Mysterious Dark Matter - What It Is, The History Of Dark Matter, Detecting Dark Matter and My Own Thoughts!

Dark matter. It is something that makes up almost 80% of the mass of our universe, yet we know so little about it. We only know it exists because of how it interacts with the rest of the universe through its gravity. It was discovered in the 1930’s by Swiss astronomer, Fritz Zwicky, who had been studying Hubble’s observations of the Coma Cluster of galaxies, which is a galactic supercluster which contains more than 1000 galaxies, when he noticed something strange. From what he was able to see, galaxies were moving way too fast for the cluster to remain attached together. He assumed that there was some kind of ‘invisible mass’ holding them together, and he called it dark matter. 

Now, what exactly is dark matter? Although scientists and astronomers know very little about dark matter, we do know a few things. Firstly, dark matter is a form of matter that cannot be observed. In other words, it is invisible or dark. It makes up 27% of the universe, and 80% of the mass of the universe. Secondly, it is not made up of the same particles that make up normal matter, such as stars and planets. Normal matter is made up of particles called baryons, which are able to absorb radiation that passes through them. We know that dark matter is not made up of baryons because we would be able to detect the absorbed radiation, which we cannot do. Scientists believe that dark matter is partially made up of a type of particle called neutrinos. Neutrinos are particles that do not emit light which leads people to think that they could possibly be the particles that form dark matter, but neutrinos are very light and move very fast so they would only be able to form a portion of dark matter. Another possible candidate is WIMPS, or weakly interacting massive particles, but this is not confirmed as they do not interact with normal matter, making them almost impossible to detect. We also know that dark matter is not antimatter, as antimatter produces gamma rays, which is a form of radiation, when it comes into contact with normal matter. Finally, dark matter is so hard to study and observe because it doesn’t interact with electromagnetic forces, meaning it does not emit, absorb, or reflect light or energy. 

Because astronomers cannot see dark matter directly, the only way they can study it and actually know it exists is by seeing how it affects the normal matter around it. Astronomers can see light being bent due to the gravitational effect of dark matter by using instruments that detect dark matter by the way it distorts starlight, and using these instruments they were able to create a map of dark matter in the visible universe. Astronomers can also measure the rate at which stars and galaxies are orbiting to see whether or not they are travelling faster than they should be, showing them if dark matter is there or not. Astronomers used to think that objects in the center of galaxies would travel faster than on the outer edges, due to higher amounts of gravity. To their surprise, they found that stars and other objects travelled at about the same speed, no matter where they were located in the galaxy. This led them to think there was more matter that could not be seen, or as we now know, dark matter. 

As stated earlier, Fritz Zwicky was the one to discover dark matter in 1933 when he was studying images of the Coma Cluster of galaxies, taken by the Hubble space telescope, but theories and speculation of dark matter started way earlier than 1933. The first theories can be traced back all the way back to the 1600’s, a little while after Newton had shown the world his theory of gravity. Astronomers had started to wonder and hypothesize about objects in space that emit little to no light, but still can be known by the effect of their gravity on objects like stars and planets surrounding it. Pierre Laplace, who was a French mathematician, took this theory one step further by arguing that there might be objects in the universe that could be massive enough to trap light. This may sound familiar because this is a very simple idea of a black hole. In the 1800’s Urbain Le Verrier and John Couch Adams did something similar to what astronomers do today, by using gravitational anomalies in the orbit of Uranus to predict the existence of Neptune. This is similar to what astronomers do because astronomers look at the effects of dark matter’s gravity on matter surrounding it to predict the existence of it in that area. Fritz Zwicky discovered dark matter when studying the motion of galaxies with the Coma Cluster. Since these galaxies are kind of attached together with gravity, the speed at which these galaxies travel can give us an approximate number for the cluster’s mass. Edwin Hubble had predicted that there were about 800 galaxies in this supercluster, but Fritz Zwicky calculated that the cluster actually had a mass 500 times greater than the one predicted by Hubble, leading him to think that there were large amounts of dark matter in this cluster, likely even greater than the amount of matter we can see. Essentially, theories of dark matter and similar ideas were being talked about 100’s of years before Zwicky, but he was the first to have proof and truly discover it. 

I find dark matter very fascinating because scientists and astronomers know very little about it, and there is so much more to discover about it. I believe that there are larger amounts of dark matter in the universe than what astronomers know of right now, and that dark matter could possibly play a part in the invisibility of black holes, but this is just a hypothesis from me. I also believe that dark matter has been around since the time of the big bang or shortly after it happened, and that the particles that form dark matter evolved from other particles to create dark matter. I am not exactly sure what particle makes up dark matter as there are so many different possibilities and also astronomers have a hard time detecting these possible particles due to their behavior. All in all, dark matter is a very fascinating subject as there is so much that is still unknown about it. I am excited to continue researching about the topic and hope to hear about new studies and discoveries made by scientists and astronomers that can take us one step closer to discovering the unknown. 

I will continue to post more research and discoveries about dark matter that I find, as well as my own thoughts and opinions as I continue to research the mysterious topic of dark matter, but thank you for reading and be ready for many more like this!