At the core of everything we’ve ever touched, seen, or interacted with here on Earth is the same humble physical structure: the atom. Each human body possesses around 10²⁸ of them, and they come in just under 100 different species, or elements, through natural processes, and we’ve synthesized several dozen more in laboratory experiments. Combined, atoms bind together to make unfathomably intricate, complex structures on both microscopic and macroscopic scales, and compose every living and nonliving object presently known to humanity.
But atoms weren’t always around; they only formed in the aftermath of the hot, early stage of our Universe known as the hot Big Bang. How did they arise, and what made their existence possible? That’s the question of Dave Drews, who wants to know: “Out [of] the primordial soup after the Big Bang, how did atoms come to be?
How did protons and neutrons come to be to make atoms? Were there free-floating quarks combining in the right combinations to form protons and neutrons? How did quarks come to be?
Were there free-floating gluons that came together to create them? Free-ranging electrons were flying about, but what caused them to bind with protons to create hydrogen atoms and so on?” Let’s start by recounting our own cosmic history, which did indeed lead to the formation of atoms, and then take a look back at the key steps that made their ubiquitous existence possible. At the high temperatures achieved in the very young Universe, not only can particles and photons be spontaneously created, given enough energy, but also antiparticles and unstable particles as well, resulting in a primordial particle-and-antiparticle soup.
Yet even with these conditions, only a few specific states, or particles, can emerge, and by the time a few seconds have passed, the Universe is much larger than it was in the earliest stages. As the Universe begins expanding, the density, temperature, and expansion rate of the Universe all rapidly drop as well. At the start of the hot Big Bang, we didn’t have any atoms at all.
We also didn’t have their core constituents: the atomic nuclei, nor did we even have protons or neutrons. Electrons were present, as were their antimatter counterparts, positrons, and all the fundamental particles and antiparticles of the Standard Model. Conditions, way back then, were far too hot, dense, and energetic for any bound structures to form at all; anytime any two particles even attempted to bind together, the extraordinary conditions at that time led to another quantum interacting with them and blasting them apart.
Extract — continue reading at the source.
