Follow your curiosity

What discovery has been shared with you?

FACTREE gives you something interesting to discover every day — and something worth talking about together.

Start with one fact. Explore it, go deeper, then follow whichever branch catches your imagination.

Choose subjects for a surprise

Exploring any topic

Begin your discovery

Your next discovery is one click away.

Choose one or more subjects above, or leave Any Topic selected and let curiosity decide.

Physics

Photon Propagation in Vacuum

Quick fact

Photons move at approximately 300,000 kilometers per second in a vacuum, which is the maximum speed allowed by the laws of physics.

Why this is interesting

Have you ever wondered why light from the Sun reaches Earth so quickly, even though space is mostly empty? The answer lies in how photons travel through a vacuum.