;colony/science / Heat & Energy
♨ Heat & Energy
Heat & Energy
The rules energy can’t break — why heat flows one way, why engines can’t be perfect, and why you can’t unscramble an egg.
Read it your way
Every answer here is written twice. Flip the switch and the page rewrites itself.
Try it now · Plate 62
How does a fridge make cold?
Slow the cycle and follow one dot change colour — the back runs hot.
PLATE 62 · HEAT, PUMPED UPHILL
Cycle speed ×1.00
Slow it down to watch one dot change colour at each station.
At the back coils
hot · dumps heat
Inside, by the food
cold · soaks heat
Follow one dot all the way round. The compressor squeezes it and it turns
red-hot. At the coils on the fridge's back it gives that heat to the room and
fades. Then the valve lets it spread out fast and it goes icy blue. Inside,
it soaks up warmth from your food and the loop starts again. The fridge never makes cold —
it carries heat outside, which is why the back is warm.
Every question
Heat & Energy, answered twice.
Plate 62Open → How does a fridge make cold? A fridge doesn’t make cold — there’s no such thing to make. It pumps heat out of the box and dumps it into your kitchen, which is why the back is warm. Plate 63Open → Why can't you unscramble an egg? Nothing in physics forbids an egg un-scrambling — it’s just so overwhelmingly unlikely that it never, ever happens. That one-way street is the arrow of time. Plate 64Open → How does an engine turn heat into motion? An engine doesn’t run on heat — it runs on a temperature difference. And no matter how clever it is, it can never turn all of that heat into motion. Plate 96Open → Why does ice cool your drink? Ice doesn't add cold to your drink — there's no such thing to add. It soaks heat out of the drink to melt itself, and stays at 0 °C the whole time it does. Plate 97Open → What is the coldest anything can get? Heat is just particles jiggling. Slow them all the way down and you hit a hard floor — −273.15 °C, where there's no jiggle left to take away. Plate 139Open → How does a thermos keep things hot? Heat has only three ways out of a hot drink: it seeps through the walls, it gets carried off by air, and it beams away as an invisible glow. A thermos blocks all three at once. Plate 140Open → Why does water take so long to boil? Put the same flame under water and under a lump of metal the same weight, and the metal races to hot while the water crawls. Water is just unusually thirsty for heat. Plate 141Open → Why does sweat cool you down? Sweat doesn't cool you by being wet. It cools you by leaving — the fastest molecules escape as vapour and carry your heat away with them. Plate 172Open → How does a microwave oven heat food? A microwave doesn't heat from the outside like a flame. It fills the oven with a field that flips billions of times a second, and water molecules twisting to keep up rub against each other, turning that motion straight into heat. Plate 176Open → How can a heat pump heat a home from cold outdoor air? A heat pump does not burn fuel to make heat. It moves heat that is already in the cold outdoor air into your home, so one unit of electricity can deliver around three units of warmth.
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