Professor Hannah Fry, a mathematician and upcoming star of the Celebrity Traitors, has shared a quick and fuel-efficient hack to cool down a car that has been sitting in the sun. The trick, based on fluid dynamics, can make a vehicle comfortable in just a few seconds without using air conditioning.
How the Hack Works
In a video posted on her Instagram page, Fry explained the technique while sitting in her car. She advised drivers to open one window on the opposite side of the driver's door, then quickly open and close the driver's door several times. This action creates a low-pressure area that draws out the hot air and replaces it with cooler air from outside.
Fry, who holds a PhD in fluid dynamics, said: "You know that thing when you get into your car in the summer and it's absolutely boiling hot, there's actually a fluid dynamics trick that you can use to quickly cool your car down." She added: "So don't bother putting on the aircon, that would take about five minutes, it's not worth it."
Science Behind the Trick
Fry explained the physics: "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 sweeps out all of the air that's in its way, creating this sort of area of low pressure. That then sets up something called bulk flow, which is where all of the hot, sweaty, horrible air inside the car is drawn outwards and the only way to refill it is with nice, fresh, easy air from over that side. It only takes about two or three goes and suddenly it's absolutely, beautifully temperate."
The hack comes as temperatures soared across the UK and Europe, with Scotland recording its hottest day of 2026 on June 25, reaching 31.2°C in Threave, Dumfries and Galloway. Many drivers have been reluctant to enter their sun-baked vehicles, but this method offers a quick solution.
Public Reaction
The video has garnered comments from viewers who plan to try the hack. One person wrote: "I genuinely saw a woman doing this today with her mini and thought wth is she doing lol now I know, and will give it a go. I burnt my bum on my seats getting in my car today and I’m seven months pregnant, the heat is not my friend!" Another said: "I’ve been doing this, thanks to seeing your video last year! Yes, I get looks, but one of the great things about being a woman of a certain age is that I don’t care what anyone else thinks." A third commented: "Awesome! I’m willing to go through some embarrassment to cool my car down. Funny looks from the neighbours are a small price to pay."
Celebrity Traitors Appearance
Fry will appear in the highly anticipated return of the Celebrity Traitors, filmed earlier this year in the Scottish Highlands. She joins 20 other celebrities, including Maya Jama, James Blunt, Michael Sheen, and Miranda Hart, as they work together to identify the Traitors among them and win a cash prize of up to £100,000 for their chosen charities.
