Math professor shares thermo-dynamic hack to cool your sweltering car in seconds
You don't even have to use your A/C.

A woman in a hot car.
Cars can become unbearably hot in the summer. Even at a seemingly mild 80 degrees outside, the temperature inside can soar to a scorching 109°F within 20 minutes. According to the CDC, in just 40 minutes it can escalate to a blistering 118°F. After an hour, it can peak at a searing 123°F. And that’s just the air temperature; a dark dashboard or seat can reach a staggering 200°F.
"These objects (e.g., dashboard, steering wheel, child seat) heat the adjacent air by conduction and convection and also give off longwave radiation (red) which is very efficient at warming the air trapped inside a vehicle," the CDC explained in their report. It can take five to 10 minutes for your car to cool down on a hot day by turning on the air conditioning, which probably means you burn your buttocks and thighs on the hot seat. That’s why Hannah Fry shared an amazing hack on TikTok, demonstrating how to cool your car down in seconds using the laws of thermodynamics.
Fry is Professor of the Public Understanding of Mathematics at the University of Cambridge. She is a mathematician, a best-selling author, an award-winning science host, and the host of numerous popular podcasts and television shows.
@fryrsquared That age-old dilemma of choosing between having a non-sweltering car or baffling a passerby because you look like a fool who doesn't know how to use a door
Fry suggests that instead of turning on the air conditioning, which she claims is “not worth it” because of the time it takes, open one of the windows on the opposite side of the door. Then, rapidly open and close the driver’s side door, so it moves back and forth like a fan.
“The reason why it works is that when you open and close the door, especially if you do it quickly, the door, as it's moving outwards, it sweeps out all of the air that's in its way, creating this sort of area of low pressure that you get here,” Fry said. “And then that sets up something called bulk flow, which is where all of the hot, sweaty, horrible air inside the car is drawn outwards.”
A man sweating in his car.via Canva/Photos
Fry’s super practical approach to a problem everyone deals with blew many people’s minds in the comments. “If I ever catch someone in real life doing this, I’m gonna know they’ve watched this exact video,” a commenter wrote. “I will give it a go, but while opening and closing the door, scream, ‘Be gone, heat demons! BE GONE!’” another added. “Going to remember this the next time my partner farts in the car,” someone joked.
The fact that the inside air temperature in a car and the outside temperature are often drastically different, especially in the summer, serves as a crucial reminder to dog owners everywhere to never leave their pet unattended in a parked car. "Most dog owners know that you can’t leave a pet in a hot car," the American Kennel Club writes. "Temperatures can rise to dangerous levels in just minutes, putting your dog at risk of heatstroke. But what if you open a window a little bit? Does that make it safe to leave your dog in the car? The answer is simple. You should never leave a dog alone in the car, even with the windows cracked. In some states, it’s even illegal."
The following video by The Dodo explains why leaving a dog in a hot car can be deadly, even when it doesn’t feel that hot outside.
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