-273 Celsius
Most recent answer: 10/22/2007
- Greg (age 16)
Emmanuel College, Perth, WA, Australia
There’s a natural absolute temperature scale , in which temperature is the measure of how likely things are to be found with extra energy above the minimum possible energy, i.e. in states other than the ground state. Formally, the temperature is a measure of how much extra energy is needed to increase the number of available states by a certain factor. The Kelvin scale is an example of such an absolute temperature scale. 0 K means that everything has settled into the lowest possible energy state.
Everyday temperature scales have no fundamental significance. They were just devised to have some easily reproducible reference points in familiar ranges. For Celsius, that’s just the freezing point (0°C) and boiilng point (100°C) of water at some standard pressure. It’s basically an accident that true absolute zero lands at -273.15 on that arbitrarily chosen scale.
Mike W.
Motion hasn’t all ceased at 0 degrees Kelvin, it just means that there are no lower energy states and no probability for the system to be found in a state that’s not the lowest energy state (no more energy can be extracted from the system). Electrons will still move in their orbits, and nucleons will still orbit in the nuclei.
Tom
(published on 10/22/2007)
Follow-Up #1: energy at low temperature
- Indrajit Kuri
New Delhi, India
Temperatures T>0 are not characterized by saying specifically which state a system is in, or even what energy the system has. A temperature corresponds to a set of probabilities for the system being in different states. When the system is big, those probabilities cluster in a collection of states with a relatively narrow range of energies. Only at T=0 does that collapse to a single state. (Or two states, if the system has half-integer spin.)
Mike W.
(published on 07/04/2011)