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  #1  
Old 09-10-2003, 02:37 PM
The Chao Goes Mu The Chao Goes Mu is offline
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What is the coldest possible temperature?

Ok…so….I’ve been reading a little about the “Hot Big Bang Theory” and it mentions that at the moment before the “bang” the singularity was infinitely hot but 1 second after the bang the universe had cooled to something like 10 thousand million degrees and now is in most regions a couple of degrees above absolute zero (I think that’s about –275 degrees.. anyone?) This got me thinking….what is the coldest temperature possible? Is there anything colder than the cooling universe? Is "cold" just the absence of "heat?"
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  #2  
Old 09-10-2003, 02:43 PM
friedo friedo is offline
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They call it absolute zero for a reason. Molecular motion stands still at about -273 degrees celsius. Can't get colder than that.
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Old 09-10-2003, 02:46 PM
wet marble wet marble is offline
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OR...

0° Kelvin

OR ...

~-459° Farenheit
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  #4  
Old 09-10-2003, 02:57 PM
Whack-a-Mole Whack-a-Mole is offline
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It should be noted that Absolute Zero is impossible to reach. You can get arbitrarily close to it but you'll never quite get there.

Deepest outer space (i.e. as far from any star or planet as you are able to get) is about 3o above absolute zero.

Scientists have been able to do a lot better here on earth and have cooled atoms down to 0.000000001 (a few billionths of a degree) above absolute zero. When they did this they saw a starnge and rare creature called a Bose-Einstein Condensate form. Essentially the atom they cooled 'smeared' out in space to much larger than its normal size. It did this to keep within the Heisenberg Uncertainty Principle (that you cannot know both the position and velocity of a particle with perfect accuracy...the better you know one detail [of the two] the less accurate you are about the other detail. By slowing an atom down to very close to absolute zero you know the velocity of the atom with great precision. One would think you would then also know the location (barely moving at the bottom of your detector). The Universe is hip to this trick though and smears out the particle such that its position is not known well at all.
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Old 09-10-2003, 03:02 PM
Phage Phage is offline
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Absolute Zero is impossible to reach currently, but who knows what we will be able to do? Absolute Zero is the coldest temperature possible, we just can't do it yet.
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Old 09-10-2003, 03:08 PM
MC Master of Ceremonies MC Master of Ceremonies is offline
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Quote:
Originally posted by Phage
Absolute Zero is impossible to reach currently, but who knows what we will be able to do? Absolute Zero is the coldest temperature possible, we just can't do it yet.
Absoluite zero is impossible to reach theoritically in thjermodynamics, that said given the statisical nature of thermodynamics, it could just be possible with a lot of luck.
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Old 09-10-2003, 03:20 PM
The Chao Goes Mu The Chao Goes Mu is offline
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Ok got it! Thank you all for the clarification. So here's another related question. What would happen if absolute zero could be reached somehow.? Are there any calculations for this possibility? Theories? Would everything cease to exist? I'm getting sci fi here and thinking of Vonnegut's Ice-9 in the "Cat's Cradle"
Ok so in "our" universe or absolute zero would have to be unattainable for our universe to be able to support the laws that exist in it but are there any notions that in another universe those particular laws do not exist so that absolute zero could be reached?
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Old 09-10-2003, 03:27 PM
squid squid is offline
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Quote:
Originally posted by Phage
Absolute Zero is impossible to reach currently, but who knows what we will be able to do? Absolute Zero is the coldest temperature possible, we just can't do it yet.
Using my "beer in a bucket of ice" theory...you need ice at 32 degrees to chill down a beverage but you won't chill it beyound 32 degrees. Wouldn't you need something colder then absolute zero to cool something to absolute zero.
Pardon my puney brain thinkin'.
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  #9  
Old 09-10-2003, 03:34 PM
friedo friedo is offline
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Quote:
Wouldn't you need something colder then absolute zero to cool something to absolute zero.
Pardon my puney brain thinkin'.
Not that puny, since it's absolutely correct. Energy wants to move from a source to a sink. You can't create cold, though you can move heat from one place to another. In order to move heat, you need something cold to warm up.
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  #10  
Old 09-10-2003, 03:42 PM
Bryan Ekers Bryan Ekers is offline
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Quote:
Originally posted by CURIOUS_GEORGIE7
What would happen if absolute zero could be reached somehow.? Are there any calculations for this possibility? Theories?
One's nipples would become hard enough to cut diamond.

It's true. I saw it on Nova.
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  #11  
Old 09-10-2003, 03:45 PM
MC Master of Ceremonies MC Master of Ceremonies is offline
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Quote:
Originally posted by CURIOUS_GEORGIE7

Ok got it! Thank you all for the clarification. So here's another related question. What would happen if absolute zero could be reached somehow.? Are there any calculations for this possibility? Theories? Would everything cease to exist? I'm getting sci fi here and thinking of Vonnegut's Ice-9 in the "Cat's Cradle"
Ok so in "our" universe or absolute zero would have to be unattainable for our universe to be able to support the laws that exist in it but are there any notions that in another universe those particular laws do not exist so that absolute zero could be reached?
The laws of thermodynamics are some of the strongest laws in physics they hold in just about every situation (though as I said before given their statistical nature there's always a minucle possibilty they won't, especially on very small scales). If absolute zeroes reach, nothing magical happens (well except the odd Bose-Einstein condensate) and particles still have vibrational energy (so-called zero-point energy).
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  #12  
Old 09-10-2003, 03:45 PM
Whack-a-Mole Whack-a-Mole is offline
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Quote:
Originally posted by squid
Using my "beer in a bucket of ice" theory...you need ice at 32 degrees to chill down a beverage but you won't chill it beyound 32 degrees. Wouldn't you need something colder then absolute zero to cool something to absolute zero.
Pardon my puney brain thinkin'.
That makes sense on the face of it but remember that temperature is an indicator of motion. To go cold all you want to do is slow down the object (or atoms in that object) that you are trying to cool. In the case fo the guys who got to within a few billionths of a degree of absolute zero they did it with lasers. Lasers ringed the chamber containing the atom they wanted to cool down. If the atom moved one way a laser would fire and push back. Then anopther laser would fire nudging against its motion. Think of stopping a thether ball by poking in opposite directions to its motion with your finger till it stopped and you kinda have the idea.

Unfortunately I think you'll run into issues as the thing gets slower and slower. There are limits (maybe Planck?) to just how small a measurment you can take. Eventually you'll be unable to distinguish which way the particle is moving to counteract its motion. This will be exceedingly cold and slow but still not absolute zero.
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  #13  
Old 09-10-2003, 03:52 PM
CurtC CurtC is online now
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But what if it's absolute zero... and the wind was blowing? How cold would it feel?
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  #14  
Old 09-10-2003, 04:03 PM
Thaumaturge Thaumaturge is offline
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The motion of the wind would raise the temperature, so it would feel slightly warmer.
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Old 09-10-2003, 04:07 PM
UncleBeer UncleBeer is offline
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But you'd still wish you had your mittens.
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  #16  
Old 09-10-2003, 04:17 PM
Schnitte Schnitte is offline
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Quote:
Originally posted by wet marble
OR...

0° Kelvin
Nitpick: It's not 0° Kelvin, it's simply zero Kelvin, or 0 K. Kelvin is the name of the SI unit of temperature.
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  #17  
Old 09-10-2003, 04:18 PM
NurseCarmen NurseCarmen is offline
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Quote:
Originally posted by Bryan Ekers
One's nipples would become hard enough to cut diamond.

It's true. I saw it on Nova.
Who cares about nipples! Think about the shrinkage!
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  #18  
Old 09-10-2003, 04:19 PM
The Griffin The Griffin is offline
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At absolute zero there would be no wind, because even hydrogen would be frozen.
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  #19  
Old 09-10-2003, 05:32 PM
Whack-a-Mole Whack-a-Mole is offline
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Quote:
Originally posted by CURIOUS_GEORGIE7
Ok got it! Thank you all for the clarification. So here's another related question. What would happen if absolute zero could be reached somehow.? Are there any calculations for this possibility? Theories? Would everything cease to exist?
Nothing especially spectacular (I think). Unless you'd get a Bose-Einstein Condensate the size of the Universe. Frankly it'll take Chronos and company to answer that one.

WAG:
At Absolute Zero a particle might conceivably grow over time. Since the velocity is known with 100% precision I suppose the position would need to be known with a 100% lack of precision. Thus the probability function that represented the particle's position would grow ever larger to include all possible points the particle might theoretically make it to within that timespan. Of course you could collapse the whole thing as soon as energy was added back to the particle to raise it back above 0 Kelvin. That wouldn't take long as there is lots of energy available in the universe. The guys who got to a billionth of a degree above 0 K had to isolate the equipment from vibrations that came from a highway over a mile away. Supposedly walking in the room with the equipment (vibrations again) would affect the temperature. Doesn't seem like it would take much to get the BEC back up in temp. This also suggestes that even if MC Master of Ceremonies is correct that staistically a particle might drop to 0 K it will likely not stay there for long at all (a really, really short span of time I would guess).
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  #20  
Old 09-10-2003, 05:39 PM
Malacandra Malacandra is offline
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Quote:
Originally posted by squid
Using my "beer in a bucket of ice" theory...you need ice at 32 degrees to chill down a beverage but you won't chill it beyound 32 degrees. Wouldn't you need something colder then absolute zero to cool something to absolute zero.
Pardon my puney brain thinkin'.
Don't think "beer in a bucket of ice", then. Here's a couple of ways to lower temperature without having something colder than the temperature you want to reach:

Take an insulated bucket of crushed ice and stir lots of salt in it. The ice melts, 'cos the freezing point of salt water is lower than the freezing point of fresh, but to turn liquid it has to reassign some of the heat energy that's in it... This is slightly complex, but when something is liquid a certain amount of the heat in it isn't expressed as "temperature" but just as "energy keeping this thing liquid". Latent heat of fusion, is the technical term. So the amount of heat in the insulated bucket stays constant, but some of it has turned into latent heat of fusion, and there's less left over to keep up the temperature - so the temperature drops. You can get all the way to 0 degrees Fahrenheit this way, and this is exactly how Fahrenheit arrived at the zero point for his scale.


Take some air and compress it in a pump. It gets warmer. Allow it to cool back to room temperature. Now allow it to expand. It gets cooler - cooler than you started with. This is how your fridge works. An extension of this technique will let you create liquid air.

And if this isn't an occasion to use the smilie, when is?
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  #21  
Old 09-10-2003, 05:49 PM
MC Master of Ceremonies MC Master of Ceremonies is offline
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I've just looked this one up, apparently matter undergoes a phase transition at 0K in quantum theory as it becomes governed by quantum fluctuations.
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  #22  
Old 09-10-2003, 05:59 PM
Achernar Achernar is offline
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Ignoring quantum for a minute, theoretically speaking, you can't cool a block down to Zero. This is part of the Third Law of Thermodynamics. This applies to a block with enough particles that it can be treated as a statistical system. You could in theory stop all motion of a single particle. However, at that point it's kind of silly to say that it's at Absolute Zero, since thermodynamic temperature itself is a statistical property, not very good at dealing with single particles. We don't really think of a single atom as having a temperature.

However, that's in classical theory. As has been noted, quantum physics makes it even more difficult, in that you can't even stop all motion of a single particle. There's something called zero-point energy, which oddly enough is not zero. It's the least energy that a particle can have, but it's still positive. Even if all the particles in your block were at their zero-point energy, the block would still be a few femtoKelvin above Absolute Zero.
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  #23  
Old 09-10-2003, 08:30 PM
Dr_Paprika Dr_Paprika is offline
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The lowest temperature, IIRC, is absolute minus twelve.
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  #24  
Old 09-10-2003, 08:56 PM
Apoptosis Apoptosis is offline
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Hey Whack-a-Mole,
Quote:
Deepest outer space (i.e. as far from any star or planet as you are able to get) is about 3 [degrees] above absolute zero.
This is something that puzzles me. I understand that temperature is an indicator of molecular motion. How can you describe the temperature of a vacuum when, by definition, it doesn't even possess any molecules?

Here's Cecil's stab at it.

-Apoptosis
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  #25  
Old 09-10-2003, 09:58 PM
Whack-a-Mole Whack-a-Mole is offline
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Quote:
Originally posted by Apoptosis
Hey Whack-a-Mole,

This is something that puzzles me. I understand that temperature is an indicator of molecular motion. How can you describe the temperature of a vacuum when, by definition, it doesn't even possess any molecules?

Here's Cecil's stab at it.

-Apoptosis
Are you askig me to answer? Cecil put it better than I could have. You are correct that a vaccuum has no temperature but as Cecil notes whatever you place in space will not cool below 3o K due to background radiation and the odd particle flitting about. I'm reasonably certain this temperature is cooling however and will continue to do so forever eventually resulting in the heat death of the Universe.

Hmm...I guess the Universe someday will be composed of nothing but Bose-Einstein Condensates. Humans will of couse be LONG gone before then.
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  #26  
Old 09-10-2003, 10:47 PM
gscotb gscotb is offline
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You know when you are close to that temperature:

Lawyers have their hands in their own pockets.
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  #27  
Old 09-10-2003, 11:08 PM
wolf_meister wolf_meister is offline
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And for those sticklers for accuracy, absolute zero is:

-273.15 Celsius and
-459.67 Fahrenheit
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  #28  
Old 09-10-2003, 11:19 PM
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My X is much more frigid than absolute zero. Maybe scientists should check into her to see how she breaks the rules of thermodynamics and quantum mechanics... she does what she pleases.
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  #29  
Old 09-11-2003, 08:37 AM
Whack-a-Mole Whack-a-Mole is offline
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Quote:
Originally posted by Apoptosis
Hey Whack-a-Mole,

This is something that puzzles me. I understand that temperature is an indicator of molecular motion. How can you describe the temperature of a vacuum when, by definition, it doesn't even possess any molecules?
I forgot to add that while speaking of the temperature of deep space might be technically wrong and a little loose with the concept in some ways you can still think of it that way. When you place a glass of water on your desk it eventually comes into equilibrium temperature-wise with the ambient temperature in the room. Place an object in deep space and its eventual equilibrium temperature with the space around it will be about 3o K. Since all of that is a hassle to explain everythime you want to talk about the idea you usually just hear it as space being around 3o K in temperature.
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Old 09-11-2003, 12:19 PM
alimarx alimarx is offline
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Quote:
Originally posted by Deathstatic
My X is much more frigid than absolute zero. Maybe scientists should check into her to see how she breaks the rules of thermodynamics and quantum mechanics... she does what she pleases.
That explains those love handles! What you thought was fat was actually just a Bose-Einstein Condensate smear!
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  #31  
Old 09-11-2003, 12:37 PM
wet marble wet marble is offline
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Ok,

So if absolute zero is the same as zero movement, and scientists have gotten a particle to within a billionth of a degree of absolute zero, how do the scientists acount for the rotational movement of our solar system and it's affect on the particle?

Or is absolute zero now being defined as zero movement relative to all of the other particles around it?
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  #32  
Old 09-11-2003, 01:48 PM
Charlie Tan Charlie Tan is offline
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Very interesting thread. And related I want to ask if there is no upper limit to temperature? The OP mention 10 000 million degrees (which would almost be the same in F and C, no? Or at least and infinite number of degrees F is the same temperature as an infinite number of degress C?)
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  #33  
Old 09-11-2003, 02:43 PM
Whack-a-Mole Whack-a-Mole is offline
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Quote:
Originally posted by The Gaspode
Very interesting thread. And related I want to ask if there is no upper limit to temperature? The OP mention 10 000 million degrees (which would almost be the same in F and C, no? Or at least and infinite number of degrees F is the same temperature as an infinite number of degress C?)
This was asked just yesterday in a recent thread Is there a maximum temperature? Cecil also covered it here.

To summarise (if you don't want to read those threads) is that the highest temperature possible is called the Planck Temperature and is around 1032 degrees Kelvin. Compare that to the interior of our sun which is around 15*106 (or 15 million degrees). The hottest stars will push up into 109 degrees (or billion degrees) but I suspect hotter temperatures occur in supernova explosions and maybe some other special cases. However, 1032 degrees Kelvin is WAY up there and presumably only reached instants after the Big Bang.

Apparently the limiting factor here is that at 1032 degrees Kelvin an individual particle has enough energy to form its own, mini-black hole. Remember that mass and energy are interchangeable. Even though the particle doesn't haev much mass (normally) at that energy it effectively does and will collapse on itself. I don't know if a singularity inside a black hole could be said to have a temperature but at a guess I would think it is infinite. Of course getting close enough to one to stick a thermometer into it would make you a part of the singularity and you wouldn't be able to tell anyone anyway.
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Old 09-11-2003, 03:26 PM
The Chao Goes Mu The Chao Goes Mu is offline
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Originally posted by The Gaspode
Very interesting thread. And related I want to ask if there is no upper limit to temperature? The OP mention 10 000 million degrees (which would almost be the same in F and C, no? Or at least and infinite number of degrees F is the same temperature as an infinite number of degress C?)


Interestingly enough....we can create this temperature when we explode an H-bomb.

I can't even conceive of 10,000,000,000 degrees Farenheit.
After that what's a few million degrees? Wow! It really cooled down today! It's only 9,000,000,000 degrees! Better grab a sweater
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  #35  
Old 09-11-2003, 11:15 PM
Ale Ale is offline
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Quote:
To summarise (if you don't want to read those threads) is that the highest temperature possible is called the Planck Temperature
Planck this, Planck that; geez, that guy Planck must be doing cartloads of money with the royalties.

Hey, quick, what sound do two Quarks when they crash into each other?

"Planck!!!" of course.

*runs away in shame*
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  #36  
Old 09-12-2003, 12:36 AM
d12 d12 is offline
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"I used to walk to school in temperatures below absolute zero, 'course that was on a warm day."

/Grandpa
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  #37  
Old 09-12-2003, 02:17 AM
DrMatrix DrMatrix is offline
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Quote:
Originally posted by Whack-a-Mole

I'm reasonably certain this temperature is cooling however and will continue to do so forever eventually resulting in the heat death of the Universe.
I've seen heat death refer to the cooling down of the universe, but the first use of heat death was when it was thought that the universe was static. Heat death referred to when max entropy was reached and all energy was in the form of heat and unusable. Cold death more accurately describes what we now expect.
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Old 09-12-2003, 06:38 AM
MC Master of Ceremonies MC Master of Ceremonies is offline
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Quote:
Originally posted by DrMatrix
I've seen heat death refer to the cooling down of the universe, but the first use of heat death was when it was thought that the universe was static. Heat death referred to when max entropy was reached and all energy was in the form of heat and unusable. Cold death more accurately describes what we now expect.
'Heat death' describes when an isolated system reaches it's maximum entropy, it can be applied to any (isolated) thermodynamic system.
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  #39  
Old 09-12-2003, 06:41 AM
alterego alterego is offline
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A new coldest temperature has been recorded just today.

the researchers cooled a sodium gas to only a half-billionth of a degree

bRRRRRRR!!!!!
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  #40  
Old 09-12-2003, 06:52 AM
refusal refusal is offline
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Quote:
Originally posted by Whack-a-Mole
I don't know if a singularity inside a black hole could be said to have a temperature but at a guess I would think it is infinite. Of course getting close enough to one to stick a thermometer into it would make you a part of the singularity and you wouldn't be able to tell anyone anyway. [/B]
IANAPhysicist, but because black holes have a finite entropy, and radiate like a black box of temperature (6 x 10^-8)/M kelvin (where M is the mass in units of the sun's mass), I believe they can be viewed as having a finite temperature, albeit a very cold one. Although I don't believe what is happening in a black hole is entirely understood (pending a proper theory of quantum gravity).

http://math.ucr.edu/home/baez/physic...s/hawking.html
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Old 09-12-2003, 09:24 AM
filmore filmore is offline
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Originally posted by Whack-a-Mole
That makes sense on the face of it but remember that temperature is an indicator of motion. To go cold all you want to do is slow down the object (or atoms in that object) that you are trying to cool.
I hope people are still reading this thread because here's something I've always wondered about Bose-Einstein Condensate: How does the atom know it's stopped? It's only stopped relative to the table top on which the experiment is being peformed. It's still rotating around the earth rotating around the sun and so on. If I was on an airplane zooming over the "stopped" atom, would I be able to observe the Bose-Einstein Condensate since the atom was not stopped relative to me? Or if the experiment was being performed on a moving train, would an observer standing still outside the train be able to observe the condensate?
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  #42  
Old 09-12-2003, 09:30 AM
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If you've never seen anything colder than absolute zero you haven't met my ex-wife.
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  #43  
Old 09-12-2003, 10:33 AM
flonks flonks is offline
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Originally posted by friedo
Not that puny, since it's absolutely correct. Energy wants to move from a source to a sink. You can't create cold, though you can move heat from one place to another. In order to move heat, you need something cold to warm up.
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  #44  
Old 09-12-2003, 07:15 PM
MC Master of Ceremonies MC Master of Ceremonies is offline
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Originally posted by Hampshire
If you've never seen anything colder than absolute zero you haven't met my ex-wife.
Your ex-wife is easy, what the F--- you complaning about?
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  #45  
Old 09-13-2003, 01:43 AM
culov culov is offline
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http://www.rednova.com/news/stories/.../story001.html


heres another link...
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  #46  
Old 09-13-2003, 01:54 AM
carrielikewhoa carrielikewhoa is offline
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Of COURSE it's possible to reach absolute zero--just stop by your local movie theatre!

/bad joke
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  #47  
Old 09-14-2003, 06:34 AM
Napier Napier is offline
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There is a sense in which parts of a system can get to temperatures below 0 K. That is, you can have two kinds of particles in a system, say electrons (the so-called "electron gas") and nuclei (the part with practically all the mass) in a metal, and the two subsystems can have different temperatures. Then you have an average for the whole thing. It is important because other properties such as the diffusivity can be different for the two subsystems. There are situations where one of the subsystems can have a negative temperature.

Reference, IIRC: "Temperatures Very Low and Very High", forget author, published by Dover.
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  #48  
Old 09-14-2003, 06:57 AM
eburacum45 eburacum45 is offline
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Here is a link to some stuff about Bose-Einstein Condensates;
http://www.colorado.edu/physics/2000/bec/index.html

some interesting educational games to play concerned with low temperature physics
Having lost this link somebody kindly retrieved it for me...
Thank you!
_________________
SF worldbuilding at
http://www.orionsarm.com/main.html
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