Is Earth getting heavier or lighter?

This week's question comes from Graham Richard in Haida Gwaii, B.C., who asked the following: "It occurred to me that the Earth might gain weight as a result of meteor encounters. If this is true, how much weight does the planet gain in this way?"

Dr. Joanne O'Meara, a professor and associate chair in the Department of Physics at the University of Guelph, explains that the Earth does gain weight as the result of meteor showers.

She says that space dust, including remnants of meteors and asteroids, contributes a weight gain of about 40,000 tonnes every year. However, our planet also loses weight.  Hydrogen gas that escapes into the Earth's gravity is so light that gravity cannot retain it in the atmosphere. About 90,000 tonnes of hydrogen escapes the Earth annually.

The resulting 50,000 tonne loss is fairly insignificant, given the total mass of the planet. According to O'Meara, it's about the equivalent of an average-sized adult elephant losing a couple of red blood cells a year.