The Coldest Place in the Universe

[n2doc]

Physicists in Massachusetts come to grips with the lowest possible temperature: absolute zero

By Tom Shachtman
Smithsonian magazine

Where's the coldest spot in the universe? Not on the moon, where the temperature plunges to a mere minus 378 Fahrenheit. Not even in deepest outer space, which has an estimated background temperature of about minus 455°F. As far as scientists can tell, the lowest temperatures ever attained were recently observed right here on earth.

The record-breaking lows were among the latest feats of ultracold physics, the laboratory study of matter at temperatures so mind-bogglingly frigid that atoms and even light itself behave in highly unusual ways. Electrical resistance in some elements disappears below about minus 440°F, a phenomenon called superconductivity. At even lower temperatures, some liquefied gases become "superfluids" capable of oozing through walls solid enough to hold any other sort of liquid; they even seem to defy gravity as they creep up, over and out of their containers.

Physicists acknowledge they can never reach the coldest conceivable temperature, known as absolute zero and long ago calculated to be minus 459.67°F. To physicists, temperature is a measure of how fast atoms are moving, a reflection of their energy—and absolute zero is the point at which there is absolutely no heat energy remaining to be extracted from a substance.

But a few physicists are intent on getting as close as possible to that theoretical limit, and it was to get a better view of that most rarefied of competitions that I visited Wolfgang Ketterle's lab at the Massachusetts Institute of Technology in Cambridge. It currently holds the record—at least according to Guinness World Records 2008—for lowest temperature: 810 trillionths of a degree F above absolute zero. Ketterle and his colleagues accomplished that feat in 2003 while working with a cloud—about a thousandth of an inch across—of sodium molecules trapped in place by magnets.

more:

http://www.smithsonianmag.com/science-nature/12359501.html

Of course, someone out there could have beaten us already!

[Orrex]

1. Point of order

In episode #68 of The Adventures of Superman, a mad scientist threatens Superman with a freeze-ray which he clearly states is capable of projecting a beam "two thousand degrees below zero."

That's a heck of a lot colder than -459.67° F. Are you going to argue with a mad scientist with a freeze-ray?



I didn't think so.

[n2doc]

2. But what scale was he using? n/t

[Orrex]

4. I don't know . The thing looked life-size to me.

You'd have to ask Supes.

[annabanana]

3. cool beans!

I love this stuff... I wonder what could be done with super-chilled stuff . . .

[Warpy]

7. Stopping light and holding it in a steady state

and releasing it at will looks fascinating and makes me wonder what happens with superheated plasmas.

They're just starting to find out what they can do with this stuff.

[Speck Tater]

5. Forget black holes from the super collider...

What if this thing unleashes a Giant Slushy Ball, the spreads out, freezing everything it touches until the entire earth is frozen solid!!! OMG! We're all going to die I tell you!!!

[Orrex]

8. Kill the scientists! Every last one of them!

Before it's too late!!!!!1!

[ashling]

6. What about Cheney's heart.

Every time somebody says "they can't go any lower," they go lower .... I wonder if it works that way with this?

[gtar100]

9. How about the furthest reaches of space where light has not yet reached

Empty space so far away from anything that light from any source has not yet reached it. Could that area be at absolute zero?

[phantom power]

10. No, for two reasons...

The first is that there is no region untouched by light, at least according to our current cosmology.

The second is that even a perfect vacuum has nonzero energy, due to quantum fluctuations.

[caraher]

11. Which brings up what you must bear in mind about numbers like Ketterle's...

The temperature is a measure of the random thermal motion of the sodium atoms only. The vacuum chamber in which these cold atoms reside is immersed in all sorts of energy; never mind vacuum fluctuations, there's blackbody radiation corresponding to the temperature of the vacuum chamber walls, some kinetic energy from background gas atoms (kept to as low a level as their vacuum pumping system allows), not to mention the trapping fields themselves (which can be turned off; in fact, that's how you measure these temperatures - shut off the trap and watch the ball of atoms expand; the expansion rate tells you how fast they were rattling about and therefore how "hot" they were.)

There's a lot of difference between low temperature and the ability of a system to absorb thermal energy without changing temperature. These "cold" atoms are collected in a room temperature environment; you won't see balls of ice forming on their equipment.

It's great physics, but it's not about chilling things with all the usual connotations.