Slipstream space

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The UNSC Infinity entering slipspace around Earth.

Slipstream space,[1] colloquially known as slipspace,[2] or the Slipstream[3] and formally known as Shaw-Fujikawa space[4] or subspace[5] by the United Nations Space Command, is a dimensional subdomain[6] of alternate spacetime consisting of eleven non-visible infinitesimal dimensions used for faster-than-light travel.[7][8] Making a transition from one place to another via slipspace is known as a "slip", or "jump". A device which allows a spacecraft to perform slipspace transitions is generally referred to as a slipspace drive.


The Covenant Fleet of Particular Justice coming out of slipspace.

Slipstream space is a specific set of eleven "nondimensions" existing in a very small bundle "above" the one temporal and three spatial dimensions perceptible to human beings.[7][9][10] By moving matter from the three space dimensions and one time dimension of normal space to slipstream space, one effectively changes the laws of physics for that piece of matter. This allows faster-than-light travel without relativistic side-effects i.e., the occupants do not "warp" time, despite their superluminal speed.

In the year 2291, physicists Tobias Shaw and Wallace Fujikawa were the first humans to successfully implement a device that could safely transition normal matter in and out of slipstream space, the Shaw-Fujikawa Translight Engine. This enabled humanity to begin colonial expansion beyond their home system.

The Covenant utilizes the same eleven dimensions of slipstream space for travel, though the means they use to make the transition are more sophisticated than those used by humans, as evidenced by their markedly faster journeys from point to point.

The Forerunners had a far greater understanding of slipstream space, with the abilities to travel nearly instantaneously over galactic distances, transport massive objects through the use of portals, to disrupt slipstream travel from normal space and track slipspace jumps across the galaxy. In addition, they had developed a great variety of other applications, often involving the manipulation of time and space within a slipspace field.


A Covenant assault carrier opens a slipspace vortex.

Slipspace is a tangle of intertwined non-spatial dimensions,[9][11][12] comparably similar to a wadded up piece of paper; rather like taking the classic "flat sheet" used to represent gravity and crumpling it up into a ball, thereby creating extra dimensions and shorter spaces between points.[13] Our plane of existence is thought to have four dimensions (up-down, front-back, side-to-side and time), but slipspace is an eleven-dimensional spacetime. Slipspace is entwined with the physical universe to the extent that phenomena in one realm can affect the other, and with sufficiently sophisticated equipment, transitions between the two forms of spacetime are possible.[7] Slipspace is not the only such alternate realm: others include denial of locale, natal void, shunspace, trick geodetics and a photon-only realm known as the Glow, all of which were once discovered and studied by the Forerunners.[8]

Described as non-Euclidean and non-Einsteinian,[14] the slipstream possesses markedly different laws of physics than "normal" space.[15] Due to its different laws of physics, times, masses, positions or velocities in slipspace are impossible to accurately measure based on the standards of normal space.[3] Although they are often used in colloquial contexts, the conventional notions of acceleration, velocity, distance, and time are technically meaningless within slipspace.[16] Even the name "slipspace" is technically a misnomer because the subdomain is non-spatial.[11][12][14] Ordinary matter cannot exist in the raw slipstream without being torn apart; ships traveling in slipspace are shielded by carefully-tuned quantum fields which wrap them in envelopes of normal space. Any construction in slipspace itself would have to be composed of specialized forms of exotic matter.[10]

Slipspace is not completely empty; clouds of primordial atomic hydrogen are relatively frequent. Occasionally, even comets are known to somehow find their way into slipspace.[3] Objects close to one another such as fleets often group together in mass slipspace transit and may appear to sensors as a large, singular object.[17] Objects in normal space are intangible in slipspace: an object in slipspace can pass through a mass, such as a planet, without causing a collision in normal space; such an event may often go completely unnoticed.[17] However, there may be risks involved if a ship is still early in slipspace transit and passes through a large object, such as another ship.[18]

Slipspace itself is nonvisible to the human eye, as there is nothing in the visible spectrum to see. To observers aboard spacecraft traveling through slipspace, this means that alternate domain appears pitch black.[2][19][Note 1] Slipspace-associated phenomena in normal space, such as the radiation from a slipspace transition, are most commonly luminous blue. In some cases (most prominently in teleportation) these effects may also appear yellow and orange.[20][21]

The curvature of spacetime inside slipspace is affected by the gravity wells of planets outside the slipstream, leading to the formation of transit points that allow for easier access into slipspace. These transit points link together to form slipspace "routes", providing faster and more optimal travel time than ordinary slipspace travel.[22] The Forerunners employed these navigation techniques heavily, in a process referred to as a "Rational Journey".[23]


Mantle's Approach emerges from slipspace, engulfed in an aura of causal reconciliation.

While faster-than-light travel is bound to generate chronological and causal paradoxes by nature, ships traveling through slipspace rely on a self-healing effect of space-time called reconciliation,[24] more formally known as causal reconciliation[25] or particle reconciliation,[26] to eliminate any paradoxes that may otherwise occur. The severity of this effect, which scales in a nonlinear fashion, is determined by the amount of discrepancy in information transfer between locations, as well as strain on the local space-time brane, as opposed to the apparent length of the voyage alone.[27] Mass, or size, is also a contributing factor, at least in the transport of abnormally large objects.[28][29]

The Forerunners were forced to place significant importance on this phenomenon due to their routine galactic-scale travel. For example, reconciliation has a limited range and time dilation effects may occur if a ship performs a very long jump.[26] The Forerunners prevented this by completing unusually long slipspace journeys in a number of individual jumps, allowing reconciliation to take effect between each.[30] Despite the limitations it placed on them, the Forerunners could also control reconciliation to an extent, enabling them to use its effects against their enemies, hampering and even cutting off their channels of slipspace travel.[31] Early on in their history, the Forerunners used time-phased mirrors to reconcile space-time on a large scale.[32] The Forerunners also employed the overwatch network to monitor interstellar traffic as to prevent the build up of reconciliation debt.[33]

Reconciliation has a "budget"—extensive slipspace travel exerts strain on space-time on a large scale as causal paradoxes accrue a "debt". When these aftereffects build up, it can impede with, or in extreme cases, entirely halt other superluminal traffic and communication. Slipspace returns to its normal state as reconciliations are allowed to take effect, gradually causing the space-time debt to disappear into the quantum background.[30][34] This effect is noticeable if large amounts of mass are transported over long distances frequently, slowing down slipspace travel throughout the galaxy and requiring ships to perform more individual jumps during a journey.[35] This was seen when Master Builder Faber used slipspace portals to transport the Halos,[29] or when the Audacity traveled to the Large Magellanic Cloud.[30] The latter voyage demonstrates the nonlinear scaling of reconciliation: although physically shorter than the trip to the Arks, for example, the other factors involved led to the journey being the most challenging one in the Forerunners' recent memory.[27] Elaborate slipspace traffic management by the ecumene's overwatch network authorities never fully mitigated the effects of their civilization's abuse of slipspace, which restricted their military options during the early years of the Forerunner-Flood war.[34] Personal slipspace units were banned except by special license of the Ecumene Council because billions of souls regularly using personal transports across four million worlds would create such an immense buildup of reconciliation that it would've been impossible and highly dangerous for any other space travel to occur.[36]

The effect of reconciliation works both forward and backward in the linear time of our universe: by the final weeks of the Forerunner-Flood war, slipspace had already stabilized almost completely due to the galaxy-wide cessation of slipspace travel which would shortly follow with the activation of the Halo Array.[37]

Reconciliation is briefly experienced once a ship returns to normal space, and manifests as a shimmering blue glow radiating out of the ship[38] and static electricity building up in the occupants' bodies;[25] on extremely long jumps or in strained slipspace, the effects experienced by the occupants may by significantly more severe.[25] With Forerunner ships, the effects of reconciliation are clearly noticeable for several seconds after a ship exits slipspace.[39][Note 2]

Because of modern-day humanity's inferior grasp of reconciliation technology, the time slipspace travel takes to normal-space observers varies substantially; one cannot depend on the same amount of time passing in slipstream space and normal space. With human slipspace travel, there is generally a five- to ten-percent variance in travel times between stars. A fleet that transitions to slipstream space at the same time may or may not transition back to normal space at the same time. Furthermore, if ship 'A' and ship 'B' both were to enter slipstream space at the same time and exit at the same time, the crew on ship 'A' could have experienced a longer journey subjectively, and the crew of ship 'A' could be a week older than that of ship 'B' despite appearances in normal space. Though no human scientist is sure why travel time between stars is not constant, many theorize that there are "eddies" or "currents" within the slipstream. This temporal inconsistency has given military tacticians and strategists fits, hampering an uncounted number of coordinated attacks.[40]

Compared to that of the Forerunner era, the overall level of reconciliation debt in the modern day is low. This is largely due to the significantly smaller amount of slipspace traffic compared to what was demanded by the Forerunners. However, this decreased slipspace usage is partially offset by the comparatively crude slipspace travel technologies used by modern civilizations, remaining anomalous disturbances in slipspace's dimensional manifolds caused by the activation of the Halo Array, and the inefficient use of surviving Forerunner transportation systems.[34]

Drive operation[edit]

A sequence of stills of the UNSC Pillar of Autumn exiting slipspace near Installation 04.

The Shaw-Fujikawa Translight Engine generates a resonance field, which when coupled with the unusual physics of the slipstream, allows for dramatically shorter transit times between stars. UNSC slipspace drives use particle accelerators to rip apart normal space-time by generating micro black holes. These holes are evaporated via Hawking radiation in nanoseconds. The real quantum mechanical marvel of the drive lies in how it manipulates these holes in space-time, squeezing vessels weighing thousands of tons into slipspace.[6] The Shaw-Fujikawa Translight Engine itself provides no actual motive power outside slipspace, and ships equipped with such a device still require conventional engines for sublight travel.[41]

Starships and their occupants are not directly exposed to the eleven-dimensional spacetime while moving through slipspace; instead, the ship is enveloped in a quantum field generated by the drive. The field acts as a medium between the ship and the higher dimensions, translating its presence as a normal-space object to the arcane physics of slipspace and enabling it to "squeeze through" the higher dimensions.[42] This field requires an enormous amount of constant calculations to maintain, with the number of needed calculations increasing with the size of the ship. For example, the slipspace translations for a Phoenix-class colony ship require 4.3 quadrillion calculations of the quantum field per second.[43] The vessel's mass is a noted consideration in the generation of this "buffer" as well as the energy expenditure of the drive in general.[27]

Before jumping into slipspace, human ships must first reach a Safe Slipspace Entry Point, or SSEP, where it can be ensured they will not drag anything from normal space into the slipstream as the ship initiates the transition.[44] In addition, star systems have specific slipstream space transfer points known as "interstellar jump points", or IJPs, locations designated ideal for initiating a slipspace transition.[45]

The Covenant have a very finely tuned version of slipspace technology, far superior to the human Shaw-Fujikawa Translight Engine. Instead of simply tearing a hole into slipspace, Covenant slipspace drives cut a very fine hole in the fabric of space-time and slips into slipspace with precision, much like a scalpel compared to a butcher knife. It exits with the same pinpoint accuracy, takes less time during travel, and is able to plot a course with error not exceeding an atom. This is why in battle Covenant ships are able to slip by human defenses by using slipspace.[46] It has also been theorized by the UNSC that Covenant drives generate several 'microjumps' within a single slipspace transition to measure dilation, allowing them to reach their destinations faster.[47] Standard Covenant tactics include using short slipstream jumps to gain positional advantage and surprise other ships, in addition to avoiding incoming ordnance. The Covenant's superiority in drive technology, combined with differing weapon and shield technology, allows a small number of Covenant ships to effectively engage a much larger UNSC force. Missiles, especially, can be defeated by a brief slipstream jump, as they cannot track through slipstream space.

The Forerunners' advanced slipspace technology allowed them to perform smooth and ultraprecise transitions, enabling ships to reach their destinations with superior velocities, unerring accuracy and without the temporal anomalies commonly experienced by human ships.[48] The restrictions on Forerunner slipspace travel had less to do with technology and more with the inherent nature of space-time which limited their slipspace travel by forcing them to take into account the effects of reconciliation and the overall space-time debt it accumulated.[30] Forerunner slipspace drives used a form of crystal to control and stabilize their slipspace passages; forgoing these crystals would force them into much more chaotic and unpredictable transitions.[49] The Slipspace flake utilised in Forerunner drives reduced travel times by considerable amount over the crude alternatives developed by both Humanity and the Covenant.[50]

Navigation and precision[edit]

The plotting of slipspace jumps is known as astrogation, and is typically performed by a navigation computer or an AI,[51] although humans are capable of conducting at least some of the calculations involved.[52] The trajectory of a slipspace jump is already determined by the time the ship enters slipspace; thus, pursuing ships are able to follow the ship which made the transition. This also enables the pursuers, provided they are equipped with superior drives, to overtake the ship they were following through "slipspace supersession"; this occurred when the Covenant Fleet of Particular Justice followed UNSC Pillar of Autumn to Installation 04, allowing the Covenant ships to arrive long before the human vessel.[53]

In addition to having to deal with temporal anomalies, UNSC ships are not able to jump with exact precision. A ship may transition back to normal space millions of kilometers from its intended destination.[54] As a result, UNSC ships often transition in and out of slipspace far from any gravity well of celestial bodies. In-system jumps are also generally considered impractical, even dangerous, by the UNSC due to this lack of precision.[55] A notable exception of this is during the Battle of Psi Serpentis, when the Battle Group India, under command of Admiral Preston Cole, performed an in-system jump. Even though Cole had made thorough calculations for the jump a week in advance and guidance beacons were used as navigational assists, a part of the battle group scattered, reappearing outside the main group.[56]

The Gravemind was able to use the UNSC In Amber Clad to make a successful precision jump into High Charity. This may be due to an improvement on the ship due to the recent capture of Covenant Slipspace technology, the Gravemind adjusting it or possibly using Installation 05's teleportation grid or related systems to move the ship.[57] Cortana was able to jump the Covenant flagship Ascendant Justice into slipspace inside the atmosphere of the gas giant Threshold following the Battle of Installation 04, a feat previously thought impossible even by the Covenant.[58] Following the Human-Covenant War, a number of UNSC ships, such as the UNSC Infinity, have been fitted with Forerunner drive technology, granting them near-perfect jump accuracy in addition to far greater velocities.[48]

The Covenant employ a device known as a kelguid to plot slipspace, reverse-engineered from similar Forerunner equivalents. Covenant kelguid's visualise slipspace as appearing like a "dinner of spaghetti and meatballs that had entered zero-g and floated up off the plate". In this visualisation, the "spagehetti" represents the curvature of space-time and the "meatballs" represent gravity wells of various sizes. Where the "spaghetti" bends so tightly as to touch itself, this creates a connection point that can be employed as a transit node by a suitable vessel.[22]

As a testament to the Forerunner's understanding of slipspace, Installation 00, located far distant from the galaxy itself, is able to locate vessels within the galaxy and spontaneously open precision slipspace portals between itself and locations in the galaxy. The UNSC Spirit of Fire was drawn to Installation 00 in such a manner after drifting in space for 28 years without a slipspace drive.[59]

Gravitational effects[edit]

Although they are not present as tangible objects within slipspace, the gravitational pull of large masses, such as stars, affects the geometric trajectory of objects traveling in slipspace much like it would in normal space. This effect typically distorts and scatters clouds of dust drifting in the Slipstream.[17]

Gravitational fields of significant size, such as those generated by a planet, affect the superfine quantum filaments that a slipspace drive must use to calculate an entry point to the slipstream, and UNSC calculations are unable to offset this effect.[60] Covenant drives, in turn derived from Forerunner technology, have a much higher resolution of the filaments, and use more accurate calculations, and though the Covenant do not use this ability, are capable of making slipstream transition in and out of a planet's gravity well. Indeed, while using the captured Ascendant Justice to make a slipspace jump within Threshold's atmosphere, Cortana remarked that "It was as if she was blind before."[60] After observing this innovation, a Covenant AI managed to leak the data out to the rest of the Covenant in a transmission. During the Battle of Mombasa, the Prophet of Regret used this newfound knowledge to transition into slipspace while directly over New Mombasa in Earth's gravity well, damaging the city and causing the weakening and eventual collapse of the orbital elevator there.[61] These events show that, while the Covenant often cannot innovate their own solutions, they are quick to adopt any practice that increases their combat prowess.

The effect of a gravity well on the curvature of space-time inside slipspace often allows for the right conditions to form to allow for the formation of a transit point, allowing easier access to slipspace than may otherwise be possible.[22]


A Forerunner slipspace portal.

The mechanics of the slipspace drive and the way it manipulates the slipspace field have an effect on the time it takes for a ship to cross distances, with more sophisticated drive technology allowing for various methods of crossing distances more efficiently.[46][47] The size of a ship's engines correlates with the velocity at which it traverses slipspace; ships with larger engines will move faster within the Slipstream.[62] Frequent traffic, especially when moving objects of considerable mass, will also slow slipspace traffic down on a galactic scale, although this is only known to have occurred when the Forerunners moved the Halo installations across the galaxy.[35]

However fast it may appear, human faster-than-light travel is by no means instantaneous; "short" jumps routinely take up to two months, and "long" jumps can last six months or more for the crew. Certain UNSC ships are known to be able to travel at a speed of 2.625 light years per day,[Note 3] while certain Covenant ships can reach speeds of more than 1,368 light years per day.[Note 4] After the end of the Human-Covenant War, the discovery and reverse-engineering of Forerunner technologies allowed humanity to achieve significantly greater velocities. By early 2553, the UNSC Port Stanley and UNSC Infinity had been equipped with upgraded drives which enabled them to cross interstellar distances in mere hours.[48][63] More efficient routes can be discovered over time. The earliest slipspace routes required over a year of travel to cover the twelve light-year distance from Earth to Harvest, while modern ones have it down to weeks.[64]

Further complicating matters is that transit times between different star systems are not consistent. While Epsilon Indi is only approximately 12 lightyears from Earth, and 83.3 lightyears from 23 Librae, Madrigal is described as the "closest" colony to Harvest, at only a few weeks transit time for a pre-war human freighter, as opposed to just over two months to the much closer Epsilon Eridani system which lies only 14 lightyears from Epsilon Indi. The military starship UNSC Spirit of Fire took only three days to reach Arcadia from Harvest, a star system 11.488 lightyears from Epsilon Eridani.[65] These discrepancies are due to the fact the internal topology of slipstream space differs from that of normal space in certain areas, sometimes resulting in major inconsistencies in the distances traveled.[27]

One example of the differences between speeds is comparing the Covenant carrier Ascendant Justice with the UNSC Halcyon-class light cruiser UNSC Pillar of Autumn. It took 21 days (3 weeks) for the Pillar of Autumn to get from Reach to Installation 04, yet the Ascendant Justice could get from Installation 04 to Reach within thirteen hours from the occupants' frame of reference. However, this may have been due to the influence of the Forerunner crystal, which simultaneously caused the Ascendant Justice to go back in time for several days as a result of its occupants being on an event path intersecting the crystal.[66]

Though the Covenant use a modified version of Forerunner systems, true unaltered Forerunner slipspace technology was first observed in the form of the Portal transporting UNSC and Covenant vessels from Earth to the Ark, transporting them hundreds of thousands of light years in 23 days, which equates to approximately 11,400 light years per day.[Note 5] However, Forerunner slipspace portals were capable of much greater velocities as proven in 2555 when a task force was sent to the Ark to attempt to stop another activation of the Halo Array. After the portal at Voi was reactivated the team traveled through it, a journey that should have taken weeks with the Covenant slipspace drive only took a matter of hours. This is because the Ark's energy conduits that powered the portal's slipspace drive systems were generating much more than they were designed for which allowed the Covenant corvette to travel tens of thousands of light years per hour.[67]

Dangers and risks[edit]

Solemn Penance entering Slipspace over New Mombasa.

Direct exposure to the slipstream is incredibly dangerous. Despite the presence of a quantum field which effectively keeps the ship within a "bubble" of normal space,[42] people traveling on a slipspace-capable craft can experience a range of symptoms, from nausea, to heart failure or even death. It is also known that some people react to slipspace jumps stronger than others.[68] Even more uncommon, but still known to happen, is the total disappearance of a person while in the slipstream.[69]

Slipspace travel is also dangerous due to the high level of radiation encountered during the trip, which can be extremely hazardous to the crew. This is negated by the use of lead foil in UNSC ships, which absorbs the radiation. Fissile materials also emit radiation, specifically Čerenkov radiation, upon exiting slipspace; this is not harmful to humans, however it does make emerging from slipspace very noticeable. It is not known how the Covenant deal with radiation, but it is presumed that either they also utilize a shielding material, or with their improved slipspace technology and energy shielding, it does not affect them at all.[70] In addition, slipspace travel generates a great deal of static electricity on the ship's hull. To discharge the static energy, humans have developed a piezoelectric material known as polymerized lithium niobocene.[71]

Since the slipstream is constantly shifting, and its laws of physics are different to our own, the magnetic coils of slipspace drives drift out of phase when entering and leaving a slipspace field, requiring constant maintenance. During the 2490's, technicians had to manually repair slipspace drives, exposing themselves to the Slipstream and occasionally suffering injury, death, or simply disappearing.[72] Mechanical failures like Slip Termination, Preventable, or STP, can also occur with slipspace drives, usually resulting from poor maintenance.[73][23] An improperly mounted slipspace drive can also result in catastrophic accidents, as was the case with a colony ship en route to the Cygnus system in the mid-2550s: as a result of a maintenance failure, the drive tore the ship apart, transporting half of it into an unknown location. During the Fall of Reach, the UNSC intentionally recreated the conditions of this accident to destroy the Covenant Sh'wada-pattern supercarrier Long Night of Solace.[74]

Regret's jump into slipspace from a mere several kilometers above Earth's surface inflicted enormous damage on New Mombasa.

Prior to 2552, entering slipspace from the gravity well of a planet had never been attempted, either by the UNSC or the Covenant. The effect of gravity upon the creation of a slipspace entrance usually collapsed UNSC-generated holes, and was assumed to be the same with Covenant technology. The flagship Ascendant Justice, however, was able to escape from a gas giant's gravity well after Cortana realized that it had a far higher resolution of the quantum filaments that allowed a transition, and she was able to compensate for the gravity. Subsequently, the ability was transmitted by a Covenant AI, and the Prophet of Regret used an in-atmosphere slipspace jump to escape Earth, with the resulting shockwave dealing devastating damage to the city of New Mombasa. Slipspace jumping inside an atmosphere, however, is extremely dangerous to the surrounding people and objects. When a ship transitions into normal space in-atmosphere, the air that was there is pushed aside, causing a massive shockwave centered at the ship. If a ship transitions to Slipstream space inside an atmosphere, on the other hand, it leaves an empty space that air quickly rushes to fill, causing an implosion. An in-atmosphere jump is also known to cause prominent meteorological aftereffects; the air becomes saturated in an electric blue haze and luminescent clouds emanating from the point of the transition for nearly half an hour.[75] Exiting slipspace in-atmosphere is generally far less destructive than entering it, as ships have done so numerous times without disastrous effects.

Entering and exiting the slipstream is normally only attempted by ships of large mass, their gravity wells stabilizing the constantly fluctuating slipspace to a degree that allows safe passage.[76] Small ships, such as dropships, do not possess the same gravity and are placed under considerably more stress than a warship, able to crack the hull and buckle reinforcing struts.[77] It is not impossible, and UNSC slipstream monitoring probes make the transitions all the time, but require heavy reinforcement to survive the stresses, and are unmanned, having no need to protect internal occupants.[76] Specialized craft like Long range stealth orbital drop pods can make the transition, but are still an extremely uncomfortable ride.[70] A Slipspace-to-normal space transition has been successfully attempted by a Spirit dropship, but it had been extensively equipped with Titanium-A battleplates, lead, and carbon-molybdenum steel I-beams.

Even the Forerunners had potential dangers when traveling through slipspace. During the assault on the Capital by Mendicant Bias, seven of the twelve original Halo rings in existence at the time attempted to flee using a slipspace portal. Only one of them, along with Bornstellar Makes Eternal Lasting's ship made it through. The rest were destroyed when the slipspace portal closed due to the stress of the Halo installations passing through. The enormous amount of mass passing through simultaneously also put massive strain on the slipspace portal, causing any occupants to be dangerously exposed to the foreign physics of slipspace. This resulted in causal reconciliation effects far more severe than normal, as well as symptoms involving the loss of perception of reality and time, massive amounts of electrical charge, even depriving the occupants of solidity for a time.[25] After such an event, a slipspace channel may not return to a stable state for years.[78] In situations where reconciliation debt is extreme, there can be devastating consequences for those traversing slipspace, including the creation of reference-frame anomalies and the erosion of ships and the crew within them across multiple dimensions.[34]

There are also realms of slipspace distinct from the one typically used for travel. A spacetime-manipulating crystal found on Reach caused the UNSC-captured Ascendant Justice and the Covenant ships which pursued it to enter an anomalous slipspace dimension different from the normal slipspace used for travel.

Slipspace wake[edit]

A "Slipspace wake" is a phenomenon occurring for some time after a ship has made a slipspace transition. When another, slower ship encounters a slipspace wake, they will be pushed to the speed of the ship that left the wake, thus propelling them through Slipspace at the same velocity. The UNSC Dusk took two weeks to get to Installation 05 via the Solemn Penance's weakening "wake",[79] but came back to Earth within hours by following the Forerunner Dreadnought's wake.[Note 6] The crew of the Dusk later exploited the Bloodied Spirit's outbound wake to get to Onyx, thirty-eight light years away, within an hour.


Main article: Slipspace anomaly

In rare cases, various types of anomalous phenomena occur in slipspace. These may be caused by specific artifacts or devices. The effects of these anomalies are diverse, but often harmful. The Forerunner crystal found on Reach was capable of creating a distortion in Slipspace, but it also generated massive amounts of radiation. In November 2552, the slipspace transition of the Forerunner Dreadnought caused an anomaly within the dimension YED-4.[80]



Main article: Superluminal communications

Slipspace has been used as the basis for some (although not all) forms of faster-than-light communications system, enabling communication across the vast distances of space in reasonable timescales. First utilized by the Forerunners, such technologies were later appropriated for use by the modern civilizations of the Covenant and humanity. Communications can be routed through slipspace through "Wavespace", layers of slipspace with proximate terminations.[23][81]


John-117 translocating via Installation 04's teleportation grid.
Main article: Slipspace translocation

Slipspace can also serve as means of virtually instantaneous transport over short distances. Originally developed by the Forerunners, Slipspace translocation technology allows its user to safely pass between two locations by enveloping the user in a Slipspace field and transporting them to the intended destination.[82] The Forerunners utilized this technology to a great effect, using it in teleportation grids and transportation pads encountered on many of their installations. Forerunners utilised unmediated slipspace cores in translocation grids that were able to generate stable slipspace pathways across installations that sacrificed the flexibility of destination for security, speed, and safety.[50] Later, the Covenant also adopted this technology and are known to have used it in their gravity thrones and spires.

AI housing[edit]

A possible application of slipspace is the use of its eleven-dimensional spacetime as a platform for abstract fractal housing and processing structures for "smart" artificial intelligence constructs. The extra dimensions would grant AIs faster-than-light processing speeds but more importantly, it would give unlimited room for extended neural linkages—by extension, making the AI virtually immortal, free from the limitations of a Riemann matrix, which normally cause a smart AI to descend to rampancy. So far, this has only been attempted once, by Dr. Catherine Halsey in an unsanctioned experiment in 2547. Though the experiment was a failure, the AIs of the Assembly recognized it as a viable means of gaining permanent independence from their creators.[10][83]

Forerunner applications[edit]

The Forerunners had developed a great deal of applications for the slipstream. These included the ability to create bubble-like enclosures of slipstream space, in which the flow of time could be manipulated or stopped altogether while keeping the contents of the bubble either visible or invisible in normal space. The Forerunners were also capable of containing these bubbles of alternate space-time within one another.[84] These bubbles could be used to store considerable masses and volumes in slipspace stably for thousands of years and potentially for all of time, and to transition matter from normal space to the inside of a construct in slipstream space without requiring the construct to transition back to normal space. The same technology was utilized in slipspace field pods that were essentially a Forerunner equivalent of cryo-chambers, effectively preserving a living organism inside a slipspace field. Slipspace bubbles were also employed in a type of Forerunner prison cell in which the passage of time could be manipulated so that a period of a billion years would pass inside the field, while only seconds had transpired in normal space.[85]

In addition, the Forerunners had the ability to construct weapon systems that could fire into slipspace and affect targets in normal space or within slipspace. This is demonstrated by the Line installations of the Jat-Krula boundary, which were capable of intercepting ships in slipspace.[86] In its final battle against Mendicant Bias, the Forerunner AI Offensive Bias used slipspace ruptures generated by its warships to warp the laws of physics around them and tear Mendicant's ships apart.[87] The Mantle's Approach employed a weapon of the Didact's imagining known as a stasis tension driver, which paired quantum singularity projectors with repurposed torsion drivers, allowing the weapon to create localised space-time distortions that impeded the formation of slipspace ruptures and jammed all superluminal communications.[88]

Slipspace portals created by the Forerunners could be used to send objects into slipspace and have them exit in different locations.[89] The Forerunners were also capable of generating slipspace conduits which could anchor objects in normal space into place, as shown when the UNSC Infinity was constrained over Requiem by an array of slipspace artifacts.[90]

Production notes[edit]

Slipspace fills a common niche found in most space science fiction media, allowing ships to travel vast distances in a small amount of time, allowing convenient travel through the galaxy. Though other series use different methods, it is most similar to hyperdrives, which similarly burrow into other dimensions where faster than light (FTL) travel without the relativistic side-effects is possible. Other series use different methods, allowing actual FTL travel in normal space, or instantaneous teleportation, but the principles still follow a similar trend.

Slipspace can be likened to the discovery of matterwave transport without transit. In this process, all seven hidden spatial dimensions, three known spatial dimensions and two time dimensions appear to collapse into a singularity to an outside observer. But in reality, this is only an illusion. In this type of field, relativity predominates, for instance the reality is dependent on the radial displacement from the source that generates the field. At small distances, reality is relatively intact. The further away from the field source, the less sense it makes to talk about reality; a cause can occur after an effect, time has no linear flow. Nothing has a definite momentum or velocity. Objects can occur at multiple positions simultaneously. When an object enters a field, it produces a burst of neutrinos, antimatter and other types of radiation. Slipspace is also similar to a controversial theory known as the Heim Theory.


List of appearances[edit]


  1. ^ While all descriptions in written works maintain slipspace is pitch black, all depictions in visual media diverge from this. Halo Wars: Genesis depicts slipspace as resembling purplish nebulae. Halo: Fall of Reach - Boot Camp depicts it as a bluish-white tunnel of lines and quadrilateral figures. Halo 4 depicts it as a prismatic, though largely blue-shifted expanse. In Halo: Nightfall it appears as a blue-white tunnel. These are artistic liberties for the sake of presentation.
  2. ^ Pre-Halo 4 media do not depict the telltale shimmer and distortion surrounding ships undergoing particle reconciliation. While the Doylist explanation is simply that the concept had not been added to the setting at the time, this may also have canonical implications. One may infer that reconciliation debt became a comparative non-issue after the time of the Forerunners; to wit, the spacefaring civilizations of the 26th century have fewer slipspace-capable vessels and other constructs than the Forerunners by several orders of magnitude. Despite this, several Covenant light cruisers are seen experiencing causal reconciliation in Halo 4's campaign as they enter Requiem's core, though this may be a result of entering Requiem's core, due to the nature of Requiem itself; later, the Didact's flagship is seen experiencing reconciliation, as are the Covenant dropships that have been traveling through slipspace under the larger ship's power. Strangely, UNSC Infinity is never seen experiencing this effect in Halo 4 or in any subsequent works, despite greatly outmassing all known human and Covenant vessels with perhaps one exception. As even the UNSC Infinity and most Covenant ships are dwarfed by the size and mass of Forerunner vessels, this may be due to the lesser impact they have on Slipspace. Additionally, while UNSC ships "punch a hole" in Slipspace, Covenant ships execute a series of micro-jumps, but neither method is fully on-par with Forerunner slipspace travel's efficiency and speed; because of the relatively lesser impact, even including the UNSC's method of entering slipspace, UNSC and Covenant vessels may not create the level of disruption that Forerunner vessels did.
  3. ^ In Halo: First Strike, Lieutenant Wagner's prowler traveled from Reach to Earth—a distance of 10.5 light years—in four days. Velocity=Distance/time (V=10.5 light years/4 days=2.625 l/d)
  4. ^ In Halo: Ghosts of Onyx, the Covenant destroyer Bloodied Spirit travels from Earth to Onyx within less than 40 minutes. The distance from Sol to Zeta Doradus is 38 light years. Velocity=Distance/time (V=38 light years/40 minutes=57 l/h or at least 1,368 ly/d)
  5. ^ The Sol system is located between 25,000 and 28,000 lightyears from the galactic centre, while the Ark is 218 ly from it (262,096 ly). If the Earth was at its nearest to the Ark (that is, 28,000ly away from the centre and on the Ark's side of the galaxy), it would be 234,096ly away - at its furthest it would be 290,096ly away. 234,096/23 days= 10,178 ly/day and 290,096/23 days= 12,613 ly/day which equals to 11,395.5 ly/d in between. It should be noted that the Ark had been used by the Forerunner Dreadnought shortly beforehand; its wake could exaggerate the velocities within the slipspace portal.
  6. ^ It is never directly stated that the wake the Dusk followed was left by the Forerunner Dreadnought; however, it is implied on page 289: "The Dusk's journey back to Earth had occurred in record time. They had caught a wake in slipstream space, one indeterminably larger than the Covenant wake they had followed." This creates an inconsistency with later canon, such as this timeline, which reveals that the Dreadnought took five days to reach the Sol system and another nine days to reach Earth, instead of a few hours. Therefore, the Dusk's speedy return to Earth may have been the result of a Slipspace anomaly. Indeed, Incorruptible's navigation officer Zasses 'Jeqkogoee notes the presence of anomalies within the dimension YED-4 around the timeframe of the Dreadnought's transition.


  1. ^ Halo: The Fall of Reach, p. 13
  2. ^ a b Halo: The Fall of Reach, p. 15 (2001)
  3. ^ a b c Halo: The Fall of Reach, p. 136 (2001)
  4. ^ Halo: The Fall of Reach, p. 141 (2001)
  5. ^ Halo: Combat Evolved, campaign level The Pillar of Autumn: opening cinematic
  6. ^ a b Halo: Ghosts of Onyx, p. 53
  7. ^ a b c Halo: First Strike, p. 87 (2003)
  8. ^ a b Halo: Cryptum, p. 100
  9. ^ a b Halo: Ghosts of Onyx, p. 186
  10. ^ a b c Halo: Reach, Dr. Halsey's personal journal
  11. ^ a b Halo: First Strike, p. 211 (2003)
  12. ^ a b Halo: First Strike, p. 338 (2003)
  13. ^ Halo: First Strike, p. 216 (2003)
  14. ^ a b Halo: First Strike, p. 191 (2003)
  15. ^ Halo: Ghosts of Onyx, p. 55
  16. ^ Halo: First Strike, p. 152 (2003)
  17. ^ a b c Halo: the Fall of Reach, p. 137
  18. ^ Halo: Cryptum, p. 99
  19. ^ Halo: Ghosts of Onyx, p. 288
  20. ^ Halo: Combat Evolved, campaign level Two Betrayals
  21. ^ Halo 4, campaign level Midnight
  22. ^ a b c Halo: Silent Storm, chapter 22
  23. ^ a b c Halo: Warfleet, Glossary - p.90-92
  24. ^ Halo: Silentium, p. 62
  25. ^ a b c d Halo: Cryptum, page 322
  26. ^ a b Halo: Cryptum, page 135
  27. ^ a b c d Halo Waypoint: Catalog Interaction (post 2969317)
  28. ^ Halo: Silentium, page 91
  29. ^ a b Halo: Cryptum, page 223
  30. ^ a b c d Halo: Silentium, pages 60-61
  31. ^ Halo: Primordium, page 240
  32. ^ Halo: Silentium, pages 110-111
  33. ^ Halo: Warfleet - Page 91
  34. ^ a b c d Halo Encyclopedia (2022 edition), page 339
  35. ^ a b Halo: Cryptum, p. 266
  36. ^ Halo: Point of Light, chapter 19
  37. ^ Halo: Silentium, p. 301
  38. ^ Halo: Cryptum, page 312
  39. ^ Halo: Cryptum, p. 100, 135, 266
  40. ^ - Halo Timeline
  41. ^ Halo: Contact Harvest, chapter 1
  42. ^ a b Dr. Halsey's personal journal, December 25, 2534
  43. ^ Halo Wars: Genesis
  44. ^ Halo: Contact Harvest, p. 34
  45. ^, Halo: Reach Project Page (Retrieved on Jun 1, 2020) [archive]
  46. ^ a b Halo: First Strike, p. 86
  47. ^ a b Halo: First Strike (2010), Tug o' War
  48. ^ a b c Halo: The Thursday War, page 247
  49. ^ Halo: Silentium, p. 105
  50. ^ a b Halo: Warfleet, p.11
  51. ^ Halo: Contact Harvest, p. 96
  52. ^ Halo: Evolutions - Essential Tales of the Halo Universe, The Impossible Life and the Possible Death of Preston J. Cole, p. 426
  53. ^ Halo: The Flood (2010), Priority Broadcast Log/Eleventh Cycle, Third Unit
  54. ^ Halo: The Fall of Reach, p. 136
  55. ^ Halo: The Fall of Reach, p. 104
  56. ^ Halo: Evolutions - Essential Tales of the Halo Universe, The Impossible Life and the Possible Death of Preston J. Cole, p. 477
  57. ^ Halo 2, campaign level Gravemind
  58. ^ Halo: First Strike, p. 80, 87
  59. ^ Halo Wars 2, campaign level The Signal
  60. ^ a b Halo: First Strike, p. 85
  61. ^ Halo 2, campaign level Metropolis
  62. ^ Halo: Ghosts of Onyx, p. 187
  63. ^ Halo: Glasslands, p. 68
  64. ^ Halo: Warfleet, p.86-87
  65. ^ Halo Wars
  66. ^ Halo: First Strike, p. 247-248 (2003 edition)
  67. ^ Halo: Hunters in the Dark, p. 347
  68. ^ Halo: Glasslands, p. 84, 87
  69. ^ Halo: Contact Harvest, p. 175
  70. ^ a b Halo: Ghosts of Onyx, p. 13
  71. ^ Dr. Halsey's personal journal, July 30, 2511
  72. ^ Halo: Ghosts of Onyx, p 146
  73. ^ Halo: Contact Harvest, p. 24
  74. ^ Halo: Reach, campaign level Long Night of Solace
  75. ^ Halo 3: ODST, campaign level Tayari Plaza
  76. ^ a b Halo: First Strike, p. 289
  77. ^ Halo: First Strike, p. 296
  78. ^ Halo: Cryptum, p. 341
  79. ^ Halo: Ghosts of Onyx, Chapter 22, page 186
  80. ^ Halo: Ghosts of Onyx, p. 198-199
  81. ^ Halo Waypoint, The New Halo Encyclopedia is Out Today (Retrieved on Mar 11, 2023) [archive]
  82. ^ Halo: Ghosts of Onyx, p. 311-212
  83. ^ Halo: Reach, Data pad 17
  84. ^ Halo: Glasslands, p. 306, 311
  85. ^ Halo: Primordium, p. 366
  86. ^ Halo: Blood Line - Issue 1
  87. ^ Halo 3, Terminal 6
  88. ^ Halo: Warfleet, p.86-87
  89. ^ Halo Legends: Origins
  90. ^ Spartan Ops, S1E8 Expendable