[over_bridge]

Seems like we've got a few of these imbalances now where you'd expect 50:50 but instead it's skewed to one side where nature had a different idea

Matter-antimatter ratio

Left vs right handed molecules

Now galaxy spin directions

Maybe there are others I missed too

[otikik]

The fact that we have found left-handed neutrinos but not right-handed ones seems like another one.

https://en.wikipedia.org/wiki/Sterile_neutrino

[yboris]

Cosmic Rays May Explain Life’s Bias for Right-Handed DNA

"the rapid decay of pions is governed by the weak force — the only fundamental force with a known mirror asymmetry"

https://www.quantamagazine.org/cosmic-rays-may-explain-lifes...

[albertzeyer]

For the matter-antimatter ratio, you would not expect 50:50, or would you? Because 50:50 would be a highly unstable system? In any case, you would expect that unstable states would be highly unlikely, and it would converge into a stable state.

I'm not sure about the other examples. But maybe it's a similar reason that it is not a 50:50 ratio?

[hhjinks]

A 50/50 matter/anti-matter system could still house stable local pockets of mostly matter or anti-matter. The problem is, from what I understand, that the universe seems to have sprung into existence with way more matter than anti-matter, and we don't know why.

[BlarfMcFlarf]

Not a physicist, but here is my understanding of the cosmology physics:

High energy can spontaneously form matter antimatter pairs. In the early universe, the heat of the universe was very high, so this was common, constantly happening.

The problem as always if fine tuning. If the early universe was 60-40, that would be understandable. If the early universe was precisely 50-50, that’s fine too. But the universe was 50.0001-49.9999 or something like that, and then all annihilated. It’s too big a difference to easily be random chance, and too small a difference to be easily explained by a starting condition what wasn’t precisely tuned by some mechanism.

[btilly]

In all known physical processes, the baryon number is conserved. Particles with a positive baryon number are the heavy particles in matter. Think protons, neutrons, and so on. Particles with a negative number are antimatter. Think antiprotons, and antineutrons. And particles with a 0 baryon number are not made of quarks. Think leptons like electrons and neutrinos, or bosons like photons and the Higgs boson.

This means that all known ways to create or destroy matter, also creates or destroys an equal amount of antimatter.

It turns out that most attempts to extend the Standard Model allow violations of baryon conservation. This could explain the dominance of matter in our universe. However none of those attempts have been able to make any predictions that matched experiment. And so it remains true that all known physical processes perfectly conserve the baryon number.

(It is also possible that baryon number really is conserved, and dark matter is actually dark antimatter. But we lack a theory of what dark matter could be that predicts this.)

[mystified5016]

You would expect a 50/50 ratio because when energy is converted into matter, it's typically in the form of matter/antimatter pairs.

There's nothing special about matter or antimatter. Same energy, just opposite charge. All else being equal, they should be created in equal amounts. As far as we're aware, there is no special property that would make the universe preferentially create more matter than antimatter.

There's also no requirement that the configuration of matter and antimatter be "stable" for whatever definition you want to apply. The only rule is that conserved quantities stay conserved.

[permo-w]

but I was under the impression that equal parts of matter and antimatter annihilate, which would make a 50:50 system remain as such, which is why its such a mystery?

[anomaloustho]

Isn’t there a different observation for why planets tend to orbit in the same direction in a solar system?

[deepsun]

It's easily provable that any matter rotating other way gets expelled or thrown to center (Sun). So majority wins.

[Ygg2]

> Left vs right handed molecules

Organic chemistry found on meteors shows that non-terrestrial sources are equally left vs right-handed.

However, the rest might be caused by one or more errors in our premise. The most likely culprit being cosmological principle.

[anal_reactor]

I honestly start thinking that the idea "everything should be symmetric in some way..." is completely wrong, and an example of wishful thinking "...because it would be cool if it did". Even if nature is in some way balanced on a scale large enough, it's extremely unlikely for us not to be in some local pocket. Most likely we're a part of some bigger structure that has certain properties, and this affects our perception of the laws of physics.

[Nevermark]

> Most likely we're a part of some bigger structure that has certain properties, and this affects our perception of the laws of physics.

Which would also be the reason we have the laws of physics we do in general.

Anything seemingly ad hoc in our universal (from our vantage) viewpoint is potentially explainable as a pocket among all other possible distributions/combinations of relations.

[stainablesteel]

there's also that famous experiment by Chien-Shiung Wu, veritasium did a video on it somewhere

[gerad]

Dark matter / regular matter