COSMIC ALCHEMY

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ìIt was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.î óERNEST RUTHERFORD, describing his experiments with atomic structure.

Out of the white-hot heat of the Big Bang arose everything that exists in the universe today. The long road that leads from this ultra-dense soup of elementary particles and radiation to atoms, stars, planets, and life becomes one of the central paths in cosmologistsí efforts to understand how the universe is put together. Ironically, the physicists who unraveled the structure of the atom paved the way for those who ultimately figured out how the atoms themselves came to be.

         The Greek philosopher Democritus, in the 5th century B.C., developed the first theory of the atom. He believed atoms were tiny and indestructible, the smallest constituents that made up the four Greek elements of earth, water, fire, and air. In fact, the word atom comes from the Greek word for ìindivisible.î For 2300 years, Democritusí concept remained a cornerstone in our thinking about how the universe is put together. When  scientists of the 19th century  began to delve deeper, it began to lay the groundwork for answering one of cosmologyís central questions: How did the elements in our universe form and evolve?
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The Big Bang

Dmitri Mendeleev

 
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Marcelo Gleiser:
Where Does Matter Come From?

       The first inkling that atoms might have structure came in the 1860s, when the Russian scientist Dmitri Mendeleev developed the periodic table. By then, of course, scientists knew that there were many more elements than the Greeksí four. What Mendeleev realized was that when the elements were arranged according to their atomic weight, he could group different elements into families with similar characteristics.

       Sodium and potassium, for instance, share similar properties, as do carbon, silicon, and titanium, but the attributes of each family are very different from each another. Mendeleev found gaps in his periodic table, which he correctly interpreted to mean that other, yet undiscovered, elements existed. But neither he nor his contemporaries made the conceptual leap to realizing that an atomís weight and properties were a measure of its internal structure. As had happened so many times before, the ingrained beliefs of the time (in this case, that the atom is indivisible) made such thoughts inconceivable.
 

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