C3550 Five-thousand-li Flaming Beacon Smoke

The ancient beacon communication was not slow. It was completely dependent on the visual system. In other words, it was transmitted at the speed of light.

As soon as the beacon smoke rose, people could faintly see the black smoke from dozens of miles away. If it was night time, it would be even simpler, the flickering flame was even more obvious.

Light speed was the fastest speed