Energy is never lost. It can change from one form to another, but the total amount of energy never changes. That principle has allowed scientists and engineers to create the power systems that run your lights and house and fuel your car.
It’s called conservation of energy and is one of the most important discoveries in all science. It has been called the most fundamental concept of all nature. It forms the first law of thermodynamics. It is the key to understanding energy conversion and the interchangeability of different forms of energy.
When Hermann von Hemholtz assembled all of the studies and individual pieces of information to discover this principle, he changed science and engineering forever.
Born in 1821 in Potsdam, Germany, Hermann von Hemholtz grew up in a family of gold merchants. At the age of 16, he took a government scholarship to study medicine in exchange for 10 years of service in the Prussian Army. Officially he studied to be a doctor at the Berlin Medical Institute. However, he often slipped over to Berlin University to attend classes on chemistry and physiology.
While serving in the army, he developed a research specialty: proving that the work muscles did was derived from chemical and physical principles and not from some “unspecified vital force.” Many researchers used “vital forces” as a way to explain anything they couldn’t really explain. It was as if these “vital forces” could perpetually create energy out of nothing.
Helmholtz wanted to prove that all muscle-driven motion could be accounted for by studying physical (mechanical) and chemical reactions within the muscles. He wanted to discredit the “vital force” theory. During this effort, he developed a deep belief in the concept of conservation of effort and energy. (No work could be created without coming from somewhere or lost without going somewhere.)
He studied mathematics in order to better describe the conversion of chemical energy into kinetic energy (motion and work) and the conversion of physical muscle changes into work in order to prove that all work could be accounted for by these natural, physical processes.
Helmholtz was able to prove that work could not be continually produced from “nothing.” That discovery led him to form the principle of conservation of kinetic energy.
He decided to apply this principle of conservation to a variety of different situations. To do that, he studied the many pieces that had been discovered by other scientists, James Joule, Julius Mayer, Pierre Laplace, Antoine Lavoisier, and others who had studied either the conversion of one form of energy into another or the conservation of specific kinds of energy (momentum, for example).
Helmholtz augmented existing studies with his own experiments to show that, time and time again, energy was never lost. It might be converted into heat, sound, or light, but it could always be found and accounted for.
In 1847 Helmholtz realized that his work proved the general theory of conservation of energy: The amount of energy in the universe (or in any closed system) always remained constant. It could change between forms (electricity, magnetism, chemical energy, kinetic energy, light, heat, sound, potential energy, or momentum), but could neither be lost nor created.
The greatest challenge to Helmholtz’s theory came from astronomers who studied the sun. If the sun didn’t create light and heat energy, where did the vast amounts of energy it radiated come from? It couldn’t be burning it own matter as would a normal fire. Scientists had already shown that the sun would consume itself within 20 million years if it actually burned its mass to create light and heat.
It took Helmholtz five years to realize that the answer was gravity. Slowly the sun was collapsing in on itself, and that gravitational force was being converted into light and heat. His answer was accepted (for 80 years, until nuclear energy was discovered). More important, the critical concept of conservation of energy had been discovered and accepted.
Conservation of energy plus the Big Bang tell us that all of the energy that ever was or ever will be anywhere in the universe was present at the moment of the Big Bang. All of the fire and heat burning in ever star, all of the fire and energy in every volcano, all of the energy in the motion of every planet, comet, and star, all of it was released at the moment of the Big Bang. Now that must have been one BIG explosion.