1The two things you need
Rising air, and how size changes falling
Two simple ideas do all the work. Watch each one move:
Air keeps puffing up
Air isn't empty. Warm air near the ground rises, like a slow invisible fan blowing straight up. It pushes on anything light.
Size changes falling
Water can be split into different sizes. A big drop contains much more water than a tiny droplet. Compare their sizes here; test their motion in the rising air below.
Try the ingredient below. Make a prediction before you compare the completed cases.
2Your turn — set the size
Drop one droplet into the rising air
The puff of air blows up at the same gentle speed the whole time. You only change one thing: how big the droplet is. This practice range contains only small droplets. The bigger sizes are saved for your prediction.
3Now grow the whole cloud
What if every droplet got bigger?
Here's a whole cloud of tiny droplets, all floating. The rising air stays just as gentle. You're going to grow every droplet at once. But first — a guess.
Guess before you find out
You grow the droplets bigger and bigger while the puff of air stays the same gentle speed. What happens to the floating cloud?