Is the weight of the Earth changing? © Getty Images

Is the weight of the Earth changing?

Asked by: Aaron Hacon

Scientists estimate that the Earth gains about 40,000 tonnes of material each year from the accretion of meteoric dust and debris from space. They also estimate that about 95,000 tonnes of hydrogen gas are lost from the Earth’s atmosphere to outer space each year.

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Although there are other processes involved, such as the loss of mass due to radioactive decay within the Earth’s core (about 160 tonnes a year), and helium loss from the atmosphere (about 1,600 tonnes a year), these are small effects. Annually, the amount of mass launched into Earth orbit is negligible by comparison, of the order of a few hundred tonnes.

A conservative estimate therefore implies the Earth is losing something like 50,000 tonnes of mass every year. That sounds like a lot. But, since the Earth’s mass is about 5.97 billion trillion tonnes, it would take about 120,000 trillion years for it to completely disappear at this rate of depletion. That’s many millions of times the age of the Earth. In fact, it’s many millions of times the age of the Universe! So, this loss of mass has no effect on planet Earth – or on humans.

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