You cannot have real democracy when there is a ruling minority class, as in capitalism, simple as that.

Things don't need to be opposites to affect each other in predictable ways.

They are both decision making processes where different groups hold power over society's resources. Democracy very much has economic power and Capitalism is very much about who gets to make certain decisions.

They have what you might call... friction.

I can list at least one.

Can't think of a communist democracy, though.

Technically aether theory was never ruled out. People love to claim that the Michelson-Morley experiment ruled it out, but this is historical revisionism. The MM experiment was conducted in 1887. Hendrik Lorentz proposed his aether model in 1904. Obviously Lorentz was not such a moron he would not take into account the findings of MM, but that is what people are unironically suggesting when they say MM somehow retrocausally ruled out his model. Indeed, both Michelson and Morley did not believe their own experiments ruled it out either but continued to promote such models.

Lorentz's aether model and Einstein's relativity are actually mathematically equivalent so they make all the same predictions, so no possible experiment could rule out Lorentz's aether theory that would not also rule out Einstein's relativity. Indeed, if you read his 1905 paper where Einstein introduces special relativity, his criticism of Lorentz's model is only a philosophical objection. He never posited that an experiment can rule it out. MM only rules out some very early aether models, not Lorentz's model.

I would recommend also checking out John Bell's paper "How to Teach Special Relativity," where he also discusses this fact, and how the mathematics of special relativity are perfectly consistent with a reality with an absolute space and time. Taking space and time to be relative only comes at the level of metaphysical interpretation.

To paraphrase Tim Curry, communism and capitalism are both red herrings.

Oh that big punch up between the Soviet Union and the United States, decadent capitalism vs brutalist communism. Who won? According to the scoreboard as of 2026: Israel.

The catch phrase I've always heard about communism is "the people own the means of production." Has that ever been true in practice? Did Soviet citizens own any piece of the means of production? Did anything resembling "from each according to his ability, to each according to his need" ever once happen under the hammer and sickle? Or was that the false narrative the idiot asshole in charge used to cow the unwashed masses?

Similar questions could be asked of my fellow capitalist Americans. Capitalism is allegedly about the free market, supply and demand, if there is a demand someone will provide a supply, probably multiple someones, competitors will compete, those who do it faster, cheaper or better will succeed until someone else does it even fasterer, cheaperer and betterer repeat until someone else comes along with a completely different idea, welcome to the infinite cycle of meritocracy where the cream rises to the top. How's that working out? Some substance has risen to the top, not sure it's cream.

A common problem I see between the Soviet Union and the United States: Weak systems for preventing psychotic despots from ruining it all.

Further expanding on this: My understanding of the Soviet Union: Something something the Bolsheviks, something something communist revolution, They just about have an election, that Lenin overthrows because it isn't going his way. Lenin is King Shit Of Turd Mountain until his death, then the dumb guy from the ghetto he kept around because he's good at hurting people, Josef "probably worse than Hitler" Stalin takes the throne. The entire run of the Soviet Union is essentially a dictatorship with a command economy and remains thoroughly miserable.

The United States, meanwhile, has gone through phases. Tides have ebbed and flowed, robber barons have come and gone, consumer protection laws have come and gone. Times when a very few, very rich men have been mostly miserable for most people; times when those assholes get knocked down a peg and the common man has a chance to make a decent living get better.

The problem is a few ultimately rich assholes in charge.