Here are some of my first conversations when I came to Imperial College.  They are with people doing all sorts of different research, some working on vast international projects, others in small groups or partnerships; some are PhD students, beginning their careers and others are seasoned experts.

They are written up mostly in the form of an essay attempting to capture the essence and narrative of the discussion and find a resonance. These writings are shown with the permission of the physicist.

Entries in Mike Tarbutt (1)


The shape of the electron and questions of existence

Image: The Pier 10, by Piet Mondrian

We’re eating sandwiches on the green, on the sunny day before the rain.

When I ask you, you say we imagine the electron to be a point particle surrounded by all the virtual particle pairs there are.  Ceaselessly coming and going.  And when I ask if this is an imaginary mathematical device, you insist this is really the case, as much as the tree on the other side of the green is there.

We laugh that when we both tell our friends about your experiment and the latest result that the electron is round, they laugh.  They raise their eyebrows and say of course what else would it be?  What have you been wasting your time doing? 

We all expect beautiful symmetry; a little cloud defined by a single number, but contrarily, actually need asymmetry to explain why we’re here.*

We imagine that nearly 14 billion years ago, our universe began symmetrically, with as much matter as anti-matter.  This would cancel out in spectacular annihilation, leaving no matter, no earth, no you or me, just light. 

So, to solve this problem, amongst other conditions, we think that the shape of this scintillating crowd needs to be an egg.  Though at the moment your experiment of staggering accuracy (a hairs breadth versus the span of our galaxy) stubbornly continues to say it is round.  You will keep looking with greater accuracy and you satisfyingly know how you’re going to do this. 

But, if you don’t find the egg, we will need to find the asymmetry somewhere else.

Mike Tarbutt is an experimentalist working in a small team to measure the shape of the electron.  

See some of my drawings of the team in discussion here


*The logic of symmetry and why the electron must be egg shaped for us to be here

We need CP symmetry violation to explain why we are here - to give a little more matter than anti-matter, this is a condition of our universe and our existence.

We know that we have CPT symmetry; this appears to be a law of Nature.   It is always preserved as far as we can tell: a change in charge, a mirror image reflection and a reversal in time, will always leave our world unchanged.

For these two statements to be true, T symmetry must be violated.  We should always be able to tell the difference between a system running forward and one running backwards.

An egg-shaped electron proves that T-symmetry is violated

Therefore, the electron should be an egg shape or it wouldn’t be here for us to see and we in turn (comprising electrons and other things) would not be here to see it. 

Further note:  we find that nature has a preference for one handedness (or chirality) over another and this is evidenced in the weak interaction.  It is a profound question whether this is related to chirality found in molecules.