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--- courses:ast100:1.2 [2026/01/26 11:46] – [Origin of the particles] asad
+++ courses:ast100:1.2 [2026/01/26 11:56] (current) – [Origin of the particles] asad
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-====== 1.3. Formation of elementary particles ======
+====== 1.2. Formation of elementary particles ======
 ===== The elementary particles =====
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 The outermost ring contains the **fermions**, the "bricks" that constitute all material structures. These are split into **quarks** (blue), which combine to form protons and neutrons, and **leptons** (light purple), such as the electron and the ghostly, nearly massless neutrino. To maintain cosmic symmetry, every one of these particles has a mirror-image antiparticle, such as the positron (the antimatter version of the electron). While matter and energy are often viewed as distinct, they are fundamentally linked; for instance, if an electron meets a positron, they undergo annihilation, instantly canceling each other out to release a flash of pure energy in the form of gamma-ray (extremely high energy or frequency) photons. Yet, this inventory remains incomplete, as it has yet to incorporate the "mortar" of gravity into its quantum architecture.
 ===== Origin of the particles =====
+{{:courses:ast100:elementary.webp?direct|}}
 The genesis of the material universe was a process governed by the dynamic equivalence of matter and energy, formulated by Einstein’s celebrated principle, $E=mc^2$. In the intensely energetic environment of the infant universe, subatomic particles did not exist as stable entities; instead, they "materialized" from radiant energy through pair production—a mechanism in which high-energy bosons collided to generate a particle and its corresponding antiparticle. This creative flux was balanced by immediate annihilation, wherein particle pairs reverted to pure energy upon contact. However, as the universe expanded and underwent cooling caused by its rapid growth, the energy density dropped below the specific "threshold temperatures" required to sustain the production of massive particles. As a result, various types of particles "froze out" of the radiation field, becoming permanent features of the universe. This occurred because the cooling environment no longer provided enough energy to create new particle pairs, meaning that those destroyed by annihilation were no longer being replaced.