How Thermodynamics Unlocks the Secrets of an Expanding Universe

The shift from a decelerating expansion regime (in the radiation- and matter-dominated era) to an accelerating expansion regime (in the dark energy-dominated era) resembles a thermodynamic phase transition, according to an article in Results in Physics by scientists affiliated with São Paulo State University.

The idea that the Universe is expanding dates from almost a century ago. It was first put forward by Belgian cosmologist Georges Lemaître (1894-1966) in 1927 and confirmed observationally by American astronomer Edwin Hubble (1889-1953) two years later. Hubble observed that the redshift in the electromagnetic spectrum of the light received from celestial objects was directly proportional to their distance from Earth, which meant that bodies farther away from Earth were moving away faster and the universe must be expanding.