Abstract
Primary Cosmic Rays (CRs) are fully ionized atomic nuclei and other particles accelerated at astrophysical sources and reaching the Earth. In this book, usually we indicate with the acronym “CRs” protons and nuclei in the cosmic radiation. The electron, \(\gamma \)-ray, and neutrino components of CRs will be always specified. The discovery of CRs (Sects. 2.1 and 2.2) made it possible the verification of both the Einstein relation between particle’s mass and energy and the Dirac theory about the existence of antimatter (Sect. 2.3). Particle detectors play (Sect. 2.4) a fundamental role in this history.
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- 1.
In the book, we use the \(\varGamma \) (uppercase) for the Lorentz factor to avoid confusion with the \(\gamma \)-ray.
- 2.
A major difference between the c.g.s. and SI units is in the definition of the unit of charge. The c.g.s. unit of electrical charge (the statcoulomb, statC) can be written entirely as a dimensional combination of the mechanical units (gram, centimeter, second). In this book, we use the notation that \(e=4.8\times 10^{-10}\) statC is the proton charge; \(-e\) will be the electron charge.
- 3.
For these reasons, in later bubble chamber techniques two or more views of the event were used.
- 4.
In his work (Anderson 1933), Anderson reported a 63 million volt positron passing through a 6 mm lead plate and emerging as a 23 million volt positron. Our result is not so bad.
- 5.
At the time of the Anderson picture, only protons and electrons were known as charged particles. Try to work out that the observed particle cannot be a charged \(\pi ^+\) meson, with \(m_\pi =139.6\) MeV/c\(^2\).
- 6.
The subscript \( \odot \) conventionally represents the Sun and \(\oplus \) the Earth.
- 7.
In the language of astronomers, all elements heavier than He are often called metals.
- 8.
See Extras # 2 for the astronomical coordinate systems.
- 9.
In astronomy, the luminosity measures the total amount of energy emitted by a star or other astronomical object per unit time over the whole electromagnetic spectrum or a defined part of it.
- 10.
I was always fascinated by “2001: A Space Odyssey”, a science fiction film produced and directed in 1968 by Stanley Kubrick. A space voyage to Jupiter tracing a signal emitted by an unknown object (a monolith) was organized with a spaceship. Most of spaceship’ operations are controlled by a computer on board, HAL 9000 (or simply “Hal”, as Hal interacts and speaks with the human crew), and double-checked by a twin computer on Earth. Hal states that he is “foolproof and incapable of error”. The main problem arises when Hal foresees an imminent failure on a device. The twin computer on Earth is of the contrary advice. Humans on board of the spaceship discover that Hal is really wrong. They decide to disconnect it and to assign the spaceship operations to the computer on Earth. This decision induces a fight between humans and Hal. We are interested on the reason why there is a discrepancy between the prevision of the failure carried out by Hal and by the twin computer on Earth. The only plausible reason is the fact that the processor units of the Hal on board of the spaceship were damaged by cosmic rays. Although it is a science fiction movie, it fully grasped one of the main problems for long time permanence of humans in space. Computer failures can be prevented by increasing the number of units. This solution cannot be adopted for humans.
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Spurio, M. (2015). The Cosmic Rays and Our Galaxy. In: Particles and Astrophysics. Astronomy and Astrophysics Library. Springer, Cham. https://doi.org/10.1007/978-3-319-08051-2_2
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