Negative Temperatures

This is nuts:

The Escapist : News : Scientists Chill Atoms to Negative Temperatures


How to create temperatures below absolute zero - physics-math - 01 December 2010 - New Scientist

Scientists Chill Atoms to Negative Temperatures

German physicists have discovered that at negative temperatures, atoms are approaching infinitely hot.

Research physicists at the University of Munich in Germany have built what was previously only theoretically possible: a system with negative temperature. While absolute zero, the temperature of minimum molecular motion, is still unreachable, these scientists have pushed to the other side of zero and found a negative temperature system. Negative temperatures don't actually have "less" energy than zero, or actually take up some state "below" zero, but they do have some strange and bizarre properties. Whereas in a normal system atoms spread out evenly across all available states as energy increases, leading to an increase in entropy, in a negative system the atoms begin to occupy the maximum possible energy state at the same time - leading entropy to decrease as energy increases. This is the point where you've reached negative temperature. As one scientist put it, "the gas is not colder than zero Kelvin, but hotter. It is even hotter than at any positive temperature - the temperature scale simply does not end at infinity, but jumps to negative values instead."

Theoretically, this innovation could lead to more than 100% efficient engines, because of the way heat would flow around the entropy sink that is a negative system. "Heat would flow from a negative to a positive temperature system," said a study scientist, "because negative temperature systems can absorb entropy while releasing energy, they give rise to counterintuitive effects."

The authors' major hope is that the behavior of a negative system will lead to greater understanding of dark matter, the mysterious force that might be behind the expansion of the universe, because it appears that the "negative pressure" effect dark matter has is similar to what negative temperatures do. Any new developments will have to wait, though, because as it stands the negative system was stable for only hundreds of milliseconds - enough time to gather data and do little else.

Reverse entropy, that breaks the foundation of physics/ 2nd Law of Thermodynamics!?
Perhaps, but that's a very big deal.

It might mean things like perpetual motion machines could exist and unlimited energy etc.

The universe is meant to get unstable because entropy increases with time. If entropy decreases in time the entire world has been turned upside down. It's akin to a cup of tea warming up from the temperature of the room rather than the temperature of the tea dissipating into the room temperature.
I had a similar problem with a leg of wild boar in my deep freeze, I'd turned the deepfreeze to supercool to cope with the very large joint, the effect was the leg froze so fast that it was still warm!


Kit Reviewer
Book Reviewer
The old conundrum of does hot water freeze faster than cold?
IOT finally had a programme about it but failed to cover this story in detail:

BBC Radio 4 - In Our Time, Absolute Zero

Absolute Zero
Duration: 43 minutes
First broadcast: Thursday 07 March 2013
Melvyn Bragg and his guests discuss absolute zero, the lowest conceivable temperature. In the early eighteenth century the French physicist Guillaume Amontons suggested that temperature had a lower limit. The subject of low temperature became a fertile field of research in the nineteenth century, and today we know that this limit - known as absolute zero - is approximately minus 273 degrees Celsius. It is impossible to produce a temperature exactly equal to absolute zero, but today scientists have come to within a billionth of a degree. At such low temperatures physicists have discovered a number of strange new phenomena including superfluids, liquids capable of climbing a vertical surface.


Simon Schaffer
Professor of the History of Science at the University of Cambridge

Stephen Blundell
Professor of Physics at the University of Oxford

Nicola Wilkin
Lecturer in Theoretical Physics at the University of Birmingham

Producer: Thomas Morris.
Well if I can't get a Nobel prize for solving this, my other ambition is to shit in a woman's handbag for the sheer badness of it. Do you think I'm in with a chance?
I wouldn't like to comment on your chances, but I think it an entirely admirable ambition. Go for it and let us know how you get on

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