Matters that we know such as planets, stars, galaxies, trees, rocks, etc they are only 5% of the universe. About 27% is dark matter and 68% is dark energy. Both dark matter and dark energy are invisible to us. Dark matter is made up of such particles that do not absorb, reflect, or emit light, that is why they cannot be seen directly nor be detected by observing electromagnetic radiation.
So, how do we know that dark matter exists? What is it made of? What research has been done about it? If all these questions come to your mind and you want to know about them, then this article is for you. Today, I am going to unlock the details of dark matter. In this article, you will know -
1. What is dark matter?
2. What is dark energy?
3. Dark matter research
What is dark matter?
We already know that dark matter is made up of such particles that do not absorb, reflect, or emit light, that is why we cannot see it directly nor be detected by observing electromagnetic radiation such as x-rays or radio waves. But it covers about 27% of the universe so it is even more important to know about this matter.
Over the past few years, we have found from research that the gravitational attraction of all matters present in the universe is not strong enough to make galaxies and other complex structures. If the gravitational attraction not strong enough, today's stars would be scattered all over the universe instead of coming together as galaxies, but that is not the case.
This means that there is some material that maintains the existence of galaxies in the universe. Because such material is not visible to us, it has been named as Dark Matter. But what exactly is this dark matter and how is it?
Unfortunately, we have not found any clue so far that we can know what is the dark matter and how it works. Till now we only know that it definitely exists in the universe because it reacts with the action of gravity. Because it has some effect on objects that is why scientists have pretty sure that it exists. They study dark matter by looking at its effects on visible objects.
According to Albert Einstein's theory of general relativity, huge and heavy celestial bodies such as black holes distort space and time and also turn the direction of light. Dark matter in the universe is a type of matter that divert the direction of light, which indicates their presence. This process is called gravitational lensing. It acts like a natural lens, which helps us to see the distant galaxies.
Dark matter is probably made up of a complex and unique matter that does not react with any kind of substance and light. We know that dark matter is not antimatter because antimatter reacts with normal substances to produce gamma rays. We also know that dark matter is not made up of black holes as it is present in large quantities. It is not even a dark cloud made of ordinary materials, so what can it be made of?
Most scientists believe that it may be made of nonbaryonic material. All the substances we know so far, such as electron, proton, and neutron, all come in the baryonic matter. This means that dark matter is made up of such particles that we do not yet know.
The discovery of such particles can take our science forward many times. According to scientists, the particles that they are searching for are named WIMPs (Weakly Interacting Massive Particles).
Their mass is 100 times the mass of a proton. But they do not react with ordinary particles, due to which it is quite difficult to detect them. Neutralinos are also a potential candidate that heavier than neutron but slow in nature. But such particles have not been seen yet.
Some scientists even believe that dark matter is a group of matters of galaxies that are invisible and the law of physics works differently there. In spite of all this, we have been able to gather very little information about Dark Matter.
This means we still have many questions that are yet to be answered. And all the theories that we have about Dark Matter are still the only theories that might solve these topics in the future.
What is dark energy?
Dark energy occupies about 68% of the universe. It appears to be associated with the vacuum in space. It is evenly distributed throughout the universe, not just in space but also in time. In other words, its effects do not mix with the expansion of the universe.
If we talk about its gravitational force, then the dark energy has no local gravitational effect but has a global effect on the universe as a whole. This leads to a repulsive force that helps to accelerate the expansion of the universe.
The rate of expansion and its acceleration can be measured by observing the expansion of the galaxy with the Hubble Telescope. These measurements, along with other scientific data, have confirmed the existence of dark energy which provides an estimate of how much of this mysterious substance exists.
Dark matter research
As we already know that dark matter is invisible to us. They don’t emit, reflect, or absorb light or any type of electromagnetic radiation such as x-rays or radio waves. Dark matter cannot be detected directly, because all of our observations of the universe, except the detection of gravitational waves, involve the capture of electromagnetic radiation in our telescopes.
Dark matter demonstrates some measurable gravitational effects on huge structures in the universe such as galaxies and clusters of the galaxy. That is why, astronomers were able to map the distribution of dark matter in the universe, even though they could not see it directly. There is currently a huge international effort to identify the nature of dark matter.
To solve the problem of this mysterious substance, scientists have created complex and sensitive detectors of advanced technology. Scientists believe that this dark matter might be composed of non-baryonic subatomic particles which are completely different from what scientists call baryonic matter (made of ordinary atoms built of protons and neutrons).
This hypothesized non-baryonic sub-atomic particles that scientists are talking about are called WIMPs (Weakly Interacting Massive Particles). Although a theory called supersymmetry predicts the existence of particles with properties similar to WIMPs. But after searching for such particles repeatedly, nothing was found.
Very famous experiments with the Large Hadron Collider (LHC) to detect the expected presence of supersymmetry have completely failed to find it. Different types of detectors have been used to detect WIMPs. The most sensitive detector ever built is the XENON1T to detect it but so far no evidence has been found that these substances exist. However, the search for this type of particle is still going on.
But there is still enough observational evidence that proved dark matter exists such as Galaxy rotation curves, Velocity dispersions, Galaxy clusters, Gravitational lensing, Cosmic microwave background, and Structure formation, etc.
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