What about with C' (being the current state-of-the-art/max)? I guess the current speed, judging by [1] is about 200000 km/s (for light in optical fibre), which

What about with C' (being the current state-of-the-art/max)? I guess the current speed, judging by [1] is about 200000 km/s (for light in optical fibre), which leads to 2000 km radius (or diameter, if more than 2 parties are involved). [1] https://news.ycombinator.com/item?id=7862412 https://news.ycombinator.com/item?id=7862412