Every kind of matter that we know about makes up less than 5% of the believed matter in the universe. What's the rest? "Dark matter" and "dark energy" which are effectively empty placeholders. We know almost nothing about them, and yet they're the overwhelming majority of what exists.

Maybe they'll turn out to be boring and useless. Maybe they have even more complex interactions than ordinary matter does. About all we can say today is that there's a mystery 20x more massive than all known matter.

'Almost nothing' is not quite right. We know the fraction to 3 or 4 decimal places. 'What it is' may still be a question but we know precisely what it does

Describing the amount there is and that it exerts gravitational pull says almost nothing about it, assuming it's as complex as anything else in the universe.

We also know that, other than via gravity, if it does interact with matter or EM radiation at all it does so spectacularly weakly.

Erm, seriously?

Or do you only mean classical, newton physics?

Because as far as I know, (quantum) physic is far from explained. Shure we do know a LOT more than we did 100 years ago, but I doubt we have fewer questions. I even suspect it can never be fully understood. Some basic principles, yes. But if the universe is infinitely big and small and it seems it is, there is no full understanding nor resolving all questions. I thought that mindset died out allready. Because before quantum mechanics etc. physicist actually did thought they allmost solved all questions. And then: oh. There might be more ...

I thought the whole idea behind quantum physics is that the universe is NOT infinitely small and that the minimum size / amount is a quantum.

Not at all! -> https://physics.stackexchange.com/questions/9720/does-the-pl...

Sometimes I wonder, how confident were our ancestors when they thought fire was an element, or when the Egyptians made mummies and hoped they would come back to life. Did they have the same level of confidence as we do today? That the "fundamental values have all been measured to a high degree"?

If that's the case, then we can be as wrong as they were.

We don't know what we don't know.

That doesn't imply that we don't know what we do know, however.

It doesn't seem likely that everything we've observed, discovered and experimentally verified about the universe since the beginning of recorded history is simply wrong, or that our level of ignorance about the nature of reality remains constant regardless of the data amassed.

We have absolutely no idea whether the universe or its complexity are infinite. With that out there, it leave the possibility that no matter how much knowledge we amass, it's at best infinitesimal in comparison to all that is possible to know, and at worst, our models will be completely contradicted by some new knowledge that puts previous learning in a different context.

The set of all primes is also infinite, but that doesn't mean it's possible to find an even prime number greater than 2... the universe can be infinite but that doesn't imply the laws governing it are also infinitely varied.

My point was not to state the truth but to show the possibility. Unlike prime numbers, the historical pattern is that our model of reality has changed fundamentally several times.

An easy, however unlikely, example of what could change it again is to find out we are in a simulation.

> nature of reality remains constant regardless of the data amassed.

It does not remain constant. But it remains indeterminable. Ie we can say we know something about the universe. But we cannot say we know x % of the universe simply because we have no way of knowing what 100% is...

We do know that we don't know what we don't know though, which should hopefully reduce the urge to make overly confident statements about the limits of reality.