A Slam Dunk Solution
The fastest way to cool down a car is to create a vacuum to suck out hot interior air and draw in cooler outdoor air. The science behind this hack is explained in this video from mathematician Hannah Fry. In the video, she notes that the solution has to do with fluid dynamics, the subject of her Ph.D. Here’s a breakdown of the steps involved — we’ll explain why they work afterward.
1. Start the car and roll the rear passenger-side window all the way down.
2. While standing outside of the car, open and shut the driver’s door in rapid succession five to 10 times. Repeat this step as often as needed.
3. Get in the car and roll down the rest of the windows. As you begin driving, this will help flush out the remaining hot air.
4. Turn on the AC while the car is in motion to lower the temperature further.
5. Once the car’s interior reaches a comfortable temperature, close the windows.
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Why It Works
By rolling down a rear window and repeatedly opening and closing a door on the opposite side, you create a makeshift air pump. This motion physically pushes the hot air out through the open door, while drawing in fresh, cooler air through the window. (The quicker you open and shut the door, the more successful your efforts will be.)
Swinging the door causes a pocket of low pressure to form inside the car. The pressure difference in the cabin forces the trapped hot air to rush toward the low-pressure zone and exit through the open door, while simultaneously pulling in fresh air from the open rear window.
You may be wondering: Isn’t the air outside just as hot as the air inside the car? The answer is no. Even if it’s 90 degrees Fahrenheit outside, the air inside a hot car can reach 140 degrees Fahrenheit or more. If you displace the 140-degree air with 90-degree air, it makes it easier to cool down the car further.
