Why do small things like electrons act quantum mechanicaly?

Question

If you could shrink a car down to the size of an electron. (Yeah, I know. Lets just pretend we can) would it start to exhibit wave properties? If so, why? What is it about being small that causes things to behave that way?

Answer 1

Not so much small, as small in mass. Quantum mechanical properties become apparent when the wavelength is comparable to the size of the apparatus--as in the electron/slits experiment. As the wavelengths get shorter, diffraction is less of an issue. The wavelength of a car is ridiculously small compared to the wavelength of an electron, because the wavelength is inversely proportional to the mass, and the mass is ridiculously large.

Answer 2

And the correct answer goes to those who mention the de Broglie wavelength...

The de Broglie wavelength of a car is so much smaller than that of a single electron that a car doesn't behave like a wave.

Electron diffraction was predicted by de Broglie, but it was experimentally verified on accident by electrons diffracting off of a crystal. The reason why the crystal is important is because the 'slit size' that is needed to diffract an electron is about the size of atomic spacing in a crystal. Since it's so hard to detect (or at least it was back then), no one detected it until the 1920s or so. Plus, you sort of have to have the detectors just right.

To add to the answer:

The de Broglie wavelength of a particle becomes really really important in a particle collider. When ever you hear about physicists wanting to measure how Nature works on smaller and smaller distance scales, due to the de Broglie condition, this means you need more and more momentum/Energy (i.e., the particles have to be moving faster and more bunched up). This is because when measuring or observing something, you can only resolve things that are not much smaller than the wavelength of whatever you are using to look at it. So to see quarks and how they interact within a proton or neutron (or other particle), you need very high energy (to get a very small wavelength).

This principle also limits how small an optical microscope can see. Optical microscopes are limited to objects on the order of 500nm (give or take a few hundred), the wavelength of greenish light. Of course, there are focusing issues, but assuming you can focus that small with a lens, that's about your limit. We have to use special microscopes (many of which don't use light directly) to see that small and smaller.

Answer 3

Plank put forth the "quantum hypothesis" in order to explain some very weird phenomena. For example, why doesn't an electron spiral in towards the nucleus and collide with the protons, which they would have to do by Maxwell's Equations. This problem was solved, and the world of quantum mechanics began, with the theory that there exist orbits around the nucleus which, when electrons are in those orbitals, will not radiate energy away.
This isn't even mentioning De Broglie waves or the Uncertainty Principle.

Answer 4

I know next to nothing about quantum physics but physicists themselves are probably still scratching their heads because of the same question. The super string theory, which describes tiny strings as the smallest existing particles, attempts to explain the behavior of particles, but up to this point nobody has been able to explain why things behave the way they do, we just know they do behave in such a manner to a certain degree.

Answer 5

But you can't - that's the point.

sub-atomic particles exist in the quantum world of probability - extremely large systems (such as molecules or compounds) theoreticially could exhibit quantum properties - but the probability is insanely low for the same property to occur to so many particles at one time

Answer 6

basically due to de-Broglie wave,
momentum, P = h/ lambda
h=planck constant
lambda = wavelength
because P = mv
the wave character, the wavelength is equal to h/mv
when the mass m is small, the wavelenght became large and the wave character of a particle became dominant.
When this happened, you have to use quantum theory.

Answer 7

Atoms are made from protons, neutrons and electrons, hence electrons are honestly smaller than atoms. Smaller nevertheless than protons, neutrons and electrons are quarks. as far as their function, one might want to assert that is to stability the fee of the proton, generating a impartial entity. How were electrons created? this question might want to be more desirable helpful requested in the philosophy section!

Answer 8

See if you can find a copy of 'Where Does All the Weirdness Go?' by David Lindley. It does a fairly good job of explaining the transition from 'microscopic' to 'macroscopic' without too terribly much heavy math.


Doug

Answer 9

All things act quantum mechanically. It's just that quantum phenomena are dwarfed by macroscopic interactions in large objects.

Answer 10

we dont really know. and anyone who claims that they understand quantum mechanics, is full of bunk.