International Space Agencies – Missions and Discoveries

What is Dark Energy?


From UPSC perspective, the following things are important :

Prelims level: Dark Energy, Dark Energy

Mains level: Theory of expansion of the universe

Last week, an international team of researchers has made the first direct detection of dark energy.

About the Project

  • The XENON1T experiment is the world’s most sensitive dark matter experiment and was operated deep underground at the INFN Laboratori Nazionali del Gran Sasso in Italy.
  • The finding also suggests that experiments like XENON1T, which are designed to detect dark matter, could also be used to detect dark energy.

What is Dark Energy?

  • Dark energy is an unknown form of energy that affects the universe on the largest scales.
  • The first observational evidence for its existence came from measurements of supernovae, which showed that the universe does not expand at a constant rate; rather, the expansion of the universe is accelerating.
  • Prior to these observations, it was thought that all forms of matter and energy in the universe would only cause the expansion to slow down over time.
  • Measurements of the cosmic microwave background suggest the universe began in a hot Big Bang, from which general relativity explains its evolution and the subsequent large-scale motion.
  • Without introducing a new form of energy, there was no way to explain how an accelerating universe could be measured.

Does it exist?

  • Since the 1990s, dark energy has been the most accepted premise to account for the accelerated expansion.
  • As of 2021, there are active areas of cosmology research aimed at understanding the fundamental nature of dark energy.

Dark energy Vs Dark matter

  • Everything we see – the planets, moons, massive galaxies, you, me, this website – makes up less than 5% of the universe.
  • About 27% is dark matter and 68% is dark energy.
  • While dark matter attracts and holds galaxies together, dark energy repels and causes the expansion of our universe.


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