Dark Matter

Ordinary matter is a very small part of all matter in the universe and the rest is dark matter. The ratio between ordinary matter and dark matter present in the universe is 1:5. Dark matter is not dark in reality, it is completely invisible. The lack of emission of light or energy makes it impossible for conventional detectors or sensors to detect it. The composition of dark matter can be the real culprit behind its elusiveness, believe scientists. The composition of dark matter is still a subject of speculation. Many scientists have opined that it is difficult to say whether the composition of dark matter is baryonic or non-baryonic. The point to be noted here is that ordinary visible matter is composed of baryons. Subatomic particles like protons, electrons, and neutrons are called baryons.

The significance of dark matter is huge as more than 80% of all matter in the universe is dark matter. The behavior of stars, galaxies, and planets can’t be explained without accepting the presence of dark matter and hence the assumption of the existence of dark matter despite it being unseen is understandable. The assumption that dark matter is composed of non-baryonic particles is gaining acceptance among scientists. WIMPS (weekly interacting massive particles) is the lead assumed candidate to be building blocks of dark matter. Its mass is believed to be 10 to 100 times of a proton. Other assumed candidates are neutrinos and neutralinos.

Antimatter is not dark matter

Unlike dark matter, the composition of antimatter is not subject to speculation. Antimatter is composed of the same particles that compose visible matter but carry an opposite electrical charge. These particles are called positrons and antiprotons. Unlike dark matter, antimatter can be manufactured in a lab. People tend to confuse antimatter with dark matter. If too many antiparticles existed in the universe then the existence of the universe itself would have been impossible as particles and antiparticles destroy each other when matter and antimatter collide. Obviously, too little antimatter exists in the universe. On the contrary, dark matter existing in the universe is about five times of visible matter existing in the universe.

The explanation for the assumption of the existence of dark matter

Dark matter is invisible and no one has seen it then why have scientists assumed that dark matter exists? The gravitational force exerted by objects made of matter is always proportional to their masses. Gravitational forces working in the universe seem to be disproportionate to the mass of visible matter present. This means some part of gravitational forces working in the universe is being exerted by matter that is not visible presumably. Such assumed matter is called dark matter.

It is believed that dark matter is spread across the universe but it seems dark matter concentration in galaxies is not uniform.