The Dark Matter: The Mysteries Of The Universe

Humans have been studying the universe for generations. Scientist, astronomers are constantly unraveling the mysteries of the universe. Until about 30 years ago astronomers were of the opinion that the universe was composed of "baryonic matter". What do we understand by this term? If we go by definition baryonic matter should only include protons, neutrons and all the objects that are composed of protons and neutron, take for example atomic nuclei, but it excludes thingssuch as electrons and neutrinos which are actually leptons the subatomic particles such as electron, muon or neutrino which are elementary particle of half-integer spin that cannot or rather do notundergo strong interactions.

So what is Dark Matter? It is a form of matter thought to account for approximately 85% of the matter in the universe. This Dark Matter also constitutesabout a quarter of the Universe's total energy density. Most scientists are of the opinion that Dark Matter is composed of non baryonic matter. Dark Matter is also considered as the hypothetical mass that is responsible for adding gravity to the galaxies and other celestial bodies.

The theoretical models of the composition of the universe as per scientists have been described as ~68% dark energy, ~27% dark matter, `5% normal matter. So what is Dark Matter after all? Firstly, it is dark and hence it isnot in the form of stars and other planets that we see. Secondly it cannot be in the form of dark clouds of normal matter like the onesmade up of the baryonic particles because we could have been able todetect baryonic clouds by their absorption of radiation passingthrough them. However, Dark Matter is not antimatter either. When antimatter annihilates with matter unique gamma rays are produced,and this does not happen in case of Dark Matter, hence it definitely does not fit the tag of antimatter.

The physicists are trying to categorize types of dark matter and searching for few possible explanations. Like the Dark matter could be small, weak and found everywhere and categorizing them as WIMPS or Weakly Interacting Massive Particles, or Big, dark and few which are categorized under MACHOS or Massive Astrophysical compact halo objects. The thirdoption being the chances of this entire hypothesis actually turningout to be incorrect. This also points out to the fact that it might completely change our idea about how gravity actually works to keepbig structures together. Scientist have been constantly testing and retesting Einstein’s theory of General Relativity to check forany tiny discrepancy that could actually give some wiggle room to explain dark matter without having to look for new kind of particlesor other objects , however, till now Einstein’s general relativity still holds strong.

By: Madhuchanda Saxena
Content: https://www.sciencealert.com/dark-matter