space-technology-8

# Beat the Heat!

### Birthday in 1686 of Gabriel Daniel Fahrenheit, inventor of precise thermometers.

Play Beat the Heat. It has a thermometer to test how well you do.

Beat the Heat!

Play "Beat the Heat!" Match scrambled up words with real words before the thermometer tops out.

## To Freeze or Fry in Space?

Outer space is colder than the North Pole in December! But it can also be hotter than an erupting volcano. On Earth, air helps even out the temperature. But there's no air in space. You can fry on one side while freezing on the other.

For a spacecraft, that spells big trouble!

Some instruments on the spacecraft get hot just doing their jobs and need to get rid of the excess heat. Other spacecraft parts need extra heat to work properly.

Space engineers know all about heating and cooling even tiny spacecraft. The small ones are especially hard to keep comfortable. That's because they have very little space inside for heaters and coolers. They have very little extra electric power for them either.

So how do the engineers solve this problem?

They call on their friends! Their names are Conduction, Convection, and Radiation. These are the ways heat energy moves from place to place.

### Conduction

Even in solid matter, like hot pots and cold feet, the atoms and molecules are always doing a dance, jiggling up and down and all around. We can't see them jiggle, but we can feel their energy. How? As heat!

Adding heat energy to matter makes its atoms and molecules jiggle even faster. As they speed up, they bump against their neighbors, and get them jiggling faster too.

Put a cool pan on a hot stove, and soon the pan is hot. If the handle is metal, it will get hot too, as the faster-moving molecules in the metal pass their energy along.

That's conduction: Matter "conducting" energy throughout itself, through molecules bumping into each other.

### Convection

Like conduction, convection happens in matter too, but only in liquids and gases?like water and air. The atoms and molecules in liquids and gases are farther apart than in solids. Because they have more room between them, they are freer to move around. As they heat up and jiggle faster, they move much farther, carrying the heat energy with them.

The atoms and molecules themselves move in currents. For example, a candle flame (which is made of gases so hot they glow) heats the air right around it. The warmed air rises, making a current. Cooler air moves in to replace the warmed air, gets warmed up too, and rises into the current.