Is dark matter real?

Humans urge to understand the world we live in has propelled science and the rate is seemingly accelerating. Things that was thought impossible only decades ago is common knowledge today. It’s exciting to be human, right?
Some types of sciences have reached greater heights than others. In physics we keep discovering new particles and mathematical formulas and in medical science, new medicines and vaccines are discovered for illnesses that were lethal just a few years ago. Wow!
Most sciences are researched in advanced laboratories and experiments are conducted time and time again. In astronomy however, this is not possible for all branches. Experiments must be performed in space or by observing phenomenons through different kinds of telescopes. This makes discoveries hard to confirm 100%, but we still wonder and fantasise about the heavens…trying to understand!

When I was young, I had a subscription for a science magazine, but no articles in these magazines were read more than the ones concerning Astronomy. Every time I read, I travelled into space in my mind, to the planets in our solar system and to planets around distant stars that I just knew had to be out there. No planets had been discovered around other stars in those days…

Astronomy has existed more or less since the first humans turned their eyes towards the heavens and stars. Humans have always tried to understand what they observed and some of the theories are still mainly valid, even today. For example planets (wanderers) were seen to change position in the sky and the position could be foreseen. Our ancestors figured out that these were not regular stars. I eventually turned out that planets aren't even stars, but bodies like our own Earth.

Because a large number of the hypothesis in Astronomy cannot be fully confirmed in laboratories, these same hypothesis stay unconfirmed. In some cases the “known truths” are only approximations or “best guesses”. There are for example different methods of calculating distances in the universe. These cannot be fully verified because, well, we are incapable of doing the exact measurement without travelling the distance. Since warp drives are still to be fully understood, and according to Einstein, only possible in sci-fi, we are left with approximations. And this is OK. The methods seem logical.

Progress in science is done by making a hypothesis and testing its validity. If the tests fail, the hypothesis is discarded and new hypothesis are stated. New tests are performed to confirm the new hypothesis until we find them plausible. This is how models are either verified to be plausible or verified to false.
Newton and Kepler laws were found to not be completely accurate when speeds exceeded what we normally experience on Earth. In space, these laws were modified by Einstein and we were once again on the roll. Newtons laws are used successfully on Earth, because they are good enough approximations for the objects observed behaviour. The modified laws are used for space travel because they are good enough for successful travel inside our solar system and planetary landings. Beautiful!

But…there are some problems even with these modified laws and the solution is one that I really could’t quite settle my mind with when I followed an astronomy class at the University. There is a problem with for example how stars rotate around the galaxy cores. From planetary motion in our solar system, one would expect that stars rotate slower and slower the farther away from the galaxy core the star orbits, but this is not the observed behaviour of galaxies. Even the fact that galaxies keeps together cannot be explained by normal physics.

Throughout the history of astronomy we have seen many shifts. “We thought it was like this, but the observations showed this to be false, so we modified the model”. Let me describe one example…Ptolemy’s model of our solar system (or Universe at that time) had Earth placed in the centre. To account for retrograde planetary motion, the epicycle was introduced for some planets. You see the small circles that the planets have in addition to the orbit around Earth?

(Image found at http://users.clas.ufl.edu/ufhatch/pages/03-Sci-Rev/SCI-REV-Home/resource-ref-read/chief-systems/08-0PTOL3-WSYS.html)

With these constructs, the model was actually capable of foreseeing positions of the planets. How these epicycles worked however is left uncommented…The model was good enough to fit naked eye observations. Hey…they did not have telescopes in those days. Approximately correct is good enough.
Even though Copernicus tried to discard the model by placing the Sun in the centre and also successfully removing the epicycles, making the model much more pleasing and simple, this was not enough because both models were about the same when it came to predicting planet positions. It was first when Galieo Galiei turned his crude telescope towards Jupiter and Venus that Copernicus’s model was found to be the most plausible. Jupiter had moons, which was thought to be impossible because everything should revolve around Earth according to Ptolemy. Some of the phases of Venus could only be explained when placing the Sun in the centre. But…the humans figured it out eventually! Just give it time! We are great creatures aren’t we? Fantastic!

Sorry…enough talk about our solar system…back to the problems with galaxies and large scale motion of the universe. Because the current model cannot explain the observations, I would guess that the model would have to be discarded. But no! Einstein cannot have been wrong! Could he? The problem with the current model is that about 90% of the mass needed to account for the observations is simply not there. “Let’s discard the model. It can’t be correct” you say? Well, no…instead of discarding the model, the astronomers introduced what I would call "The epicycle of the 20th century". Something called dark matter. Dark matter is unlike any known matter we have seen before and this is not all. We can’t see it. We only know it is there. Seriously? When first reading about this, I slowly turned to the next page of my astronomy book, hoping to see the continuation “…but we found this to be false and changed the model”…but I did not find this. This is actually thought to be the solution. Dark matter? I was, and still am 20 years later, speechless!

Several models have tried to explain the observations without introducing dark matter. An example of this is MOND (MOdified Newtonian Dynamics), and I leave it up to you to read more about this and the other alternative models, but the majority of todays scientists still find the dark matter solution to be most plausible. I must say that I am mildly put surprised about this. Scientific models explained by introduction of magic ingredients that no one has seen before? This breaks with all scientific evidence. I really hope we are able to perform enough experiments in space to find MOND or one of the other models more plausible. I cheer for these alternate models. They simply smell and taste more like real science.
I don't think Einstein physics is wrong. Too many observations have confirmed it to be plausible. I just think that the laws need to be modified to make them applicable for the scale and speed of galaxy motion and interaction. On this scale they are simply not accurate. The inaccuracies get very visible as the scale gets larger.

I would love to hear your thoughts on this. What do you think? Please leave a comment.