The random walk problem — the “mathematical formalization of a path that consists of a succession of random steps” — can be applied to sunlight… not the sunlight that travels from the sun to Earth, which takes only 8 minutes, but the sunlight that travels to the Sun’s core to its surface. How long does that take? This TED Ed explains: Sunlight is way older than you think.

Watch this next: How Do We Know How Old the Sun Is?

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