As I understand it, in General Relativity, the definition of energy is such that the normal kinetic energy of matter is balanced by the potential energy of the universal gravitational field (considered to be negative). I don’t understand all the details, but when you get down to it, energy is an accounting device. It’s the particles and the fields that are real. This chart isn’t a complete classification of all forms of energy (presumably, that would require the laws of physics to be complete). Rather, it shows the relative influence of the forms that affect the Hubble expansion.
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How do you know that?
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I’m not sure what you mean by that. There are a lot of particles in the universe, which means that there are a lot of a lot (a lot factorial) of possible pairs. A better way to put it is that space is inflating everywhere; including at points that happen not to be between two particles. (If there are any such.)
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I believe the post’s title is misleading. Per Katie: “Visible matter makes up only 5% of our universe…”
The 5% refers to the portion of the Universe that is open to visible observation. Vnnuff-Ba on Zobbo IV can probably see ‘visible things’ that we can’t.
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Neither do am i, completely.
ETA: D’oh!
I think that’s slightly mischaracterising what’s going on here. It’s not like OJ talking about the “real killer” to defend the false theory that he didn’t do it. Scientists fully recognise that our present understanding is only a temporary working model; that condition of not knowing what we don’t know is the whole reason science exists.
Our current guess about gravity is empirically excellent – more than good enough for almost all our needs – so we act as if it were The Truth, but that in no way means we’ve ruled out other explanations in which the need for “dark matter” may vanish. It’s well understood that, as an accounting construct, “dark matter” might be real or it might indicate a flaw in the accounting process; but until we know more, we proceed as if it’s the former, simply because that’s how you get the books to balance.
Currently the smart money is on dark matter literally existing, but there is also respected theoretical work on the possibility that gravity doesn’t work quite how we think with respect to very empty space. It’s not a religious argument; each approach generates useful questions for the other, and both contribute to making the overall picture clearer.
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Well, my statement certainly doesn’t qualify as a full argument, and I could see how an actual scientist might find it insulting, even. It just mirrors my own feelings about it. I haven’t liked this theory from the beginning(which, of course, doesn’t actually have any bearing on whether or not it is correct). The currently fruitless search for it just enforces my intuitive opinion that it’s wrong. I am firmly in the “There is no dark matter” camp, but I am not an astrophysicist, just a low-rent philosopher with aspirations towards being a theoretical physicist, so I can only watch the story as it unfolds. I bet ya a buck that there is no dark matter. 
I see your Monty Python and raise you The Hawk1) singing the Monty Python song:
https://youtube.com/watch?v=XfcC6FYyL4U
1) Or Rolling Thunder, as he is known as in “The States”.
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I told her.
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