The first law of thermodynamics states that energy cannot be created or destroyed, but can be converted into different forms. It has been used to describe many things, including how refrigerators and car engines work. It is one of the pillars of physics.

The first law of thermodynamics, created in the 1850s, is only valid for systems in equilibrium or a state where a temperature can be accurately determined. For example, a cup of cold water and a cup of hot water will gradually reach a warm temperature when combined. This warm temperature is the equilibrium. However, the water is out of equilibrium if the hot and cold water have not yet reached that end point.

Similarly, systems need balance in many branches of modern research. The first law has been extended for more than a century for common materials that are out of equilibrium. However, such ideas only hold true when the system is roughly there, for example when the hot and cold water are almost mixed. For example, in space plasmas, which are far from equilibrium, the ideas do not apply.

Physicists at West Virginia University have made a breakthrough in an age-old constraint on the first law of thermodynamics. The study is expected to renew scientists’ understanding of how plasmas heat up in space and laboratories, and may have a wide range of further applications in physics and other sciences.

Paul Cassak, professor and associate director of the Center for KINETIC Plasma Physics, said: “We have generalized the first law of thermodynamics for systems that are not in equilibrium. We did a pencil and paper calculation to find out how much energy is associated with matter that is not in equilibrium. It works whether the system is close to or far from equilibrium.”

There are several possible applications for their study. The idea will help scientists understand space plasmas, which is crucial for space weather planning. Massive explosions in the solar atmosphere that release superheated plasma into space are the cause of space weather.

cassack said, “The result represents a major step in our understanding. Until now, the state of the art in our research area has been to account for energy conversion associated only with expansion and heating, but our theory provides a way to calculate all the energy resulting from non-equilibrium.”

Graduate research assistant Hasan Barbhuiya, in the Department of Physics and Astronomy, said: “Because the first law of thermodynamics is so widely used, we hope scientists in a wide variety of fields can use our result.”

Pioneering research related to Cassak and Barbhuiyas is being conducted in PHASMA, the PHAse Space MApping experiment, at the WVU Center for KINetic Experimental, Theoretical, and Integrated Computational Plasma Physics.

Magazine reference:

  1. Paul A. Cassak, M. Hasan Barbhuiya, Haoming Liang, and Matthew R. Argall. Quantification of energy conversion in higher order phase-space density moments in plasmas. Physical assessment letters. DOI: 10.1103/PhysRevLett.130.085201