Positive temperatures make up one part of the loop, while negative temperatures make up the other part. When temperatures go either below zero or above infinity on the positive region of this scale, they end up in negative territory. Your Basic Physics Questions Answered ].
With positive temperatures, atoms more likely occupy low-energy states than high-energy states, a pattern known as Boltzmann distribution in physics. When an object is heated, its atoms can reach higher energy levels. At absolute zero, atoms would occupy the lowest energy state.
At an infinite temperature, atoms would occupy all energy states. Negative temperatures then are the opposite of positive temperatures — atoms more likely occupy high-energy states than low-energy states. It is even hotter than at any positive temperature — the temperature scale simply does not end at infinity, but jumps to negative values instead.
As one might expect, objects with negative temperatures behave in very odd ways. For instance, energy typically flows from objects with a higher positive temperature to ones with a lower positive temperature — that is, hotter objects heat up cooler objects, and colder objects cool down hotter ones, until they reach a common temperature.
However, energy will always flow from objects with negative temperature to ones with positive temperatures. What if the temperature were so cold that the height of the air column became zero? Therefore it seemed that a minimum temperature would exist. After the laws of thermodynamics were discovered, we have a clearer picture of what is going on. Temperature is an indication of the average amount of internal energy an object possesses.
You can think of it classically as a measure of how vigorously the atoms and molecules in the object are moving around randomly. The higher the temperature, the faster the movement; and it is this movement of the molecules of air in the air column that supports the mercury in Amontons' air thermometer, as the molecules slam into the bottom of the mercury.
Now imagine the particles in an object moving slower and slower, so that its temperature decreases. But this cannot go on forever. At one point, the particles have to stop moving, and this corresponds theoretically to the coldest possible temperature. The space environment, combined with mechanical and cryogenic refrigeration systems using hydrogen and helium, chill the coldest instruments to 0. The lowest temperature ever recorded was back here on Earth in a laboratory. Earlier, scientists at the Helsinki University of Technology in Finland achieved a temperature of 0.
However, this was the temperature for just one particular type of motion — a quantum property called nuclear spin — not the overall temperature for all possible motions. In everyday solids, liquids and gases, heat or thermal energy arises from the motion of atoms and molecules as they zing around and bounce off each other. This means that the atoms exert a negative instead of a positive pressure.
As a consequence, the atom cloud wants to contract and should really collapse — just as would be expected for the universe under the effect of gravity. But because of its negative temperature this does not happen. The gas is saved from collapse just like the universe. Materials provided by Max-Planck-Gesellschaft. Note: Content may be edited for style and length. Science News. Journal Reference : S. Braun, J. Ronzheimer, M. Schreiber, S. Hodgman, T. Rom, I. Bloch, U. Science , ; : 52 DOI: ScienceDaily, 4 January
0コメント