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  • 11 December, 2023

  • 2 Min Read

Cosmic Expansion

Euclid telescope observed that galaxies belonging to the Perseus Cluster and others move further away showing the expansion of universe.

Euclid telescope, designed and built by European Space Agency (ESA) to explore dark matter and dark energy which are thought to make up 95% of the universe.

  • Cosmic expansion – The universe was born with the Big Bang as an unimaginably hot, dense point and at 10-34 of a second of big bang, it had an incredible burst of expansion known as inflation which expanded faster than the speed of light.
  • Expansion rate – After inflation, it continued at a slower rate as the matter in the universe pulled on itself via gravity.
  • About 5 or 6 billion years after the Big Bang, dark energy began speeding up the expansion again that continues even today.

Measuring the rate of expansion

  • It is calculated using 2 models such as Lambda-cold dark matter (ACDM) and Modified Newtonian Dynamics (MOND).
  • Lambda-cold dark matter (ACDM) – It is based on observation of the light left over from the Big Bang called as cosmic microwave background (CMB).
  • Hubble’s constant – A value to predict how fast an astronomical object (star or galaxy) is moving away from us.
  • It is about 43 miles (70 km) per second per Megaparsec meaning, a galaxy gains about 50,000 miles per hour for every million light years it is away from us.
  • Hubble tension – It refers to the discrepancies in the expansion rate when measured using nearby galaxies and supernovas (exploding stars).
  • It is 10% larger than when we predict it based on the CMB.
  • Modified Newtonian Dynamics (MOND) – It suggests that Newton’s law of gravity breaks down when the gravitational pull is very weak and the structure (such as galaxy clusters) would grow faster.
  • Bulk flow – It is the average velocity of matter in a given sphere, which varies with the radius of the sphere.

The universe’s expansion makes galaxies move away from each other. The further away they are from us, the more quickly they move.


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