In his famous lecture, "Life in the Universe," Stephen Hawking observed that what we normally think of as 'life' is based on chains of carbon atoms, with a few other atoms, such as nitrogen or phosphorous. We can imagine that one might have life with some other chemical basis, such as silicon, "but carbon seems the most favorable case, because it has the richest chemistry."
Several eminent scientists think otherwise, that life in the universe could have a myriad of possible biochemical foundations ranging from life in ammonia to life in hydrocarbons and silicon. Silicates have a rich chemistry with a propensity for forming chains, rings, and sheets. One of the founders on modern genetics, Cairs-Smith, argued that layers of crystalline silicates functioned as a primitive form of life on early Earth, before they evolved into carbon-based life forms.
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