# Are electrons smeared objects prior to measurement?

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1. Oct 10, 2015

### ajv

before measuring an electrons position, is it physically a smear,like a wave? Or is it just nothing?

2. Oct 10, 2015

### phinds

It's not "nothing" but it has no defined position. I think "smear" is an English language word that doesn't really say what's going on.

3. Oct 10, 2015

### Geofleur

Doesn't it depend on which interpretation of quantum mechanics you adopt? For instance, the pilot wave approach says there is a particle the whole time, whose path is governed by the wave function. It's a particle with a crazy trajectory though, if I understand correctly - this is by no means my specialty!

4. Oct 10, 2015

### Staff: Mentor

If you measure the position, then you know that it was there when you measured it.

If you measure its position again immediately afterwards, the odds are that you will find it somewhere very close to where it was (offset by $v\Delta{t}$ if it is moving at speed $v$ and you waited for time $\Delta{t}$ before you made the second measurement). The longer it is before you make that second measurement, the more likely it is that you will find it farther away from the expected position.

This situation is commonly described as the electron being "smeared out" but acquiring a definite position when it is measured. However, as Phinds points out, "smeared" is not exactly precise scientific language; and as Geofleur points out we aren't really talking about what and where the electron is, we're talking about the probability of finding the electron at a given position at a given time.

Last edited: Oct 10, 2015
5. Oct 10, 2015

Staff Emeritus
I woulld argue that the question "what is it doing when we aren't measuring it" is not something science can answer. This comes up often more in quantum mechanics than classically, but it's really more about the domain of validity for scientific investigation than anything else.

6. Oct 10, 2015

### bhobba

In QM you have the formalism and interpretations of that formalism. Everyone agrees on the formalism - its interpretations that are argued about - and there are a myriad of them. The formalism is silent about what's going on when not observed. Note the word - SILENT. It has no take one way or the other. Interpretations however have all sorts of takes that you can read about in a comparison between them:
https://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics

Thanks
Bill

7. Oct 11, 2015

### atyy

As Geofleur says, it is a matter of interpretation. Certainly, there are circumstances under which one can consider an electron to be a smeared object before measurement, and the measurement of position to then collapse the wave function into something less smeared.