Light Time Calculator
Calculate how long it takes for light to travel between celestial objects in our solar system and beyond
Starting Point
Destination
Light Travel Time Results
Select objects to see how long light takes to travel between them.
Breakdown
Detailed calculation will appear here.
🌌 Solar System Light Time Facts
Sun to Earth
8 minutes 20 seconds - This is called an Astronomical Unit (AU)
Earth to Moon
1.28 seconds - Apollo astronauts communicated with this slight delay
Sun to Pluto
5.5 hours - New Horizons took 9.5 years to make the same journey
Sun to Alpha Centauri
4.37 years - Our nearest stellar neighbor is 4.37 light-years away
Andromeda Galaxy
2.5 million years - The light we see left when early humans were evolving
Voyager 1
22 hours - Current one-way light time to our most distant spacecraft
📊 Light Speed Reference
| Medium | Speed | Comparison |
|---|---|---|
| Light in vacuum | 299,792 km/s | 7.5 times around Earth in 1 second |
| Light in water | 225,000 km/s | 25% slower than vacuum |
| Light in glass | 200,000 km/s | 33% slower than vacuum |
| Sound in air | 0.343 km/s | 874,000 times slower than light |
| Commercial jet | 0.25 km/s | 1.2 million times slower than light |
| Fastest spacecraft (Parker Probe) | 0.0002 km/s | 1.5 million times slower than light |
Note: Light speed in vacuum is the ultimate speed limit of the universe according to Einstein's theory of relativity.
Note: This calculator provides estimates based on average distances. Actual distances between celestial bodies vary due to elliptical orbits. Light speed in vacuum is 299,792 km/s (186,282 miles/s).