Research Paper on Galaxies and Dark Matter


In 1930, a Swiss scientist named fritz Zwicky, while studying a coma cluster of galaxies he noticed something weird about the way they move. The galaxies were going way too fast, so fast that they should have flown past each other because all the stars in all those galaxies had far too little gravity to hold the cluster together. Zwicky thought, that something else must be binding all these things together, and that mysterious missing component would have to weigh something approximately 50 times as much as the stars themselves, But at that time no one paid much attention to this crazy assumption.

If we observe our solar system, the innermost planers like mercury, Venus, and earth revolve around the sun much faster than outermost planets like Uranus and Neptune. Laws of physics define these movements and variation of velocities of these planets since the planets close to the sun will experience greater pull due to stronger gravitational force resulting in them moving at a faster rate, where the outermost planets will move comparatively at a slower speed due to weak gravitational force they experience.

We will expect these laws of physics to apply to all the planets and all the galaxies. Outermost stars in a galaxy should give us the same result as our solar system gives.

But in 1970, an astronomer named Vera Rubin was studying the Andromeda galaxy, she discovered that the outermost planets do not obey these laws of physics. The outermost stars in the galaxy were revolving around at the same speed as the innermost stars. This speed was way faster than the laws of physics tell us. Rubin studied more galaxies to see if they obey the planetary laws of physics but out of 60 galaxies she studied, she got the same result for all these galaxies.

This observation doesn't mean that the laws which Newton gave us were wrong but that there exists a massive invisible object or Particles whose gravity was bringing this change in their speed.

This unknown matter whose force of gravity was defying all the laws of physics was "Dark Matter" which Fritz Zwicky had observed in 1933 only.

We cannot see or observe this dark matter the only way we know that it exists is due to anomalies in gravity that we observe in our universe.

Out of the total energy and mass which exist in our universe about 73% is dark energy, 23% is dark matter, and the remaining 4% is just a tiny bit of total energy that we have been able to discover.

But how do we know something exists if we can't see it. About 22 years ago, in 1988 two projects naming Supernova Cosmology Project and High-Z Supernova Search Team, discovered that the speed of expansion during the very early universe was far shorter than the current speed of expansion of the universe. Our galaxies are not only expanding but they are accelerating. We assumed that this expansion would be slowing down due to mutual force between the planets. But this expansion will require enormous energy to accelerate the entire universe which we today knew as dark energy.

But how can a universe remain intact while experiencing this massive force? There must be something that is keeping all the things together in the universe. To keep all these stars and planets together there should exist something with at least 80-90% of the mass of these all-stars combine.

Albert Einstein describes gravity as a curvature of time and space. Anything with mass should bend space around it. A picture from the Hubble space telescope in which astronomers aimed the telescope at the galaxy cluster RCS2 032727-132623, which is 10 billion light-years from Earth. This distant galaxy was three times bigger than any other seen through a telescope. These astronomers discovered a phenomenon that now we know as gravitational lensing. Gravitational lensing is created when a massive object, like a black hole or galaxy cluster, falls in between an observer like Hubble Telescope. In a perfect case, it comes from all the sides of the object creating a ring which is also called as Einstein Ring. Hundreds of gravitational lenses are currently known and half a dozen of them are partial Einstein Rings. Using these gravitational lenses also known as arcs we found that they contain about 90% more mass than expected.

These galaxies show us that a mysterious type of particle known as dark matter, an invisible force binding these galaxies together exists. Dark Matter is also known as WIMP (weakly interacting massive particles) meaning dark matter doesn't interact with the normal matter of which we and most of the known matter is made off.

Since it's a weakly interacting nature we are not able to detect it. Since we can't observe this dark matter, CERN which is a European research organization, the largest particle physics laboratory located in Geneva, Switzerland is trying to recreate the conditions of the big bang to study particles at an unprecedented level. Since we know that dark matter was created in the process of the big bang where all other types of the matter were created. If we can recreate the big bang we will be able to produce the dark matter.

So can we create dark matter? We've yet to directly observe the dark matter but scientists have theorized that we may be able to create it. The Large Hadron Collider (LHG) is the world's largest and most powerful particle accelerator. It is spread over 27 kilometre-long situated in Geneva, Switzerland.

In the LHC, two proton beams move in the opposite direction and travel at close to the speed of light. There are four points where the beam pipes are made to intercept. We know that protons are made of quarks and gluons, in a most ordinary collision this proton passes through each other without any reaction, but about 1 in a million collision these protons hit each other so violently that it explodes and the collision energy is set free in this collision producing millions of new particles, the collision points are surrounded by detectors containing millions of sensors in them. They collect the data during this collision and send it to a computer, that computer created an image with the data sensors sent to it. This data helps the scientist to study the nature of these particles and what they are made of.

Many scientists assume that dark matter particles are very light and therefore they can be created at LHC. If scientists are successful in creating these particles these particles would be able to escape through detectors unnoticed. But using all the data like energy and momentum before the collision, scientists can notice the difference in energy and momentum since these dark particles will carry away energy and momentum if are produced during the collision.

Using all the data through numerous experiments and upcoming experiments we'll able to collect enough data to provide evidence for these particles.

Dark Matter is just simply what we call this thing about which we don't know anything, responsible for almost 85% of the gravity of the cosmos. We've known about the dark matter since 1930, but still, we are yet to discover the whole chapter about dark matter. We may think that humans have made so much exciting and great discovery and on the other hand, we know so little about our universe and how it works. The quest to find these answers is beginning now, a new generation of technology making it possible to see millions and billions of light-years in space. These technologies and a new way of looking at our universe will help us to answer some fundamental questions like who we are and what's the nature of the universe, and what is the stuff that makes us who we are. With this technology and discoveries one day we will be able to see not only detectable and things we can see but invisible things.

One day we will be able to reveal mysteries about the cosmos beyond our wildest dreams. The new quest is looking for this hidden universe. From the time Galileo looked at the sky first time till now we've been searching for answers, a revolution in technology and race to search these answers given us discoveries that have been revolutionary, earth-shattering, and profound. At each stage, we've pushed the boundaries of our universe a little further and further. Beyond our planet, beyond our galaxy and billions of galaxies like ours and virtually back to the big bang, who knows what we will find in the future.

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