How many dimensions are there, and what do they do to reality? | Aeon Essays

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Relativity says we live in four dimensions. String theory says it’s 10. What are ‘dimensions’ and how do they affect reality?

Writing away at my desk, I reach my hand up to turn on a lamp, and down to open a drawer to take out a pen. Extending my arm forward, I brush my fingers against a small, strange figurine given to me by my sister as a good-luck charm, while reaching behind I can pat the black cat snuggling into my back. Right leads to the research notes for my article, left to my pile of ‘must-do’ items (bills and correspondence). Up, down, forward, back, right, left: I pilot myself in a personal cosmos of three-dimensional space, the axes of this world invisibly pressed upon me by the rectilinear structure…

How many dimensions are there, and what do they do to reality? | Aeon Essays

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