MCQ Detailed View

High-energy subatomic particles that come from outside the Earth and strike our atmosphere are called cosmic rays. They were first discovered in the early 20th century and remain one of the most fascinating topics in modern physics and astronomy.

Cosmic rays are not a single type of particle but a mixture. The majority of them are protons (about 90%), while others include helium nuclei (alpha particles), electrons, and a small fraction of heavier atomic nuclei. These particles travel through space at nearly the speed of light and carry extremely high energy, much greater than what human-made particle accelerators can usually achieve.

The origin of cosmic rays is linked to energetic astrophysical events. Many are believed to come from supernova explosions, which are the deaths of massive stars. Others may come from active galactic nuclei, black holes, or even distant galaxies. When cosmic rays enter Earth’s atmosphere, they collide with air molecules and produce a shower of secondary particles such as pions, muons, and neutrinos. This is why scientists study cosmic ray interactions using detectors on the ground, in balloons, and on satellites.

It is important to note that cosmic rays are not electromagnetic radiation like light or X-rays. Instead, they are actual particles with mass and charge. Their interaction with Earth’s magnetic field can affect their path, which is why we observe differences in cosmic ray intensity at the poles and the equator.

Cosmic rays also have practical importance. They contribute to natural background radiation on Earth, and studying them helps scientists understand both the universe and fundamental particle physics. Technologies like particle detectors and even early discoveries of new particles, such as the muon, came from cosmic ray research.

In summary, the high-energy subatomic particles that arrive from outer space are called cosmic rays, making them a crucial concept in physics, astrophysics, and space science.