Einstein’s special theory of
relativity has formulas, called Lorentz transformations, that
convert time or distance intervals from a resting frame of reference
to a frame zooming by at nearly the speed of light. But how about
temperature? That is, if a speeding observer, carrying her thermometer with her, tries to measure the temperature of a gas in a stationary bottle,what temperature will she measure? A new look at this contentious subject suggests that the temperature will be the same as that measured in the rest frame. In other words, moving
bodies will not appear hotter or colder.
You’d think that such an issue would have been settled decades ago, but this is not the case. Einstein and Planck thought, at one time,that the speeding thermometer would measure a lower temperature,while others thought the temperature would be higher. One problem is how to define or measure a gas temperature in the first place.
James Clerk Maxwell in 1866 enunciated his famous formula predicting that the distribution of gas particle velocities would look like a Gaussian-shaped curve. But how would this curve appear to be for someone flying past? What would the equivalent average gas temperature be to this other observer? Jorn Dunkel and his colleagues at the Universitat Augsburg (Germany) and the Universidad de Sevilla (Spain) could not exactly make direct measurements (no one has figured out how to maintain a contained gas at relativistic speeds in a terrestrial lab), but they performed extensive
simulations of the matter.
(email@example.com ) says that some astrophysical
systems might eventually offer a chance to experimentally judge the
issue. In general the effort to marry thermodynamics with special
relativity is still at an early stage. It is not exactly known how
several thermodynamic parameters change at high speeds. Absolute
zero, Dunkel says, will always be absolute zero, even for
quickly-moving observers. But producing proper Lorentz
transformations for other quantities such as entropy will be
trickier to do. (Cubero et al., Physical Review Letters, 26 October