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The Ghost Surrounding Us


In my childhood, I was fond of reading fairy tales. I spent most of my time fantasizing about ghosts. Whenever I thought of some ghost passing through me, chills went down my spine. The fear disappeared as I grew up. Still, I think about it sometimes. Whether ghosts from fairy tales exist or not, there is a ghost passing right through us every time. Shocked? Yes, there is a ghost passing through us. The name of that ghost is dark matter.

In 1932, John Oort was studying orbital speeds of stars in galaxy when he noticed some irregularities in speeds. A year later, Swiss astronomer Fritz Zwicky viewed it when he noted inconsistency between the mass of visible matter and the calculated mass of a galaxy cluster called the ‘Cosizema Cluster’. The cluster calculated by Zwicky had 400 times more mass than it should have, based on what he saw with the help of telescope. The motion of the stars was too fast to be held by gravity if we count visible mass alone. If there wasn’t some extra mass causing an additional gravitational effect, the stars would fly apart and there would be no galaxies. Zwicky theorized that some invisible dark mass is present which doesn’t interact with other mass normally, but it has same gravitational effect as the normal mass. This discovery was worthy of Nobel Prize, but unfortunately, no one gave attention to this theory. Because finding concrete evidence of this elusive substance was incredibly difficult, Zwicky became laughing stock of the astronomical community.

The subject remained in the dark until in 1950 physicist Vera Rubin, a graduate student at Cornell University, saw that bodies at the furthest edges of galaxies didn’t move more slowly than those at the center did. According to Newton’s laws, if a group of objects is rotating about a central object, the objects apart from center will move with slow orbital speed and those which are closer to the center will have high orbital speed. But, this wasn’t the case. The stars in the outskirts of the galaxy had the same speed as those closer to the center. There was only one scientific explanation, the distant stars have more mass than expected. She theorized that something is present in the outskirts of galaxies causing these objects to move faster than expected. It had to be dark mass that Zwicky once speculated. Scientists continued to search for invisible mass but there was no practical evidence.

In 1973, at Princeton University, two physicists Jeremiah Ostriker and Jim Peebles tried computer simulations for our galaxy. Simulations suggested more mass to be present in the Universe than accounted for. The search for this invisible mass continued. With time, it led to the formation of the “dark matter theory.” Dark matter is hypothesized to account for gravitational effects that appear because of the invisible mass. Telescopes directly cannot see direct matter. It neither emits nor absorbs light or other electromagnetic radiation at any significant level. It is simply a matter that is non-reactant to light. The models of the dark matter are made through computer simulations. According to present calculations, dark

matter forms 84.5% of the total matter in the Universe. The most convincing evidence that dark matter exists comes from a particle physics detector attached outside the international Space Station. Its detector records the number of particles passing through it, their mass, speed, as well as direction.

Now that we know that dark matter does exist, what is it made of? Theories suggest that dark matter consists of yet to be found WlMPs. WIMPs are weakly interacting massive particles in particle physics. The Ice-Cube detector (Antarctic snow telescope) in the South Pole and CERN’s Large Hadron Collider (LHC) are searching for WIMPs. The problem with this theory is that dark matter doesn’t respond to any of the four basic forces of the Universe; the electromagnetic force, the weak force. the strong force. and the gravitation. There is a proposal to use dark matter as an energy source. If it becomes possible. it ‘ll be the greatest discovery of this century. The proposal has been given by physicists from two American universities. Our current technology can ‘t sends us far into the space. We can only put limited fuel into a spaceship. If an engine running on dark matter particle annihilation is made, travelling to other stars wouldn’t be a dream. Dark matter is present everywhere. so the spaceship will never run short of fuel. It is still a theory. though.

Discovery of dark matter particle will give us clues about the birth (and even death) of the Universe. Millions of dark matter particles pass through us every moment. Yet. they remain a mystery. There is a hope for the discovery of nature of dark matter within this decade. No one can foresee the future. but it is certain that finding evidence of the dark matter will provide us with a greater understanding about the nature of our Universe.



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