Below Absolute Zero? Gas Is Negative-Kelvin Material

For the first time, scientists have created an atomic gas that has a sub-absolute-zero temperature. Ulrich Schneider, a physicist at the Ludwig Maximilian University in Munich, Germany, and his colleagues created an ultra cold quantum gas made up of potassium atoms.

Using lasers and magnetic fields, they kept the individual atoms in a lattice arrangement. At positive temperatures, the atoms repel, making the configuration stable. The team then quickly adjusted the magnetic fields, causing the atoms to attract rather than repel each other. “This suddenly shifts the atoms from their most stable, lowest-energy state to the highest possible energy state, before they can react,” says Schneider. “It’s like walking through a valley, then instantly finding yourself on the mountain peak.”

At positive temperatures, such a reversal would be unstable and the atoms would collapse inwards. But the team also adjusted the trapping laser field to make it more energetically favourable for the atoms to stick in their positions. This result, described today in Science1, marks the gas’s transition from just above absolute zero to a few billionths of a Kelvin below absolute zero.
( Quantum gas goes below absolute zero )


(Temperature depends on the energy landscape
Ludwig Maximilian University of Munich)

Above absolute zero, adding more energy corresponds to an increase in entropy. Picture a hill next to a valley (see image above) with the height of the landscape corresponding to the energy of a particle – and the chance of finding a particle at a certain height representing entropy. At absolute zero, particles are motionless and all have no energy so are all at the bottom of the valley, giving a minimum entropy.

As the gas heats up, the average energy of the particles increases, with some gaining lots of extra energy but most just a small amount. Spread along the side of the hill, now the particles have different energies, so entropy is higher.

According to temperature's entropic definition, the highest positive temperature possible corresponds to the most disordered state of the system. This would be an equal number of particles at every point on the landscape. Increase the energy any further and you'd start to lower the entropy again, because the particles wouldn't be evenly spread. As a result, this point represents the end of the positive temperature scale.

In principle, though, it should be possible to keep heating the particles up, while driving their entropy down. Because this breaks the energy-entropy correlation, it marks the start of the negative temperature scale, where the distribution of energies is reversed – instead of most particles having a low energy and a few having a high, most have a high energy and just a few have a low energy. The end of this negative scale is reached when all particles are at the top of the energy hill.

The resulting thermometer is mind-bending with a scale that starts at zero, ramps up to plus infinity, then jumps to minus infinity before increasing through the negative numbers until it reaches negative absolute zero, which corresponds to all particles sitting at the top of the energy hill.
( Cloud of atoms goes beyond absolute zero)

Fans of sf author Alan E. Nourse may recall his description of below-absolute zero temperature materials in his 1951 story The Universe Between:

Things were going along very well until one of my men devised a radically new refrigerating pump that worked far better than anybody dreamed it could. We got our test material—a block of tungsten supported on an insulated tripod in the refrigerating vault—down closer to absolute zero than we'd ever hoped for. Maybe we hit absolute and dropped below it…I don't even know that for sure."

The phychologist blinked. "I don't follow. From absolute zero, just where can the temperature drop to?"

"A good question," McEvoy said. "I can't answer it. Below absolute zero you might speculate on some kind of negative molecular motion. Maybe that's what we did get. Certainly something changed. The test block simply evaporated. Vanished. The tripod vanished, and so did the temperature-recording device. All we could see in the vault was a small, glowing hole in the center of the room where the block had been. Nothing in it, nothing. Just a pale, blue, glowing area about six inches across that looked to some of us very strangely like a hypercube."
(Read more about Nourse's negative molecular motion)

The discovery that negative-Kelvin materials are possible has interesting implications for a variety of fields, including cosmology. The sub-absolute-zero gas mimics 'dark energy', which pushes the universe to expand against the inward pull of gravity.

Thanks to Winchell Chung of Project Rho for contributing the tip on this story, and the technovelgy reverence.

Scroll down for more stories in the same category. (Story submitted 1/4/2013)

Follow this kind of news @Technovelgy.

| Email | RSS | Blog It | Stumble | del.icio.us | Digg | Reddit |

Would you like to contribute a story tip? It's easy:
Get the URL of the story, and the related sf author, and add it here.

Comment/Join discussion ( 2 )

Related News Stories - (" Materials ")

3D Printing Your Science-Fictional Metals
I love science-fictional materials!

Self-Healing Plastic Fixes Even Big Holes
'The room had been strained and healed faultily....'- JG Ballard, 1962.

Living Root Bridges Of India
Grow your own infrastructure and housing using ecologically sound materials.

Artificial Magnetic Monopoles Created
Could monopoles exist in nature? Might they be found in exotic materials in space?

 

Google
  Web TechNovelgy.com   

Technovelgy (that's tech-novel-gee!) is devoted to the creative science inventions and ideas of sf authors. Look for the Invention Category that interests you, the Glossary, the Invention Timeline, or see what's New.

 

 

 

 

 

Current News

MIT's Robotic Cheetah Runs Free - And Frolics In The Grass
'THEY sent A SLAMHOUND on Turner's trail...'

Flying Robot Has An Arm
Drones with arms.

Strati 3D Printed Car
'You rode in it - you know how good it is.'

Tracking Spinning Space Junk
'Loose nuts and bolts... had been accumulating in Earth orbit'

Baidu Kuaisou Dune Poison Snooper Chopsticks
'Unobtrusive inspections with... snoopers... Will it be chaumas - poison in the food?'

Crystalized Light Created At Princeton
'It will be matter, matter made of light...'

The Amazing Gravity-Assisted Journey Of Rosetta
'...We used the [moon's] attraction to give us additional starting speed'

AirDog Auto-Follow Drone Captures Your Awesomeness
'Tight mid-shot and pull out on but behind me...'

Dell's Venue 8 7000 Tablet With RealSense Depth-Mapping
Focus on any part of a picture later.

Google's Cartographer Backpack For Indoor Mapping
'He reached to unsnap the cartograph from his belt.'

T-Mobile Sues Huawei Over Button Pushing Robot Idea From The 1930's
'Not the slightest change in their working betrayed the fact that they were now being directed by a machine instead of human beings.'

Hayabusa-2 Asteroid Cannon Strategy From 1950's SF Novel
'Fire streaked in a thin line from the muzzle of a cannon-like tube...'

Dyson 360 Eye Robot Vacuum Cleaner
'It vacuum-cleaned... or polished, consulting tapes in its idiot memory to decide which.'

First 3D Printer In Space?
'It can be mass-produced only in the orbiting factories...'

Google's Project Wing Will Find You
'Mechanical entities that flit at the edges of our vision, that can go anywhere, that are in our very midst...'

3D Printed Space Pizza For Astronauts
Put those butcher knives aside, and let me save that meal!

More SF in the News Stories

More Beyond Technovelgy science news stories

Home | Glossary | Invention Timeline | Category | New | Contact Us | FAQ | Advertise |
Technovelgy.com - where science meets fiction™

Copyright© Technovelgy LLC; all rights reserved.