Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: latebind on 28/04/2009 01:54:17

Title: Newtons Third Law in Quantum Terms?
Post by: latebind on 28/04/2009 01:54:17

How does quantum mechanics go about explaining newtons third law?

Does each individual atom collaborate to provide an equal and opposite force? How does the energy get split between the atoms and how does each atom react?

Title: Newtons Third Law in Quantum Terms?
Post by: JP on 28/04/2009 06:23:54

At its most basic level, Newton's Third Law is just a statement of the conservation of momentum.  Force is a measurement of change in momentum per unit time.  If two particles interact, the change in momentum of particle 1 has to be equal and opposite to the change in momentum of particle 2.  This means that the interaction forces have to be equal and opposite.

If you want to go deeper, the fundamental forces are all generated by particles exchanging "virtual" particles.   These virtual particles carry momentum, and so the real particles can push/pull on each other by the exchange of virtual particles.  Since momentum is conserved, the momentum gained by one real particle has to be equal and opposite to the momentum gained by the other real particle.  If you think of these momentum changes as forces, this is Newton's third law.