Contributions of Henry Cavendish to Our Understanding of Space
written by: Daniel P. McGoldrick•edited by: RC Davison•updated: 5/19/2011
When Henry Cavendish died in 1810, the first trains running on rail lines were barely in existence yet the work and findings of this British physicist and chemist became integral to the understanding and exploration of space two centuries later. He literally weighed our way into history.
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Truly a Man of Science
Henry Cavendish was a renowned chemist and physicist who lived from 1731 to 1810, long before humans believed they could fly in our own atmosphere, let alone space. Yet his keen scientific mind made discoveries about our own planet that essentially paved the way for humans to first understand, and then explore outer space. The irony in that lies in the fact that Mr. Cavendish never married, and barely interacted with anyone, so he might as well have lived his life in a tiny capsule that housed his laboratory in space. But that same reclusive personality enabled him to attack problems and mysteries in science like no one else. He dedicated his entire life to science and thanks to a large inheritance, he was able to study and conduct complex experiments in astronomy, chemistry, optics, electricity, geology, physics, and pure mathematics. This extremely shy and humble man made astounding contributions to the scientific community which still hold sway today.
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How Did Henry Cavendish Discover Hydrogen?
He is perhaps most known for first discovering and then describing the properties of hydrogen as an integral element in water, which we all of course know today as H2O. His keenly scientific mind led him to explore the relationship between zinc or iron, and water. It was known at the time that when either zinc or iron was dropped into water, a gas was produced. Cavendish dubbed this gas "inflammable air" and determined its properties and distinguished it from ordinary air. This "inflammable air" is actually hydrogen, and by combining it with oxygen in his experiments, he found out how water was formed. As was usually the case in that era of science, another scientist tried to take credit saying he discovered it first, but when Cavendish's notebooks were finally published in the mid-nineteenth century, he was fully credited for the find (after his death). A History of Hot Air and Gas Balloons will give you an intriguing look into the practical applications of some of his work in chemistry.
So what does this discovery have to do with outer space? Cavendish’s tenacity in probing, testing, and pushing the bounds of human knowledge until he broke through to a deeper level of understanding was exactly the kind of spirit and drive that it took to unlock the secrets of space. We know today that there is an extraordinary amount of Henry’s hydrogen throughout our Universe. From the beginning, NASA has utilized the distinctive properties of hydrogen for its missions, making liquid hydrogen the fuel of choice for propelling people and machinery into space. The element Cavendish discovered and closely recorded the properties of, through clever experimentation, has the lowest molecular weight of any known substance and it burns at 5,500°F. If you've ever seen footage of a NASA lift off than you know how intense that heat is. You wouldn’t be wrong to say that there was a little bit of Henry Cavendish behind everything we sent to space.
Image courtesy of Wikimedia Commons
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Important Work in Understanding the Behavior of Gravity and the Density of the Earth
Even today, scientists have not been able to come up with one universal theory regarding the mechanisms of the force and nature of gravity throughout the Universe. However, beginning with Newton in the seventeenth century, the behavior of objects affected by gravity has been thoroughly described and understood. Newton’s Law of Universal Gravitation essentially stated that objects in the Universe are attracted to other objects in the Universe according to a mathematical relationship between force, mass, and distance. But it was Cavendish that ingeniously confirmed this theory a century later with an experiment he designed specifically for that purpose. It was known as the Torsion Balance. There is a school of thought within the scientific community who believe it was Cavendish who conducted the first modern physics experiment because of his meticulous attention to every facet of his experimental process, including the errors.
His scientific contraption led him to determining the mass and density of the Earth with simple calculations since Newton's formula was already established. You can read about the exact formulas in Understanding the Surface Gravity of the Planets. Cavendish became famous for this work, which he published under the title “Measuring the Mass of Earth." The precision and meticulously measured nature of his experimental process became a model for all other scientists to follow.
Think about how staggering that finding is, one scientist, one individual among all the billions of people who ever walked on planet Earth, was able to determine the mass of the entire planet thanks to his firm understanding of earlier scientific discoveries. Future scientists used this information to help them understand how the planets orbit around the Sun and interact with each other. This knowledge also contributed to figuring out what it would take for a rocket to escape the gravity of the Earth and negotiating the significantly lower gravitational forces of the Moon in order to land (and come back, thanks to a quick burst of the only engine they had on the lunar module). So, just like Cavendish built upon the work of the scientists who came before him, future scientists built upon his discoveries about gravity to help us navigate the vast space in our tiny neighborhood in the Universe.