Nothing travels faster than light, yet across the Solar System even light is slow. Guess seven one-way delays before each reveal, then use the delay explorer to see what a radio message to Mars really costs.
The slider is logarithmic: each step along it multiplies the time, so a tick is not a fixed amount.
Planets keep changing their distance from Earth, so the delay is not one number. Pick a target to see the delay bounds.
Each delay is computed as distance divided by the speed of light (299,792,458 m/s, exact by definition). Distances are mean distances from NASA's fact sheets: Sun to planet for the planets, Earth to Moon for the Moon. Delays are computed, not measured. The explorer's bounds are computed from orbit extremes: the closest possible approach is not less than the planet's nearest orbit point minus Earth's farthest (or the reverse for Venus), and the farthest is not more than both far points added. Real closest and farthest passes sit inside those bounds. The Sun-to-Earth figure uses 149.6 million km, giving 499 s, or 8.3 minutes.
NASA Goddard, Planetary Fact Sheet, distance from Sun, perihelion and aphelion: nssdc.gsfc.nasa.gov/planetary/factsheet
NASA Goddard, Earth Fact Sheet: earthfact.html
NASA Goddard, Moon Fact Sheet, semimajor axis 0.3844 million km: moonfact.html
NIST CODATA, speed of light in vacuum: physics.nist.gov/cgi-bin/cuu/Value?c
Data read 23 October 2026.