Dark Matter – UPSC Prelims

Dark Matter:
  • Dark matter, though never detected, is believed to be present in the entire universe.
  • It is presumed that primordial black holes, those that were formed in the early age of the universe, are a source of dark matter. It was proposed by Professor Stephen Hawking.
  • It is believed that combined with dark energy, it makes up more than 95% of the universe.
  • Its gravitational force prevents stars in our Milky Way from flying apart.
  • However, attempts to detect such dark matter particles using underground experiments, or accelerator experiments including the world’s largest accelerator, the Large Hadron Collider (LHC), have failed so far.
Dark Matter and Dark Energy:
  • While dark matter attracts and holds galaxies together, dark energy repels and causes the expansion of our universe.
  • Despite both components being invisible, a lot more is known about dark matter, since its existence was suggested as early as the 1920s, while dark energy wasn’t discovered until 1998.
Dark Energy:
  • The Big Bang occurred nearly 15 billion years ago and expanded.
  • Earlier, astronomers believed that eventually the expansion of the Universe will slow down because of gravity and it will recollapse.
  • However, data from the Hubble Telescope suggested that the Universe’s expansion is accelerating.
  • The astronomers theorize that the faster expansion rate is due to a mysterious, dark force or energy that is pulling galaxies apart.
  • The term ‘dark’ is used to denote the unknown.
  • The following diagram reveals changes in the rate of expansion since the universe’s birth 15 billion years ago.

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