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Dark Matter

GS Paper-3

Syllabus: Science and Technology

 

Source: The Hindu

Context:

One of the most sensitive dark matter detector experiments named LUX-ZEPLIN (LZ) in the U.S.A, has been used for finding evidence of dark matter in the universe.

 

What is dark matter and why is it so elusive?

All interactions in the universe are a result of four fundamental forces acting on particles — strong nuclear force, weak nuclear force, electromagnetic force and gravitation.

Dark matter is particles that do not have a charge — which means they do not interact through electromagnetic interactions.

  • dark”: because they do not emit light.
  • matter”: because they possess mass like normal matter and hence interact through gravity.

Dark matter is elusive because: Gravitational force is extremely weak. A particle that interacts so weakly becomes rather elusive to detect.

 

Fig: Composition of Universe

 

 

Current Affairs

 

Evidence for Dark Matter:

  • By observing the rotation of galaxies: there are discrepancy changes in how stars revolve around the galaxy centre than what should be the ideal path. This has been contributed to the presence of dark matter along the path.
  • By the observations of the Bullet Cluster of galaxies: The Bullet cluster is formed through the merging of two galaxy clusters. The merger didn’t take place as per the observable calculations, signifying the presence of another massive matter particle, ‘the dark matter’.

Dark matter particles are made up of: No definite answer is known, but scientists say:

  • neutrino’ would have been an excellent candidate if it had been more massive, but being too light, it doesn’t fit the bill.
  • Other postulated entities include the supersymmetric partner of the Z boson, a particle that mediates the electro-weak interaction.

 

Dark energy: It is a hypothetical form of energy that exerts a negative, repulsive pressure, behaving like the opposite of gravity.

  • It is causing the rate of expansion of our universe to accelerate over time, rather than to slow down. That’s contrary to what one might expect from a universe that began in the Big Bang.

 

Current Affairs

Did you know about the XENON1T experiment?

  • It is the world’s most sensitive dark matter experiment and was operated deep underground at the INFN Laboratori Nazionali del Gran Sasso in Italy.
  • It uses the dual-phase (liquid/gas) xenon technique and is located underground at the Laboratory Nazionali del Gran Sasso of INFN, Italy.

 

Insta Links

What are dark energy and dark matter?

Practice Questions

  1. In the context of modern scientific research, consider the following statements about ‘IceCube’, a particle detector located at the South Pole, which was recently in the news:
  1. It is the world’s largest neutrino detector, encompassing a cubic kilometre of ice.
  2. It is a powerful telescope to search for dark matter.
  3. It is buried deep in the ice.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

Answer: D

The IceCube Neutrino Observatory is a neutrino observatory constructed at the Amundsen–Scott South Pole Station in Antarctica. The project is a recognized CERN experiment. Its thousands of sensors are located under the Antarctic ice, distributed over a cubic kilometre.