Last updated: October 2026 Β· 3 min read
Light lets us see the world, powers plants and even carries our internet data. Yet it behaves in surprising ways. Here are 10 incredible facts about light.
10 incredible facts about light
1. It is the fastest thing in the universe
Light travels at about 299,792 km per second in a vacuum. According to Einstein’s theory of relativity, nothing with mass can reach that speed.
2. It could circle Earth 7.5 times in a second
At that speed, a beam of light could travel around Earth’s equator about seven and a half times in just one second.
3. Moonlight is about 1.3 seconds old
Light reflected from the Moon reaches Earth in about 1.3 seconds, while sunlight takes about 8 minutes and 20 seconds.
4. White light is a mix of colours
In the 1660s, Isaac Newton used a glass prism to show that white sunlight splits into a spectrum of colours.
5. Light is both a wave and a particle
Light behaves like a wave in some experiments and like a stream of particles called photons in others, a key idea in quantum physics.
6. Light slows down in water and glass
Light travels about 25% slower in water and even slower in glass. This change in speed bends light, a process called refraction.
7. An Indian scientist won a Nobel Prize for light
In 1928, C.V. Raman discovered that light changes colour slightly when it scatters off molecules, now called the Raman effect. He won the Nobel Prize in Physics in 1930, and India celebrates National Science Day on 28 February to mark his discovery.
8. The internet travels as light
Fibre-optic cables carry internet data as rapid pulses of light through thin strands of glass, including the undersea cables that connect continents.
9. Sunlight starts its journey long before 8 minutes
Energy made in the Sun’s core can take tens of thousands of years or more to work its way out to the surface before it races to Earth as light.
10. Some living things make their own light
Fireflies, some fungi and many deep-sea creatures produce light through chemical reactions, a phenomenon called bioluminescence.
Frequently asked questions
What is a light-year?
The distance light travels in one year, about 9.46 trillion km.
Why can’t anything travel faster than light?
In Einstein’s theory, as an object with mass speeds up, it needs ever more energy; reaching light speed would require infinite energy.
What colours make up white light?
Red, orange, yellow, green, blue, indigo and violet, the colours of the rainbow.
Keep exploring
- How rainbows form
- Why is the sky blue?
- More Science explainers on Tiwaripedia
- Browse all incredible facts
Facts are based on widely accepted scientific, historical and official sources at the time of writing. Spotted something that needs updating? Let us know.
