We’ve all thought about sitting atop a floating cloud, but have you ever considered what might happen if a cloud sat on you? Don’t be fooled by these seemingly weightless collections of water molecules, enormous clouds actually carry an enormous amount of mass.
Of course, for the same reason a person couldn’t sit on a cloud, thankfully a cloud also wouldn’t be able to sit on us. They’re made from water vapor condensing to form tiny water droplets that sit together to form what we see as a cloud, similar to what happens in the bathroom after a hot shower.
So, how can something with no solid structure have weight? The answer is in the collective mass of the water molecules.
Considering the density of water molecules directly affects the weight of a cloud, different types of clouds would all weigh different amounts. For the sake of clarity, we’ll refer only to the iconic cumulus cloud (think of The Simpsons opening credits).
Researchers at the US National Centre for Atmospheric Research calculated the density of a cumulus cloud to be around 0.5 grams (0.018 ounces) of water per cubic meter, so a 1 cubic kilometer (0.24 cubic mile) wide cloud would contain 1 billion cubic meters (35 million cubic feet). If you calculate the number of cubic meters times by the density, 1,000,000,000 x 0.5, you’ll be left with the total weight of a cumulus cloud of that size – 500,000 kilograms (1.1 million pounds).
The dispersion of this weight over such a large area means the mass in any one place is much smaller, clouds are also mostly made up of water droplets that are so small gravity doesn’t have much of an effect on them. Surprisingly, dry air is also denser than a cloud, meaning clouds are able to sit comfortably atop a cushion of dry air without passing through it.
Next time you look up and see an enormous cloud, just be thankful it’s not able to fall on your head.