Symmetry and newton's laws

[xboy]

Is it possible to show directly from Newton's Laws that conservation of momentum and energy follow from principles of symmetry?

 

[AlephZero]

See http://math.ucr.edu/home/baez/noether.html

NB Newton would not have understood the proof, since the concept of energy had not been clearly defined (let alone conserved) when he was alive.

 

[vanesch]

Is it possible to show directly from Newton's Laws that conservation of momentum and energy follow from principles of symmetry?

I think you also need to postulate that there is some variational principle. After all, frictional systems can be time invariant, and nevertheless, there is no conservation of energy.