Gravity and Charge: Physics' Blind Spot
Since the days of Galileo, it was believed that in a vacuum all bodies fall identically. Einstein elevated this to a principle: gravity travels at the speed of light and is the curvature of spacetime.
How Waves Tell Us About the World
A stone drops into a pond — ripples spread across the water. Do short waves outrun long ones? No, in deep water it's the opposite: long waves overtake short ones. In metal, sound of one pitch travels at one speed, another pitch at another.
Echo of the Void: How to Catch the Invisible
A palm hovering over a hot stove feels the heat even when the surrounding air seems cool. Something similar happens to electrons in the Aharonov–Bohm effect: the particle senses an electric voltage even though it enters a region where the field has already been switched off.
The Silent String of Gravity: Hunting for κ
The weak equivalence principle, silently tested since the time of Galileo and laid at the foundation of general relativity, states: all bodies fall equally, regardless of their internal composition.