Question: more people are living today than ever before. does that mean the world is heavier with all the extra people?

Pete Etchells answered on 28 Apr 2012:

Nope! Matter isn’t created out of nothing; we are created from elements that already exist on earth. This is what’s known as a closed system – stuff might change from one thing to another, but the total amount of stuff stays the same. So the weight of the world will only increase if things from outer space enter our atmosphere (like meteors).