...herd stars into lovely, swirling spiral arms, to confine other huge groups of stars into lovely, oval ellipticals, and to form star clusters and galaxy clusters and super-clusters.

Dark matter bubbles--like the beads in this experiment scattered among the rods and suddenly bringing order where there was chaos or randomness. New studies of the universe certainly indicate that visible matter gathers along gigantic filaments that form the borders of great bubbles in space which are almost empty of matter. This principle of spheres inducing order could be the key to discovering what dark matter is and how it works.

These filament structures in the universe bear a striking resemblance to the human brain neurological system--to my eye anyway. I've often wondered about this: is our brain a small (very small) version of the universe? I don't really understand what is known about dark matter. Is there dark matter within visible matter (for instance, within galaxies, or within us), or is it outside of visible matter acting as a pushing or pulling gravitational force? And, frankly, I don't know if scientists know this. But if dark matter is outside of visible matter, and is within these big airy bubbles in space, then these spherical shapes could be acting upon the filaments of visible matter like the steel balls in the experiment act upon the rods.

Well, this is just speculation by a non-scientist here--but fun!

...no hard evidence yet, but I hadn't read of any alternative theories. Thanks for pointing this one out. It certainly could be true that galaxies are so-o-o-o large, and galaxy clusters even larger, that our physical theories are simply inadequate to address them. I must say that the notion of "dark matter" often strikes me as a catch-all--just this big vague THING that accounts for huge puzzles that we are stumbling across as our technology for imaging the universe catapults forward, way ahead of our physics.

Maybe the answer will be to re-tool Newton to better fit what we are seeing now, rather than invent a weird, pervasive entity like "dark matter" about which scientists know nothing except that it "must" be there. And maybe the same will turn out to be true of "dark energy" (supposedly responsible for the accelerating expansion of the universe-as-we-see it). Indeed, I find the Big Bang theory very weird, too--especially this recent "inflation" theory, which strikes me as another catch-all. ('We can't really explain how all the matter in the universe once could fit on the head of a pin, so we imagine a sudden inflation...'.) I have nothing but the average citizen's understanding of physics and mathematics, so I can't discuss this scientifically. I'm relying on word-descriptions of these concepts. In words, they seem like utterly preposterous fantasies. All matter concentrated on the head of a pin? Yeah, right!