How Aaswath Raman and SkyCool are modifying an ancient practice to create carbon-free cooling systems on Earth
Long ago, in lands that were always warm, people got ice from the heavens.
At sunset, they poured water into shallow earthen pits or ceramic trays insulated with reeds. All through the night the water would radiate its heat into the chilly void of space. By morning, it turned to ice — even though the air temperature never dropped below freezing.
This wasn’t magic; it was science.
For centuries, desert dwellers in North Africa, India and Iran tapped into a law of physics called radiative cooling. All objects — people, plants, buildings, planets — give off heat in waves of invisible light. On a clear, starry night, that radiation can rise through the atmosphere until it escapes Earth entirely. Coldness, which is really the absence of heat, is created through this invisible connection to the cosmos.
The world now cools off with the help of more than 3.5 billion refrigerators