This is why you should never leave a water bottle in your car.

In an experiment conducted by Dioni Amuchastegui, an electrical engineer in Idaho (USA), it was shown that a water bottle can refract sunlight and generate heat exceeding 100°C. When placed on a dark surface—such as a car seat—the concentrated heat could ignite a fire and cause a disaster.

In fact, for a bottle of water to start a fire inside a car, several conditions must be met. Yet that doesn’t mean it cannot happen. Amuchastegui himself nearly experienced such an incident, which prompted him to conduct the experiment as a public warning.