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A vast majority of people believe that in space, beyond the Earth’s atmosphere, there is nothing. Mere emptiness. And it may seem like that at first. But that is not at all true. What if I told you, that in interstellar space, in the middle of nowhere, there is a type of foreign substance that is different from the matter around us? This may sound like an idea for a science fiction movie, but this is completely true.
The “thing” which I am referring to is called ‘dark matter’, and it is definitely more than just science fiction.
What is dark matter?
Dark matter is a “substance” of sorts. But it is no ordinary substance. Its characteristics do not match any known form of matter. It would be inaccurate to even call it a form of matter. It cannot be seen with the human eye. It cannot be touched. It cannot be felt. We know very little about it. We don’t even know what it is made up of. But before diving into this ocean of uncertainty, we must ask ourselves — How do we even know it exists?
How do we know it exists?
The term ‘dark matter’ was first coined in the 1930s, when astronomer Fritz Zwicky was observing the Coma Cluster (A cluster is a group of galaxies located within close proximity of one another). However, his observations deviated from his calculations. He observed that the galaxies were moving much faster than they were supposed to. No scientific theory or law known to man could explain this invisible force, which was causing the galaxies to move much faster than expected.
It would go on to take almost another half a century, for the existence of dark matter to finally be proven.
In the 1970s, astronomer Vera Rubin was observing the Andromeda Galaxy (the closest galaxy to our galaxy, i.e. Milky Way), which is a spiral galaxy, i.e. it is in the shape of a spiral. The expected observation was that the stars located near the centre of the galaxy would orbit faster around it, and the stars located further away from the centre would orbit comparatively slower. However, the actual observation was that the stars located near the centre and further from the centre were orbiting at nearly the same speed. The only reasonable explanation is that there is something between the stars that we cannot see, but it is there.
This gave birth to the science of dark matter.
What we know about it
Dark matter is called what it is because we know very little about it. However, there is no longer any doubt about its existence. There is, in fact, more of it in the universe than ordinary matter! Calculations have shown that there is at least 5 times as much of it in the universe in comparison to normal matter.
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Dark matter detection
Detecting dark matter is a big challenge due to several reasons.
It does not react to light, or any type of electromagnetic rays for that matter, making it
impossible to see.
It cannot be touched, as it can simply pass through normal matter. It does not react with normal matter. It doesn’t even react with itself. However, it does bend light, as it has a lot of gravitational force.
Particle accelerators are used to study dark matter and its characteristics. They basically work by bombarding particles together at massive speeds (near-light speed) and simulate an environment similar to that of space. They are situated underground to prevent any bombardment of cosmic rays (high-energy particles from space). The most prominent of these particle accelerators is the Large Hadron Collider (LHC) situated at Geneva in Switzerland.
Misconception
A common misconception, which even I had, was that dark matter and anti-matter refer to the same thing. However, they are 2 distinct fields of study. Dark matter does not react with normal matter; and its existence has been proven. Whereas, anti-matter and normal matter annihilate upon contact. There is no proof of the existence of anti-matter, and several hypotheses remain unproven.
What is dark energy?
The study of dark matter and dark energy go hand-in-hand. In the 1920s, astronomer Edwin Hubble (the Hubble Space Telescope is named after him) discovered that the universe is not stationary. In fact, it is constantly accelerating and expanding. Expansion of the universe has been proven, and it causes galaxies to move further and further away from each other. However, the cause of this expansion was unknown at the time. The energy which causes this expansion is called dark energy.
Its effect is opposite to that of gravity, as it pushes things apart, rather than attracting them. Just like dark matter, we have very little knowledge of dark energy at this time. However, we do know that dark energy constitutes about 68% of the universe, whereas 27% is constituted by dark matter, leaving just 5% of ordinary matter. Ordinary matter, is truly, the tip of the iceberg.
Einstein’s “blunder”
During Einstein’s research of the universe, he believed that there had to be a force opposing the force of gravity, in order for the universe to be stable. He concluded that this value had to be a constant, and also included the constant in a few of his equations. However, when Edwin Hubble discovered the expansion of the universe, Einstein scrapped the constant and later went on to call it his “greatest blunder”. However, after the discovery of dark energy (after Einstein’s death), many scientists said that Einstein’s only blunder was to call his constant a blunder. His only mistake was to assume that he had made a mistake.
Conclusion
Dark energy and dark matter, both are somewhat intangible topics, considering current technology and research. However, looking at the current rate of technological advancement, we may just find out something new about it in the near future. When do you think the next breakthrough in this field will be? Let us know in the comments below.
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