Absolute Zero and the Conquest of Cold  



Low-Temp Basics


Scientists who study low-temperatures have changed practically everything about the way we live on earth. Refrigeration. Air conditioning. Production of computer chips. Oxygen storage in hospitals. Rockets to the moon. The incredible range of products is mind-boggling -- and these are but a few of the areas that have been advanced by studying the science of the cold.

The ability to create cold temperatures affects the modern world in dramatic ways most of us don't even notice. In the19th century, for example, only the rich could afford the luxury of ice cream and cold drinks in the summer heat -- with the help of boats that carried huge blocks of ice from up north down to the warmer climates. But today we think nothing of grabbing a popsicle out of the freezer, eating fruits and vegetables shipped in refrigerated crates all around the world, and keeping cool indoors on a sweltering day.

Besides modern-day conveniences, the study of cold has advanced rocket fuels and the semiconductor chips in every electronic device. It has revolutionized agriculture and improved medicine. But the study of low-temperature physics isn't only about devising technology -- it's about understanding the very nature of cold. What is it? Is there a limit to how cold things can be? What happens to matter when subjected to the very extremes of freezing temperatures?

What Makes Something Cold? Things are hot or cold for a very simple reason -- it simply depends on how fast its atoms are moving. Hot steam is made of fast moving H2O molecules; cold ice has slow ones.

What's the Coldest Anything Can Be? In 1703, even before anyone understood what made cold things cold, Guillaume Amontons deduced that there was a limit to just how cold anything could be. Now we know that limit is simply the place where particles stop moving altogether -- a point known as absolute zero. Absolute zero is at 459.67 °F ( 273.15 °C). Getting a material all the way down to absolute zero is impossible, but since 1995, researchers have made a dramatic leap in how close they can get -- the current record is a mere 20-billionths of a degree away.

What Happens to Matter at Absolute Zero? While it's impossible to bring matter to a stand still altogether -- and thus reach a true absolute zero -- odd things happen to atoms when they get down to extreme temperatures. As the atoms get colder, which just means they're moving more slowly, they lock into step with each other. Where once there was random jostling, the particles now join up into a giant superatom that moves as a single unit. As scientists learn how to control this cold superatom it will open doors for even more new technology.

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