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The worst pie - Dark Apple Pie. QED

That's that funny thing, they've tried different scales. They've tried radically different ways of measuring it, and always come up with the same discrepancy.

If summing energy works differently on a large scale, why? Since we don't know what we can do is start measuring the difference between observable energy and the "extra" that appears when we add it up. We could call that "unobservable energy" so we can see if there is a pattern, or if it's actually something else. You know "unobservable energy" is a mouthful, why not just call it dark energy?

We don't know what it is. We have tested lots of theories and dark energy doesn't seem to fit any answer, hence the name. I get thinking that it can't be that hard to reconcile and scientists must be missing an obvious conclusion, but it's likely that your theory has already been tested. Maybe you have the solution and can resolve the discrepancy, but right now all data shows that dark energy is a large part of the universe.

I'm not sure what you're getting at. Dark matter has been proven numerous times, is a predictive model, and is the only explanation that has held up to scrutiny and observations. It's very clearly the right explanation and we know how dark matter generally behaves, we just don't know specifically what it is.

See, for example, the behavior of the bullet cluster merger.

As far as we're aware, dark matter only interacts with the universe gravitationally. It doesn't even interact with itself, which is why we don't see dark planets/stars/galaxies popping into existence. It only follows normal matter around.

As for why it's not called cold, is for two reasons:

1. Cold gases of normal matter can condense to form stars. Dark matter doesn't interact with itself, which implies it cannot condense into more concentrated forms of itself the way a gas cloud can eventually form a star.
2. We just don't know what the stuff is, it could be clouds, planets, black holes, neutron stars, brown dwarfs, etc. But our best observations of dark matter are from very large distances away where we can measure the distortion of spacetime due to dark matter. We can't see these smaller objects at these distances. But we should be able to see other clues that would indicate it's normal matter.

If it happened to be clouds of gas and dust that overall had a net gravitational effect on the background galaxies, we'd be able to detect the spectral lines of these clouds. Same for just about all the other objects in that list. In some cases we do detect intergalactic gas clouds. But in places where there's very clearly unaccounted for gravitational lensing, there isn't any sign of this. So far the only things we can match up to the observations is a mathematical model of the stuff.

No, because those would also interact with other things like electromagnetic radiation, light, etc. Dark matter only interacts with normal matter via gravity.

Dark matter is admittedly a bit of a misnomer but that's what everyone's been using for years 🤷🏻‍♂️

As far as I understand it, the way stars, planets, gas clouds and galaxies move wouldn't make sense with just the gravity of the visible objects. There needs to be so-far-undetectable (directly, at least) dark matter in the otherwise empty space? I don't really remember if it was understood to be a universally equal distribution, or if it is understood to be concentrated in blobs/clouds/noodles or whatever.

I don't really have a lot at stake riding on it, while it's interesting physics and to an extent I care about it, I don't really care enough to either ridicule, push for solid answers "NOW", hunt down frauds, etc.. Some people really care about that, I don't really take it that seriously. I don't think life should be a rat race where you're either immediately useful and correct, or cut off and dead. The scientific consensus seems to be that there isn't really a good alternative to dark matter. Was it string theory that tried? I might be misremembering, but as far as I've heard, that's basically dismissed and disproven regardless of whether it had anything to do with dark matter.

On a final note, is there any reason to expect that the giant deep Antarctic ice-telescope will be able to observe dark matter? Apparently it's supposed to be able to pick up on wavelenghts that we so far haven't had the chance to observe, iirc by triangulating rare flashes of light from neutrino collisions with particles in the extraordinarily clear ice.