If the sun instantly switched off like a light bulb–which can’t happen, by the way–then we wouldn’t know for almost 8 and a half minutes. Light travels at the fastest speed there is, but it still takes almost 500 seconds to get to Earth. That’s how long it would take before we knew the sun went dark.But the most amazing thing about the sunlight we see is it’s actually really old. SUPER old. AMAZINGLY OLD! Tens of thousands of years old. How is that possible? Because of the physics and mathematics of random walks.