It should be fairly intuitive. Sending electromagnetic radiation through copper or fiber will add physical distance versus a direct line of sight link. And the refractive index of light in the atmosphere is significantly lower, so the radiation actually propagates faster. Over long distances, those microseconds will add up.
The best example of this is the stock exchange in Chicago (and elsewhere) uses a low latency microwave link to save several milliseconds over the fiber links.
Says who?
My PhD in electrical engineering.
Care to elaborate or point to a reliable source?
It should be fairly intuitive. Sending electromagnetic radiation through copper or fiber will add physical distance versus a direct line of sight link. And the refractive index of light in the atmosphere is significantly lower, so the radiation actually propagates faster. Over long distances, those microseconds will add up.
The best example of this is the stock exchange in Chicago (and elsewhere) uses a low latency microwave link to save several milliseconds over the fiber links.