Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. In doing so, the excess heat from the gaseous state dissipated and the system achieved a temperature merely six kelvins above absolute zero—the closest attempt of its time. Get smart. Sign up for our email newsletter. Sign Up. Read More Previous. Support science journalism.
Knowledge awaits. Masanes compares this act of cooling to computation - we can watch a computer solve an algorithm and record how long it takes, and in the same way, we can actually calculate how long it takes for a system to be cooled to its theoretical limit because of the steps required to remove its heat. You can think of cooling as effectively 'shovelling' out the existing heat in a system and depositing it into the surrounding environment.
How much heat the system started with will determine how many steps it will take for you to shovel it all out, and the size of the 'reservoir' into which that heat is being deposited will also limit your cooling ability. Using mathematical techniques derived from quantum information theory - something that Einstein had pushed for in his own formulations of the third law of thermodynamics - Masanes and Oppenheim found that you could only reach absolute zero if you had both infinite steps and an infinite reservoir.
This is something that physicists have long suspected , because the second law of thermodynamics states that heat will spontaneously move from a warmer system to a cooler system, so the object you're trying to cool down will constantly be taking in heat from its surroundings. And when there's any amount of heat within an object, that means there's thermal motion inside, which ensures some degree of entropy will always remain.
This is nature's way of enforcing the Heisenberg Uncertainty Principle. Additionally, thermodynamics states that perfectly cooling an object to absolute zero would require an infinite number of steps. Despite the inaccessibility of a temperature at exactly absolute zero, scientists have been able to get very close. A nuclear demagnetization refrigerator cools a material by aligning the spin of nuclei using a strong magnetic field.
It currently holds the record—at least according to Guinness World Records —for lowest temperature: trillionths of a degree F above absolute zero.
Ketterle and his colleagues accomplished that feat in while working with a cloud—about a thousandth of an inch across—of sodium molecules trapped in place by magnets. I ask Ketterle to show me the spot where they'd set the record. We put on goggles to protect ourselves from being blinded by infrared light from the laser beams that are used to slow down and thereby cool fast-moving atomic particles.
We cross the hall from his sunny office into a dark room with an interconnected jumble of wires, small mirrors, vacuum tubes, laser sources and high-powered computer equipment. Ketterle's achievement came out of his pursuit of an entirely new form of matter called a Bose-Einstein condensate BEC. The condensates are not standard gases, liquids or even solids.
They form when a cloud of atoms—sometimes millions or more—all enter the same quantum state and behave as one. Albert Einstein and the Indian physicist Satyendra Bose predicted in that scientists could generate such matter by subjecting atoms to temperatures approaching absolute zero. Seventy years later, Ketterle, working at M.
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