How long does it take sunlight to reach Earth?

Sunlight seems to reach us instantly, but the distance is enormous. Light has a measurable travel time. How long does it take a ray of light to cover that distance?

  • A. About 8 seconds
  • B. About 8 minutes
  • C. About 8 hours
  • D. About 8 days

💡 Need a hint?

Light travels almost 300,000 kilometres per second. The distance to the Sun is approximately 150 million kilometres. Divide one by the other and you’ll find yourself closer to minutes than seconds.

✅ View the answer

The correct answer is B. Sunlight takes approximately 8 minutes and 20 seconds to reach Earth.

The average distance between Earth and the Sun is about 150 million kilometres, and light travels at almost 300,000 kilometres per second. Divide those two numbers and you get just over 500 seconds — a little more than 8 minutes.

📚 More background information

That distance of 150 million kilometres has its own name in astronomy: the astronomical unit. A useful one too, because without a unit like that you’d have to write out a long string of zeroes every time you described a distance within our solar system.

There’s something else worth pausing to consider: the Sun you see is not the Sun as it is right now. You are always looking at how it appeared just over 8 minutes ago. With stars that are much further away, this effect becomes truly mind-boggling — you can be looking thousands or even millions of years back in time.

Earth doesn’t travel in a perfect circle around the Sun, but in a slightly elongated orbit. This means the distance varies a little throughout the year, which in turn means the exact travel time of sunlight isn’t quite the same every day. But the difference is so small that the rule of thumb of about 8 minutes remains perfectly useful — even if you find yourself defending it against an astronomically pedantic neighbour.