Science
What is The speed of light?
The speed of light is the fastest anything can travel — about 300,000 kilometers per second in a vacuum. It's a fundamental limit of the universe, and nothing carrying information or mass can go faster.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains the speed of light.
Key things to understand
- 1Light travels about 300,000 km per second in a vacuum.
- 2It's the universe's ultimate speed limit.
- 3Nothing with mass can reach it.
- 4It links space and time in Einstein's relativity.
Frequently asked questions
- How fast is the speed of light?
- About 299,792 kilometers per second in a vacuum — roughly 300,000 km/s.
- Why can't anything go faster than light?
- Relativity shows that reaching light speed would require infinite energy for anything with mass.
- How long does light take to reach us from the Sun?
- About 8 minutes and 20 seconds to travel from the Sun to Earth.