Absolute zero, measured using the Kelvin scale, occurs when matter has reached the lowest possible level of entropy, when its atoms are utterly and totally ‘frozen.’ It is the coldest temperature anything in the universe can possibly reach, or so we thought.
Physicists at the Ludwig Maximilian University in Munich, Germany have done the impossible; they have created a quantum gas made up of potassium atoms that is colder than absolute zero.
Using lasers and magnetic fields, the infantile toys of researchers studying the quantum realm, the physicists were able to stabilize the atoms in a lattice arrangement. While the atoms normally repel each other at positive temperatures, the researchers decided to have some fun and abruptly alter the magnetic fields, causing all of the atoms to instantly attract. Ulrich Schneider, part of the team of physicists, explains that
This suddenly shifts the atoms from their most stable, lowest-energy state to the highest possible energy state, before they can react. It’s like walking through a valley, then instantly finding yourself on the mountain peak.
Whoa. In the quantum world, anything goes.
Now, at a positive temperature, attraction between all of the atoms would cause the gas to become unstable and collapse in on itself, ultimately producing contempt and self loathing in already sensitive quantum physicists Luckily, as usual for physicists, they protected the delicate balance of their emotions with trapping lasers, which were used to hold the atoms in place. Boom! The result is:
The gas’s transition from just above absolute zero to a few billionths of a Kelvin below absolute zero.
Working with negative temperatures opens up all new realms of possibilities in the laboratory. Wolfgang Ketterle, a man with a better name than you, as well as a physicist and Nobel laureate at the Massachusetts Institute of Technology in Cambridge, reveals to us the profundity of this feat. He says that doing quantum experimentation while working with negative temperatures is like experimenting in an environment where:
you can stand a pyramid on its head and not worry about it toppling over. This may be a way to create new forms of matter in the laboratory.
By far, the weirdest part about the negative temperature gas is that it behaves identically to dark energy, the force that pushes the Universe to expand at an exponential rate despite the ever persistent pull of gravity. The atoms in the gas also seem to want to collapse inward, but the negative temperature holds them in place. Schneider remarks that:
It’s interesting that this weird feature pops up in the Universe and also in the lab. This may be something that cosmologists should look at more closely.
Researchers believe negative temperatures will give rise to the creation of matter with anti-gravitational properties, rising, despite gravity throwing a temper tantrum over wanting it to fall. For all you Egyptian pyramid conspiracy theorists out there, here’s some extra fodder for the anti-gravity theories. The Egyptians must have created negative kelvin temperatures first!
Sources:
http://en.wikipedia.org/wiki/Absolute_zero
http://www.sciencemag.org/content/339/6115/52
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