John Catania of Bel Air asks, "Is the Earth heavier or lighter ... [than] it was a million years ago? Please don't answer that all things are weightless in space." Where do you get these questions? Well, Earth is "weightless," but it has mass. And there's no doubt that its mass is always growing. We've hurled hundreds of tons off the planet. (The space station's mass alone is 235 tons.) But scientists estimate tens of thousands of tons of space dust and meteors fall to Earth each year.