Star Trek: What Is Subspace?

In the world of "Star Trek," just about every technology that makes Starfleet's explorations possible hinges on the existence of one discovery: subspace physics. An amorphous fictional construct dreamed up for the "Star Trek" universe that frequently gets thrown around in bridge crew and engineering technobabble, subspace is one of the most important concepts in the franchise. And even if it's not entirely clear how subspace works, it seems to function as a space between realities. Functionally speaking, subspace serves as a way to cheat spacetime physics and get around FTL limitations by exceeding warp speed — something that is explicitly noted in the 1967 third revision of the official Writers/Directors Guide for "Star Trek: The Original Series." According to the writers' guide, "We use the term 'subspace' since it is necessary that communications from the Enterprise to its bases are a 'space warp' effect which travels at speeds far exceeding even that of the Enterprise."

"The Original Series" contains quite a few references to subspace as it relates to communications. Uhura (Nichelle Nichols) regularly reports on her monitoring of subspace frequencies, and references to subspace chatter and messages come up from time to time among the bridge crew. The concept of subspace marriage — a 23rd-century take on mail-order brides — even plays a central role in the plot of "Mudd's Women." Through "Star Trek: The Next Generation" and later series, the concept of subspace gets expanded upon, evolving into a much more complex plane of existence with a lore all its own.

Moving forward to "Star Trek: The Next Generation," the franchise paints subspace as a strange variant of reality that's not quite space and not quite another plane of existence. In "Schisms," Geordi La Forge (Levar Burton) emphasizes that subspace has "an infinite number of domains," describing it as "a huge honeycomb with an endless number of cells." And the iconic episode "Remember Me" sees the ship's doctor Beverly Crusher (Gates McFadden) trapped in a subspace bubble where her thoughts create a rapidly collapsing universe.

Echoing the idea that reality and thought are somehow entwined in subspace in the "Star Trek: Voyager" episode "Cold Fire," an Ocampan named Tanis (Gary Graham) tells Kes of a subspace layer of "pure thought, pure energy." It's from this realm of subspace that the Caretaker and other members of the Nacene race originate. And they're not the only beings that hail from subspace. The "TNG" episode "Schisms" sees members of the Enterprise-D crew clandestinely abducted and experimented on — in one case fatally — by subspace-dwelling aliens with physiology based on solanogen, a compound that is only stable in subspace. 

Tetryons, a type of dangerous subatomic particle that cannot be tracked by ship sensors, also originate in subspace. When these particles end up in normal space, they become highly unstable and create tetryon radiation that can potentially be weaponized, as seen in the "Star Trek: Deep Space Nine" episodes "Blood Oath" and "Necessary Evil."

Whether or not subspace makes complete sense, it seems to be the oil that keeps the Federation running. According to "Star Trek: The Next Generation Technical Manual," a book developed with help from "Star Trek" writers," subspace technology is integral to Starfleet operations — particularly warp drive and interstellar communications. As outlined in the "TNG" writer's bible, by tapping into subspace and communicating via subspace radio waves, ships can connect almost instantly as long as both parties are within a "few dozen light years." Further transmissions can still be received within a matter of days in most cases.

The existence of subspace was also essential to Zefram Cochrane's early warp theory breakthroughs. According to the "TNG" technical manual, Cochrane's design works by creating and exerting force on nested warp field layers, a process that forces radiated energy into subspace and "facilitates the slippage of the spacecraft through the sequencing layers of warp field energy" (p. 54). The units of measurement used to calculate subspace field distortion and stress are millicochranes and cochranes.

Many — if not most — of the essential technologies aboard a Federation starship rely on subspace physics to operate. The ship's navigational deflector system uses subspace field distortion amplifiers and subspace field coils, and tractor beams rely on a subspace graviton force amplifier to impose spatial stress that locks onto their target. Torpedoes, tricorders, near-warp transport, sensor arrays — even Starfleet officers' comm badges and personal phasers work by tapping into subspace with their subspace transceiver assembly (STA) circuits.