Leonardo was one of the first to study friction in any systematic fashion. While he studied all kinds of friction, he drew a distinction between sliding and rolling friction.
He stated the basic laws of friction 200 years before Newton defined what force is. He stated that:
1) The area of the points of contact has no effect on friction.
2) If the load of an object is doubled, its friction will also be doubled
However, since Leonardo never published his theories, he got no credit for his work until several centuries after Newton published his work.
Leonardo was interested in many things, as most people know. So perhaps it will not surprise you to learn that geology was one of his interests.
At one point he lived in Milan, serving as the court artist to Ludovico Sforza. As this was close to the Alps, he often went walking in the mountains.
His notebooks detail how he explored a mountain cave and found massive fossil bones. His notebooks say he was famous for his interest in rocks and strange forms hidden within them. Which he then no doubt studied with the great care and astute mind with which he studied everything.
His research led him to the following conclusions:
Shells and fish bones must be the remains of animals that once swam in places that were once oceanic. So, therefore some parts of the Earth which were once covered by seas were no longer covered by seas. And therefore, the surface of the Earth must have changed over time.
Water is the most powerful natural force. Water has sculpted the largest features of Earth’s landscape over long periods of time
All this indicates that slow and relentless natural processes have shaped our planet.
If this sounds quite familiar, it is because geologists would come to realize it centuries later.
His geological discoveries led him to conclude that the Earth must be much older than the few thousand years the Bible seemed to imply and to conclude that natural geological forces, not divine ones, were responsible for the drastic geological changes he observed inferred must have taken place.
Credit for the invention of the first practical parachute typically goes to Sebastian Lenormand in 1783. However, Leonardo designed one much earlier.
He made a sketch of the invention, with this description: “If a man has a tent made of linen of which the apertures [openings] have all been stopped up, and it be twelve braccia (23 feet) across and twelve in depth, he will be able to throw himself down from any great height without suffering any injury”
Given it has a triangular, rather than rounded design, many questioned whether it would work. They questioned whether it would have enough air resistance to float. Or whether it’s linen covering over a wooden frame might be too heavy.
As is typical with his inventions, it was never built or tested during his lifetime. Given how many of his inventions later proved to work well, wasn’t this a shame?
However, in 2000, the daredevil Adrian Nichols constructed a parachute based on Leonardo’s design and tested it. Despite widespread skepticism, it worked and provided a safe landing!