You’re correct. That hypothesis has not aged well, and it is thought that there are not antimatter galaxies hiding out there. So for this academic exercise, it is included for philosophical completeness.
Right, if some galaxies were antimatter, then there’d have to be some place where it transitions, where both matter and antimatter would be found. And even the intergalactic voids aren’t sparse enough that that would go unnoticed.
And today’s XKCD is relevant.
If we rely on the Wu experiment, does its result depend on the orientation of the polarizing magnetic field? And do we have to state the direction of that field if we want to use the Wu experiment to define left and right? If so, how do we do that? I mean, what is the difference between magnetic north and magnetic south, independent of how we describe the magnet (such as a coil with current flowing “clockwise” or “counterclockwise”)?
I’m just curious. There are enough clever people bought into this disproof of symmetry that I doubt I found the flaw; it’s just that I can’t picture that part.
Once you have a charge convention, a magnetic field convention is the same as an angular momentum convention or a rotation convention.
Thank you, Pasta, that’s exactly what I was asking for. But I’ll have to read it a few more time to really get it.
But before I do, I have to ask: Do we know how antimatter cobalt-60 works? Do we know whether it decays the same as regular cobalt-60 or not? (I’ve always presumed that antimatter is pretty exotic stuff, and I’d be happily surprised to learn that it is abundant enough that these kind of experiments might have already been done.)
I’m certain nobody has ever produced nor studied antimatter cobalt. But the same phenomenon occurs for all beta decays, and I wouldn’t be surprised if it’d been studied for antineutrons.
As Chronos says, anti-cobalt is too much to ask for, but anti-other-stuff is produced and used / studied on a daily basis, so we know how it would behave through a broader understanding of antimatter and the Standard Model of particle physics.
For the up-thread question about antimatter in the universe: electron-positron annihilation photons at the characteristic energy offers one constraint, but also important are direct searches for anti-nuclei streaming through space – anti-helium or heavier would be a smoking gun – and measurements of a more obscure quantity, the baryon-to-photon ratio, that relates to the balance of antimatter vs. matter through the evolution of the universe.