Every look into space is a look back.

Light travel time

Discover how long light takes to cross the solar system and the distances between stars.

Light travel timeInteractive model

Light travel499 s

In minutes8.32 min

In years1.58e-5 years

Your experiment

Distance unit

Distance AU

1.50e+8 km ÷ 299,792.458 km/s = 499 seconds (0.01 days).

How it works

time = distance / c · c = 299,792.458 km/s

Even light has a finite speed. A light-year is the distance light travels in a Julian year, not a unit of time. Light travel makes remote observations a view of the past.

Read the field note ↗

About this model
Travel in a vacuum at constant distance. This simple model excludes cosmic expansion, changing orbital positions, and gravitational delays.

Keep wondering

Light travel time: common questions

Is a light-year a time unit?

No. It is a distance: about 9.46 trillion kilometers, traveled by light in one Julian year.

Is this a spacecraft travel calculator?

No. These times apply to light in a vacuum. Spacecraft travel far below light speed.

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