Dark Matter

Being a science enthusiast, you may have come across the word dark matter, or maybe you already have a theory of your own. Well, let’s take a deeper dive into the dark matter, and let’s find out what is dark about it. Dark matter may be defined as a form of matter considered to be approximately 95 percent of the matter of the universe. After several scientific studies, it is assumed that dark matters are about 27% of its total mass-energy density or about 2.241×10⁻²⁷ kg/m³. In this article, we are going to discuss dark matter theory, the meaning, and its discovery in detail. 

The Discovery

The existence of the ‘missing mass’ or ‘dark matter’ was first proposed by Swiss American astronomer Fritz Zwicky. In 1933, he discovered that only 1 percent of the mass of all the stars in the Coma cluster is needed to keep the galaxies from escaping the gravitational pull of the cluster. In the 1970s, this theory was approved upon observations by American astronomers, Vera Rubin and W. Kent Ford. They observed, within a galaxy, the mass of the visible stars is only about 10 percent that is required to keep the stars orbiting the center of the galaxy. To account for the slightly increasing (or constant) orbital velocity of the stars, the mass of the galaxy within the orbit of the star must be increasing linearly with the distance of the center of the galaxy from the stars.

Dark Matter Meaning

There are several observations to imply the presence of dark matter such as gravitational effects. Until and unless more matter is present beyond our observations, they are not explained by accepted theories of gravity. Dark matters are substances that do not absorb, reflect or emit light and hence not visible. Dark matter is a non-interacting substance, and this is what makes it dark and mysterious. It is considered that about 5 percent of the universe is known to us. The rest 95 percent includes about 27 percent of dark matter and 68 percent of dark energy. We are pretty sure of the existence of dark matter, but still to find out what dark matter is and how it exactly works.

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Dark Matter Theory

The existence of dark matter can be confirmed upon the discoveries of Swiss American astronomer Fritz Zwicky and Jan Oort. According to them, the motion of the galaxies and nearby stars of the Coma clusters violates the expected motions according to Newton's law of gravity. But still, any direct evidence of the presence of the dark matter is not encountered.

According to NASA, we know more about what a dark matter isn’t than what it is. Dark matter cannot be seen in the form of our known cosmic objects such as stars and planets. It is not in the form of baryons as we know we would be able to detect baryonic clouds by their absorption of radiation passing through them. Again, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter collides with another matter. Based on how many gravitational lenses we see, we can rule out large galaxy-sized black holes. High concentrations of matter cause the bending of light, which passes near them from objects further away. But we cannot see enough lensing events so that it can suggest that such objects have the required 25% contribution of dark matter. There must be several theories about the existence of dark matter, but no direct evidence is acquired till now. 

Did You Know?

Dark matter is a subject that gives us goosebumps, thinking about the fact that it is yet to be discovered. The Discovery of dark matter and dark energy would give us a better picture of the universe and how it exactly works. Here are some facts about dark matter. The substance of dark matter doesn't interact with light and that is why dark matter is invisible. Though dark matter cannot be seen, it can be felt for its powerful cosmic impact. It is predicted that the powerful impact of dark matter binds the galaxies together. According to some research, dark matter might be cold in nature. Also, dark matter might not have any existence.