Equation 3 · Part 1 · Physics Optimizes, Evolution Satisfices: Two Kinds of Perfection

Symbol n_1

n_1 \sin\theta_1 = n_2 \sin\theta_2

n_1

What this part means

$n_1$ is part of the quantity the equation computes from the expression on the right.

Its job in the formula

$n_1$ is part of the quantity the equation computes from the expression on the right.

Full expressionSymbol n_1Article meaning

The passage around this formula

…that gets it through in the least possible time. Pierre de Fermat stated this as a principle in the 1660s, and the consequence collapses into one line of algebra: for a ray crossing between two media of refractive index $n_1$ and $n_2$ , $n_1 \sin\theta_1 = n_2 \sin\theta_2$ . Snell’s law, in other words, is not an independent fact about glass. It is what falls out of a single global stipulation — least time — applied to one path among infinitely many. Pierre-Louis Maupertuis generalized the same move to all of mechanics in the 1740s,…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the surrounding passage

[11] General Relativity: Einstein's Geometric Gravity ↗

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