Darkness Travels Exactly as Fast as Light

Darkness moves at exactly the speed of light. The moment a light source is extinguished, the void that follows travels toward you at 186,282 miles per second.

This is because darkness isn't a "thing" that exists on its own, but the state of the universe when photons are missing. If the Sun were to instantly vanish, we wouldn't see the sky go black for eight minutes and twenty seconds. That is because the "last" photons emitted are still traveling toward us at light speed, with the darkness trailing directly behind them.

However, in certain geometric scenarios, shadows can actually appear to move faster than the speed of light. If you flick your wrist while pointing a laser at the Moon, the red dot across the lunar surface would technically move faster than 186,000 miles per second.

This isn't breaking the laws of physics because no actual information or matter is traveling that fast. It is simply a sequence of light particles hitting different spots in rapid succession.

While darkness in a vacuum travels at light speed, it can move slower through materials like glass or water, just as light does. In these substances, the "disappearance" of light is buffered by the atoms the photons must interact with on their way out.