Jacques-Alexandre-César Charles

1746-1823

French Inventor and Scientist

Jacques-Alexandre-César Charles, with Nicolas Robert, ascended in the world's first hydrogen balloon in 1783. He was also a physicist and mathematician and is perhaps better known in this capacity as the person who developed Charles's law, which relates gas temperatures and pressures. In both roles, he made important scientific and technical contributions that have had lasting effects on both science and society.

Charles was born in 1746 in Beaugency, France. Very little is known about his childhood, but he began his professional life as a clerk in the French finance ministry. From there he turned increasingly to science, experimenting with electricity at first. In fact, it may have been Charles's experiments with electricity that showed him how to pass an electrical current through water, separating it into its components of oxygen and hydrogen.

In September 1783 the Montgolfier brothers' first balloons ascended into the air, lifted by hot air. Not knowing that simply heating air could create lift, the Montgolfiers believed that a special gas was formed by burning straw, which they called "Montgolfier gas." Charles mistakenly thought that Montgolfier gas was hydrogen, and he hastened to duplicate their experiment by filling his own balloon with hydrogen. In November 1783 Charles and Nicolas Robert climbed into the balloon they had built and rose into the air as the first truly lighter-than-air flight began. Ascending to an altitude of over a mile (1.61 km), they drifted for several miles before setting down in a field, scaring the peasants who thought they were being attacked by a strange creature. The peasants "killed" the balloon by stabbing it, then dragged it away.

The major advantage of Charles's design was that, without a fire burning beneath the balloon, the risks of a blaze were greatly reduced. In fact, with the substitution of helium for hydrogen, today's balloons are very similar in design to Charles's.

Following his first flight, Charles made additional balloons, financed in part by charging admission to see the balloon fly. His ballooning experiences piqued his curiosity about heated gases, and he spent much of the rest of his life experimenting and formulating what is now known as "Charles's law." This states that, under conditions of constant pressure, a heated gas will expand in volume. This is also known as Gay-Lussac's law, in honor of its codiscoverer.

Over the following decades, Charles's law, Boyle's law, and others that describe the properties of gases under a variety of changing conditions were shown to be part of a more universal ideal gas law. The ideal gas law describes how, in a gas, pressure, temperature, volume, and the number of molecules of a particular gas all relate to each other under a variety of changing conditions. This law is used to predict the behavior of gases when compressed, heated, expanded, and the like. In fact, air conditioning, refrigeration, and similar industries absolutely depend on the proper application of these gas laws to help transfer heat from one point to another, cooling in the process.

In 1795, in honor of his many accomplishments, Charles was elected a member of the Académie des Sciences in France. Later, he became a professor of physics, continuing his work with the characteristics of gases under a variety of conditions. Interestingly, most of his scientific publications deal with mathematics instead of with those discoveries for which he is best known. Charles died in April 1823 in Paris.

P. ANDREW KARAM