How long does light take to reach Mercury?
3.2 minutesfrom the Sun
Light from the Sun takes about 3.2 minutes to reach Mercury, crossing 58,343,169 km of nothing at 299,792 km every second.
▶ Watch light race to Mercury in 3D
From Earth, the answer changes constantly as both planets move. When we're closest, light (or a radio signal) makes the trip in about 5.1 minutes; when Mercury is on the far side of the Sun it takes up to 12 minutes. That's a real engineering problem: no message, command or cry for help can ever travel faster.
Light is the fastest thing that can exist — it could circle Earth 7.5 times in one second. The fact that it needs 3.2 minutes to reach Mercury is the size of the solar system, stated plainly.
You can watch this happen. In the interactive view, press ☄ Light speed: a photon leaves the Sun in accurate scaled time and you wait — genuinely wait — while it crawls across the emptiness. It's the single best way to feel what these numbers mean.
Keep going
✓ Facts verified July 2026
Every figure on this page is a real, rounded value checked against primary sources. Found something out of date? See how we keep it accurate.