The Electron is Spherical - As In Really, Really Spherical

TLDR Summary:

• An electron's field is almost perfectly spherical.
• An electron is very, very, very small.

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The electron might be the most spherical object that humans have ever measured. Researchers in the UK have made painstaking measurements of the dipole moment of the electron and have essentially found it to be missing.

To be clear the researchers were measuring how spherical the electric field surrounding an electron is. They were not measuring how spherical the electron as a physical object is (if that even makes sense).

As an analogy, imagine a sphere the size of the solar system representing the electron field measurement. The researchers' work has shown that this sphere is perfect to within at least the width of a human hair. That is a really, really spherical field.

If the electron were not spherical but instead some type of spheroid or misshapen blob then its electric field would not be spherically symmetric and this would have profound implications on the current Standard Model of particle physics. The impact of this result is that it eliminates some variants of a hypothesis called supersymmetry.

The Size Of The Electron

At the start of this post I mentioned that the size of electron was not measured in this experiment. As far as I know the size of the electron has never been measured other than to say it is smaller than our current technology is capable of probing.

The electron may be a literal mathematical point (which presents problems in terms of self-energy but that is a topic for another post) or it may be something like a string (as in string theory).

Aside:

• A string from string theory is incredibly small (1 x 10^-35 m in length (a Planck length).
• The ratio of a string to the size of a hydrogen atom is about 2 x 10^-25.
• The Observable Universe (OU) is about 90 billion light years in diameter which is about 879,854,400,000,000,000,000,000,000 metres.
• Mulitply the size of the OU by 2 x 10^-25 and you get roughly 170 m.
• The tallest tree in the world is about 115 m in height.
• So the ratio of the tallest tree in the world to the size of the Observable Universe is about the same as the ratio of the size of a string to the size of a hydrogen atom.
• In other words an electron is very, very, very small.

Sources

1. Sixty Symbols on YouTube
2. Article in Scientific American
3. J. J. Hudson, D. M. Kara, I. J. Smallman, B. E. Sauer, M. R. Tarbutt, E. A. Hinds. Improved measurement of the shape of the electron. Nature, 2011; 473 (7348): 493 DOI: 10.1038/nature10104