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(Interesting side note: the presence of the CMB is the reason why an official "third law" of thermodynamics is that one can't ever completely reach Absolute Zero, at least until the CMB does. No matter how cold atoms become -- and scientists have cooled them to within fractions of degrees above Absolute Zero, as in Bose-Einstein condensates -- there is still the slightest movement, and therefore heat. The atoms can't become any cooler than the surrounding universe, which is roughly 2.7 degrees K.

I'm not at all an expert on the microwave background, but I work in a lab that does atom trapping, so I know that trapped atoms can get down to a few milliKelvin. And I understand that BECs are in the nanoKelvin range. (Which is why CU Boulder had "the coldest place in the universe" for a little while...)

Also, I'd think that the logic behind the "you can't reach absolute zero" law has to do with the quantum mechanical fact that there's always an uncertainty in your energy.

Nitpicks on the interesting aside, otherwise a very good post, from which I learned stuff I didn't know before.

And once again, I fall victim to late-night sloppiness in how I word things. :) Mary is correct, although cooling the atoms in a BEC so low required carefully isolating them in the lab and all kinds of physics-tricks like evaporative cooling, laser trapping, etc. Which is why it took so long to actually produce a BEC decades after Einstein and Bose predicted this new state of matter. I was trying to make things easier for a non-scientist to grasp, and fell into my own trap of thereby getting it wrong. It happens. :)

astute readers, like commenter Mary, will notice that my late-night attempt to explain this isn't quite right. BECs are colder than the CMB -- mere millikelvins above Absolute Zero, in fact, although in order to accomplish this feat, scientists must perform all kinds of "tricks" like evaporative cooling and laser traps, in isolated, tightly controlled lab conditions.

Actually, if you want to get really picky, BEC's in dilute atomic vapors get much colder than that-- nanokelvin are pretty typical, and with a bit of work, the KEtterle group got down to less than half a nanokelvin (450 picokelvin, IIRC).

Nernst's original statement of the Third Law came out before quantum mechanics was invented. A "classical" treatment of the Third Law involves describing how it becomes harder to remove heat from an object as the temperature drops, which is tied to the way the Law is often stated: "The entropy of a system at absolute zero is zero." The best link I could find on short notice is the following:

This also looks like a good general backgrounder:

The handy mnemonic for the Three Laws which that link provides (attributed to C. P. Snow, he of the "two cultures" idea) shows up in Thomas Pynchon's short story "Entropy".

What always gobsmacks and flabbergasts **me** is that thanks to Ketterle and the Bose-Einstein condensate crowd, we can **routinely** make things in our laboratories which are colder than intergalactic space. Colder. Than. Intergalactic. Space.

That T-Shirt is fabulous. I love the proliferation of Geek T-Shirts. I wore one many years ago with Maxwell's Equations ( on the front and the phrase "... and God said, 'Let there be light.'" on the back. I hope I still have it in the basement somewhere...

wow, you pour a lot into you entries. despite mary's astute correction, this is much better than most (if not all) of the published news stories i've seen.

good job, Jen-Luc

a very cool ;-) post - and that cartoon is really awsome!

By the way, there are even extended regions in the universe that are colder than the 2.7 Kelvin - the Boomerang Nebula for example:

I was quite surprised when learning that. It seems to be so because that planetary nebula has been expanding very fast, and has cooled adiabatically, and temporarly, below the background temperature.

"But in order for that model to be correct, there should be the equivalent of a cosmic afterglow of about 3 degrees K, per the prediction of Princeton physicist Robert Dicke."

Dicke did, independently, come to this conclusion, but I think it's worth noting that Gamow, Alpher, and Herman beat them to it by more than a decade.

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    • Heavy G
      The perfect pick-me-up when gravity gets you down.
      2 oz Tequila
      2 oz Triple sec
      2 oz Rose's sweetened lime juice
      7-Up or Sprite
      Mix tequila, triple sec and lime juice in a shaker and pour into a margarita glass. (Salted rim and ice are optional.) Top off with 7-Up/Sprite and let the weight of the world lift off your shoulders.
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      The perfect nightcap after a long day struggling with QED equations.
      1 oz dark rum
      1/2 oz light rum
      1 oz Tia Maria
      2 oz light cream
      Crushed ice
      1/8 tsp ground nutmeg
      In a shaker half-filled with ice, combine the dark and light rum, Tia Maria, and cream. Shake well. Strain into an old fashioned glass almost filled with crushed ice. Dust with the nutmeg, and serve. Bongos optional.
    • Combustible Edison
      Electrify your friends with amazing pyrotechnics!
      2 oz brandy
      1 oz Campari
      1 oz fresh lemon juice
      Combine Campari and lemon juice in shaker filled with cracked ice. Shake and strain into chilled cocktail glass. Heat brandy in chafing dish, then ignite and pour into glass. Cocktail Go BOOM! Plus, Fire = Pretty!
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      3/4 Triple sec
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      Any mad scientist will tell you that flames make drinking more fun. What good is science if no one gets hurt?
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      1-1/2 oz sour mix
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      Warning: may result in amplified stimulated emission.
      1 oz Southern Comfort
      1/2 oz Amaretto
      1/2 oz sloe gin
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      1/4 oz Grand Marnier
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      So called because after one of these, you have already passed the event horizon of inebriation.
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