The half-second lag
The half-second lag isn't for reaching geostationary and back; it's for reaching geostationary and back twice, which is what the signal has to do when you communicate with a second terrestrial station via the satellite.
If you had two people on different, non-cooperating satellite telephone services talking to each other then the lag would presumably be a whole second as the signal would have to make the 36000 km journey 8 times for you to get a response.


