The travel time is not always exactly the same, incidentally. Earth moves in a slightly oval orbit rather than a perfect circle, so the distance to the Sun varies a little throughout the year. The delay does, however, remain around eight minutes.

That average distance is used so frequently in astronomy that it has its own name: the astronomical unit. It is a convenient way to keep distances within our solar system manageable without having to write out nine zeros every time.

And then there is the most striking consequence of that delay: if the Sun were to vanish at this exact moment, we would not notice until just over eight minutes later. Until then, simply light — as if nothing had changed. By comparison, light from the Moon reaches us in just over a second. Light from the nearest stars outside our solar system takes years, which is why astronomers use the concept of the light-year. It is not a measure of time, but of distance — even though it does not quite sound that way.