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Early on, advocates of big bang cosmology realized that the universe is evolutionary. In the words of one famous cosmologist, George Gamov, “We conclude that the relative abundances of atomic species represent the most ancient archaeological document pertaining to the history of the universe.” In other words, the periodic table is evidence of the evolution of matter, and atoms can testify to the history of the cosmos. But early versions of big bang cosmology held that all the elements of the universe were fused in one fell swoop. As Gamov puts it, “These abundances …” meaning the ratio of the elements (heaps of hydrogen, hardly any gold—that kind of thing), “… must have been established during the earliest stages of expansion, when the temperature of the primordial matter was still sufficiently high to permit nuclear transformations to run through the entire range of chemical elements.” It was a neat idea, but very wrong. Only hydrogen, helium, and a dash of lithium could have formed in the big bang. All of the elements heavier than lithium were made much later, by being fused in evolving and exploding stars. How do we know this? Because at the same time some scholars were working on the big bang theory, others were trying to ditch the big bang altogether. Its association with thermonuclear devices made it seem hasty, and its implied mysterious origins tainted it with creationism. And so, a rival camp of cosmologists developed an alternate theory: the Steady State. The Steady State held that the universe had always existed. And always will. Matter is created out of the vacuum of space itself. Steady State theorists, working against the big bang and its flaws, were obliged to wonder where in the cosmos the chemical elements might have been cooked up, if not in the first few minutes of the universe. Their answer: in the furnaces of the very stars themselves. They found a series of nuclear chain reactions at work in the stars. First, they discovered how fusion had made elements heavier than carbon. Then, they detailed eight fusion reactions through which stars convert light elements into heavy ones, to be recycled into space through stellar winds and supernovae. And so, it’s the inside of stars where the alchemist’s dream comes true. Every gram of gold began billions of years ago, forged out of the inside of an exploding star in a supernova. The gold particles lost into space from the explosion mixed with rocks and dust to form part of the early Earth. They’ve been lying in wait ever since.
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Mark Brake (The Science of Harry Potter: The Spellbinding Science Behind the Magic, Gadgets, Potions, and More!)