In Brief
  • Without the billions and billions of dust particles floating about in our atmosphere, water wouldn't be able to form clumps large enough to truly form water droplets.
  • This is just one example of how the complexity of our environment bends and sometimes breaks the rules established by our basic understanding of physics.

A rainstorm moves through, breaking the dry spell. Once it leaves, the outside world has a different vitality. The quiet after a storm is often followed by the soft chirping of birds and new perspectives on life. This rather beautiful phenomenon brings a refreshingly clean smell that is known as “petrichor.

However, according to basic physics, raindrops (and therefore, rainstorms) are mathematically impossible.

Fortunately, the world doesn’t operate according to our basic understanding of physics. Rather, a complex array of factors come into play.

To begin with, in the air, water vapor clings together all the time. However, thanks to heat (and the movement that it causes), it also breaks apart frequently. As a result, in order for water to truly accumulate, the temperature needs to cool enough for it to stick together in clumps. The problem is, in order for rain to form these clumps (or droplets), they need to form a clump that is actually larger than what they can form by themselves.

This seems a little counterintuitive. To form raindrops, water needs to be in a clump larger than it can possibly form?

That’s right. By way of explanation, when you have a small accumulation of water in the air, water molecules on the outside don’t have enough neighbors to bond to because the shape is so rounded. This rounded shape makes it easy for the molecules to break off. Thus, water shouldn’t ever be able to form clumps large enough to actually form water droplets (aka rain).

But of course, they do.

And this is all made possible thanks to the billions and billions of dust particles floating about in our atmosphere. In other words, without dust, there would be no water cycle and we would all be dead. Here, MinuteEarth breaks down the science of rain and how magnificent rainstorms are possible.