This wasn’t at all obvious. Hold a pencil out with your hand. Let go. Did the pencil just stay there in midair?
The fact that things fall because earth imparts an invisible force on everything around us, and that in fact, every massive object imparts that same invisible force on everything else around it, was pretty revolutionary.
It’s hard to overstate how unintuitive this would be to someone who had grown up at that time. Believing that something sufficiently far from earth would just float around and not fall was probably too much for most people at the time.
It’s also a bit incomplete because he also said a object keeps the same speed, even if it’s not zero (not moving). And the speed also has to keep the same direction. This does explain a lot about gravity, orbits etc…
And that’s only the first law, it’s a premise to the other even more helpful laws.
He also said definitely, not probably.
While gravity can to a degree obscure this fact, it’s corollary that an object in motion will stay in motion is pretty alien to anyone who has grown up on earth, under the daily affects of atmosphere/friction.
Not as many people know that he was the father of calculus (along with Gottfried Leibniz who figured it out independently around the same time). That’s really where all the heavy lifting was in elementary mechanics, where by using the laws as something of a base case (especially the 2nd, F=dP/dt), calculus could be used to project an objects future motion. So in a way, it was by calculus that the laws could be shown as accurate in the first place.
I think Kepler deserves some credit too, that dude basically figured out a specific application of calculus in the motion of orbitals before Newton’s and Leibniz’s general calculus even existed.
