Why does wind blow from one place to another?

You can't see it, but something invisible is pushing those leaves across the yard. What decides which way the wind goes — and why it blows at all? Let's find the hidden rule… then try to break it.

1Two things to know first

Air is real stuff, and it can get crowded

Air is made of zillions of tiny bits, zooming and bumping all the time. Squeeze more bits into a space and the air gets crowded. Crowded air pushes harder.

Air is tiny bits

You can't see them, but they're there — flying around, bouncing off everything. That's the air all around you right now.

Crowded vs loose

Lots of bits packed in = crowded air that pushes hard. Just a few bits = loose air that barely pushes at all.

2Two boxes of air, side by side

Even, or lopsided?

Picture two boxes with a wall between them. They can be set up two ways:

Balanced boxes

Both sides equally crowded.

Crowded & empty boxes

One side packed, one side loose.

3Your turn — pack the air

Crowded air pushes harder

Slide to cram more bits into the box and watch the little flag. The more crowded the air, the harder it gets shoved.

How crowded is the air?just right
LOOSEPACKED

4Now open the gate

Which setup makes wind? 💨

Two boxes, a closed gate between them. You set how lopsided the air is, then open the gate. Sometimes a wind blows across. Sometimes nothing happens. Which is which?

Guess before you open it

Two boxes of air, gate about to open. Which one makes wind?