Light is the fastest thing in the universe. At 299,792 km/s, nothing is faster. But is it fast enough?
| Journey | Distance | Light Time |
|---|---|---|
| Earth → Moon | 384,400 km | 1.28 seconds |
| Earth → Mars | 54.6 million km | 3 min 2 sec |
| Earth → Sun | 149.6 million km | 8 min 20 sec |
| Earth → Jupiter | 588 million km | 32 min 43 sec |
| Sun → Proxima Centauri | 40.2 trillion km | 4.246 years |
A text message to Mars takes 3-22 minutes one way
Netflix on the Moon would have a 2.6-second lag
If you could drive to the Sun at highway speed, it would take 170 years
The universe is incomprehensibly vast. Light is the fastest thing that exists, and even it takes 4 years to reach the nearest star.
Speed of Light is a free online interactive visualization that lets you watch a photon of light travel between celestial bodies in real time. Light travels at 299,792 km/s — fast enough to circle Earth 7.5 times per second. Yet it still takes 1.3 seconds to reach the Moon, 8 minutes to reach the Sun, and over 4 years to reach the nearest star. This experience makes those numbers feel real by showing the journey as it happens.
Watch a glowing photon travel across 5 cosmic journeys: Earth to Moon, Earth to Mars, Earth to Sun, Earth to Jupiter, and Sun to Proxima Centauri. Each journey plays in real time (or accelerated with speed controls). Live counters show distance traveled, elapsed time, and progress. Speed controls let you watch at 1x, 10x, 100x, or 1000x — or experience the full real-time wait.
Light travels at exactly 299,792,458 meters per second (approximately 300,000 km/s) in a vacuum. At this speed, light could circle the Earth 7.5 times in a single second. Nothing in the universe can travel faster.
Light takes approximately 8 minutes and 20 seconds to travel from the Sun to Earth, covering about 149.6 million kilometers. If the Sun suddenly disappeared, we would continue to see it for over 8 minutes.
Proxima Centauri is 4.246 light-years away (about 40.2 trillion km). Even at light speed, it takes over 4 years. The fastest spacecraft, the Parker Solar Probe, would take about 6,300 years to make the journey.
If you enjoyed this, try these: Size of Space · Center of Earth · Earth in a Day · Ocean Depth
Last updated: March 2026 · whatifs.fun — Free interactive games, experiments & simulations