Dark Energy

• 27 Sep 2021

Why in News

Recently, an international team of researchers made the first direct detection of dark energy. The experiment named XENON1T, is the world’s most sensitive dark matter experiment and was operated deep underground at the INFN Laboratori Nazionali del Gran Sasso in Italy.

• Dark energy is the mysterious form of energy that makes up about 68% of the universe, and has intrigued physicists and astronomers for decades.

Key Points

• About the Experiment:
  
  • The XENON1T is a dark matter research project, operated at the Italian Gran Sasso National Laboratory.
  • It is a deep underground research facility featuring increasingly ambitious experiments aiming to detect dark matter particles.
  • The experiments aim to detect particles in the form of Weakly Interacting Massive Particles (WIMPs) by looking for rare interactions via nuclear recoils in a liquid xenon target chamber.
• Other Dark Matter and Energy Experiments:
  
  • LUX-Zeplin – a next generation dark matter experiment located at the Sanford Underground Research Facility, US.
  • PandaX-xT – project at China Jinping Underground Laboratory.
• 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.
• About 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.

• Possible Explanations of Dark Energy:
  
  • Property of Space: Albert Einstein was the first person to realize that empty space is not nothing.
    
    • One version of Einstein's gravity theory, the version that contains a cosmological constant, implies that "empty space" can possess its own energy.
    • Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the universe to expand faster and faster.
  • Quantum Theory of Matter: Another explanation for how space acquires energy comes from the quantum theory of matter.
    
    • In this theory, "empty space" is actually full of temporary ("virtual") particles that continually form and then disappear.
  • Fifth Fundamental Force: There are four fundamental forces in the universe, and speculative theories have proposed a fifth force – something that can’t be explained by the four forces.
    
    • To hide or screen this fifth force, many models for dark energy use special mechanisms.
    • Some theorists have named this "quintessence," after the fifth element of the Greek philosophers.
  • However, none of the theories have been proved. Due to this, Dark energy has been noted as “the most profound mystery in all of science”.

Note

• The Four Fundamental Forces of Nature are Gravitational force, Weak Nuclear force, Electromagnetic force and Strong Nuclear force.

Source: IE