[deadgrey19]

Fair point about only taking half the ping distance.

On the other issues, I disagree. They are the precisely the point of my objection. Assuming that latency is governed by the speed of light fails to take into account all of those other effects. Many of which can be mitigated. And, this is an extreme case. London to Sydney is probably one of the longest paths you can take (except maybe London Auckland?) with many stretches of fibre. On shorter paths, the overheads stack up much more heavily. In datacenters, the time of flight is a few nano-seconds, but the overall latency is tens of micro-seconds to tens of milli-seconds.

Isn't it odd that we accept 2x-5x (sometimes even 1000x) overhead over the best case and yet still argue that it's governed by the speed of light? How many other places in computing are we willing to accept that?