Relationship between Newton's Laws and Quantum Physics?

Question

Hi! Do the three laws of Newton break down at the quantum level (for protons, electrons, neutrons, quarks, anti-matter) or we do not apply Newtonian mechanics at all at quantum level?
What is an electron? Does it exhibit wave like properties or magnetic properties, besides its usual electrostatic charge of -1? How does it travel? In a cloud of electrons or in straight lines?
Do Newtonian mechanics work at astrophysical level? In black holes, galaxies, Pluto, Saturn and other planetal level?

You may answer selectively. Thank you. I am not looking for a complete answer.

Thank you all for your insightful answers, especially Frank N. I was not expecting a thesis, but just some insights into physics. Physics is fairly intutive at classical mechanical level but becomes a bit bizarre at quantum physics, in my personal opinion. Is what we see in the physical world the reality, considering the implications of quantum physics? That's a question I would rather not ask or ponder too much. I would rather stay away from quantum physics as much as I can, if possible.

Answer 1

Remember that many of the subatomic particles are travelling at relativistic speeds, so N's laws have to be modified by using Einstein's mass equation. For example, a proton going around a circle requires a force mv^2/r. But the m is not its rest mass; the m is m/root(1-v^2/c^2).
Second, when an electron travels it is a wave. N's laws are for particles. However, when the electron interacts with material, it interacts as a particle, so N's laws apply. For example, in the Compton effect, where a photon hits an electron and bounces away in a new direction with altered wavelenth, causing the electron to recoil, N's laws do hold. That is, the collision conserves energy and momentum.
At the astrophysical level, N's laws work great, but remember that Einstein's formulas work better for high speeds (e.g. successfully accounting for the precession of Mercury's axis of revolution.)
Inside a black hole, N's laws do not apply. The black hole has zero volume, occupies zero space. Outside a black hole, N's laws (modified by Einstein, of course, for the strong gravitational field) do hold in that you could go into orbit about a black hole of a given mass with the same speed (for that radius of orbit) as you would orbit any normal planet of equal mass.

Answer 2

You asked a basket full! You expect a lot for your meager expenditure of points :-)

Newton's laws don't really break down, but they cease to be continuous. They still hold for all these particle (after accounting for relativistic effects), but at the quantum level, their properties can take on only certain discrete values.

Isolated quarks have never been detected, so if they take on properties of their own, we don't know about them.

See the first reference for more information about the electron. See the second reference for detail about how it interacts with electromagnetic fields. It is affected by magnetic fields only when it moves. It travels through space as any other particle, affected by the forces acting on it (gravitational and electromagnetic). An electron cloud is just a bunch of electrons, each interacting with its environment.

Newtonian mechanics do operate at the astrophysical level, again considering relativistic effects.

Answer 3

Newton's Laws can be though of as a generalization of a macroscopic system, neglecting the quantum effects.

Does an electron exhibit wave like properties? The answer is very strange. Depends on how you observe it. This means that the behavior of an electron can be effected just by observing it.

And to the guy above me who referred to "Einstein's Quantum Physics", lol

Answer 4

this was on discovery science channel a few days ago... but like Newtons three laws only work in certain circumstances and like Einsteins Quantum Physics explains the motion of everything from a planet to the electrons that soround a atom
hope that helps a bit