The idea that electric current flows at the speed of light is a simplification and isn't entirely accurate. While the electric field associated with a changing current propagates at the speed of light, the actual flow of electrons in a conductor is much slower.

Here's why:

* Electric fields travel at the speed of light: When you switch on a light, the electric field that causes the light bulb to turn on propagates at the speed of light. This is because the electric field is a disturbance in the electromagnetic field, and electromagnetic waves travel at the speed of light.

* Electron drift velocity is much slower: The individual electrons in a wire don't actually travel at the speed of light. Instead, they drift slowly through the conductor due to the electric field. This drift velocity is typically on the order of millimeters per second.

Therefore, no single individual "discovered" that electric current flows at the speed of light, because it's not entirely true. However, many scientists contributed to our understanding of electricity and electromagnetism, including:

* James Clerk Maxwell: He formulated the equations that describe electromagnetic waves and predicted that they travel at the speed of light.

* Heinrich Hertz: He experimentally verified Maxwell's predictions by generating and detecting radio waves.

* Oliver Heaviside: He developed the concept of the electromagnetic field and its propagation.

It's important to remember that while the electric field propagates at the speed of light, the actual flow of electrons in a conductor is much slower.