This is actually a much deeper question than it appears on the surface. The simple answer most textbooks give is technically correct but misses a lot of nuance. Let me try to explain it in a way that captures the full picture.

Great question! The math behind this is complex but the concept is actually straightforward once you see it the right way. Forget what you learned in school for a moment and think about it from first principles.

Scientists love this kind of question because it's how real discoveries start. 'That's funny...' is supposedly how a lot of breakthroughs begin. Keep that curiosity — it's worth more than memorizing facts for a test.

The math looks scary but it's mostly just a precise way of saying something you can understand in plain English. Once you get the concept, the equations are just bookkeeping. Focus on the idea first, the symbols second.

I'm a physics grad student and this is one of my favorite questions to explain. The key insight is that our everyday intuition doesn't always apply at extreme scales — very small (quantum), very large (cosmological), or very fast (relativistic).