eli5 How does gravity pull down a light feather but not a rain cloud that weighs 1 million pounds?

280 views

eli5 How does gravity pull down a light feather but not a rain cloud that weighs 1 million pounds?

In: Physics

Gravity also pull out other stuff, like air, and they’re a lot better at filling the space below the cloud than the cloud. Cloud is heavy, but the air below them – which they would displace if they fall – is even heavier. Unlike a feather, which is small so the amount of air it would displace is small, and the weight of the feather is enough to beat out the amount of air it will displace.

From what I understand, there are a few things going on.

1- Most clouds are made up of small (think micro) individual water droplets. So the “million pounds” is distributed among the individual parts.

2- These parts are individualized and one part can leave without disturbing the rest.

3- Falling speed is not only dependent on weight but also surface area. So these water droplets are not only small (again micro) which also means they have a smaller surface area to pull on.

4- Finally there are gust of air flowing up. These gusts are mostly stronger than the gravity pulling down.

Edit: forgot to include where I read some of [this](https://www.scientificamerican.com/article/why-do-clouds-float-when/).

Your problem is thinking of it as a “weight”. 1 million pounds describes the total mass of the cloud, how much “stuff” it consists of. But a cloud is not a solid object, it behaves like a fluid and will easily move in the air due to thermal/pressure differences or wind. The other thing you’re missing is buoyancy, in fluid dynamics something can only fall if it is denser than the fluid below it; the same reason a plank of wood can float in water despite gravity pulling it down.