Dark Matter

Supposed distribution of dark matter in the galactic halo

Our series about ill-guided science would not be complete without discussing a very "dark" chapter of modern science - the topic of so called "Dark Matter".

After scientists found out that the measured density of matter in the universe could not explain its flatness and that there needed to be about ten times more matter than could actually be observed; that the observable matter could not explain intergalactic super-structures; and that galaxies rotated with such a high velocity that its matter would not be able to hold them together; it was obvious that there was something wrong with the existing models of the universe. But everybody had become so accustomed to the well-known models of gravity, the Big Bang and black holes, that nobody was willing to throw them over board so easily. Something needed to be done to save these beloved theories and reality could not be allowed to get into the way of such nice models.

So scientist introduced some mysterious variable into the equations. The "dark matter" was born. They could also have resorted to some supernatural power like a god who would keep things together and do what the missing matter in the universe was not able to do, but the term "dark matter" simply sounds more "scientific". People had already become used to things like "black holes", so "dark matter" fitted quite well into the faith of theoretical physics.

In fact "dark matter" has a lot of things in common with a god: First of all it is invisible. This is an important advantage, because it makes it difficult to disprove it. Second, since it is undetectable, you can give it any attribute you need to support your model of the world. So theoretical physicists were exactly able to calculate the amount of dark matter as 83% of the total matter in the universe, which was the amount they needed to save the existing models. Since there was no way to detect dark matter, there was also no need to measure this number, which is always quite convenient. Since nobody could see or understand this mysterious dark matter, the priesthood of theoretical physics had the sole authority to interpret and describe this esoteric substance.

Unfortunately some heretical astrophysicists have recently spoiled the fun for the theoretical physicists (http://arxiv.org/abs/1204.3924). They measured the dynamical surface mass density in the galactic neighborhood of the sun and found no indication for the presence of dark matter as common theories would suggest. This will probably not be the final death blow of "dark matter" and theoretical physicists will most likely come up with some adjustments to their theory, but it shows that a lot of those models of theoretical physics are just invented out of thin air and always circumvent any experimental proof.

If a measurement deviates a whole magnitude from the predictions of a theory, like the measured density of matter does, the normal reaction should be discarding the theory as useless. Why are theoretical physicists not reacting this way? If the observable matter in the universe is not able to explain the observable effect of gravity, then probably our theory of gravity is wrong. The scientifically correct attitude would have been to declare Newton's law of universal gravitation as wrong. 

Possibly wrong.

May be it is only an approximation for planetary distances but incorrect for interstellar or intergalactic scales.

We have no explanation for the surprising discovery that the universe expands at an accelerating rate, although gravity is supposed to slow it down. Perhaps gravity has a reversed effect over intergalactic distances. But this cannot explain, how galaxies are held together by such little matter. It seems that the effect of gravitation is higher than it actually should on a galactic scale. There are so many unanswered questions regarding gravity, that we should simply admit that we don't have a working model of gravity at the moment. 

Instead we invent theories of speculative objects like black holes and other singularities with arbitrarily extrapolated values of our flawed law of universal gravitation. May be there is an upper limit for the density of matter, perhaps in the magnitude of atomic nuclei, which is by coincidence also the density of a neutron star, an astronomic object that can actually be observed, different from black holes, which are just based on speculations. We even have theories about so called "Hawking radiation" that causes black holes to slowly evaporate and other descriptions of odd phenomena of singularities like wormholes, white holes etc. We have faster than light inflation of the universe in order to save the otherwise failed theory of a Big Bang, we have a string theory with up to 26 dimensions, of which only four are apparently observable.

When is it finally enough with such weird speculations? What does this have to do with science, which should primarily be occupied with explaining actual observations?

This has nothing to do with what science is supposed to be. This is at best some philosophical exercise. We need to bring back rationalism into scientific research. And we need to limit science to what we can actually observe. We should get our feet back on the ground, think about what we really know and only make research about subjects where we have an actual chance to find answers instead of inventing more or less unfalsifiable speculations.

Let's be honest. We have no idea how the laws of physics work outside our solar system. We have no idea about the origin or the future of the universe. We cannot jump to conclusions based on theories. We have to observe the world and then come up with possible models of our observations. As long as we haven't seen a black hole or some dark matter, we don't even need to ask a question about it.