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Author Topic: Why can't we reach 0 Kelvin (absolute zero)?  (Read 12259 times)

Nizzle

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Why can't we reach 0 Kelvin (absolute zero)?
« on: 19/08/2009 14:22:33 »
I've read on wikipedia that it's theoretically impossible to reach the absolute zero temperature of 0K.

First question: Why can't we reach 0 Kelvin?
Secnd question: Imagine we would be able to, what would happen at 0 Kelvin?
« Last Edit: 19/08/2009 17:59:25 by chris »

syhprum

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Re: Why can't we reach 0 Kelvin (absolute zero)?
« Reply #1 on: 19/08/2009 14:34:30 »
Here I have broken my own rule and quoted from an authorative source!

http://www.thefreedictionary.com/absolute+zero

"A Closer Look The temperature of a substance is determined by the average velocity of its molecules: the faster they move, the warmer the substance. At absolute zero molecules have minimal kinetic energy (or zero-point energy) and heat energy cannot be extracted from them. The molecules are not motionless, however, due to the uncertainty principle of quantum mechanics, which entails that the atoms cannot have both a fixed position and zero momentum at the same time; instead, the molecules of a substance at absolute zero are always "wiggling" in some manner. Absolute zero is zero degrees Kelvin, equal to -273.15 degrees Celsius and -459.67 degrees Fahrenheit. The coldest known place in the universe is the Boomerang Nebula, where the temperature is -272° Celsius. Scientists at Massachusetts Institute of Technology have gone much lower than that by using laser traps and other techniques to cool rubidium to 2 × 10-9 degrees Kelvin."

Nizzle

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Re: Why can't we reach 0 Kelvin (absolute zero)?
« Reply #2 on: 19/08/2009 17:38:37 »
I know what it is, but thx anyway.
My question is more about why it is, even theoretically, impossible to get there..

lyner

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Why can't we reach 0 Kelvin?
« Reply #3 on: 19/08/2009 18:00:59 »
A simple reason is this.
To lose heat, or internal energy, you need to share it with something else. However big a fraction of the energy you manage to lose, there is always some left - always giving you a finite temperature.
I think it's a mistake to look at the temperature scale as linear. It fails to give the right impression about what is happening at very low temperatures.
We could think of it like a logarithmic type of scale in which each step represents progressively more and more effort to achieve- not unlike trying to achieve light speed or discussing smaller and smaller times after the BB.

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Why can't we reach 0 Kelvin?
« Reply #3 on: 19/08/2009 18:00:59 »