Schlieren

Schlieren is a really cool way to see invisible things moving around. Imagine if you were blowing up a balloon, you can't actually see the air going in, but you can sometimes feel it. Schlieren lets us see that invisible air moving around.

Now, let's imagine if you tried to see the wind. It's also invisible, right? But if we use the schlieren technique, we can make it visible! We need a special camera and a few other things to make it work, but essentially we are using light to see differences in the air.

When the air is all the same temperature and pressure, the light moves straight through it and doesn't get bent. But, when there are different pressures or temperatures of air, the light gets bent and we can see it as little lines or shadows. These shadows show us the movement of the air and can help us figure out what is causing it, like maybe a fan or someone blowing on something.

So, schlieren is like a magical way of seeing things that are invisible like air, gas, or heat moving around us. It's like having x-ray vision for things we can't normally see!