Lesson 5 of 15
Across empty space: radiation
Show on a big screenThe Sun warms us every day. But space has almost no air. How does the heat get here?
Step 1 of 4
- The Sun and the Earth.
- Between them is empty space. There is almost no air there.
- Still, the Sun's heat reaches the Earth.
- This way of moving heat is radiation.
The Sun's heat crosses empty space by . No air is needed.
The new word
- Radiation — heat moving with nothing in between. It needs no solid, liquid or gas.
- You feel radiation near a fire, too.
Dark or light?
Some surfaces absorb more heat. Absorb means take in. A dull surface is not shiny.
| Tank surface | Takes in the Sun's heat | The water inside |
|---|---|---|
| dark and dull | more | gets warmer |
| light and shiny | less | stays cooler |
The rule
Heat can move with nothing in between. This is . It does not need air. Dark, dull surfaces take in more of it than light, shiny ones.
Now try it. Pump out the air. Then block the lamp with a card.
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Try the lab to finish this lesson.