Speed and rate of data transfer

[sophiecentaur]

On the topic of latency of data communications links here are some stats you may find interesting:

At 100 gigabit Ethernet, the spacing between bits on the fiber optic cable is a mere 2mm.
A long reach (40Km) 100GBE link will contain 20 million bits in flight.
Corning Glass has shipped over 30 million Km of long haul (LEAF) fiber.

Thus, at any frozen moment in time, this corresponds to 15 terabits of data in flight within these cables.

There is a directly similar acoustic situation. When you shout at someone in the distance, your whole sentence may be hanging in the air, on its way to them after you close your mouth finally.
Latency is only a problem when synchronism is important. This can be on a circuit board where line lengths on a Bus need to be equalised to within a mm or two.