makes these normally eggheaded subjects interesting. His touch of humor helps make the essays accessible and fun to read even if you couldn't care less about how the elements of the periodic table got their names.