How Cold Can It Get?
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Old Man Winter has hit America hard this week. Today, he even knocked out your friendly KnowledgeNews correspondent–with an ice storm that cut power for hours. Still, we’ve got no cause to complain. Earlier this week, the temperature in International Falls, Minnesota, fell to -40 degrees Fahrenheit (which is -40 degrees Celsius, too).
No question, that’s cold. But no matter how cold it gets this winter, old-timers will say it could be worse. And they’re right. It could be colder–a lot colder. It could be absolute zero, with no heat at all.
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Turning Off the Heat
What we call temperature is just an easy way to measure thermal energy. Everything in the universe has thermal energy, which exists in the form of vibrations in atoms and molecules. If you add thermal energy to an object, its atoms and molecules vibrate more, and it warms up. If you remove thermal energy, its atoms and molecules vibrate less, and it gets colder.
How cold can it get? We’ll use your car as our experimental chamber (hope you don’t mind). We’ll start at a nice warm temperature, say 75 degrees Fahrenheit (24 degrees Celsius). You only need to wear a shirt and shorts, and you might even want a cold drink. Except that now, you’re starting to feel a little chill in the air. The temperature is dropping to 45 degrees F (7 degrees C). You’d better grab a coat and long pants. Don’t worry about the heat–we’ve turned that off.
Ice, Ice, Baby
A few more minutes, and we’re at 32 degrees F (0 degrees C). You need a hat and gloves, and you can see your breath in the air as the water vapor from your lungs condenses in the cold, fogging up your windshield. Another moment, and we reach 0 degrees F (-18 degrees C). Your body is shivering, using muscular energy to generate heat to keep you warm. And your cold drink has frozen solid (not that you’d want it now).
A little longer, and we’ve reached -44 degrees F (-42 degrees C). Time to switch to the Kelvin scale, where it’s a balmy 231. Regular thermometers don’t work anymore–their mercury has frozen solid. You’ve probably never felt cold like this. You’re numb, and your extremities are frostbitten. As the temperature drops further, substances that were once pliable become brittle. Your leather seat begins to crack and crumble under your weight, and a rubber tire wouldn’t bounce on the floor–it would shatter.
Your Last Drink of Air
Our next stop is 184 K (-129 degrees F or -89 degrees C), the lowest temperature ever recorded on Earth. Now things really get strange. The air itself starts to condense. First, carbon dioxide condenses, forming tiny frost-like crystals. Then, at around 90 K (-298 degrees F or -183 degrees C), oxygen condenses. Pretty soon, the air that once filled your car is a pool of liquid on the floor. But don’t worry about that. You’re no longer breathing anyway. Even the warmest parka in the world couldn’t save you at this temperature.
There is some good news, though. Your car’s electric system just improved. Usually, even really conductive materials like copper wire lose energy because of electrical resistance. But at about 133 K (-220 degrees F or -140 degrees C), as vibrating molecules slow down, certain metal-oxide ceramics lose their resistance, becoming superconductive. At even lower temperatures, metals like lead and tin become superconductive, too.
Eventually, the inside of your car reaches the temperature of the darkest parts of space: about 3 K (-454 degrees F or -270 degrees C). This is as cold as the universe gets. There’s just enough ambient thermal energy bouncing around to keep us from ever shedding those last three degrees. Naturally, at least. In the lab, scientists have managed to drop the temperature below 3 K–down to just a few billionths of a degree above absolute zero (0 K or -460 degrees F).
–Christopher Call
