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MinuteEarth

WATCH: Why Are There Clouds?

FIONA MACDONALD
22 APR 2015

Clouds are confounding objects. Sure, they may look light as they dance across a cobalt blue sky on a warm summer's day, but don't be deceived - the average white fluffy cumulus cloud weighs hundreds of tonnes, and releases the equivalent of 270 tonnes of TNT worth of energy, as Emily reveals in the latest episode of MinuteEarth. But the really tricky part is exactly how all that water vapour gets up there in the first place.

 

It all begins with solar energy, which evaporates water from oceans, plants and soil by breaking down the bonds that hold water molecules together. And although it sounds contradictory, these evaporated water molecules are actually lighter than the dry air around them, as two hydrogens and an oxygen is lighter than two nitrogen atoms or two oxygen atoms that make up the rest of our atmosphere.

This means that buoyant patches of damp air begin to rise, and as they do so, the heavier air around them pushes down and seals the water vapour off into little balloon-like rising pockets of gas. This gas keeps rising and rising, spreading out as the the pressure drops around it, until eventually it reaches an altitude where it's cold enough for the water vapour to condense into droplets, forming what looks from afar like a thin wisp of cloud.

As the balloon of water vapour continues to rise, clouds grow into big, pillow-y marshmallows. But in the meantime, they're busy shedding all of the energy they sucked up from the Sun back on Earth, and this is where things get interesting. Watch the video above to find out how this energy can cause tennis ball-sized hail pellets, because MinuteEarth manages to draw it way better than we could ever explain it.

Science, you tricky little devil, this is why we love you.

And just in case you were wondering what makes these complicated clouds stay afloat, It's Okay To Be Smart has got that covered for you: