Before you close this has a duplicate !
A lot of posts on stack exchange have demonstrated that Newton's laws can be derived / or proved
(A couple of posts have shown that you could derive the 3rd law and potentially the first from the 2nd).
But the 2nd is almost always referred to as an axiomiatic law - i.e. something that is believed to be true - on who's foundation Newtonian mechanics is built.
I'm aware that it has been experimentally proved - in school laboratories countless times (at small scales) etc,.
But - do we have any understanding of WHY this law holds? Is this something fundamental about the universe that it tells us or is the best explanation that it is an approximation of relativistic mechancics at sub-speed of light time frames.
So my question is:
"Why are Newton's Laws true - what does it tell us about space, time and matter - and is there any way to develop any more fundamental "laws" that are grounded in more "lower level" axioms. For example - Euclidean Geometry is built on a relatively small set - 5 of axioms - that most of us would intuitively believe to hold true on a plane http://en.wikipedia.org/wiki/Euclidean_geometry#Axioms " - are there any similar axioms that could underpin Newtonian (or indeed Lagrangian / Hamiltonian) Dynamics.