299,792 km every second
Light travel time
Nothing outruns light, and radio is light too. See how long a signal takes from Earth to the Moon, the Sun, each planet and the nearest stars: at the closest, at the farthest and on any date you choose.
Sunlight to Earth
8 min 16 s
on 30 Oct 2026
Mars, one way
12 min 1 s
216.1 million km away
Moon, one way
1.28 s
at its mean distance
| From Earth to | Distance | Closest | Farthest | On 30 Oct 2026 |
|---|---|---|---|---|
| The Moon and the Sun | ||||
| MoonMean perigee to mean apogee | 363,300–405,500 km | 1.21 s | 1.35 s | see range |
| SunPerihelion in early January, aphelion in early July | 147.1–152.1 million km | 8 min 11 s | 8 min 27 s | 8 min 16 s148.6 million km |
| Planets and Pluto | ||||
| MercuryClosest near inferior conjunction | 77.3–221.9 million km | 4 min 18 s | 12 min 20 s | 5 min 47 s103.9 million km |
| VenusThe nearest planet at its closest | 38.2–261 million km | 2 min 7 s | 14 min 31 s | 2 min 18 s41.45 million km |
| MarsClosest at a perihelic opposition | 54.6–401.4 million km | 3 min 2 s | 22 min 19 s | 12 min 1 s216.1 million km |
| JupiterClosest at opposition | 588.5–968.5 million km | 32 min 43 s | 53 min 51 s | 45 min 55 s825.8 million km |
| SaturnClosest at opposition | 1,206–1,659 million km | 1 h 7 min | 1 h 32 min | 1 h 11 min1,277 million km |
| UranusClosest at opposition | 2,581–3,154 million km | 2 h 23 min | 2 h 55 min | 2 h 34 min2,774 million km |
| NeptuneClosest at opposition | 4,319–4,711 million km | 4 h 0 min | 4 h 22 min | 4 h 2 min4,347 million km |
| PlutoIts orbit is very eccentric | 4,285–7,528 million km | 3 h 58 min | 6 h 59 min | see range |
| The nearest stars | ||||
| Proxima CentauriThe nearest star to the Sun | 4.24 light-years | 4.24 years | ||
| Alpha Centauri A and BThe bright pair beside Proxima | 4.36 light-years | 4.36 years | ||
| Barnard's StarA red dwarf in Ophiuchus | 5.98 light-years | 5.98 years | ||
| Wolf 359A faint red dwarf in Leo | 7.78 light-years | 7.78 years | ||
| SiriusThe brightest star in the night sky | 8.58 light-years | 8.58 years | ||
Worked out Time = distance ÷ the speed of light, 299,792.458 km/s. Mars on 30 Oct 2026: 216,108,204 km ÷ 299,792.458 = 721 s one way.
One way
1.28 s
1.28222 seconds
Round trip
2.56 s
there and back
384,400 km is 238,855 miles.
Reading the delays
Every time here is distance divided by the speed of light in a vacuum, exactly 299,792.458 km/s. Radio, the way we talk to spacecraft, travels at the same speed. Planets move round the Sun at different rates, so their distance from us swings between a closest approach, when they line up on our side of the Sun, and a farthest, when they sit behind it.
The on this date column places each planet with JPL's approximate orbital elements, good to a few seconds of light time between 1800 and 2050. The Moon and Pluto show their range only, and the stars are so far away that the time is simply their distance in light-years, counted in years.
Tick round trips for how long you wait between asking a question and hearing an answer. With Mars at least 3 minutes away, and up to 22, rovers have to drive themselves between instructions.
Sources
- Closest and farthest distances from Earth: the individual NASA Planetary Fact Sheets, including the Moon (mean perigee and apogee) and the Sun.
- Planet positions on a date: E. M. Standish, Approximate Positions of the Planets, JPL Solar System Dynamics, Table 1 (1800–2050).
- Star distances from trigonometric parallaxes in RECONS, The One Hundred Nearest Star Systems (Research Consortium On Nearby Stars, recons.org, list as of 1 January 2012).
- Speed of light: NIST reference on constants. Astronomical unit, 149,597,870.7 km: IAU 2012 Resolution B2. Light-year: c × 365.25 days.
Questions and answers
Does sunlight really take eight minutes to reach us?
Yes. At the average distance of one astronomical unit it takes 499 seconds, 8 minutes 19 seconds. In early January, when Earth is closest, it is about 8 minutes 11 seconds; in early July about 8 minutes 27 seconds.
Could you have a phone call with someone on Mars?
Not a normal one. Each reply would wait at least 6 minutes for the round trip, and up to about 45 minutes when Mars is on the far side of the Sun, so messages would work more like letters.
Why does Pluto's range overlap Neptune's?
Pluto's orbit is stretched and tilted. For 20 years of each 248-year circuit it is closer to the Sun than Neptune, which last happened from 1979 to 1999, so its closest distance from Earth is slightly less than Neptune's farthest.
Why is the starlight table a single number?
Earth's yearly orbit changes a star's distance by only a few light-minutes out of light-years, far too little to show. Light from Proxima Centauri left it about 4.24 years before you see it.