Ever since astrophysicists discovered a discrepancy between the mass of the observed matter in galaxies and gravitational effects that gave them structure and hypothesized the existence of dark matter, some spoil-sports have tried to insist that dark matter doesn’t exist at all. Numerous theories have tried to hide dark matter – including attempts to modify gravitational theory itself. The latest blow against dark matter came from a team of astronomers who simply measured stars in the Milky Way and concluded that their motion could be entirely explained by visible mass – that there was no need for dark matter.
Galaxy Cluster Abell 1689 (Credit: NASA/ESA)
Why are people so hostile to the idea of dark matter? Well, maybe it’s because it compromises more than eighty percent of the matter in the universe (it has to, in order to have the gravitational effect that it does), yet we can’t see it and don’t know anything about it. It’s an elephant in every room and we can’t even see it there. That sort of thing tends to frustrate people – especially people who like to think that they already know everything about the universe.
Maybe a more interesting reason is the excessive fun theorists have with trying to figure out what the dark matter is. They come up with whimsical names for the stuff like WIMPs (Weakly Interacting Massive Particles) and MACHOs (Massive astrophysical compact halo objects) which might rub more serious folks the wrong way. They spend billions of dollars for atom-smashers trying to find the stuff, potentially taking money from other projects. Dark matter has also gotten a lot of attention in the media, with hypotheses about dark matter grabbing more headlines than actual experimental results in other areas. So, there may be a contingent of scientists who are a bit ticked off with the pro-dark matter crowd, and want to bring them down a peg by finding out it doesn’t actually exist.
Well, I’m thoroughly in favor of dark matter – not because I’m a physicist able to evaluate the evidence, but because I’m a sci-fi writer, and dark matter is bloody useful plot device. I really take attempts to rewrite equations in order to adjust for dark matter as a personal affront – as if the astrophysicists are deliberately trying to make life more difficult for me – and take great delight when I see that they haven’t been able to incorporate relativity into their mangled versions of Newton’s equations.
And I take similar delight in noting that those astronomers who found no need for dark matter in the Milky Way were proved wrong. Jo Bovy and Scott Tremaine from the Institute for Advanced Study pointed out that they had made an error. You see, the astronomers had assumed that distance from the galactic center didn’t affect a star’s speed when, in fact, stars far above or below the galactic plane have extremely eccentric paths, and their speeds do change depending on where they are. Bovy and Tremaine recalculated the results and are publishing their own findings, which show that the dark matter is necessary after all!
So there you go: don’t mess with the dark matter.