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Tonight on BBC Two, a team of scientists will take to the skies in one of the world's largest airships - to look at clouds.

Flying coast to coast across the United States, the team begin their expedition exploring clouds, with expedition leader and meteorologist Felicity Aston examines how clouds capture and store liquid water in the skies with an ambitious experiment to try and weigh a cloud.

But just how much does a cloud weigh. Well, in a nutshell - a lot. The good people of the National Centre for Atmospheric Research have worked it all out.

Put simply, clouds shift around 1.4 trillion tonnes of water from the oceans to inland each and every day - which is rather a lot.

The average cloud - which is around a kilometer cubed - weighs as much as 100 elephants, but still remains floating in the atmosphere.

(Image: BBC/YouTube)

In tonight's documentary, former paratrooper Andy Torbet sets out to measure the forces that keep clouds afloat by parachuting through the turbulent and potentially dangerous air that surrounds one. Which seems entirely sensible.

His study reveals that clouds generate vast amounts of energy. A typical cumulus cloud - similar to the one Andy measures - generates enough heat energy to power the average home for 17 years.

Meanwhile, also on the ship is microbiologist Dr Chris Van Tulleken who is attempting to prove that some clouds are alive. Yeah, alive alive.

* Operation Cloud Lab is on BBC Two tonight at 8pm

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