Question of the Week

Is the Earth getting heavier?

Is the Earth getting heavier? As the human population grows, are we putting on weight as a planet? David Hubble, US

Chris - Yes but perhaps not for the reason that he was suggesting. People often think that as we increase our population the weight of the people comes from nowhere. People just weigh more and the Earth therefore weighs more. That's not true. The Earth is a sealed unit where all the of the weight that was on it to start with doesn't go anywhere. You don't make weight from nowhere so people have got to gain weight by taking weight from elsewhere on the Earth. Eating food that's come out of the Earth into their bodies. The planet as a whole, does that get heavier over time? The answer is yes, it can. Every year Earth gains about the weight of two aircraft carriers landing on it – two HMS Ark Royals. 40,000 tonnes-worth of debris lands on Earth. You can demonstrate this for yourself. If you put a big plastic sheet or a white sheet on your grass in the garden on a nice day, leave it for a few hours and then run a magnet over it. You can often find specks have just fallen down from outer space and landed on your magnet. Debris, dust and other stuff raining in from space contributes a huge amount of weight to the Earth every single year. Yes, we do gain weight.

October 2008