Math professor's hack can help cool your sweltering car in seconds
You don't even have to use your A/C.
A man sweating in his car.
Cars can become unbearably hot in the summer. Even at a seemingly mild 80°F outside, the temperature inside can soar to a scorching 109°F within 20 minutes. According to the Centers for Disease Control and Prevention, 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 National Weather Service said.
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, 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 says is “not worth it” because of how long it takes to become effective—you should open a window on the opposite side of the car. 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 says. “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.”
Fry’s practical approach to a problem everyone deals with blew 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 air temperature inside a car and the temperature outside are often drastically different—especially in the summer—serves as a crucial reminder to dog owners never to leave their pets unattended in a parked car.
"Most dog owners know that you can’t leave a pet in a hot car," the American Kennel Club's Anna Burke 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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This article originally appeared in June.