Hi, I had a thought recently which gave rise to a rather interesting query. A helicopter works and is able to fly due to Newton's third law of motion. The propellers rotate at a high speed and exert a force on the air beneath them. By N3L, the air therefore exerts an upwards force on the propellers, thus causing the helicopter to lift off the ground and begin to fly. An understanding of Newton's laws is integral to the design and operation of the modern-day helicopter. The first modern-day helicopters came about in the 1940s so the laws were well known by then...but here's the thing. Newton published his laws in the Principia in 1687, but Leonardo Da Vinci had already invented the 'Aerial Screw' which was one of the earlier helicopter-like machines. But according to the internet, Da Vinci first published his detailed plans of the aerial screw in 1485, a staggering 202 years before Newton published his laws and of course well before Newton himself was born. Clearly Da Vinci had to have an understanding of at least something akin to the basic laws governing motion, so why did they only become a breakthrough in 1687 and not many years before? With Da Vinci possessing perhaps one of the greatest minds in history, one would believe that he would have explored this in greater detail. You can't build (what was considered in that era...) such advanced and pioneering inventions as that of the aerial screw without understanding these underlying principles. Does anybody have any thoughts on this, or am I missing out any crucial details? I'd be interested to hear! Thanks in advance.