Dark matter is a mysterious non-luminous element that makes up the overwhelming bulk of the cosmos. Even though dark matter’s gravitational effects have been studied for decades, no one knows exactly what it is.

Who discovered dark matter?

In the late 1800s, astronomers started talking about things that couldn’t be seen. They talked about things like faint stars and gas and dust. Researchers started to figure out how much the object weighs in a 2018 review of Modern Physics. Most people thought that this mysterious material was just a small fraction of the total mass in the universe, but it wasn’t.

During the 1930s, Fritz Zwicky noticed that distant galaxies were spinning far faster than should be possible based on the things that could be seen with telescopes at the time. When he was writing in Helvetica Physica Acta that same year, he said that “we would be surprised to find that dark matter is present in a much bigger proportion than light matter.”

Many people didn’t believe Zwicky’s findings until 1970, when two scientists started looking at stars in the outer parts of a galaxy close to our own, the Andromeda galaxy. This happened in galaxies all over the universe. Astronomers found that these stars were moving too quickly as if an unknown force was pulling on them and pushing them along.

Astronomers guessed that dark matter was made up of things that were small and didn’t give off enough light to be seen by telescopes, but no one was sure what exactly made up this invisible material. In the 1990s, a satellite called the Wilkinson Microwave Anisotropy Probe (WMAP) took measurements. The results showed that dark matter outweighed visible matter five to one.

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Why dark matter remains a mystery?

Telescope surveys could never account for the huge amount of material there. Astronomers think that dark matter is made up of subatomic particles that don’t have the same characteristics as protons and neutrons, which people can see.

It’s called a Weakly Interacting Massive Particle or WIMP. This is the most common type of dark matter. No one has been able to find any evidence that these imaginary things exist in the Standard Model of particle physics. There are a lot of similarities between WIMPs and the phantom neutrino. The only difference is that WIMPs would be 10–100 times heavier than the proton. Neutrinos aren’t known to be as heavy as electrons, but they are a lot lighter than them.

They would interact with gravity and the weak nuclear force, which breaks down radioactive atomic nuclei. There are only two basic forces that WIMPs could interact with. Electromagnetism, the force that makes light, does not affect the dark matter particles because they are not charged.

Scientists have built huge detectors and buried them in the ground to protect them from cosmic rays to find WIMPs. So far, no experiment has shown that WIMPs exist. After this failed experiment, scientists are worried that they’re on a never-ending particle-hunting spree.

According to a study in the Proceedings of the National Academy of Science, the axion is a newer dark matter candidate with a mass of a millionth or even a billionth of an electron. This has led some scientists to pay more attention to the axion. Some people think these speculative particles might explain why neutrons can sense magnetic fields but not electric ones.

In June 2020, it was said that the Gran Sasso National Laboratory in Italy had found a small but surprising signal that might be caused by the presence of axions in a detector that was meant to capture WIMPs. The scientific community was shocked by the findings, but they haven’t been proven by other tests yet.

Is dark matter even real?

There are still a lot of academics who don’t know what dark matter is. Some theorists have wondered if there is a whole dark area of the universe, with many particles and dark forces that only affect dark matter, like the subatomic intricacy we see in the visible universe.

Another group of researchers thinks that dark matter isn’t real at all. Some people believe in a theory called MOND, or “modified inertia,” which says that when things are big, gravity behaves in a different way. This explains why stars and galaxies move in the way they do. But most scientists aren’t sure that making a big change to known physics, which would also change how we think about many things in the world, is necessary.

Dark matter is not, to anyone’s knowledge, linked to dark energy, which is the unknown force that makes the universe expand. The word “dark,” which is often used as a placeholder by scientists, is used by both of them, which makes sense.

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