Physics
Bell's Theorem
Quick fact
When experiments tested Bell's theorem in the 1970s and 1980s, they consistently violated the Bell inequality, confirming that the quantum world is inherently nonlocal—a result so surprising that Einstein called it 'spooky action at a distance'.
Why this is interesting
You probably assume that objects have definite properties even when you're not looking—and that nothing can travel faster than light. But what if these two commonsense ideas can't both be true at the same time?