Ray, where did you read that "95%" of the stuff of the Universe is "invisible and undetectable" That is truly throw-away Science at best.
Not at all. It's cutting-edge science and a big problem for Astrophysicists.
Until fairly recently, our theories of gravity, and theories of the origins of the universe, expressed with the catchy phrase, The Big Bang, which you must have heard of, predicted that the rate of expansion of our universe should be seen to be gradually slowing down. At some point in the very distant future, the expansion, it used to be thought, might slow to a halt and the universe would then begin contracting and eventually collapse upon itself.
I believe the brilliant physicist, Stephen Hawking described the possibility of such a scenario in his first popular book, A Brief History of Time.
However, as our telescopes and measuring devices have become more sophisticated, it's now become apparent that our universe is expanding at a much faster rate than our calculations of the total amount of mass and energy in the universe would predict, and that certain distant spiral galaxies are rotating at far greater speeds than their observed mass would account for.
In science, when our observations of 'reality' cease to correspond with the predictions of our theories, then we either have to devise new theories which match the new observations, or find a plausible explanation for why such new observations may still be consistent with our current theories.
The latter approach has been adopted by most Astrophysicists. In order to maintain the integrity of current theories, they've postulated the existence of huge quantities of invisible matter and energy. They don't use the term invisible, of course. They use the term Dark, as in Dark Matter and Dark Energy. But the blunt fact is, at present this stuff is completely invisible and undedectable in any shape or form.
Perhaps they will eventually discover particles of Dark Matter. On the other hand, perhaps they never will because it simply doesn't exist.
Current alternative theories, such as MOND (Modified Newtonian Dynamics) do not provide a completely satisfactory explanation. There are lots of references to this issue on the internet. Here are a couple of links.http://en.wikipedia.org/wiki/Modified_Newtonian_dynamicshttp://www.sciencedaily.com/releases/2012/04/120418111923.htm
Estimates of the total percentages of matter and energy which are 'Dark' (or invisible) seem to vary from around 80% to 96%. As a layperson I find this issue quite fascinating because it seems to affirm my own personal philosophy that the more we know, the more we realise how little we know.