Derek Muller of the YouTube channel Veritasium uses a nifty trick to make visible the invisible air currents, temperature gradients, and differences in air pressure around us. The process is called Schlieren photography and with the right equipment and some precision alignment, you can try it at home. As Muller explains:
I first saw a Schlieren imaging setup around ten years ago in Melbourne. I was immediately fascinated by the way I could see the warm air coming off my hand. I hadn't expected the currents to be moving that fast or to be so visible. This was a tricky setup to get right because alignment is very important and here I'm just working with what I had lying around the house mostly (plus the mirror). For the best Schlieren photography, making sure the mirror is stable is essential. I want to improve my setup so the mirror doesn't wobble back and forth too much creating the pulsing light and dark sections of this video.
