Philosophers used to ask whether we are born with or invent our sense of time. Now we know that we have clocks woven into every one of our cells. Phi… - Jonathan Weiner

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Philosophers used to ask whether we are born with or invent our sense of time. Now we know that we have clocks woven into every one of our cells. Philosophers also used to ask how we know that the sun will rise tomorrow. In a sense we have that answer built into us, too. The clock is a kind of orrery in the heart of every one of our cells, revolving to help us keep time with our world, a model of the cosmos inside our heads that cycles whether we are in or out of sight of the sun. The revolution of the stars and the seasons is written in the turns of our DNA.