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Why the universe has less ‘antimatter’ than matter?


From UPSC perspective, the following things are important :

Prelims level : Matter, Anti-matter

Mains level : Formation of the universe and the Big Bang

This newscard is an excerpt from the original article published in DownToEarth.

Try this PYQ:

Q.The known forces of nature can be divided into four classes, viz, gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?

(a) Gravity is the strongest of the four

(b) Electromagnetism act only on particles with an electric charge

(c) Weak nuclear force causes radioactivity

(d) Strong nuclear force holds protons and neutrons inside the nuclear of an atom.

What is Antimatter?

  • Antimatter is the opposite of normal matter. More specifically, the sub-atomic particles of antimatter have properties opposite those of normal matter.
  • The electrical charge of those particles is reversed.
  • Antimatter was created along with matter after the Big Bang, but antimatter is rare in today’s universe.
  • To better understand antimatter, one needs to know more about the matter.
  • The matter is made up of atoms, which are the basic units of chemical elements such as hydrogen, helium or oxygen.

Their existence

  • The existence of antimatter was predicted by physicist Paul Dirac’s equation describing the motion of electrons in 1928.
  • At first, it was not clear if this was just a mathematical quirk or a description of a real particle.
  • But in 1932 Carl Anderson discovered an antimatter partner to the electron — the positron — while studying cosmic rays that rain down on Earth from space.
  • Over the next few decades’ physicists found that all matter particles have antimatter partners.
  • Scientists believe that in the very hot and dense state shortly after the Big Bang, there must have been processes that gave preference to matter over antimatter.
  • This created a small surplus of matter, and as the universe cooled, all the antimatter was destroyed, or annihilated, by an equal amount of matter, leaving a tiny surplus of matter.
  • And it is this surplus that makes up everything we see in the universe today.

Studying the difference between matter and antimatter

  • A Quark is a type of elementary particle and a fundamental constituent of matter.
  • Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.
  • The behaviour of quarks, which are the fundamental building blocks of matter along with leptons, can shed light on the difference between matter and antimatter.
  • Since they are unstable, they will “decay” — fall apart — into other more stable particles at some point during their oscillation.

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