International Space Agencies – Missions and Discoveries

What is Dark Matter?


From UPSC perspective, the following things are important :

Prelims level : Dark Matter

Mains level : Dark Matter, Black Holes

Space scientists from the University of Sussex have found a new way to know more about dark matter. They have narrowed down the range of masses within which particles that could make up dark matter may lie in.

What is the news about?

  • Around 95 % of the Universe is unknown to human beings.
  • It is often referred to as dark which has nothing to do with the colour of any substance but to do with the unknown nature of cosmic entities known as dark matter and dark energy.

Trending in news these days is the Quantum Technology. (as it used to be until last year were- the Internet of Things (IoT) CSP 2019, Artificial Intelligence (AI) etc.)

Must read all this news in a loop:

  1. National Mission on QC
  2. Quantum Coin
  3. Quantum Supremacy
  4. Quantum Entanglement

What is Dark Matter?

  • Dark matter is composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation.
  • Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe and about a quarter of its total mass-energy density or about 2.241×10−27 kg/m3.

What does the research say?

  • Scientists carried out the research using quantum gravity, a field of study that tries to combine two of Einstein’s concepts — quantum physics and general relativity theory of gravity.
  • This is the first time anyone has thought of using what we know about quantum gravity to calculate the mass range for dark matter.
  • Their research shows that the dark matter particles can neither be super light nor super heavy unless there is a force acting on it that is yet unknown.

Quantum gravity: The concept

  • Quantum gravity is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics.
  • Quantum mechanics is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles.
  • Here quantum effects cannot be ignored, such as in the vicinity of black holes or similar compact astrophysical objects where the effects of gravity are strong, such as neutron stars.

Significance of the findings

  • This might help in finding out more about this mysterious force. There are currently four known forces in the Universe — gravitational, electromagnetic, weak and strong.
  • Scientists estimate that roughly 68 per cent of the Universe is made up of dark energy which is responsible for the accelerated expansion of the Universe.
  • Another 27 per cent is a dark matter whose existence was inferred from the observation that ordinary matter in galaxies, including the Milky Way, is far less than that required by gravity to hold the galaxies together.

Why does the ‘Dark Matter’ matter?

  • Dark matter’s gravitational effects are also necessary to explain the motions of clusters of galaxies and the structure of the entire Universe at the largest scale.
  • On smaller scales, dark matter is too diffused to impact the motion of the Solar System, Earth or the origin and evolution of humans in any significant way.
  • But the nature of that dark matter is still unclear. It is most likely made of particles that do not couple to light because of which humans cannot see them.

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