Johannes Kepler was a German astronomer and astrologer. He is a key figure in the 17th-century scientific revolution, best known for his laws of planetary motion, his books Astronomia nova, Harmonices Mundi, Epitome Astronomiae Copernicanae; these works provided one of the foundations for Newton's theory of universal gravitation. Kepler was a mathematics teacher at a seminary school in Graz, where he became an associate of Prince Hans Ulrich von Eggenberg, he became an assistant to the astronomer Tycho Brahe in Prague, the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II. He taught mathematics in Linz, was an adviser to General Wallenstein. Additionally, he did fundamental work in the field of optics, invented an improved version of the refracting telescope, was mentioned in the telescopic discoveries of his contemporary Galileo Galilei, he was a corresponding member of the Accademia dei Lincei in Rome. Kepler lived in an era when there was no clear distinction between astronomy and astrology, but there was a strong division between astronomy and physics.
Kepler incorporated religious arguments and reasoning into his work, motivated by the religious conviction and belief that God had created the world according to an intelligible plan, accessible through the natural light of reason. Kepler described his new astronomy as "celestial physics", as "an excursion into Aristotle's Metaphysics", as "a supplement to Aristotle's On the Heavens", transforming the ancient tradition of physical cosmology by treating astronomy as part of a universal mathematical physics. Kepler was born on December 27, the feast day of St John the Evangelist, 1571, in the Free Imperial City of Weil der Stadt, his grandfather, Sebald Kepler, had been Lord Mayor of the city. By the time Johannes was born, he had two brothers and one sister and the Kepler family fortune was in decline, his father, Heinrich Kepler, earned a precarious living as a mercenary, he left the family when Johannes was five years old. He was believed to have died in the Eighty Years' War in the Netherlands.
His mother, Katharina Guldenmann, an innkeeper's daughter, was a herbalist. Born prematurely, Johannes claimed to have been sickly as a child, he impressed travelers at his grandfather's inn with his phenomenal mathematical faculty. He was introduced to astronomy at an early age, developed a love for it that would span his entire life. At age six, he observed the Great Comet of 1577, writing that he "was taken by mother to a high place to look at it." In 1580, at age nine, he observed another astronomical event, a lunar eclipse, recording that he remembered being "called outdoors" to see it and that the moon "appeared quite red". However, childhood smallpox left him with weak vision and crippled hands, limiting his ability in the observational aspects of astronomy. In 1589, after moving through grammar school, Latin school, seminary at Maulbronn, Kepler attended Tübinger Stift at the University of Tübingen. There, he studied philosophy under Vitus Müller and theology under Jacob Heerbrand, who taught Michael Maestlin while he was a student, until he became Chancellor at Tübingen in 1590.
He proved himself to be a superb mathematician and earned a reputation as a skilful astrologer, casting horoscopes for fellow students. Under the instruction of Michael Maestlin, Tübingen's professor of mathematics from 1583 to 1631, he learned both the Ptolemaic system and the Copernican system of planetary motion, he became a Copernican at that time. In a student disputation, he defended heliocentrism from both a theoretical and theological perspective, maintaining that the Sun was the principal source of motive power in the universe. Despite his desire to become a minister, near the end of his studies, Kepler was recommended for a position as teacher of mathematics and astronomy at the Protestant school in Graz, he accepted the position in April 1594, at the age of 23. Kepler's first major astronomical work, Mysterium Cosmographicum, was the first published defense of the Copernican system. Kepler claimed to have had an epiphany on July 19, 1595, while teaching in Graz, demonstrating the periodic conjunction of Saturn and Jupiter in the zodiac: he realized that regular polygons bound one inscribed and one circumscribed circle at definite ratios, which, he reasoned, might be the geometrical basis of the universe.
After failing to find a unique arrangement of polygons that fit known astronomical observations, Kepler began experimenting with 3-dimensional polyhedra. He found that each of the five Platonic solids could be inscribed and circumscribed by spherical orbs. By ordering the solids selectively—octahedron, dodecahedron, cube—Kepler found that the spheres could be placed at intervals corresponding to the relative sizes of each planet's path, assuming the planets circle the Sun. Kepler found a formula relating the size of each planet's orb to the length of its orbital period: from inner to outer planets, the ratio of increase in orbital period is twice the difference in orb radius. However, Kepler rejected this formula, because it was not precise enough. As
A demon is a supernatural and malevolent being prevalent in religion, literature, fiction and folklore. The original Greek word daimon does not carry negative connotations; the Ancient Greek word δαίμων daimōn denotes a spirit or divine power, much like the Latin genius or numen. The Greek conception of a daimōn notably appears in the works of Plato, where it describes the divine inspiration of Socrates. In Ancient Near Eastern religions and in the Abrahamic traditions, including ancient and medieval Christian demonology, a demon is considered a harmful spiritual entity which may cause demonic possession, calling for an exorcism. In Western occultism and Renaissance magic, which grew out of an amalgamation of Greco-Roman magic, Jewish Aggadah and Christian demonology, a demon is believed to be a spiritual entity that may be conjured and controlled; the Ancient Greek word δαίμων daimōn denotes a spirit or divine power, much like the Latin genius or numen. Daimōn most came from the Greek verb daiesthai.
The Greek conception of a daimōn notably appears in the works of Plato, where it describes the divine inspiration of Socrates. To distinguish the classical Greek concept from its Christian interpretation, the former is anglicized as either daemon or daimon rather than demon; the original Greek word daimon does not carry the negative connotation understood by implementation of the Koine δαιμόνιον, ascribed to any cognate words sharing the root. The Greek terms do not have any connotations of malevolence. In fact, εὐδαιμονία eudaimonia, means happiness. By the early Roman Empire, cult statues were seen, by pagans and their Christian neighbors alike, as inhabited by the numinous presence of the gods: "Like pagans, Christians still sensed and saw the gods and their power, as something, they had to assume, lay behind it, by an easy traditional shift of opinion they turned these pagan daimones into malevolent'demons', the troupe of Satan..... Far into the Byzantine period Christians eyed their cities' old pagan statuary as a seat of the demons' presence.
It was no longer beautiful, it was infested." The term had first acquired its negative connotations in the Septuagint translation of the Hebrew Bible into Greek, which drew on the mythology of ancient Semitic religions. This was inherited by the Koine text of the New Testament; the Western medieval and neo-medieval conception of a demon derives seamlessly from the ambient popular culture of Late Antiquity. The Hellenistic "daemon" came to include many Semitic and Near Eastern gods as evaluated by Christianity; the supposed existence of demons remains an important concept in many modern religions and occultist traditions. Demons are still feared due to their alleged power to possess living creatures. In the contemporary Western occultist tradition, a demon is a useful metaphor for certain inner psychological processes, though some may regard it as an objectively real phenomenon; some scholars believe that large portions of the demonology of Judaism, a key influence on Christianity and Islam, originated from a form of Zoroastrianism, were transferred to Judaism during the Persian era.
Both deities and demons can act as intermediaries to deliver messages to humans. Thus they share some resemblance to the Greek daimonion; the exact definition of "demon" in Egyptology posed a major problem for modern scholarship, since the borders between a deity and a demon are sometimes blurred and the ancient Egyptian language lacks a term for the modern English "demon". However, magical writings indicate that ancient Egyptians acknowledged the existence of malevolent demons by highlighting the demon names with red ink. Demons in this culture appeared to be subordinative and related to a specific deity, yet they may have acted independent from the divine will; the existence of demons can be related beyond the created world. But this negative connotation cannot be denied in light of the magical texts; the role of demons in relation to the human world remains ambivalent and depends on context. Ancient Egyptian demons can be divided into two classes: "guardians" and "wanderers." "Guardians" are tied to a specific place.
Demons protecting the underworld may prevent human souls from entering paradise. Only by knowing right charms is the deceased able to enter the Halls of Osiris. Here, the aggressive nature of the guardian demons is motivated by the need to protect their abodes and not by their evil essence. Accordingly, demons guarded the gates to the netherworld. During the Ptolemaic and Roman period, the guardians shifted towards the role of Genius loci and they were the focus of local and private cults; the "wanderers" are associated with possession, mental illness and plagues. Many of them serve as executioners for the major deities, such as Ra or Osiris, when ordered to punish humans on earth or in the netherworld. Wanderers can be agents of chaos, arising from the world beyond creation to bring about misfortune and suffering without any divine instructions, led only by evil motivations; the influences of the wanderers can be warded off and kept at the borders on the human world by the use of magic, but they can never be destroyed.
A sub-category of "wanderers" are nightmare demons, which were believed to ca
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. Space propulsion or in-space propulsion deals with propulsion systems used in the vacuum of space and should not be confused with launch vehicles. Several methods, both pragmatic and hypothetical, have been developed each having its own drawbacks and advantages. Most satellites have simple reliable chemical thrusters or resistojet rockets for orbital station-keeping and some use momentum wheels for attitude control. Soviet bloc satellites have used electric propulsion for decades, newer Western geo-orbiting spacecraft are starting to use them for north-south station-keeping and orbit raising. Interplanetary vehicles use chemical rockets as well, although a few have used Ion thrusters and Hall effect thrusters to great success. Artificial satellites must be launched into orbit after which they must be placed in their nominal orbit. Once in the desired orbit, they need some form of attitude control so that they are pointed with respect to the Earth, the Sun, some astronomical object of interest.
They are subject to drag from the thin atmosphere, so that to stay in orbit for a long period of time some form of propulsion is necessary to make small corrections. Many satellites need to be moved from one orbit to another from time to time, this requires propulsion. A satellite's useful life is over once it has exhausted its ability to adjust its orbit. For interplanetary travel, a spacecraft must use its engines to leave Earth's orbit. Once it has done so, it must somehow make its way to its destination. Current interplanetary spacecraft do this with a series of short-term trajectory adjustments. In between these adjustments, the spacecraft moves along its trajectory with a constant velocity; the most fuel-efficient means to move from one circular orbit to another is with a Hohmann transfer orbit: the spacecraft begins in a circular orbit around the Sun. A short period of thrust in the direction of motion accelerates or decelerates the spacecraft into an elliptical orbit around the Sun, tangential to its previous orbit and to the orbit of its destination.
The spacecraft falls along this elliptical orbit until it reaches its destination, where another short period of thrust accelerates or decelerates it to match the orbit of its destination. Special methods such as aerobraking or aerocapture are sometimes used for this final orbital adjustment; some spacecraft propulsion methods such as solar sails provide low but inexhaustible thrust. The concept has been tested by the Japanese IKAROS solar sail spacecraft. No spacecraft capable of short duration interstellar travel has yet been built, but many hypothetical designs have been discussed; because interstellar distances are great, a tremendous velocity is needed to get a spacecraft to its destination in a reasonable amount of time. Acquiring such a velocity on launch and getting rid of it on arrival remains a formidable challenge for spacecraft designers; when in space, the purpose of a propulsion system is to change the v, of a spacecraft. Because this is more difficult for more massive spacecrafts, designers discuss spacecraft performance in amount of change in momentum per unit of propellant consumed called specific impulse.
Higher the specific impulse, better the efficiency. Ion propulsion engines have high specific impulse and low thrust whereas chemical rockets like monopropellant or bipropellant rocket engines have a low specific impulse but high thrust; when launching a spacecraft from Earth, a propulsion method must overcome a higher gravitational pull to provide a positive net acceleration. In orbit, any additional impulse very tiny, will result in a change in the orbit path; the rate of change of velocity is called acceleration, the rate of change of momentum is called force. To reach a given velocity, one can apply a small acceleration over a long period of time, or one can apply a large acceleration over a short time. One can achieve a given impulse with a large force over a short time or a small force over a long time; this means that for manoeuvring in space, a propulsion method that produces tiny accelerations but runs for a long time can produce the same impulse as a propulsion method that produces large accelerations for a short time.
When launching from a planet, tiny accelerations cannot overcome the planet's gravitational pull and so cannot be used. Earth's surface is situated deep in a gravity well; the escape velocity required to get out of it is 11.2 kilometers/second. As human beings evolved in a gravitational field of 1g, an ideal propulsion system would be one that provides a continuous acceleration of 1g; the occupants of a rocket or spaceship having such a propulsion system would be free from all the ill effects of free fall, such as nausea, muscular weakness, reduced sense of taste, or leaching of calcium from their bones. The law of conservation of momentum means that in order for a propulsion method to change the momentum of a space craft it must change the momentum of something else as well. A few designs take advantage of things like magnetic fields or light pressure in order to chan
A spacecraft is a vehicle or machine designed to fly in outer space. Spacecraft are used for a variety of purposes, including communications, earth observation, navigation, space colonization, planetary exploration, transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, require a launch vehicle. On a sub-orbital spaceflight, a space vehicle enters space and returns to the surface, without having gained sufficient energy or velocity to make a full orbit of the Earth. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies. Spacecraft used for human spaceflight carry people on board as crew or passengers from start or on orbit only, whereas those used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft used to support scientific research are space probes. Robotic spacecraft that remain in orbit around a planetary body are artificial satellites.
To date, only a handful of interstellar probes, such as Pioneer 10 and 11, Voyager 1 and 2, New Horizons, are on trajectories that leave the Solar System. Orbital spacecraft may be recoverable or not. Most are not. Recoverable spacecraft may be subdivided by method of reentry to Earth into non-winged space capsules and winged spaceplanes. Humanity has achieved space flight but only a few nations have the technology for orbital launches: Russia, the United States, the member states of the European Space Agency, China, Taiwan (National Chung-Shan Institute of Science and Technology, Taiwan National Space Organization, Israel and North Korea. A German V-2 became the first spacecraft when it reached an altitude of 189 km in June 1944 in Peenemünde, Germany. Sputnik 1 was the first artificial satellite, it was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957. The launch ushered in new political, military and scientific developments. Apart from its value as a technological first, Sputnik 1 helped to identify the upper atmospheric layer's density, through measuring the satellite's orbital changes.
It provided data on radio-signal distribution in the ionosphere. Pressurized nitrogen in the satellite's false body provided the first opportunity for meteoroid detection. Sputnik 1 was launched during the International Geophysical Year from Site No.1/5, at the 5th Tyuratam range, in Kazakh SSR. The satellite travelled at 29,000 kilometers per hour, taking 96.2 minutes to complete an orbit, emitted radio signals at 20.005 and 40.002 MHz While Sputnik 1 was the first spacecraft to orbit the Earth, other man-made objects had reached an altitude of 100 km, the height required by the international organization Fédération Aéronautique Internationale to count as a spaceflight. This altitude is called the Kármán line. In particular, in the 1940s there were several test launches of the V-2 rocket, some of which reached altitudes well over 100 km; as of 2016, only three nations have flown crewed spacecraft: USSR/Russia, USA, China. The first crewed spacecraft was Vostok 1, which carried Soviet cosmonaut Yuri Gagarin into space in 1961, completed a full Earth orbit.
There were five other crewed missions. The second crewed spacecraft was named Freedom 7, it performed a sub-orbital spaceflight in 1961 carrying American astronaut Alan Shepard to an altitude of just over 187 kilometers. There were five other crewed missions using Mercury spacecraft. Other Soviet crewed spacecraft include the Voskhod, flown uncrewed as Zond/L1, L3, TKS, the Salyut and Mir crewed space stations. Other American crewed spacecraft include the Gemini spacecraft, Apollo spacecraft, the Skylab space station, the Space Shuttle with undetached European Spacelab and private US Spacehab space stations-modules. China developed, but did not fly Shuguang, is using Shenzhou. Except for the Space Shuttle, all of the recoverable crewed orbital spacecraft were space capsules. Crewed space capsules The International Space Station, crewed since November 2000, is a joint venture between Russia, the United States and several other countries; some reusable vehicles have been designed only for crewed spaceflight, these are called spaceplanes.
The first example of such was the North American X-15 spaceplane, which conducted two crewed flights which reached an altitude of over 100 km in the 1960s. The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963; the first reusable orbital spacecraft, a winged non-capsule, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 SCA and gliding to deadstick landings at Edwards AFB, California; the first Space Shuttle to fly into space was Columbia, followed by Challenger, Discovery and Endeavour. Endeavour was built to replace Challenger when it was lost in January 1986. Columbia broke up during reentry in February 2003; the first automatic reusable spacecraft was the Buran-class shuttle, launched by the USSR on November 15, 1988, although it made only one flight and this was uncrewed.
This spaceplane was designed for a crew and resembled the U
E. E. Smith
Edward Elmer Smith, better known by his pen name E. E. "Doc" Smith, was an American food engineer and science-fiction author, best known for the Lensman and Skylark series. He is sometimes called the father of space opera. Edward Elmer Smith was born in Sheboygan, Wisconsin on May 2, 1890, to Fred Jay Smith and Caroline Mills Smith, both staunch Presbyterians of British ancestry, his mother was a teacher born in Michigan in February 1855. They moved to Spokane, the winter after Edward Elmer was born, where Mr. Smith was working as a contractor in 1900. In 1902, the family moved near the Pend Oreille River, in Kootenai County, Idaho, he had four siblings, Rachel M. born September 1882, Daniel M. born January 1884, Mary Elizabeth born February 1886, Walter E. born July 1891 in Washington. In 1910, Fred and Caroline Smith and their son Walter were living in the Markham Precinct of Bonner County, Idaho. Smith worked as a manual laborer until he injured his wrist, at the age of 19, while escaping from a fire.
He attended the University of Idaho. He entered its prep school in 1907, graduated with two degrees in chemical engineering in 1914, he was president of the Chemistry Club, the Chess Club, the Mandolin and Guitar Club, captain of the Drill and Rifle Team. His undergraduate thesis was Some Clays of Idaho, co-written with classmate Chester Fowler Smith, who died in California of tuberculosis the following year, after taking a teaching fellowship at Berkeley. Whether the two were related is not known. On October 5, 1915, in Boise, Idaho he married Jeanne Craig MacDougall, the sister of his college roommate, Allen Scott MacDougall. Jeanne MacDougall was born in Scotland, her father had moved to Boise when the children were young, sent for his family. Jeanne's mother, who remarried businessman and retired politician John F. Kessler in 1914 worked at, owned, a boarding house on Ridenbaugh Street; the Smiths had three children: Roderick N. born June 3, 1918, in the District of Columbia, was employed as a design engineer at Lockheed Aircraft.
Verna Jean, born August 25, 1920, in Michigan, was his literary executor until her death in 1994. Robert A. Heinlein in part dedicated his 1982 novel Friday to Verna. Clarissa M. was born December 1921, in Michigan. After college, Smith was a junior chemist for the National Bureau of Standards in Washington, D. C. developing standards for butter and for oysters. He may have served as a lieutenant in the U. S. Army during World War I, his draft card illegible, seems to show that Smith requested exemption from military service, based on his wife's dependence and on his contribution to the war effort as a civilian chemist. One evening in 1915, the Smiths were visiting a former classmate from the University of Idaho, Dr. Carl Garby, who had moved to Washington, D. C, he lived nearby in the Seaton Place Apartments with Lee Hawkins Garby. A long discussion about journeys into outer space ensued, it was suggested that Smith should write down his ideas and speculations as a story about interstellar travel.
Although he was interested, Smith believed after some thought that some romantic elements would be required and he was uncomfortable with that. Mrs. Garby offered to take care of the love interest and the romantic dialogue, Smith decided to give it a try; the sources of inspirations for the main characters in the novel were themselves. About one third of The Skylark of Space was completed by the end of 1916, when Smith and Garby abandoned work on it. Smith earned his master's degree in chemistry from the George Washington University in 1917, studying under Dr. Charles E. Munroe. Smith completed his PhD in chemical engineering with a food engineering focus. In 1919, Smith was hired as chief chemist for F. W. Stock & Sons of Hillsdale, Michigan, at one time the largest family-owned mill east of the Mississippi, working on doughnut mixes. One evening late in 1919, after moving to Michigan, Smith was baby-sitting while his wife attended a movie, he submitted it to many book publishers and magazines, spending more in postage than he would receive for its publication.
Bob Davis, editor of Argosy, sent an encouraging rejection letter in 1922, saying that he liked the novel but that it was too far out for his readers. (According to Warner, but no other source, Smith began work on the sequel, Skylark III, before the first book was accepted
Speed of light
The speed of light in vacuum denoted c, is a universal physical constant important in many areas of physics. Its exact value is 299,792,458 metres per second, it is exact because by international agreement a metre is defined as the length of the path travelled by light in vacuum during a time interval of 1/299792458 second. According to special relativity, c is the maximum speed at which all conventional matter and hence all known forms of information in the universe can travel. Though this speed is most associated with light, it is in fact the speed at which all massless particles and changes of the associated fields travel in vacuum; such particles and waves travel at c regardless of the motion of the source or the inertial reference frame of the observer. In the special and general theories of relativity, c interrelates space and time, appears in the famous equation of mass–energy equivalence E = mc2; the speed at which light propagates through transparent materials, such as glass or air, is less than c.
The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material. For example, for visible light the refractive index of glass is around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000 km/s. For many practical purposes and other electromagnetic waves will appear to propagate instantaneously, but for long distances and sensitive measurements, their finite speed has noticeable effects. In communicating with distant space probes, it can take minutes to hours for a message to get from Earth to the spacecraft, or vice versa; the light seen from stars left them many years ago, allowing the study of the history of the universe by looking at distant objects. The finite speed of light limits the theoretical maximum speed of computers, since information must be sent within the computer from chip to chip; the speed of light can be used with time of flight measurements to measure large distances to high precision. Ole Rømer first demonstrated in 1676 that light travels at a finite speed by studying the apparent motion of Jupiter's moon Io.
In 1865, James Clerk Maxwell proposed that light was an electromagnetic wave, therefore travelled at the speed c appearing in his theory of electromagnetism. In 1905, Albert Einstein postulated that the speed of light c with respect to any inertial frame is a constant and is independent of the motion of the light source, he explored the consequences of that postulate by deriving the theory of relativity and in doing so showed that the parameter c had relevance outside of the context of light and electromagnetism. After centuries of precise measurements, in 1975 the speed of light was known to be 299792458 m/s with a measurement uncertainty of 4 parts per billion. In 1983, the metre was redefined in the International System of Units as the distance travelled by light in vacuum in 1/299792458 of a second; the speed of light in vacuum is denoted by a lowercase c, for "constant" or the Latin celeritas. In 1856, Wilhelm Eduard Weber and Rudolf Kohlrausch had used c for a different constant shown to equal √2 times the speed of light in vacuum.
The symbol V was used as an alternative symbol for the speed of light, introduced by James Clerk Maxwell in 1865. In 1894, Paul Drude redefined c with its modern meaning. Einstein used V in his original German-language papers on special relativity in 1905, but in 1907 he switched to c, which by had become the standard symbol for the speed of light. Sometimes c is used for the speed of waves in any material medium, c0 for the speed of light in vacuum; this subscripted notation, endorsed in official SI literature, has the same form as other related constants: namely, μ0 for the vacuum permeability or magnetic constant, ε0 for the vacuum permittivity or electric constant, Z0 for the impedance of free space. This article uses c for the speed of light in vacuum. Since 1983, the metre has been defined in the International System of Units as the distance light travels in vacuum in 1⁄299792458 of a second; this definition fixes the speed of light in vacuum at 299,792,458 m/s. As a dimensional physical constant, the numerical value of c is different for different unit systems.
In branches of physics in which c appears such as in relativity, it is common to use systems of natural units of measurement or the geometrized unit system where c = 1. Using these units, c does not appear explicitly because multiplication or division by 1 does not affect the result; the speed at which light waves propagate in vacuum is independent both of the motion of the wave source and of the inertial frame of reference of the observer. This invariance of the speed of light was postulated by Einstein in 1905, after being motivated by Maxwell's theory of electromagnetism and the lack of evidence for the luminiferous aether, it is only possible to verify experimentally that the two-way speed of light is frame-independent, because it is impossible to measure the one-way speed of light without some convention as to how clocks at the source and at the detector should be synchronized. However
Slipstream (science fiction)
"Slipstream" is a science fiction term for a fictional method of faster-than-light space travel, similar to hyperspace travel, warp drive, or "transfer points" from David Brin's Uplift series. Quantum slipstream was a starship drive used in two episodes of the science fiction television series Star Trek: Voyager, it first appeared in the season 4 finale, "Hope and Fear". Similar to the Borg transwarp conduits, the slipstream is a narrowly focused, directed field, initiated by manipulating the fabric of the space-time continuum at the quantum level using the starship's navigational deflector array; this creates a subspace tunnel, projected ahead of the vessel. Once a ship has entered this tunnel, the forces inside propel it at incredible speed. To maintain the slipstream, a ship has to modify the quantum field with its deflector dish; when this technology was discovered by the crew of the lost and stranded USS Voyager, it was hoped this could be used to allow the starship to travel at greater speeds.
However, in the episode "Timeless", the technology proved to be dangerously unstable, resulting in the loss of all hands of the Voyager in an alternate timeline. Due to a phase variance, the slipstream tunnel, produced by a replica slipstream drive of the Voyager, collapsed during the flight and the ship crashed on a planet near the border on the edge of the Delta Quadrant. Harry Kim and Chakotay survived, because they used the Delta Flyer, which flew ahead of the Voyager, reached the Earth safely; some years after this event, they used a temporal communication device to change the timeline and rescue the ship and crew. Quantum slipstream technology was one of the items requested in the "Think Tank" episode, despite Captain Janeway's admission that they never got it to work properly. Slipstream travel is used in the science fiction television series Andromeda. Slipstream is a series of "strings" connected between planetary systems by gravity. A gravity field generator drastically reduces the mass of the ship and a slipstream drive opens a slippoint which the ship enters.
The pilot navigates the series of slipstream "tunnels" until they exit via the desired slip point. One has to enter and exit slipstream several times before reaching their final destination. An A. I. attempting slipstream travel has a 50% chance of selecting the correct route at each intersection encountered. Owing to organic "intuition", a living pilot has a 99.97% chance of guessing the correct route to take. While travellers approaching light speed will encounter time dilation, slipstream travel does not. Due to the complex nature of slipstream probability and difficulty in mapping slipstream, only biological entities are capable of navigating it. Exiting slipstream near the edge of a galaxy or in certain regions of space could be dangerous because it is difficult to find a slippoint in these areas. If a slippoint cannot be found, or a slipstream drive is damaged, the ship is stranded and limited to slower than light speed. In the episode "World War Three" the Slitheen family from Raxacoricofallapatorius uses a slipstream drive as a form of travel.
In the Microsoft video game series Halo, based in the 26th century, slipspace is the general method of faster-than-light travel. Both the alliance of alien races known as the Covenant, their human opponents, the United Nations Space Command forces, use slipspace to travel between systems, with the UNSC using the human-developed Shaw-Fujikawa translight engine. According to The Halo Library: This...engine allowed ships to tunnel into...slipspace... Slipspace is a domain with alternate physical laws, allowing faster-than-light travel without relativistic side-effects. Faster-than-light travel is not instantaneous. Entire crews of some ships have been reported to disappear with no damage to the ship what so ever....scientists noted an odd "flexibility" to temporal flow while inside the Slipstream. 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—there is a five to ten percent variance in travel times between stars.
This temporal inconsistency has given military tacticians and strategists fits—hampering many coordinated attacks. The Covenant have a finely tuned version of this technology, it is far superior to the UNSC's. Instead of tearing a hole into Slipspace, it cuts a fine slit and slips into Slipspace with precision, it exits the same way, can have pinpoint accuracy. It can do so to Slipspace within planetary atmospheres, though this is damaging to the surface of the planet. To continue the previous metaphor, the Shaw-Fujikawa drive is described as violently punching a hole through to Slipspace next to the Covenant and Forerunner surgical precision of travel; the possible method behind this precision is shown in Halo: First Strike, when the AI Cortana takes control of a Covenant ship. When attempting to jump inside of the gas giant Threshold's atmosphere, she was able to'see' the bends and distortions of real space, and'picked' her way through them into Slipspace, it has been stated that slipspace is a misnomer since "there is nothing to slip across, no space to travel through."
Slipspace has a strange property. Space-time disintegrates into two separate groups. Spatial dimensions distant from an observer in close proximity of the slipspace source appear to be randomly erratic, whereas dimensions close to the observer appea