A physics doctor reveals her trick for quickly cooling your car in summer without turning on the air conditioning thanks to fluid dynamics: "It looks a little silly, but it works."

Physicist and science writer Hannah Fry has shared on social media an ingenious fluid dynamics trick that allows you to cool the interior of your car in the summer without having to turn on the air conditioning.

"You know that situation where you get into your car in the summer and it's absolutely sweltering? Well, there's a fluid dynamics trick you can use to cool the car down quickly," he explained.

Hannah assures us that this is a quick, efficient, and, above all, free method. The key is to take advantage of the natural behavior of moving air. "Don't bother turning on the air conditioning: it takes about five minutes to kick in and it's not worth it. Instead, open one of the windows on the side opposite the driver's door, for example, a rear window," she said.

Next, he recommends, and here's the key: "Open and close the driver's door quickly. Yes, you'll look a little silly doing it, but it works."

The basis behind this technique lies in a well-known physical principle. “The reason it works is that when you open and close the door, especially if you do it quickly, the door moves outward and displaces all the air in its path, creating a low-pressure zone. This creates something called bulk flow , which causes all the hot, stuffy, and unpleasant air inside the car to be expelled,” Hannah explained.

Thanks to this air exchange, the vehicle is ventilated almost immediately. "And the only way to refill that space is with fresh, cool, and pleasant air coming in through the open window. Two or three times is usually enough, and suddenly the interior is at a surprisingly pleasant temperature," he concluded in his post.