Radiative cooling

Have you ever noticed that some things get hot when the sun shines on them? Like when you sit on a sunny rock or touch a car that's been in the sun for a while? That's because sunlight heats up things that it touches. But did you know that some things can actually get cooler when they are in direct sunlight? This is called radiative cooling.

Radiative cooling happens when an object is able to "shed" some of its heat by giving off energy in the form of electromagnetic waves (like light). When a warm object emits these waves into the colder surroundings, it can lose heat and cool down. This is similar to how you might feel cooler on a hot day when a breeze blows across your skin and carries away some of your body heat.

Scientifically, radiative cooling works because all objects emit radiation (light) in the form of heat. This is why you can see the "glow" of a hot stove burner even when it's turned off. But not all objects emit radiation equally. Some materials, like metals, are very good at reflecting radiation and not giving off much heat. Other materials, like certain plastics or paints, are better at absorbing and re-emitting radiation, which allows them to cool down more easily.

Scientists are interested in radiative cooling because it could be used to make things like solar panels or buildings more energy-efficient. By coating these objects with special materials that can absorb and re-emit radiation well, they could lower temperatures and reduce the amount of energy needed to keep things cool. So next time you feel the sun shining down on you, remember that radiative cooling is at work all around us!