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

Emission and Absorption of Light

Quick fact

Every element has a unique set of energy levels, so the specific colors it emits or absorb act like a fingerprint — astronomers use this to identify the chemical composition of distant stars.

Why this is interesting

Why do some objects glow when heated, while others seem to 'eat' light and change color?