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Why is electron presented in books, pictures as a sphere, when in fact it's not?

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2 Answers 2

Most particles are often shown as spheres. In fact, it's not as inaccurate as you might think to present the electron as a sphere, since its electric field has been measured to be very close to spherical. This is explained in articles like this one which you can find on Google.

The full paper on these measurements is available on the website of Nature as well, where I have linked to here.

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May I request your attention to my comments to the answer by Mr. Colin McFaul. –  albedo Aug 8 '14 at 12:28

Textbooks typically depict the electron as a sphere because it is a sphere, so far as it's been measured. The Nature paper @Wouter linked to is a recent measurement of the electron's shape. The lead author of that paper is Edward Hinds, who appears to be the primary person in precision measurements of the electron dipole moment. His publications page has links to other papers on this.

The most recent paper gives an upper bound of $10.5 \times 10^{-28}\mathrm{e\cdot cm}$ for the electron dipole moment. Here, $\mathrm{e}$ is the charge of the electron, so this would correspond to displacing the entire charge of the electron by $10^{-27} \mathrm{cm}$. And that's an upper bound; the measurement is consistent with the electron having no electric dipole moment at all. This is what it means for the electron to be a sphere: the electric field it gives off is perfectly spherical. (As measured. There are predictions that the electron is not perfectly spherical.)

Another way to look at it is to ask what the radius of the electron is. The best I was able to find is that the electron has a radius no bigger than $10^{-18}\mathrm{m}$. I'm sure there are better sources than that, and I'm sure there are more recent measurements, but this isn't my field. I do know that all measurements of the radius of the electron are consistent with it being a pure, mathematical point. IF you had to give a shape to a perfect point, it doesn't really make sense to call it anything other than spherical.

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I am sorry, this confuses me. If someone says that the electron is perfectly spherical, it means it is a particle which can behave (or having) properties of waves as well. Is it right? What I understood was electron cannot be said as a particle or wave, it is in fact both particle and wave. It is a particle because it has momentum; it has wave properties, so it is a wave as well. Here the discussions seems to be that electron is a particle with spherical shape which has wave property as well! –  albedo Aug 7 '14 at 9:33
One more thing, so if it is a perfect sphere, it has a boundary as well right? Can we define or draw a strict boundary for an electron? –  albedo Aug 7 '14 at 10:58
@albedo The electron (like all elementary particles) is not both a particle and a wave, that's a common misconception. It is in fact not a particle, nor a wave. In the most accurate theories we currently have about the universe elementary particles are in fact excitations of quantum fields. These excitations, also called 'quanta' (from the singular 'quantum'), exhibit both particle-like and wave-like features but the truth is that both waves and particles are classical and macroscopic concepts. There's no reason for the smallest building blocks at the micro-level to be either one. –  Wouter Aug 8 '14 at 18:54
@albedo This webpage and the answers to this PSE question might be interesting reading material for you. –  Wouter Aug 8 '14 at 19:02
@albedo Concerning your other question: note that we talk about the electric field of the electron when discussing its shape. Like Colin McFaul mentions in his answer, as far as we can experimentally tell the electron is a mathematical point. However, you can define a boundary for the electron if you want to, based on the value of its electric field. Strictly speaking this is an arbitrary choice but sometimes it may be helpful to associate a natural size with an electron and treat it as a little sphere. –  Wouter Aug 8 '14 at 19:05

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