absolute zero reached yet?

Tree

they'll never ACTUALLY reach it

Capt'n Midnight

Guinness Book Of Records 1997

280 picoKelvin 2.8E-10K in 1993 Finland
ie. slightly more than one billionth of a degree.

The Three Laws Of Thermodynamics can be restated

1/ you can't win you can only break even
2/ you can only break even at absolute zero
3/ you can't reach absolute zero.

dudara

It can never be reached due to the existence of entropy.

The general understaiding of entropy is "disorder", but it physics it refers to the amount of states in a system. If you have agas in which none of the particles are moving, ie, they are all in the same state, then the entropy of that system is very low. if you add some energy, even just a tiny bit to make the particles move, even if very slowly, then the entropy of that system has increased dramatically.

If you are trying to reach absolute zero, any system you make will have to be in some kind of contact with the rest of the universe, so there will always be a source of energy and
therefore entropy that you can never fully shield out.

The moral is, we can get very close, but we can't touch.

Deacon Blues

Surely to cool a sample to a particular temperature, you need heat to transfer out of it. This means that the surrounding material must be either at or below the required temperature. Therefore, to reach absolute zero, there must be already a material at absolute zero. As this doesn't exist, we can never reach absolute zero.

Be gentle with me. I'm an interested amateur, and this is my first post. I accept the entrophy answer, but find the heat transfer solution easier to visualise in an everyday world sort of way.

secret_squirrel

You'd think so wouldnt you Deacon blue - but you dont actually have to have someting colder than a substance to reduce its temperature. For instance (and this is a bit 'handwavey') you can use a laser to stimulate a substance so that it actually releases more energy than was put into it - effectively cooling it since how hot something is is actually a measure of how much energy something has. Its known (unsurprisingly) as laser cooling. There are a number of other techniques as well, although I have spent the last ten years slowly forgetting the stuff I learnt about them for my degree .

rubadub

Originally posted by Deacon Blues
Surely to cool a sample to a particular temperature, you need heat to transfer out of it. This means that the surrounding material must be either at or below the required temperature. Therefore, to reach absolute zero, there must be already a material at absolute zero. As this doesn't exist, we can never reach absolute zero.

Be gentle with me. I'm an interested amateur, and this is my first post. I accept the entrophy answer, but find the heat transfer solution easier to visualise in an everyday world sort of way.

a fridge in a hot room will get cool. if you leave a fridge door open it actually heats the room due to the compressor working overtime and giving off heat.

i think when these guys reach the low temps it is usually only for a split second, AFAIK it can be done with great releases of pressure. ever notice how cool deodorant bottles get when you release the pressure from tehm , or lighter gas cans

Capt'n Midnight

you'll not get below the boiling point of helium releasing compressed gas
you have to be a little sneakier - using lasers & huge magnetic fields to slow down the atoms vibrations (it's the movement that produces heat)

Peace

Yup about the pressure reducing temperature....if i ever have to drain my scuba cylinders i'm releasing 230atmosphers from the tanks in only a few monutes...say 5/10. The tanks get so cold that condensation appears on the surface and eventually will freeze solid.

Kinda cool but not very good for the tanks.