What If All Matter Suddenly Changed To Anti-matter?

[Hornbein]

Suppose all matter changed to anti matter (and anti-matter to matter) at the same instant. I searched about and the consensus was it wouldn't make much difference. The only net force that would change would be the weak force, and no cared to speculate about what difference this subtle alteration would make. But I think they all overlooked something. It wasn't specified that magnetic fields would suddenly change polarity. Why would they? So each ion would instantly have the opposite acceleration from a magnetic field. I'd think that would be very disruptive. Is this right?

 

[JimWhoKnew]

Suppose all matter changed to anti matter (and anti-matter to matter) at the same instant. I searched about and the consensus was it wouldn't make much difference. The only net force that would change would be the weak force, and no cared to speculate about what difference this subtle alteration would make. But I think they all overlooked something. It wasn't specified that magnetic fields would suddenly change polarity. Why would they? So each ion would instantly have the opposite acceleration from a magnetic field. I'd think that would be very disruptive. Is this right?

I like the question.

Suppose you have 2 charges of opposite signs at rest 1 light-second apart. They attract each other. If at one instant the signs of their charges flip, then for a second they will experience a repelling force due to the other (in the frame where they are both initially at rest).

 

[renormalize]

But I think they all overlooked something. It wasn't specified that magnetic fields would suddenly change polarity. Why would they?

Magnetic fields would change polarity because all magnetic fields are generated by electric currents (moving charges). Under matter$\rightarrow$antimatter, the sign of those currents would reverse and thus so would the magnetic fields the currents produce.
What you're really asking is: what happens to the universe under the quantum operation $C$ of charge conjugation? My understanding is that the strong, electromagnetic and gravitational interactions are all symmetric (unchanged) under the action of $C$. Only the weak-interaction is not $C$-symmetric and so it would be altered in the conjugated universe. That means radioactive decays, nuclear fission and stellar fusion could well be different there.

 

[Hornbein]

Magnetic fields would change polarity because all magnetic fields are generated by electric currents (moving charges). Under matter$\rightarrow$antimatter, the sign of those currents would reverse and thus so would the magnetic fields the currents produce.
What you're really asking is: what happens to the universe under the quantum operation $C$ of charge conjugation? My understanding is that the strong, electromagnetic and gravitational interactions are all symmetric (unchanged) under the action of $C$. Only the weak-interaction is not $C$-symmetric and so it would be altered in the conjugated universe. That means radioactive decays, nuclear fission and stellar fusion could well be different there.

But the magnetic field at a distance doesn't change at the instant that whatever is generating it changes.

Or let's say you have a black hole with charge. If it instantly changes to antimatter what happens to the external charge? I say it doesn't change.

 

[JimWhoKnew]

But the magnetic field at a distance doesn't change at the instant that whatever is generating it changes.

Moreover, in the electrostatic case we have $~\nabla\mathbf{E}=4\pi\rho~$. So when the change occurs, either this Maxwell Equation breaks down, or $~\mathbf{E}~$ changes sign simultaneously throughout the entire space, thus violating causality. We can see that Maxwell equations will run into difficulties in the general case, since $~\frac{\partial\rho}{\partial t}=-2\rho~\delta(t-t_0)\neq 0~$ where $~\mathbf{j}~$ and $~\nabla\mathbf{j}~$ are zero (charge conservation can be derived from Maxwell equations, its violation implies their breakdown).

 

[A.T.]

But the magnetic field at a distance doesn't change at the instant that whatever is generating it changes.

The same is true for the electric field, but the whole instant switch scenario is unphysical, so physics doesn't make any predictions about it. What people actually have in mind, when saying there wouldn't change much, is that it would be possible to build a very similar universe from antimatter.

 

[Hornbein]

The same is true for the electric field, but the whole instant switch scenario is unphysical, so physics doesn't make any predictions about it. What people actually have in mind, when saying there wouldn't change much, is that it would be possible to build a very similar universe from antimatter.

What I found on the Internet was variations on "If all matter in the universe were instantly changed to antimatter, nothing would fundamentally change in everyday life or how the universe operates."

I think it would be cataclysmic, but am not certain about that.

 

[Astronuc]

But the magnetic field at a distance doesn't change at the instant that whatever is generating it changes.

True, but matter doesn't abruptly change to anti-matter. One should ponder, would the 'new' EM field counter act the 'old' field.

"If all matter in the universe were instantly changed to antimatter, nothing would fundamentally change in everyday life or how the universe operates."

That seems to be an unqualified statement. What is the basis of the claim? I not aware of a physical model that addresses such an nonphysical situation. Perhaps most are considering the steady-state condition, rather than the dynamic response, which would occur in a matter of pico-seconds (?).

I'm not sure how one would experimentally investigate such a nonphysical phenomenon.

One could perhaps theoretically consider a hydrogen atom (proton-electron) then attempt to model an abrupt change to an anti-proton-positron.

 

[loop quantum gravity]

I would guess we would see something similar to the universe where sliders landed that they go somehow backwards in time. (I believe it was in their second season, one of their best episodes).
I mean in Feynman digrams anti-particles seem to proceed backwards in time w.r.t the regular particles.

 

[Roberto Pavani]

I know this is the Science Fiction section, so we're allowed to bend the laws of physics a little. But simply changing an electron into a positron (and nothing else) would be taking it a bit too far: you'd be violating electric charge conservation.

If it's only a relabeling, assign the electron charge q and the positron charge -q, and consistently change the signs of the corresponding fields and currents, then nothing physically happens.

But if you mean an actual physical conversion of an electron into a positron, with everything else left unchanged, then you have a problem: the charge changes by 2e. A Gaussian surface enclosing that particle would suddenly have the wrong electric flux for the enclosed charge.

Science fiction is fine. But creating 2e of electric charge out of nowhere is perhaps a little too fictional.

 

[A.T.]

...but am not certain about that

Taking the "instant switch" literally is basically asking:

What would physics predict, if physics was wrong?

Well, who cares if it's wrong anyway?

 

[stefun2takes]

Wouldn't we just rename them, call antimatter and matter antimatter? I can't see any other change. They do hint at being basically the same thing performing different functions

 

[berkeman]

Wouldn't we just rename them, call antimatter and matter antimatter? I can't see any other change. They do hint at being basically the same thing performing different functions

Welcome to PF.

Please re-read the preceeding posts. Matter and anti-matter have at least opposite charge, so that would create temporary force change issues.

 

[Hornbein]

Taking the "instant switch" literally is basically asking:

What would physics predict, if physics was wrong?

Well, who cares if it's wrong anyway?

It's called science fiction. If you aren't interested then you aren't interested, yes?

 

[berkeman]

Taking the "instant switch" literally is basically asking:

What would physics predict, if physics was wrong?

Well, who cares if it's wrong anyway?

It's the SciFi forum, so we will cut the OP a little slack. It's actually a fairly interesting theoretical question, IMO.

 

[Hornbein]

One could perhaps theoretically consider a hydrogen atom (proton-electron) then attempt to model an abrupt change to an anti-proton-positron.

There would be an instant change to repellant force followed very shortly by a reversion to attractive force. Would the positron fly off into space? I would expect it wouldn't have enough time to do that. Would a photon be emitted? Two? If so then you have energy coming out of nowhere. If there is enough of it then this is cataclysmic.

 

[Dale]

But the magnetic field at a distance doesn't change at the instant that whatever is generating it changes.

According to which physical laws?

Maxwell’s equations say that charge cannot suddenly change in the first place. So it cannot say anything about what would happen after.

Since this is SciFi, you will have to make up the laws that will govern it. Those laws cannot be Maxwells equations, so you can decide whether it is catastrophic or unnoticeable.

 

[Hornbein]

I crudely calculated the energy released if a hydrogen atom were instantly converted to antimatter. 4 * 10^-26 joules. If this were to occur in the same instant to all atoms on the planet Jupiter there would be no measurable effect. So it appears this radical transformation would be practically unnoticeable in this regard.

 

[A.T.]

It's called science fiction.

Then it depends on what suits the story better. Physics cannot answer this.

 

[Hornbein]

So what if a neutron star undergoes the anti matter transformation. The core of a neutron star contains a few percent of protons and electrons. This makes for the highest density of protons and electrons in the Universe. The electron-proton distance is ten thousand times less than in the case of a hydrogen atom so I thought the thermal effect is ten thousand times greater. But each particle is surrounded by particles of the same charge so the accelerations tend to cancel one another out and the net thermal effect amounts to virtually nothing.

The protons in a neutron star core form a superconductor. Would the antimatter transformation disrupt the Cooper pairs, since for short while it would appear to each antiproton that its partner was a proton. I expect that no one knows.

And no these are not personal theories, they have been standard beliefs of neutron star cosmologists for at least twenty years, published in Nature and Physical Review. There is direct evidence of the superconductivity of the core in the cooling curves of such stars. The formation of Cooper pairs releases neutrinos, cooling the star more rapidly than usual.

 

[Dale]

for short while it would appear to each antiproton that its partner was a proton.

You still haven’t indicated by which laws you make this basic claim.

I expect that no one knows.

It isn’t a type of question that has a definite answer that can be known. The existing laws of physics forbid the question itself. So the only way to answer the question is to make up some new laws. Those fictional laws could be chosen to get any desired outcome.