Physics
The Casimir Effect
Quick fact
The effect was predicted by Dutch physicist Hendrik Casimir in 1948, and the force is so small that it was first measured experimentally only in 1997 with precision of about 5%.
Why this is interesting
Imagine two metal plates floating in completely empty space, with no external forces acting on them. Yet, they mysteriously move toward each other as if pulled by an invisible hand. What is causing this attraction?