By NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans [Public domain], via Wikimedia Commons
Speed of light 300,000,000 meters per second
Circurference of the Earth is 40,000,000 meters
Half way around the earth is 20,000 meters
Time to transmit to the most distant place on earth is 20,000 / 300,000,000 is 0.067 milli seconds
A geostationary orbit, often referred to as a geosynchronous equatorial orbit (GEO), is a circular geosynchronous orbit 35,786 km (22,236 mi) above Earth's equator and following the direction of Earth's rotation.
35,786,000 meters up and down
35,786,000 x 2 / 300,000,000 is 0.239 seconds
This delay presents problems for latency-sensitive applications such as voice communication.
By Cmglee, Geo Swan [CC BY-SA 3.0 or GFDL], from Wikimedia Commons
Glenn Lyons VK4PK
Ver:gnl20182018 - pre published v0.9