Where does Newton's stuff stand today?

[Canum]

Besides the second law's issue with SR, are Newton's 3 laws still considered to be true FUNDAMENTAL laws of motion? If not, why?

[Integral]

All of Newton's laws are considered valid given speeds much smaller then c and energys above the continum limit. That means we do not use them at relativistic speeds and for quantum mechanics. Within their realm they are as valid today as they were 400yrs ago.

At relativistic speeds Newtons laws are only a first order approximation to the full equations derived by Einstein.

[Canum]

"All of Newton's laws are considered valid given speeds much smaller then c and energys above the continum limit. That means we do not use them at relativistic speeds and for quantum mechanics."

For clarification... are you saying that the first and third law also have problems when approaching c? Also, what is the continuum limit, and why does it present problems for the 3 laws?