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The First Law of Thermodynamics Has Been Rewritten

  • Researchers have made a breakthrough in applying the first law of thermodynamics to complex systems.
  • The law is a bedrock of physics, but has long failed to describe systems that are out of thermodynamic equilibrium.
  • The work could have applications in fields ranging from circuitry and quantum computing to space weather.

    The first law of thermodynamics is undergoing a huge renovation.

    A team lead by researchers at West Virginia University just released a paper detailing how the fundamental law can be applied more broadly than ever before—a finding that has the potential to rewrite the way we understand complex energetic systems.

    The first law of thermodynamics is one of the bedrock laws of physics. Even if you’re not gung-ho for physics research, you might have heard the simplified version: energy can neither be created nor destroyed, but it can be converted into different forms.“Suppose you heat up a balloon,” said Paul Cassak, lead author on the paper, in a press release. “The first law of thermodynamics tells you how much the balloon expands and how much hotter the gas inside the balloon gets. The key is that the total amount of energy causing the balloon to expand and the gas to get hotter is the same as the amount of heat you put into the balloon.”

    This law has been an incredibly helpful tool for physicists since its discovery in the 1850s. But there’s a catch—it has historically only worked when things are in or near a state of thermodynamic equilibrium. At its core, that means the temperature of a system is consistent throughout. There aren’t big hot and cold spots; it’s all basically the same temperature, which means it all has pretty much the same amount of energy.

    And because it’s no longer 1850 and we’re trying to answer more detailed questions about the universe around us, researchers have long been trying to find a way to apply the first law to systems that are not in equilibrium. While you might not have to reckon with many of these systems in your day-to-day existence, they’re very common throughout the universe in such substances as space plasma—found everywhere from the tails of comets to the outer layers of stars.

    The breakthrough for this team of researchers came in the form of a lot of complicated math. Basically, the energy conversion in systems that are in thermodynamic equilibrium can be described almost entirely by their density and pressure.

    But the behavior of the energy conversion in more complicated systems is determined by a lot more than just density and pressure.

    “Out of equilibrium, the first law of thermodynamics continues to only describe energy conversion during a process that changes the density and temperature,” Cassak tells Popular Mechanics. “What we discovered is that all of the other quantities describing the gas, liquid, or plasma when it is not in equilibrium are left out of the first law of thermodynamics.”

    What the team needed was a way to quantify all of the energy conversion that wasn’t described by density and pressure. And they found it.

    To the untrained eye, the solution will probably just look like a dense and confusing group of equations. But to a physicist, the mathematical description of these additional properties looks like opportunity. Potential applications of this work range from chemistry to circuitry and quantum computing to space weather.

    This kind of adjustment in our understanding of the basic building blocks of physics doesn’t happen often, so when it does, it has the potential to hugely influence the field and those associated with it. It just goes to show that even centuries-old laws can become new again if we look at them hard enough.