What is the physical size of an electron?

[Charles Brown]

The electron is a point particle. To say it is zero would be misleading. The instruments we use are not sensitive enough to measure the true size or location of an electron. Trying to measure the size of a single electron with our current technology is like trying to pick-up a virus with a pair of tweezers.

 

[edpell]

Back a page someone asked about quantum gravity theories and minimum size. I would agree QM Gravity Theories with there minimum area and minimum volume mean electrons, and everything else, have at least that much area and volume. Likewise string theories with minimum string length set a minimum size for an electron and everything else.

But it is just the naked electron that has this absurdly small size the effective size of the dressed electron is much bigger.

 

[humanino]

I missed to answer

And, by implication, in the course of the universe there will have been as many electrons as positrons?

I thought I made it clear that this scenario is only a consistent one rather than a necessity. As a physical scenario, it makes the pretty outlandish and untestable hypothesis that there is a reverse image of antimatter beyond our observable horizon.

But please note that there are other pretty outlandish ideas, which are still sometimes mentioned in textbooks and university lectures on introductory quantum field theory. For instance, Dirac's sea of negative energy electrons, which is essentially the historical prediction for antiparticles (although at first, Dirac hoped he could explain protons with it). The Dirac see also implies that all electrons are the same, except with a many particle view instead of a field. Its pedagogical value is now obsolete, because for one thing it cannot explain antiparticles for bosons.

 

[RonL]

As we are in the realm of quantum physics, talking about trajectories of electrons (positions changing with time) must be taken with a large grain of salt.

According to QED, we have an electron/positron field and an electromagnetic field (and, in the extension of QED as used by chemists, one field for every kind of nucleus). These are the real things. (They do not deserve being called ether; the ether of old times has no energy density.)

Trajectories make sense only if one looks at the fields from a coarse-grained point of view and studies an approximate dynamics for distinguishable local aggregations of field strength that may be called particles.
And they are not more accurate than the extensions of these local aggregations - their physical size.

Trajectories of electrons, this brings a question from me that might relate well with this thread.

If in ones mind a virtual image can be formed, an electron slowed in speed and a path inline and along side of a returning space shuttle craft, if the electron and it's magnetic field could be seen, would it not look almost the same as the vapor trail of the spacecraft ?

If this is near correct, the reduction of size to almost zero should be easy for most to see in their minds eye.