Latency is time taken to travel the distance (between the client and server). Look at http://eyes.nasa.gov/dsn/dsn.html http://eyes.nasa.gov/dsn/dsn.html, for

Latency is time taken to travel the distance (between the client and server). Look at http://eyes.nasa.gov/dsn/dsn.html http://eyes.nasa.gov/dsn/dsn.html, for Voyager the latency would be 0.74 days. For the Mars Reconnaissance Orbiter it would be 6.6 minutes. Someday people might play live action video games with someone on Mars with very little latency, but right now it's not even theoretical without a wormhole through space/time.