Context
Antimatter idea offers scientists clue to cracking cosmic mystery
About Antimatter
- Matter consists of subatomic particles that give it mass and volume.
- Protons and neutrons (baryons) are made up of quarks and gluons.
- Electrons and neutrinos (leptons) are other examples of subatomic particles.
- Antimatter is the counterpart to matter, with particles having reversed charge, parity, and time (CPT Reversal).
- For every particle in matter, there exists an antiparticle: e.g., antielectrons (positrons), antiprotons, antineutrons, antiquarks, etc.
- When matter and antimatter collide, they annihilate each other, converting into energy.
- Antimatter regions of the universe could theoretically exist, with the same physical and chemical properties as matter regions. However, they haven’t been observed in the universe.
- Antimatter Creation and Observations
- Antiparticles have been produced in particle accelerators, and anti-elements and anti-atoms have been created.
- Cosmic rays provide us with antiprotons, antielectrons, and even antinuclei.
- Potassium-40 decay in human bodies produces one antielectron (positron) every 20 seconds.
- The Big Bang and the Matter-Antimatter Asymmetry
- The Big Bang (13.8 billion years ago) is believed to have produced equal quantities of matter and antimatter.
- Today, antimatter is almost entirely absent in the universe, presenting one of the biggest mysteries in physics: Why is there so much matter and so little antimatter
- Theoretical Background on Antimatter
- An antiparticle is a particle with the same mass as its counterpart but an opposite charge (e.g., the positron is the antiparticle of the electron).
- The existence of antiparticles arises from quantum mechanics and special relativity.
Why Antimatter is Scarce
- Antimatter is detectable in certain cosmic phenomena but is extremely scarce on a large scale.
- Every proton and neutron in matter is composed of antiquarks.
- However, matter-dominated galaxies suggest an absence of significant antimatter in the observable universe.
- Early Universe Asymmetry:
- In the early universe, a small difference between protons and antiprotons allowed for the formation of matter as we know it.
- For every 1.7 billion proton-antiproton pairs, there was likely an extra unpaired proton, leading to the dominance of matter.
- Recent Discovery and Progress
- A 2024 paper suggested a loophole in the Standard Model to explain the matter-antimatter asymmetry.
- Quantum field theory allows for the variation of the masses of these new particles over time, which may have helped with the symmetry violation in the early universe.
Source:
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Previous Year Question
Consider the following statements:
1. Light is affected by gravity.
2. The Universe is constantly expanding.
3. Matter warps its surrounding space-time.
Which of the above is/are the prediction/predictions of Albert Einstein’s General Theory of Relativity, often discussed in media?
[UPSC Civil Services Exam – 2018 Prelims]
(a) 1 and 2 only
(b) 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (d)