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The Mystery of Cosmic Rays: How Do They Travel Through Space?
In the vast universe, countless mysterious particles silently pass through space and reach the earth. These particles are called cosmic rays. Cosmic rays are high-energy particles or clusters of particles, mostly composed of protons or atomic nuclei, that move at nearly the speed of light. Their sources are found throughout the Sun, outside our galaxy, and in galaxies beyond. Among them, when cosmic rays hit the Earth's atmosphere, they produce a series of secondary particles. Some of these particles can reach the surface, although most are deflected by the Earth's magnetic field or the heliosphere before entering the ground.
The discovery of cosmic rays began in 1912. This achievement was achieved through a balloon experiment by Victor Hess, for which he won the Nobel Prize in Physics in 1936.
The composition and properties of cosmic rays
About 99% of primary cosmic rays are naked nuclei, meaning they do not have an electron shell. The composition of these primary cosmic rays is mainly protons (about 90%), alpha particles of helium nuclei (about 9%), and nuclei of other heavier elements (about 1%). After colliding with the atmosphere, cosmic rays can quickly produce large amounts of secondary particles such as gluons, muons, and neutrinos. Especially at lower altitudes, the neutron content of cosmic rays can reach 40% to 80%. It is worth noting that muons can penetrate the atmosphere directly to the ground, which makes their ionization effect on the ground atmosphere an important clue for scientists to track cosmic rays.
The energy of cosmic rays
The energy range of cosmic rays is extremely wide, and the energy of the most extreme ultra-high-energy cosmic rays can reach 3 × 10^20 eV, which is 210,000 times higher than the energy of particles accelerated by the Large Hadron Collider. These high-energy cosmic rays mainly come from active galactic nuclei and supernova explosions, but the energy distribution of most cosmic rays is around 300 MeV. The formation mechanism of these energies is still a hot topic in current physics research.
History of cosmic rays
The history of cosmic rays dates back to the early 20th century, when Henry Beckere discovered radioactive substances. With the measurement of ionization rates at different altitudes, scientists gradually discovered that the ionization rate in the atmosphere increased with altitude, which promoted Hess's discovery. In 1912, he used a balloon to carry an improved ionization meter for experiments and found that the radiation intensity at high altitudes was significantly higher than at the ground. This discovery completely changed people's understanding of cosmic rays and laid the foundation for subsequent research.
Sources of cosmic rays
The cause of cosmic rays is still one of the focuses of research by scientists. Early hypotheses included supernovae, active galactic nuclei, quasars and gamma-ray bursts as possible sources. Scientists' understanding of these sources has improved significantly in recent years. In 2013, research showed that supernovae are an important source of cosmic rays, with each explosion producing cosmic rays equivalent to 3 × 10^42 to 3 × 10^43 Joules. However, the true source ratio remains to be further explored and experimented with.
Types of cosmic rays
Based on their origin, cosmic rays can be divided into two major categories: galactic cosmic rays and supergalactic cosmic rays. Most cosmic rays exist as primitive cosmic rays, particles that originate primarily from various astrophysical processes. After interacting with the Earth's atmosphere, secondary particles such as photons, hadrons and leptons are produced. These secondary particles serve as branches of cosmic rays, further enriching the structure of cosmic rays.
How does cosmological research advance our understanding of these mysterious particles?
