NOVA: "Absolute Zero" on PBS in USA

[iNow]

The good stuff: ludicrously cold atoms.

 

I've been doing homework for several hours each night after work all week, so had it recorded. Just watched it tonight. How freakin' awesome! Liquid Helium, bose-einstein condensate, 100 picokelvin!

 

MAN, science is bad ass!

[swansont]

I was a little disappointed they glossed over the laser cooling — it actually happened in two phases. First, they used "Doppler cooling" to get down to the milliKelvin level, and later they noticed that you could get colder and figured out why (you use the internal state structure of the atoms) and this got atoms down to microKelvin temperatures. They didn't interview any of the '97 Nobel winners about all of this.

 

The quantum computing and slow light stuff at the end was fluff; I don't think it really added much.

[iNow]

I was a little disappointed they glossed over the laser cooling — it actually happened in two phases. First, they used "Doppler cooling" to get down to the milliKelvin level, and later they noticed that you could get colder and figured out why (you use the internal state structure of the atoms) and this got atoms down to microKelvin temperatures.

See, now for me, I'd never encountered much of the information they presented, so I'm not sure I would have been able to digest more... my mind was already boggled.

 

With the laser cooling, they said that lasers are tuned to the same frequency of the atoms, and it causes them to vibrate less? Is that correct? I wasn't too sure how the lasers caused them to cool. Is this where your reference of "doppler cooling" comes in?

 

 

I also think whoever came up with the idea of a magnetic bowl was pretty brilliant. Allowing the more energetic atoms to pop out the sides (like a cup of coffee) to get evaporative cooling at such low temps... It makes me smile just thinking about it. It was just all so new to me, but I appreciate your point that they glossed over it. Had they spent more time, maybe I wouldn't have needed to ask the questions I did above.

[swansont]

See, now for me, I'd never encountered much of the information they presented, so I'm not sure I would have been able to digest more... my mind was already boggled.

 

With the laser cooling, they said that lasers are tuned to the same frequency of the atoms, and it causes them to vibrate less? Is that correct? I wasn't too sure how the lasers caused them to cool. Is this where your reference of "doppler cooling" comes in?

 

 

I also think whoever came up with the idea of a magnetic bowl was pretty brilliant. Allowing the more energetic atoms to pop out the sides (like a cup of coffee) to get evaporative cooling at such low temps... It makes me smile just thinking about it. It was just all so new to me, but I appreciate your point that they glossed over it. Had they spent more time, maybe I wouldn't have needed to ask the questions I did above.

 

It's atoms in a gas, so it's not vibration, it's translational KE and collisions. The photons scatter off of the atoms and slow them down. The "Doppler" part comes in because the speed of the atom shifts the frequency (closer or further from resonance) and affects the scattering rate.

 

I remember going to atomic physics meetings and hearing the progress reports as the BEC groups tried to get closer. You need a combination of high density and cold atoms, and it seemed like they were getting an order of magnitude closer each year (in the metric that they used), but they started out 4 or 5 orders of magnitude away. Evaorative cooling was the key step, and it works because the temperature drops faster than you lose atoms, since (as Eric Cornell described) you lose the most energetic atoms, so they take more than the average amount of energy away.

[iNow]

Interesting press release at my school. I haven't yet read the actual article in Physical Review Letters, but for those so inclined:

 

 

http://www.utexas.edu/news/2008/03/06/physics_atoms/?AddInterest=1284

 

To date, cooling atoms near the Absolute Zero (-459 degrees Fahrenheit) has been accomplished using laser cooling, a method that was recognized by the Nobel Prize in Physics in 1997. Despite its enormous success, laser cooling has been limited to a small set of atoms in the periodic table.

 

Raizen says his two methods can be used in tandem to trap and cool near Absolute Zero any of the paramagnetic atoms, which make up over 85 percent of the periodic table.

[iNow]

Necro'ing this old thread to share this very accessible video about extreme cooling. Would it be corny to suggest it's very cool?

 

[swansont]

Necro'ing this old thread to share this very accessible video about extreme cooling. Would it be corny to suggest it's very cool?

Great explanation of how a dilution refrigerator works.

[NATO]

If nothing can ever reach 0k would that not mean that no matter how much the universe decomposes, after all the stars have died, it can never truly go blank.

[iNow]

NOVA had another cool special recently on these topics.

 

Making Stuff Colder

 

http://video.pbs.org/video/2365109000/