How long does light take to reach Earth?
The speed of light is exactly 299,792.458 km/s by definition. Divide a distance by it and you get light travel time.
· Last reviewed
The Moon
Mean Earth–Moon distance is 384,400 km (NASA). 384,400 ÷ 299,792.458 ≈ 1.28 seconds.
The Sun
One astronomical unit — the reference Earth–Sun distance — is defined as 149,597,870.7 km (IAU). 149,597,870.7 ÷ 299,792.458 ≈ 499 seconds, about 8 minutes 19 seconds.
Why "about"
Orbits are elliptical, so real distances — and light times — vary through the month and year.
Light travel time to other places
Destination Distance Light travel time Moon (mean)384,400 kmabout 1.28 seconds Sun (1 AU)149.6 million kmabout 8 min 19 s Mars54.6 to 401 million kmabout 3 to 22 minutes Jupiter588 to 968 million kmabout 33 to 54 minutes Pluto4.3 to 7.5 billion kmabout 4 to 7 hours Voyager 1about 25 billion km (late 2026)nearly 1 day Proxima Centauri4.24 light-years4.24 years
Ranges reflect the closest and farthest points in each orbit. Times use time = distance ÷ c, with c = 299,792.458 km/s.
How much does the time vary?
Sun: Earth is closest to the Sun in early January (about 147.1 million km, roughly 8 min 11 s) and farthest in early July (about 152.1 million km, roughly 8 min 27 s).
Moon: The distance ranges from about 356,500 km at perigee (about 1.19 s) to about 406,700 km at apogee (about 1.36 s).
How to calculate it yourself
Divide the distance by the speed of light.
Example: Mars at its closest is about 54.6 million km away.
54,600,000 km ÷ 299,792.458 km/s ≈ 182 seconds, or about 3 minutes.
Want to try your own numbers? Use the light travel calculator.
Frequently asked questions
How long does it take light to travel from the Sun to Earth?
About 8 minutes 19 seconds on average. The exact time ranges from about 8 min 11 s to 8 min 27 s over the year because Earth's orbit is slightly elliptical.
Why does sunlight take 8 minutes but moonlight only about 1 second?
The Sun is about 390 times farther away than the Moon. Light travels at the same speed in both cases, so the longer distance means a longer trip. Moonlight is reflected sunlight, so it has already spent about 8 minutes traveling from the Sun to the Moon before its 1.28-second trip to Earth.
Does light take longer to reach Mars?
Yes. Depending on where Earth and Mars are in their orbits, light takes roughly 3 to 22 minutes to cross the gap.
What is a light-year?
A light-year is the distance light travels in one year, about 9.46 trillion km. It measures distance, not time.
Can anything travel faster than light?
Nothing with mass can reach or exceed the speed of light in a vacuum, according to current physics. The speed of light is defined as exactly 299,792,458 m/s in the SI system.
Do we see the Sun as it is right now?
No. We see the Sun as it was about 8 minutes 19 seconds ago.
Try other distances
Use the light travel calculator, or compare with a much slower trip in walking to the Moon.
Last reviewed: October 14, 2026
Sources
Moon Fact Sheet — NASA NSSDCA
Resolution B2 on the re-definition of the astronomical unit — International Astronomical Union
Worked examples
Moon
384,400 km ÷ 299,792.458 km/s ≈ 1.28 s.
Sun
149,597,870.7 km ÷ 299,792.458 km/s ≈ 499 s ≈ 8 min 19 s.
Assumptions
- Mean distances; light travels in vacuum.
Methodology
time = distance ÷ c, with c = 299,792.458 km/s exactly.
Sources
- Moon Fact Sheet — NASA NSSDCA. Accessed 2026-10-14.
- Resolution B2 on the re-definition of the astronomical unit — International Astronomical Union. Accessed 2026-10-14.
- The International System of Units (SI Brochure) — BIPM. Accessed 2026-10-14.