According to some calculations, the Earth is losing 50,000 metric tons of mass every single year, even though an extra 40,000 metric tons of space dust converge onto the Earth’s gravity well, it’s still losing weight.

Chris Smith, a microbiologist, and Dave Ansel, a Cambridge University physicist provided the answer in BBC Radio 4’s More or Less program. The 40,000 metric ton of mass that accumulates comes from space dust, remnants of the formation of the solar system.

When people build structures on Earth, it doesn’t add any mass since they are using baryonic matter that’s already present on the planet. It just changes shape. Launched satellites and rockets that end up in orbit will eventually fall towards Earth’s gravity well.

The Earth’s core loses energy, since much of it is consumed in a planet’s lifespan, but that only accounts for a loss for about 16 metric tons per year. The biggest mass loss comes from escaped hydrogen and helium, which escape with 95,000 metric tons of mass and 1,600 metric tons respectively. These elements are too light to stay permanently in the gravity well, so they tend to escape into space.

The net loss is about 0.000000000000001% every year, so it doesn’t account for much when compared to the total mass of the Earth, which is 5,972,000,000,000,000,000,000 metric tons. It will take trillions of years for all of the hydrogen to be depleted. Helium represents 0.00052% of the atmosphere and it’s a scarcer element.

[via BBC]