Hcfyk

The one-electron universe postulate, proposed by John Wheeler in a
telephone call to Richard Feynman in the spring of 1940, hypothesises
that all electrons and positrons are actually manifestations of a
single entity moving backwards and forwards in time. According to
Feynman:

“ I received a telephone call one day at the graduate college at
Princeton from Professor Wheeler, in which he said, "Feynman, I know
why all electrons have the same charge and the same mass" "Why?"
"Because, they are all the same electron!"
https://en.wikipedia.org/wiki/One-electron_universe

The supposition is that there is only one electron. It stands to reason that if I could change that electron, I could change the properties of the whole Universe.

Assume that the postulate is true.

Question

Given foreseeable science, what properties of a single electron could be changed? In theory, could we change the charge? Could we change the mass?

Disclaimer

Because my answer below throws a bit of shade at the other existing answers, and because I'm going for a bit of a flip, humorous, and somewhat defiant tone, I feel that I should point out that I'm a real life physicist and most certainly not a crackpot :-P

Rant

All the naysaying in the other existing answers, e.g.

• "This universe is fundamentally impossible..."




• "[There] won't be anything you can change, because there won't be just one electron. The model is completely incompatible with current understanding of physics."




• "Whether the Wheeler postulate is true or not, under the known laws of physics, you can't change any of the properties of an electron. Mass, charge, spin, magnetic moment, etc. are all intrinsic properties. "

seems out of place to me.
Even in a sober discussion with my colleagues in which we were to speculate on the future of physics, I wouldn't go around making statements about what certainly is and isn't possible.
The physics community has been so wrong so many times about how things will turn out even ten years in the future that such definitive statements of impossibility just seem imprudent.
Adding on top of that the facts that

• We're talking about quantum field theory here, which is already known to have some foundational issues and hasn't yet been reconciled with gravity, and




• This is a world building site,

I think a little bit of tempered imagination is in order.

Alright let's actually answer the question

In theory, could we change the charge? Could we change the mass?

Sure, why the hell not?
Electrons are presently thought of as excitations of the electron field, much like photons are units of excitation of the electromagnetic field.
The electron's "charge" is a word for describing how strongly the electron field interacts with the electromagnetic field.
Can we change that coupling strength?
Yeah maybe, who knows?

Imagine the first time someone discovers that sound is compression waves travelling through some kind of magical continuous medium; they might think that the speed of sound is intrinsic because that medium is unchangeable.
However, they eventually figure out that at smaller length scales, the sound-carrying-ether is not uniform and continuous, but rather a granular collection of billions of little particles of "air", all bumping into each other.
It's only when we zoom out and look at waves whose wavelength is much longer than (the space between) individual air molecules that the wave phenomenon of sound seems to exist in a continuous and uniform medium.
Once they know about the underlying structure of air molecules, they figure out that changing things about those molecules changes the speed of sound.
For example, they can heat or cool the molecules, or supplement them with some other type of molecules like $text{He}$ or $text{SF}_6$.

If the electron field has underlying structure, then it seems quite likely that we can mess with that structure to alter the properties of that field's excitations, i.e. change the properties of electrons.

...and we haven't even talked about the single-electron theory yet...

Suppose spacetime is a big old four dimensional bar with a cube-shaped cross-section.
That is, the spatial dimensions have finite extent but the time dimension goes to plus and minus infinity.
In that spacetime, the single electron's world line can be any path through this four dimensional bar.
Now suppose a being that lives in a twenty dimensional spacetime which contains our little four dimensional one comes along and pokes a hole in the electron field in our spacetime.
Now the electron's path can't be deformed in a way that would carry it through the hole.
Proper hole-punching could wind up tying our electron in knots around the holes!
Would that change it's charge or mass?
I dunno, probably not, but it would change something about the electron's physics because now the set of possible electron worldlines is topologically nontrivial.

A field's (particle's) mass is related to how much energy it costs to create an excitation in that field (a.k.a. create a particle).
Suppose the universe were a Mobius strip and suppose the energy cost of creating an electron is related to the length of the strip because the electron's world line has to make a complete unbroken trip around the strip.
Well then if a twenty dimensional alien could come in and cut a section out of our Mobius strip universe, then the mass of the electron would go down.

More?

This universe is fundamentally impossible, since some electrons have their worldlines terminated in a black hole. Without a full working model of quantum gravity, we can't make any firm predictions about what happens to such electrons, other than the singularity is likely to end their existence. The black hole will inherit the charge, mass and angular momentum, but lose all the electron-ness of the particle's information (no hair theorem).

You can also have electrons terminated in beta capture events (which turns a proton into a neutron and the electron stops existing).

So, there won't be anything you can change, because there won't be just one electron. The model is completely incompatible with current understanding of physics.

Whether the Wheeler postulate is true or not, under the known laws of physics, you can't change any of the properties of an electron. Mass, charge, spin, magnetic moment, etc. are all intrinsic properties. They are not mutable by any known (or even to the best of my knowledge hypothesized) mechanism.

As to the postulate itself, as pointed out in comments and in tylisrn's answer, there are strong reasons to not believe that the Wheeler postulate is true. In addition to problems with any mechanism that results in the creation or destruction of a lone electron or positron, the Wheeler postulate runs into difficulties in explaining the observed imbalance of matter and anti-matter. If a single electron is zipping backwards and forwards through time, we should see it moving backwards as often we see it moving forwards. This would imply equal numbers of electrons and positrons, which we simply do not observe.

Why not all properties? You "just" need to find the right fulcrum. Measurement techniques could be a good entry point.

Say you manage to change any of these universal constants, how does the universe react? Do you care to manage the consequences? What are you willing to invest?

Or do you adjust them only from your perspective? In my eye that resembles shifting into parallel dimensions. A bit broader than time travel in scope, similar in technology. Can you imagine the loneliness? Would you want to maintain your "sanity", once you're independent from all of humanity?

Perhaps you could arbitrarily expand your perspective before making the shift. Then again, is that how you want to occupy your time, with cosmic escapism? Maybe you have a very good reason.

I need more fart jokes. Good luck.