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Light Travel Time Calculator

Enter a distance to see how long a light signal would need to cross it in vacuum.

Distance

Distance unit

Light travel time8 minutes 19 seconds

How this tool works

The tool converts the selected distance into kilometres, then divides by the defined speed of light in vacuum: 299,792.458 kilometres per second.

Astronomical distances between moving objects change continuously. Preset or entered distances should therefore be understood according to the distance value supplied, rather than as a live spacecraft-navigation calculation.

Source

The speed of light in vacuum is exactly 299,792,458 metres per second in the International System of Units.

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