I am taking a physics course that very lightly touches the idea of absolute zero and doesn’t get into the juicy details so a few questions have popped in my head.
With today’s technology and all, have we ever lowered the temperature of any substance to the temperature of absolute zero (-273.15 Celsius, if I’m not mistaken)? If yes, how? If no, why?
What are the applications of this value of AZ, besides advancements of superconductors?
These are the only questions that I’ve come up with for the time being, any illumination would be appreciated.
The lower temperature attained the more difficult it is to achieve an even lower temperature, according to the Third Law.
And it would be impossible to observe a substance at absolute zero, since the fact of observation would require the interaction of photons with that substance which would by its very nature increase the energy state and destroy the absolute zero temperature state.
I have very little background in physics, and I’m sure other Dopers (like myles) will give a much better technical explanation, but here’s how I think of the situation:
When you put an object in an environment that is colder than itself, it loses heat to the surrounding environment until the system reaches equilibrium. The hot object gets a bit colder, and the cold environment gets a little bit hotter, so that neither is as cold as the original cold environment nor as hot as the initial hot object. Thus, to decrease the temperature of an object to absolute zero, you would need to expose it to a substance colder than absolute zero. This, of course, is impossible.
A much better explanation would probably involve molecular motion and the Heisenberg Uncertainty Principle, but I’d just make myself look silly if I brought those into it.
Not necessarily. Carl Weiman of UC Boulder won the Nobel Prize for achieving a temperature low enough to produce the Bose-Einstein Condensate. He achieved that temperature by using lasers to deflect photons against the particles, physically slowing their vibrations.
Here’s Wikpedia’s article on absolute zero. Needless to say (???) liquid Helium (~4K) is positively balmy compared to the current record. Sheesh, we used liquid Helium in sophomore Physics Thermo lab. Hardly a state-of-the-art situation.
(Let me tell you though, when you get down to 2.7K (?) and the Helium suddenly stops roiling it’s sweeeet.)
I was kinda wondering on the applications of AZ would there even be any? What would be the point? If something could attain AZ then how would you heat it back up again? Wouldn’t heating it up mean that it’s reacting to other atoms and if it can react would that imply that the atoms were vibrating to react in the first place?
We’ve got a magnetometer that is based on He-cooled superconducting coils. By adiabatic expansion of the He into a sample space, we can go from 4.2K to 1.5 or 1.6K. It’s cool.
Nothing in the universe is that cold… Except for my wife when she’s not in the mood.
Seriously though… AZ… the point at which all molecular motion ceases… wouldn’t that by definition be impossible? I mean, if we could do it, wouldn’t we be able to measure the motion (none) and location. of an electron with 100% certainty, thereby breaking the Heisenberg Uncertainty Principle?
Doesn’t the universe like, I don’t know, evaporate in a sudden puff of smoke or something, if you do that?
I’m not sure what you mean. If an object isn’t vibrating now, it doesn’t mean it’s incapable of vibrating or transmitting vibration. In any case there are other ways to transfer heat, e.g radiation.
In fact that’s one of the uses of extremely low temperatures; if you have a tiny block of material cooled to near absolute-zero, even one X-ray photon gives it a significant increase in temperature. If you measure the temperature with a very accurate thermometer, you can measure the energy of the photon precicely. This is currently the most accurate method of measuring X-ray photon energy, and one of the newest and most exciting tools for X-ray astronomy. (Unfortunately the Astro-E satellite, carrying the first X-ray calorimeter for orbital use, was destroyed in a launch failure. They are building a replacement now.)
Apparently (and I know otehr posters can answer this better) attempts to image atoms at near absolute zero resulted in a smear of the particles, thereby maintaining the Heisenberg Uncertainty Principle. They weren’t fooled that easily!
But still… If it was done NEAR AZ, I would still expect a “smear”, as I’d expect you’d image a probability cloud, so to speak. If we could do it AT AZ, I wonder if that would still be the case.
Then again, I suppose the act of observing would impart some energy, thereby raising the temperature some measure above AZ and preserving the HUP (exactly by definition as it so happens!)
Eh, quantum mechanics is for people that can balance their checkbook, so I’m out of it.
Eric Cornell (UC and JILA) and Wolfgang Ketterle (MIT) shared that prize.
Laser cooling starts the procedure, but a magnetic trap and evaporative cooling are required to get to the coldest temperatures. Lasers will get you to a few hundred nanoKelvin, if you do it right. The next steps get you down to the few nanoKelvin range.
How about manufacturing gold? Okay, so it is somewhat out there, but if you take a look at this thread you will find a few links I posted earlier that should prove to be interesting. Absolute Zero and Bose Einstein Condensates are fascinating stuff. At a minimum, you are going to learn a great deal about matter itself when you bring it down to close to AZ.
