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).

The honest answer is that scientists don't fully understand this yet. We have good models that make accurate predictions, but the 'why' underneath is still an active area of research. Anyone who tells you they have the complete answer is oversimplifying.

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.

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.

This is something I struggled with until a professor explained it using an analogy that finally clicked. The real world is messy and doesn't always fit neatly into the simplified models we learn in textbooks.