Dark Matter. Not the TV series. The astrophysical stuff; the stuff astronomers believe makes up some 28% of our universe. I think it's bunk. I can think of at least two good reasons why.
First off, Dark Matter was hypothesized to explain the rotation periods of stars in the outer fringes of galactic disks; the stars seemed to be moving faster than could be accounted for by the combined gravitational pull of all the rest of the visible matter in a galaxy. So, posited the astronomers, there must be a much larger mass--of invisible matter--making those stars orbit so quickly.
Over the years, the idea caught on as a way of explaining away various inconsistencies. It was so damned easy just to blame the Dark Matter. Also, over the years, dark matter 'evolved'. It was dark because it emitted no electromagnetic energy (radio, microwaves, heat, light, ultraviolet, X rays). It interacted with normal matter only through gravity (and apparently obeying the same rules with itself, too, for all those computer simulations showed the Dark Matter lagging behind the normal-matter's movements, like a comet's tail).
Recently, one team of astronomers restudied the galactic orbital speeds problem, and came to the conclusion that one did not need to invoke Dark Matter to explain the orbital velocities of the outer stars. Then another team restudied the expanding-universe problem, and discovered that, if you looked at space a certain way, you didn't even need to invoke Dark Energy--a whole separate kettle of fish.
I have a simpler, but I believe well-thought-out, argument.
If we assume that Dark Matter is actually more abundant than normal matter, and at least as mobile as normal matter (in fact, more so), then it would be reasonable to postulate that some of it would be tagging along with, for example, the earth and the sun. But that introduces problems.
Scientists have 'weighed' both the earth and the sun, and from that they can calculate the amount of gravitational force they exert. Presumably, theory matches observation. Let that be our starting point.
Now, if dark matter's gravitation is but a component of that whole, then it means we're no further ahead for having it--but dark matter was brought in precisely because scientists thought its extra gravity was needed. Worse, it really messes up some of the natural constants (especially G--Newton's Constant) that we rely on to make astronomical calculations, operate GPS networks, etc.
Carrying on with our assumption, then, we must further assume that there is no Dark Matter accompanying the Earth or the Sun (or we'd feel it; or our orbit wouldn't make sense). But is that a reasonable supposition, given what we believe we know about Dark Matter (i.e. quite mobile, can't attach itself to normal matter)? I don't think that it is. Why would the solar neighbourhood be Dark-Matter-free? Surely this can't last--eventually some Dark Matter has to catch up with us, and then our goose will be cooked.
Finally, scientists have been searching for Dark Matter for years, believing that every once in a while, a piece will collide with a piece of normal matter. Watching for years. Haven't seen a damned thing in all that time.
For me, case closed.
Now, I'm not a professional astronomer, but I have been keen on the subject for nearly fifty years (I'm 53 now and remember the Apollo 8 flight around the moon, in 1968). I've read every accessible article on it, thousands of pages of National Geographic articles, textbooks, and scientific journals (and it takes a lot to lose me). I've spent thousands of hours squinting through a succession of telescopes. I have the physical parameters of all the planets memorized--have since before I knew what a "sidereal period" was. I've probably forgotten more stuff about astronomy than most people will ever know.
In short: I know a little something whereof I speak.
Have a good one,
-Bill
