It keeps hot things hot and cold things cold because it has two walls -one on the outside and one on the inside. The air in the space between the walls has been pumped out. Because the space is empty, heat and cold can't pass through it. The airless space is called a vacuum.
Don't forget your hat!
If you wear a wooly hat, you stay warm because it keeps your body heat in. People keep houses warm in the same way. They put a special material in their roof to stop warm air from getting out.
Thermal facts
- Adelie penguins stay warm because they have an outer layer of oily waterproof feathers, an inner layer of fluffy down feathers, and a layer of fatty blubber.
- Thermal underwear keeps us toasty because it traps a layer of warm air next to the skin.
