Discussion in 'Physics & Math' started by Mind Over Matter, Nov 1, 2011.
The title says all I am asking. Many thanks in advance!
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Yes. Until it's position is measured.
An electron never exists in more than one location. Where that is, cannot be known until its location is determined or measured. An electron as a component of an atom could be anywhere around the nucleus, until its location is determined.
Because of the wave aspect of electrons, a single electron can pass through 2 different slits at the same time. This is to say the wave passes through 2 slits at the same time. But saying can an electron be in 2 places at once, I think the answer is a definite kind of a yes and sort of a no.
Electron 2 slit experiment.
Mod note: off topic posts deleted.
Whether electrons actually can or cannot exist in two places at the same time is kind of an irrelevant question. What matters in practice is whether nature behaves as if this were the case, and the answer to such a question is a definite "yes", based on the existing experimental data.
I am not sure that, the experiment linked demonstrates that a single electron is anything other than a particle, passing through a single slit.
True when many electrons are involved, usually over time, an interference pattern emerges. Is this the same as an interference pattern as seen with photons? No!
Electrons are charged particles, and cannot occupy the same location in space. More than one electron may occupy a specific energy state around an atomic nucleus, but that does not mean that they occupy the same location.
I am not strong on QM but I think the Pauli Exclusion principle applies to electrons and the issue of their co-location.
Photons are not limited in the same way.
I would doubt that an electron can be in a place. I wonder what they're doing standing on the head of a pin (that was charged)? Apparently not moving (static). Wait: not moving? Huh? But then again, if they're in a place, they have to be standing there.... dunno but sounds virtually ambiguous if you catch my drift
The Pauli exclusion principle does apply to electrons. But sending individual particles (with no wave characteristics) could not possible cause an interference pattern.
How is this relevant?
Sort of. It cannot actually be in two places at one time - but you can set up an experiment that allows it to have an equal _probability_ of being in one of two places at any given time. At a quantum mechanical level that means it effectively is in both places at the same time.
Before providing an alternate prespective, let me say that I do believe that electrons exhibit both wave and particles characteristics.
That said, above you suggest that there could be no other explanation, for a two slit experiment with electrons, resulting in an interference pattern. To that I offer the following, not as a diffinitive example, only as a alternate.
Electrons are charged particles and every thing that we have to construct the experiment is composed of "charged" materials. Assume for now that the two slits are exactly that two openings in an otherwise medium impenetrable by electrons. An electron will be far smaller than an individual slit and since both the electron and the material the slit is composed of are charged, as an electron passes through a slit its trajectory will be affected by the proximity of the material. Since the material is composed of atoms and atoms interact with electrons in discrete units, the deflection of an electron as it passes through a slit must occur in predictable patterns. Those patterns might result in the detection of the electrons after they have passed trough a double slit experiment in a pattern very much like an interference pattern. Still each electron is recorded as an independent event with only one point of detection. The interference pattern is only observed when evaluating the pattern that evolves from many detected electron's.
The answers we get in experiments like this are very often dependent upon the models we begin with. If we think of an electron as a wave, an interference pattern is a logical conclusion. If we begin thinking of an electron as a charged particle, the interaction of that charge and the material of the "slit(s)", becomes an additional variable in arriving at a conclusion.
The electron charge itself must interact with the materials the experiment is constructed from and cannot be completely eliminated from the results.
In the above I am not attempting to say this is what happens, only that there is more involved than at first appears. The particle and charge characteristics of an electron cannot be separated from its wave character. And how we interpret things that happen at quantum scales is heavily influenced by the models and theories from which we begin.
To this it should be added, "until an attempt to measure its location is made, after which it can be only in one location.
We never measure an electron to be in two places at the same time. When we try to predict where it is before measuring its location, we are never certain in which of more than one location it is.
I thought the same thing, but there is a subtle connection. It seemed that Feynman was providing an example between the difference in a predictive model and a descriptive model. The Mayans could predict, but there explanations of those predictions were, by today's standards naive.
Many experiments in particle physics, follow from theory that has been An extremely successful predictive model. The descriptions that follow are to a significant extent based on the model and in some cases are not altogether consistent.
We can describe subatomic interactions mathematically with a fair degree of accuracy. Projecting this into the world and experience is somewhat more difficult and at times questionable.
All particles have wave properties. Double slit experiments have been done with atoms and even with Buckey Balls. Same results.
If you allow an electron to be in two places at once you allow for the energy of one electron to be doubled. If the energy is doubled, it isn't the same electron.
The energy that is in the wave does not double.
So the wave is halved then? If that is the case then you just have two effects from 1 cause, which is just a fork.
I'll have to think about that some.
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