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Ultra-high-energy cosmic rays: How amazingly energetic are they?
Cosmic rays, or celestial particles, are high-energy particles or particle groups that travel through space at nearly the speed of light. They mainly exist in the form of protons or atomic nuclei. Their sources include the Sun, regions beyond our own Milky Way, and distant galaxies. When these cosmic rays encounter the Earth's atmosphere, a series of secondary particles are produced. Some reach the surface, but most are reflected back into space by the Earth's magnetosphere.
The discovery of cosmic rays can be traced back to 1912. Victor Hess discovered this phenomenon in a balloon experiment and won the Nobel Prize in Physics in 1936.
In recent years, advances in technology, especially since the launch of the first artificial satellites in the late 1950s, have made direct measurements of cosmic rays feasible. When high-energy particles from the universe hit the Earth's atmosphere, they trigger a series of reactions and produce a large number of secondary particles, including microns and mesons. The exploration of these particles is of great significance to current developments in astrophysics.
The energy source of cosmic rays
The energy of cosmic rays has attracted widespread attention in the scientific community, especially due to their impact on microelectronics and potential damage to the living environment. In particular, the energy of those ultra-high-energy cosmic rays can reach 3 × 10^20 eV, which is consistent with the design energy of particles accelerated by the Large Hadron Collider (14 TeV, or 1.4 × 10^13 eV ), which is almost 21 million times higher.
The highest-energy known ultra-high-energy cosmic rays, such as events called OMG particles, have energy equivalent to the kinetic energy of a baseball traveling at 90 kilometers per hour (56 mph).
These cosmic rays come from various sources, and scientists believe that supernova explosions may be an important source of cosmic rays. In addition, high-energy particles from active galactic nuclei are also potential sources of cosmic rays.
The composition of cosmic rays
Of the main cosmic rays, about 99% are nuclei with the electron shell removed, and about 1% are independent electrons. Of these, about 90% are protons, 9% are helium nuclei (also called alpha particles), and the remaining 1% are nuclei of heavier elements, called HZE ions. This ratio varies with the energy range of cosmic rays, with a very small proportion being stable antimatter particles such as positrons or antiprotons.
The history and discovery process of cosmic rays
After Henri Becquerel discovered radioactivity in 1896, it was generally believed that ionization in the atmosphere came only from radioactive radiation from terrestrial elements. However, in 1909, Theodore Wolfe's experiments using high-altitude balloons showed that the intensity of radiation actually increases with increasing altitude, a discovery that eventually led to the in-depth study of cosmic rays.
In 1912, Hess's balloon experiment confirmed that high-energy radiation does not come only from the sun, but from space. This discovery changed our understanding of cosmic rays.
Types of cosmic rays
Cosmic rays can be divided into two main types: galactic cosmic rays (high-energy particles originating in the Milky Way) and extragalactic cosmic rays (emanating from outside the Milky Way). Of both types, high-energy particles caused by the sun are also thought to be an important source, but most references to cosmic rays refer to fluxes from outside the solar system.
With the development of science and technology, our research on cosmic rays continues. Especially in the exploration of ultra-high-energy cosmic rays, various experiments are expected to reveal more mysteries about the universe.
In this process of exploring the unknown, questions about the source and energy of cosmic rays still arouse our curiosity, which raises a question worth thinking about: Will we be able to reveal the deeper secrets of cosmic rays in the future?
