# What defines the upper limit for speed of Subspace Communications?

Memory Alpha mentions there to be a definite upper limit as to the speed of Subspace Communications. Is the reason for this ever touched on in any of the Star Trek media (Canon or not) or is it "speed of plot"? This question would suggest speed of plot but I'm curious what would provide an upper limit if light doesn't?

• Assuming instantaneous communication, you would still have to account for processing capabilities of the endpoints. Otherwise you would overflow the recipient. Commented May 14, 2012 at 21:59

Using the period specified by Memory Alpha, the speed of subspace communications is estimated at Warp 9.999 by the 24th century. (Not quite the speed of plot, but definitely within the distance to allow a mission directive and an independent captain to make a decision without a being able to call for an update. He or she would be on their own...)

The only period I have metrics for the actual speed of a subspace communication is the 24th century when a communication between galaxies (the Milky Way and Andromeda) at 2,700,000 light years would take 51 years and ten months.

Using that metric, subspace communication speeds, assuming no degradation would be 52,123 times the speed of light. A speed so fast no Federation vessel could even come close to matching or sustaining for very long; the equivalent of warp 9.999.

But even at that speed, the distance between Earth and Alpha Centuari (a distance of 4 light years) would have a lag time of ten minutes! Perhaps in tightly populated areas the system of relaying would maintain signal speed only allowing the signal to become slower in areas without subspace relays. Sending a signal from one side of the galaxy (100,000 light years) to the other would take approximately 1.92 years.

Check out the graphic below:

Assuming a map with reliable coordinates, subspace relays and origin points, one could tell how fast each period's subspace comms traveled. It is safe to assume the technology grew progressively faster every century. Judging from the graph, subspace communications during the NX-01 would have been Warp 8 or so. During Kirk's time, Warp 9.6 might have been the average (far faster than the ships but still taking a four days to a week for most communications within 20 light years.)

It is also safe to assume, baring any reasonable disruption, ion storm, magnetic disturbance, solar flare, black hole or subspace anomaly, communications in any reasonably populated area of the Alpha quadrant can be considered near-real time by the 24th century. Only the farthest points in the Alpha Quadrant or communications with other Quadrants of the galaxy would have any significant delay.

• I'm not sure how this is supposed to make sense. With or without added relays, the fastest speed that data can travel over a given distance is governed by its initial transmission rate. If some transmission initially left Earth at Warp 9.999, then that's the fastest it will ever travel (and be readable in its original form) on its way to its destination. Any intervening "relays" could only serve as power boosters which would improve the signal quality, but not the actual speed - in fact, they would add lag to the transmission!
– Iszi
Commented May 16, 2012 at 12:38
• Considering how often something disrupts communication in the Alpha Quadrant, keeping a strong signal could be enough. Yes there would be some lag, but better a laggy signal than no signal at all. Commented May 16, 2012 at 14:05
• My point is that you're suggesting the boosters accelerate the signal, which is not something that they can do.
– Iszi
Commented May 16, 2012 at 14:07
• Noted. Damned magical technology of the Federation. Commented May 16, 2012 at 14:13
• @Iszi Warp speed is non-newtonian for ships (A object in motion requires constant energy to stay in motion). I believe it could be the same for communications. So while the signal may have been traveling at warp 9.999 when it left the transmitter it may be traveling at warp 9.9 or lower by the time it gets to the next relay station. Once it is received it is re-transmitted at 9.999 again. So to put it in modern terms: yes, you could not improve the Bits/sec of transfer at a relay station, but you could decrease the ping time. Commented Oct 19, 2013 at 8:26