Darkness – exists both, figuratively and somewhat literally in our universe. Even the invisible matter can cost us one too many years of exhausting research. Can you imagine how strenuous it would have been to progress in the matters of ‘the stars and the moon’ if Edwin Hubble did not discover other galaxies in the first place? Along with this historical discovery, certain aspects just did not add up, like a jigsaw puzzle with one peculiar piece. It turns out the 20th century was the revelation phase for us. World War I, economic depression, the space race, rise of dictatorship and of course, the grand acknowledgment of the existence of dark matter.
A Swiss-American astronomer, Fritz Zwicky, very closely observed the disturbing patterns that every galaxy of the Coma Cluster was dealing with. According to Zwicky, the velocity of the galaxy needs to be in relation to the mass that it holds. If there is more matter (stars, gas clouds, etc.), the amount of light it will emit should also be more, and similarly, the pace of spinning should be more. Also, there was not enough visible matter to justify the velocity of the galaxy which is such that without the correct amount of mass, it would crumble and fall apart. It was undisguised. There had to be some sort of invisible or ‘missing’ matter, as Zwicky initially called it, that was holding the particles of the galaxy in position.
Galaxy Rotational Curve
Vera Rubin was the one who later found out that the galactic center of a galaxy is where the particles have more mass and a stronger gravitational pull. Further away, the drag on the matter grows weaker. Now, this is the theoretical galaxy rotation curve. What she found out was unexpected. She noticed that the speed at which the matter in the galaxy was moving was the same, irrespective of its distance from the galactic center. This meant that dark matter was/is possibly adding to the mass.
All matter in our universe is baryonic. This means that particles are made of protons, neutrons, and electrons. Ordinary matter is visible because it either reflects light or emits light or absorbs light. Much to our surprise, only 5% of this is present in space. Dark matter does absolutely nothing. It does not emit, absorb or reflect light which in turn is an addition to the set of difficulties we face to define this unique casualty. Another vital contribution to the tedious research was the Bullet Cluster in 2006. Two major galaxy clusters went KaBoom!
During the collision, the solo galaxies of the cluster passed by without interacting whereas the gas collided and heated. More than one X-ray was emitted which we can still see today. But we found these on the borders of the galaxies and not along with the intra-cluster matter. This again, clarifies that dark matter does surround us. When light passes through dark matter, it bends, also known as gravitational lensing. One of the core reasons why we still believe in the halo surrounding our precious space.
Now initially there were certain theories or rather, coincidences that were misconstrued as dark matter. Black holes, the void, black holes do not emit or absorb light, and they as well are detected by gravitational lensing. But there aren’t as many black holes to coincide with the happening we are seeing. The same applies to brown dwarfs.
Neutrinos could have been another suspect, but they are incredibly lightweight and fast, and for it to classify itself as dark matter, there had to be more mass to hold ordinary matter. So, unfortunately, dark matter is a whole new species. During the big bang, dark matter formed first, and ordinary matter clung to this string. There is a theory of the ‘Hidden Valley.’ A parallel world where everything is made up of dark matter and energy with hardly anything in common. If scientists are successful in analyzing this, we can get a clearer picture of our universe and the making of it.
The AMS (Alpha Magnetic Spectrometer) is a sensitive particle detector used to help detect dark matter. All sorts of detectors and experiments only ask for positive results, but as of now, we have none. There is background disturbance, and the particles are too fast to be captured even at different temperatures.
There are also theories about how dark matter may have been a contribution to the extinction of the dinosaurs, but then again, there are too many of these to believe. Dark matter is best friends with gravity. Let us all just hope that we don’t wake up tomorrow, floating.