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Patterns, Periodicity, and Prediction

The Sanskrit word for one is eka.

Dmitri Ivanovich Mendeleev found a pattern when he was writing his textbook "Principles of Chemistry" — the properties of chemical elements seemed to repeat in the order of their atomic weight. He proposed a periodic table that arranged the elements according to their atomic weight and their chemical properties. It remains the best distillation of chemical properties of the elements — a tour de force.

But Mendeleev had a problem. It was the second half of the nineteenth century, and many of the elements were not even discovered! How do you place something in the table that hasn't even been found? For example, there was a spot below the element Silicon in the table that didn't seem to fit a known element. Rather than trying to fill in the blank space, he put a placeholder: Ekasilicon.

How do we act in a world of imperfect information? When we try to construct a mental model, pattern recognition may help us, but overfitting can lead us astray. That's why people find faces in the moon (pareidolia). Better to accept our ignorance and leave blank spaces, rather than twist our model to fit the data.

The best scientific theories not only explain, but also predict. If we know something doesn't make sense, it helps us learn about our blind spots, to turn unknown unknowns into known unknowns.

What are the practical implications? We should clarify our assumptions, keep a prediction journal, and calibrate our premonitions. Otherwise the feeling of "we knew it" will obstruct our recognition of ignorance.

More than a decade after Mendeleev's prediction, the element Ekasilicon was finally discovered and was named Germanium. Today Germanium makes advances in semiconductors and fiber optics possible.

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