Our Strange World of Dark Matter
Chasing a failing worldview is like heading down a dead-end street: the signs that the street is coming to an end may be all around you, but bullheadedness keeps your foot firmly on the accelerator; after all, this is where everyone else is going. But then the dead-end comes and, once again, you have this thought that perhaps you should have paid more attention to the warning signs. Social and peer pressure are powerful forces, however, and it is a rare soul who challenges the march of the masses.
This brings us to dark matter, which is thought to make up 83 percent of the matter in the universe. But dark matter is not really “matter;” it’s not extended in space; does not resist a force; and cannot be seen. Dark matter (like dark energy) is better thought of as a placeholder concept waiting for a better theory to explain the cosmos.
With dark matter, the law of gravity trumps observation: we see the stars in the heavenly galaxies, but the law of gravity states that these stars do not have enough total mass to maintain the shape of galaxies. Therefore, like someone who forces the wrong piece into a puzzle just to show progress, cosmologists assume that the billions of galaxies in the sky actually have eight times as much dark matter as visible matter. Of course, this invisible matter must also have exactly the same gravitational properties of real matter, except that unlike real matter, it is invisible. An invisible nothing with the attractive force of matter.
A recent issue of New Scientist discusses a further mysterious feature of dark matter: not only is dark matter invisible, it does not even interact with itself. Cosmologists reached this conclusion by studying the collision of galaxies. The authors write that “when two clusters collide, their galaxies glide past each other and leave a trail of gas behind. The dark matter, seen indirectly by gravitational effects, remains with the galaxies.”
Indeed, as the authors write, this “mysterious stuff is even more ghostly than imagined.” And, like other ghosts, it might be better to imagine that in fact our eyes do not lie: dark matter is really not there. This would mean only one thing: beauty, not the law of gravity, ultimately rules the cosmos.