Zarb-e-Momin: Zarbemomin 4th sep to 10th sep

Zarb-e-Momin: Zarbemomin 4th sep to 10th sep

astrology

Astrology
Astrology (from Greek ἄστρον, astron, "constellation, star"; and -λογία, -logia, "the study of") is a group of systems, traditions, and beliefs in which knowledge of the apparent relative positions of celestial bodies and related details is held to be useful in understanding, interpreting, and organizing information about personality, human affairs, and other terrestrial matters. A practitioner of astrology is called an astrologer or an astrologist. Numerous traditions and applications employing astrological concepts have arisen since its earliest recorded beginnings in the 3rd millennium BC. It has played a role in the shaping of culture, early astronomy, and other disciplines throughout history.Astrology and astronomy were often indistinguishable before the modern era, with the desire for predictive and divinatory knowledge one of the primary motivating factors for astronomical observation. Astronomy began to diverge from astrology after a period of gradual separation from the Renaissance up until the 18th century. Eventually, astronomy distinguished itself as the scientific study of astronomical objects and phenomena without regard to the astrological speculations of these phenomena.Astrology can be defined as the study of the positions of celestial bodies in the belief that their movements either directly influence life on Earth or correspond somehow to events experienced on a human scale. Modern astrologers define astrology as a symbolic language, an art form, and a form of divination. Despite differences of definitions, a common assumption of astrology is the use of celestial placements in order to explain past and present events and predict the future. Generally, the scientific community considers astrology a pseudoscience or superstition. Despite its rejection by virtually all scientists, 31% of Americans polled expressed a belief in astrology and 39% considered it scientific according to another study.
Core beliefs
The core beliefs of astrology were prevalent in most of the ancient world and are epitomized in the Hermetic maxim "as above, so below". Tycho Brahe used a similar phrase to summarize his studies in astrology: suspiciendo despicio, "by looking up I see downward".Although the principle that events in the heavens are mirrored by those on Earth was once generally held in most traditions of astrology around the world, in the West there has historically been a debate among astrologers over the nature of the mechanism behind astrology. The debate also covers whether or not celestial bodies are only signs or portents of events, or if they are actual causes of events through some sort of force or mechanism.Although the connection between celestial mechanics and terrestrial dynamics was explored first by Isaac Newton with his development of a universal theory of gravitation, claims that the gravitational effects of the celestial bodies are what accounts for astrological generalizations are not substantiated by scientific research, nor are they advocated by most astrologers.Most astrological traditions are based on the relative positions and movements of various real or construed celestial bodies and on the construction of implied or calculated celestial patterns as seen at the time and place of the event being studied. These are chiefly the astrological planets, dwarf planets, the asteroids, the stars, the lunar nodes, Arabic parts and hypothetical planets. The frame of reference for such apparent positions is defined by the tropical or sidereal zodiac of twelve signs on one hand, and by the local horizon (ascendant-descendant axis) and midheaven-imum coeli axis on the other. This latter (local) frame is typically further divided into the twelve astrological houses. Furthermore, the astrological aspects are used to determine the geometric/angular relationship(s) between the various celestial bodies and angles in the horoscope.The claim of astrology to predict future trends and developments, or predictive astrology, is based on two main methods in western astrology: astrological transits and astrological progressions. In astrological transits the ongoing movements of the planets are interpreted for their significance as they transit through space and the horoscope. In astrological progressions the horoscope is progressed forward in time according to set methods. In vedic astrology the focus is on planetary periods to infer the trend while transits are used to time significant events. Most western astrologers no longer try to forecast actual events, but focus instead on general trends and developments. By comparison, vedic astrologers predict both trends and events. Skeptics respond that this practice of western astrologers allows them to avoid making verifiable predictions, and gives them the ability to attach significance to arbitrary and unrelated events, in a way that suits their purpose.In the past, astrologers often relied on close observation of celestial objects and the charting of their movements. Modern astrologers use data provided by astronomers which are transformed to a set of astrological tables called ephemerides, showing the changing zodiacal positions of the heavenly bodies through time.There are many traditions of astrology, some of which share similar features due to the transmission of astrological doctrines between cultures. Other traditions developed in isolation and hold different doctrines, though they too share some features due to drawing on similar astronomical sources. TraditionsThere are many traditions of astrology, some of which share similar features due to the transmission of astrological doctrines between cultures. Other traditions developed in isolation and hold different doctrines, though they too share some features due to drawing on similar astronomical sources.
Current traditions
The main traditions used by modern astrologers are:
Vedic astrology
Western astrology
Chinese astrology
Vedic and Western astrology share a common ancestry as horoscopic systems of astrology, in that both traditions focus on the casting of an astrological chart or horoscope, a representation of celestial entities, for an event based on the position of the Sun, Moon, and planets at the moment of the event. However, Vedic astrology uses the sidereal zodiac, linking the signs of the zodiac to their original constellations, while Western astrology uses the tropical zodiac. Because of the precession of the equinoxes, over the centuries the twelve zodiacal signs in Western astrology no longer correspond to the same part of the sky as their original constellations. In effect, in Western astrology the link between sign and constellation has been broken, whereas in Vedic astrology it remains of paramount importance. Other differences between the two traditions include the use of 27 (or 28) nakshatras or lunar mansions, which have been used in India since Vedic times, and the system of planetary periods known as dashas.In Chinese astrology a quite different tradition has evolved. By contrast to Western and Indian astrology, the twelve signs of the zodiac do not divide the sky, but rather the celestial equator. The Chinese evolved a system where each sign corresponds to one of twelve 'double-hours' that govern the day, and to one of the twelve months. Each sign of the zodiac governs a different year, and combines with a system based on the five elements of Chinese cosmology to give a 60 (12 x 5) year cycle. The term Chinese astrology is used here for convenience, but it must be recognised that versions of the same tradition exist in Korea, Japan, Vietnam, Thailand and other Asian countries.
The zodiac
The zodiac is the belt or band of constellations through which the Sun, Moon, and planets transit across the sky. Astrologers noted these constellations and so attached a particular significance to them. Over time they developed the system of twelve signs of the zodiac (Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces), based on twelve of the constellations they considered to be particularly important. The Western and Vedic zodiac signs have a common origin in the tradition of horoscopic astrology, and so are very similar in meaning. In China on the other hand, the development of the zodiac was different. Although the Chinese too have a system of twelve signs (named after animals), the Chinese zodiac refers to a pure calendrical cycle, as there are no equivalent constellations linked to it like the Western or Indian zodiacs. The common choice of twelve zodiac signs is understandable considering the interaction of the Sun and Moon was central to all forms of astrology.The majority of Western astrologers base their work on the tropical zodiac which divides the sky into twelve equal segments of 30 degrees each, beginning with the first point of Aries, the point where the line of the Earth's celestial equator and the ecliptic (the Sun's path through the sky) meet at the northern hemisphere spring equinox. Due to the precession of the equinoxes, the slow changing of the way Earth rotates in space, the zodiacal signs in this system bear no relation to the constellations of the same name but stay aligned to the months and seasons.

Horoscopic astrology
Practitioners of the Vedic astrological tradition and a minority of Western astrologers use the sidereal zodiac. This zodiac uses the same evenly divided ecliptic but approximately stays aligned to the positions of the observable constellations with the same name as the zodiacal signs. The sidereal zodiac differs from the tropical zodiac by an offset called the ayanamsa, which steadily increases as the equinoxes drift further. Furthermore, some siderealists (i.e. astrologers employing sidereal techniques) use the actual, unequal constellations of the zodiac in their work. Horoscopic astrology is a system that was developed in the Mediterranean region and specifically Hellenistic Egypt around the late 2nd or early 1st century BCE. The tradition deals with two-dimensional diagrams of the heavens, or horoscopes, created for specific moments in time. The diagram is then used to interpret the inherent meaning underlying the alignment of celestial bodies at that moment based on a specific set of rules and guidelines. A horoscope was calculated normally for the moment of an individual's birth, or at the beginning of an enterprise or event, because the alignments of the heavens at that moment were thought to determine the nature of the subject in question. One of the defining characteristics of this form of astrology that makes it distinct from other traditions is the computation of the degree of the Eastern horizon rising against the backdrop of the ecliptic at the specific moment under examination, otherwise known as the ascendant. Horoscopic astrology has been the most influential and widespread form of astrology across the world, especially in Africa, India, Europe, and the Middle East, and there are several major traditions of horoscopic astrology whose origins are Hellenistic, including Indian, Medieval, and most other modern Western traditions of astrology.

The horoscope
Central to horoscopic astrology and its branches is the calculation of the horoscope or astrological chart. This two-dimensional diagrammatic representation shows the celestial bodies' apparent positions in the heavens from the vantage of a location on Earth at a given time and place. The horoscope is also divided into twelve different celestial houses which govern different areas of life. Calculations performed in casting a horoscope involve arithmetic and simple geometry which serve to locate the apparent position of heavenly bodies on desired dates and times based on astronomical tables. In ancient Hellenistic astrology the ascendant demarcated the first celestial house of a horoscope. The word for the ascendant in Greek was horoskopos from which horoscope derives. In modern times, the word has come to refer to the astrological chart as a whole.
Branches of horoscopic astrology
Traditions of horoscopic astrology can be divided into four branches which are directed towards specific subjects or purposes. Often these branches use a unique set of techniques or a different application of the core principles of the system to a different area. Many other subsets and applications of astrology are derived from these four fundamental branches.Natal astrology, the study of a person's natal chart to gain information about the individual and his/her life experience. Katarchic astrology, which includes both electional and event astrology. The former uses astrology to determine the most auspicious moment to begin an enterprise or undertaking, and the latter to understand everything about an event from the time at which it took place.
Horary astrology, used to answer a specific question by studying the chart of the moment the question is posed to an astrologer. Mundane or world astrology, the application of astrology to world events, including weather, earthquakes, and the rise and fall of empires or religions. This includes the Astrological Ages, such as the Age of Aquarius, Age of Pisces and so on. Each age is about 2,150 years in length and many people believe these massive ages correspond to major historical events and current developments in the world
History of astrology

15th century image from the Très Riches Heures du Duc de Berry showing believed relations between areas of the body and the zodiacal signs.
Origins
The origins of much of the astrological doctrine and method that would later develop in Asia, Europe, and the Middle East are found among the ancient Babylonians and their system of celestial omens that began to be compiled around the middle of the 2nd millennium BCE. This system of celestial omens later spread either directly or indirectly through the Babylonians and Assyrians to other areas such as India, Middle East, and Greece where it merged with pre-existing indigenous forms of astrology. This Babylonian astrology came to Greece initially as early as the middle of the 4th century BCE, and then around the late 2nd or early 1st century BCE after the Alexandrian conquests, this Babylonian astrology was mixed with the Egyptian tradition of decanic astrology to create horoscopic astrology. This new form of astrology, which appears to have originated in Alexandrian Egypt, quickly spread across the ancient world into Europe, the Middle East and India.
Before the modern era
The differentiation between astronomy and astrology varied from place to place; they were strongly linked in ancient India, ancient Babylonia and medieval Europe, but separated to an extent in the Hellenistic world. The first semantic distinction between astrology and astronomy was given in the 11th century by the Persian astronomer, Abū Rayhān al-Bīrūnī (see astrology and astronomy).The pattern of astronomical knowledge gained from astrological endeavours has been historically repeated across numerous cultures, from ancient India through the classical Maya civilization to medieval Europe. Given this historical contribution, astrology has been called a protoscience along with pseudosciences such as alchemy (see "Western astrology and alchemy" below).Astrology was not always uncritically accepted before the modern era; it was often challenged by Hellenistic skeptics, church authorities, and medieval Muslim astronomers, such as Al-Farabi (Alpharabius), Ibn al-Haytham (Alhazen), Abū Rayhān al-Bīrūnī, Avicenna and Averroes. Their reasons for refuting astrology were often due to both scientific (the methods used by astrologers being conjectural rather than empirical) and religious (conflicts with orthodox Islamic scholars) reasons. Ibn Qayyim Al-Jawziyya (1292-1350), in his Miftah Dar al-SaCadah, used empirical arguments in astronomy in order to refute astrology and divination.
Many prominent thinkers, philosophers and scientists, such as Pythagoras, Plato, Aristotle, Galen, Paracelsus, Girolamo Cardan, Nicholas Copernicus, Taqi al-Din, Tycho Brahe, Galileo Galilei, Johannes Kepler, Carl Jung and others, practiced or significantly contributed to astrology.
Modern approaches
Several innovations have occurred in astrological practice in modern times.
Western astrology
During the middle of the 20th century, Alfred Witte and following him Reinhold Ebertin pioneered the use of midpoints (midpoints in Astrology) in horoscopic analysis. From the 1930s to the 1980s, astrologers including Dane Rudhyar, Liz Greene and Stephen Arroyo pioneered the use of astrology for psychological analysis, with some following the lead of psychologists like Carl Jung. In the 1930s, Don Neroman developed and popularised in Europe a form of Locational Astrology under the name of "Astrogeography." In the 1970s, American astrologer Jim Lewis developed and popularized a different approach under the name of Astrocartography. Both methods purport to identify varying life conditions through differences in location.
Vedic astrology
In the 1960s, H.R. Seshadri Iyer, introduced a system including the yoga point, which became popular in the West. From the early 1990s, Indian vedic astrologer and author, V.K. Cho
udhry has created and developed the Systems' Approach for Interpreting Horoscopes, a simplified system of Jyotish (predictive astrology). The system, also known as "SA", helps those who are trying to learn Jyotisha. The late K. S. Krishnamurti developed the Krishnamurti Paddhati system based on the analysis of the stars (nakshatras), by sub-dividing the stars in the ratio of the dasha of the concerned planets. The system is also known as "KP" and "sub theory".

NASA

NASA Headquarters, in Washington, provides overall guidance and direction to the agency, under the leadership of Administrator Michael Griffin. Ten field centers and a variety of installations conduct the day-to-day work, in laboratories, on air fields, in wind tunnels and in control rooms.

NASA's mission is to pioneer the future in space exploration, scientific discovery and aeronautics research. Since its founding on October 1, 1958, NASA has pushed the boundaries of human exploration. We've put footprints on the moon and tire tracks on Mars. We've given the world breathtaking images of our home planet, our solar system and the galaxies beyond. We invented the first re-usable spacecraft and, with our international partners, established a permanent human presence in space. Along the way, we've pioneered new technologies that have improved people's lives. Now, we're blazing a new trail into the cosmos. Before the end of the next decade, NASA astronauts will again explore the surface of the moon, traveling in a new spaceship that builds on the best of Apollo and shuttle technology. And this time, we're going to stay, building outposts and paving the way for eventual journeys to Mars and beyond. To do that, thousands of people have been working around the world -- and off of it -- for almost 50 years, trying to answer some basic questions. What's out there in space? How do we get there? What will we find? What can we learn there, or learn just by trying to get there, that will make life better here on Earth?

A
Little History

President Dwight D. Eisenhower established the National Aeronautics and Space Administration in 1958, partially in response to the Soviet Union's launch of the first artificial satellite the previous year. NASA grew out of the National Advisory Committee on Aeronautics (NACA), which had been researching flight technology for more than 40 years.
President John F. Kennedy focused NASA and the nation on sending astronauts to the moon by the end of the 1960s. Through the Mercury and Gemini projects, NASA developed the technology and skills it needed for the journey. On July 20, 1969, Neil Armstrong and Buzz Aldrin became the first of 12 men to walk on the moon, meeting Kennedy's challenge. Meanwhile, NASA was continuing the aeronautics research pioneered by NACA. It also conducted purely scientific research and worked on developing applications for space technology, combining both pursuits in developing the first weather and communications satellites.

After Apollo, NASA focused on creating a reusable ship to provide regular access to space: the space shuttle. First launched in 1981, the space shuttle has had 120 successful flights. In 2000, the
United States and Russia established permanent human presence in space aboard the International Space Station, a multinational project representing the work of 16 nations. NASA also has continued its scientific research. In 1997, Mars Pathfinder became the first in a fleet of spacecraft that will explore Mars in the next decade, as we try to determine if life ever existed there. The Terra and Aqua satellites are flagships of a different fleet, this one in Earth orbit, designed to help us understand how our home world is changing. NASA's aeronautics teams are focused on improved aircraft travel that is safer and cleaner. Throughout its history, NASA has conducted or funded research that has led to numerous improvements to life here on Earth.

NASA Today

NASA conducts its work in four principle organizations, called mission directorates:

* Aeronautics: pioneers and proves new flight technologies that improve our ability to explore and which have practical applications on Earth

* Exploration Systems: creates new capabilities and spacecraft for affordable, sustainable human and robotic exploration.

* Science: explores the Earth, moon, Mars and beyond; charts the best route of discovery; and reaps the benefits of Earth and space exploration for society.

* Space Operations: provides critical enabling technologies for much of the rest of NASA through the space shuttle, the International Space Station and flight support.

In the early 21st century, NASA's reach spans the universe. Spirit and Opportunity, the Mars Exploration Rovers, are still studying Mars after more than three years. Cassini is in orbit around Saturn. The Hubble Space Telescope continues to explore the deepest reaches of the cosmos

Closer to home, the latest crew of the International Space Station is extending the permanent human presence in space. Earth Science satellites are sending back unprecedented data on Earth's oceans, climate and other features. NASA's aeronautics team is working with other government organizations, universities, and industry to fundamentally improve the air transportation experience and retain our nation's leadership in global aviation.

The Future

In the next 20 years, NASA will be laying the groundwork for sending humans not only beyond Earth's orbit, but further into to space than they've ever been. The next key steps are:

* Complete the International Space Station and retire the Space Shuttle by 2010

* Begin robotic missions to the moon by 2008 and return people there by 2020

* Continue robotic exploration of Mars and the Solar System

* Develop a crew exploration vehicle and other technologies required to send people beyond low Earth orbit

Though nearly 50 years old, NASA is only beginning the most exciting part of its existence.

SPACE CRAFT

A spacecraft is a craft or machine designed for spaceflight. On a spaceflight, a spacecraft enters space then returns to the Earth. For an orbital spaceflight, a spacecraft enters a closed orbit around the planetary body. Spacecraft used for human spaceflights carry people on board as crew or passengers. Spacecraft used for robotic space missions operate either autonomously or electromagnetically. Robotic spacecraft that leave the vicinity of the planetary body are space probes. Robotic spacecraft that remain in orbit around the planetary body are artificial satellites. Starships, which are built for interstellar travel, are so far a theoretical concept only. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and space tourism. Spacecraft and space travel are common themes in works of spacecraft subsystems A spacecraft system comprises various subsystems, dependent upon mission profile. Spacecraft subsystems may include: attitude determination and control (variously called AD AC, ADC or SACS), guidance, navigation and control (ENC or GEN&C), communications (CORMS), command and data handling (CH or C&DH), power (ESP), thermal control (TICS), propulsion, structures, and payload. Spacecraft intended for human spaceflight must also include a life support system for the crew. This can include many different types of Oxygen Systems, such as the one seen in the movie Apollo 13 that exploded and almost cost the crew their lives.

Spacecraft could do with an attitude control subsystem to be correctly oriented in space and respond to external torques and forces properly. The attitude control subsystem consists of sensors and actuators, together with controlling algorithms. The attitude control subsystem permits proper pointing meant for the science objective, sun pointing for supremacy to the cosmological arrays furthermore earth-pointing for communications. Guidance refers to the calculation of the commands (usually done by the CH subsystem) needed to steer the spacecraft where it is desired to be. Navigation means determining a spacecraft's orbital elements or position. Control means adjusting the path of the spacecraft to get together mission requirements. On some missions, ENC and Attitude Control are combined interested in individual subsystem of the spacecraft.

The CH subsystem receives commands from the communications subsystem, performs validation and decoding of the commands, and distributes the commands to the appropriate spacecraft subsystems and components. The CH also receives housekeeping data and science data from the other spacecraft subsystems and components, and packages the data for storage on a solid state recorder or transmission to the ground passing through the communications subsystem. Other functions of the CH include maintaining the spacecraft clock in addition to state-of-health monitoring.

Spacecraft need an electrical power generation and distribution subsystem for powering the various spacecraft subsystems. For spacecraft near the Sun, solar panels are frequently used to generate electrical power. Spacecraft designed to operate in more distant locations, for example Jupiter, might employ a Radioisotope Thermoelectric Generator (RT) to generate electrical power. Electrical power is sent through power conditioning equipment before it passes through a power distribution unit over an electrical bus to other spacecraft components. Batteries are typically connected to the bus via a battery charge regulator, and the batteries are used to provide electrical power during periods when primary power is not available, for example when a Low Earth Orbit (LEO) spacecraft is eclipsed by the Earth.

Thermal control

Spacecraft must be engineered to withstand transit through the Earth's atmosphere and the space environment. They must operate in a vacuum with temperatures potentially ranging across hundreds of degrees Celsius as well as (if subject to reentry) in the presence of plasmas. Material requirements are such that either high melting temperature, low density materials such as be and C-C or (possibly due to the lower thickness requirements despite its high density) W or ablative C-C composites are used. Depending on mission profile, spacecraft may also need to operate on the surface of another planetary body. The thermal control subsystem can be passive, dependent on the selection of materials with specific radiative properties. Active thermal control makes use of electrical heaters and certain actuators such as louvers to control temperature ranges of equipments within specific ranges. Science fiction.

STARSHIP

Is a theoretical spacecraft designed for traveling between the stars, as opposed to a vehicle designed for orbital spaceflight or interplanetary travel. The term is mostly found in science fiction, as humanity has not yet constructed such vehicles (while the Voyager and Pioneer probes have traveled into local interstellar space, they are not generally considered starships, mainly because they are both empowered and unmanned). However, exploratory engineering has been undertaken on several preliminary designs and feasibility studies for starships that could be built with modern technology or technology thought to be available in the near future. For examples of such studies, see Project Daedal us, Project Orion, and Project Long shot.

A common literary device is to posit a faster-than-light propulsion system (such as warp drive) or travel through hyperspace, although some starships may be outfitted for centuries-long journeys of slower-than-light travel. Other designs posit a way to boost the ship to near-light speed, allowing relatively "quick" travel (i.e. decades, not centuries) to nearer stars. This results in a general categorization of the kinds of starships: Sleeper ships, which put their passengers into stasis during a long trip. Eneration ships, where the destination will be reached by descendants of the original passengers. Relativistic ships, taking advantage of time dilation at close-to-light-speeds, so long trips will seem much shorter (but still take the same amount of time for outside observers). Faster-than-light ships, which can move between places very quickly (transcending current understanding of physics or using interdimensional 'shortcuts'). Fiction that discusses slower-than-light starships is relatively rare, since the time scales are so long. Instead of describing the interaction with the outside world, those fictions tend to focus on setting the whole story within the world of the (often very large) starship during its long travels. Sometimes the starship is a world, in perception or reality.

Faster-than-light

Travel at velocities greater than the speed of light is impossible according to the known laws of physics, although apparent FTL is not excluded by general relativity. Science fiction has, however, provided many examples Such starships are typically large, multi-passenger vehicles (compared to star fighters). They range. in size from small personal yachts and courier ships, up to vast bulk containers (used for intersystem shipping) and enormous warships Starships are usually depicted as operating under laws and guidelines similar to real-world seagoing vessels. The primary reason for this concept (beyond artistic license) is that deep space is an even more hazardous environment than the open sea, and so extreme caution would have to be taken in all starship operations. A side effect of this is that space going fleets, especially space militaries, are usually described as being organized similar to modern Earth navies.

A starship may be fitted with a wide variety of engines, weapons, equipment, and internal compartments. Small freighters used for smuggling are typically fast, modified to avoid detection, are often heavily armed, and may have secret holds for hiding contraband cargo. Large container ships usually have little in the way of or weaponry, but have huge, powerful engines necessary for moving vast quantities of cargo through (or between) star systems. Passenger vessels, are often described as being similar to modern ocean liners, containing luxurious passenger cabins, gambling halls, showrooms, restaurants, and lounges. Warships contain crew quarters, extensive weaponry and shielding, massive engines, sophisticated sensor and communications arrays, and usually a detachment of non-naval Marine-like soldiers trained in assaulting and capturing enemy spacecraft, targets on planetary surfaces, or both.

Exceptions

Exceedingly large space going craft (for example the Death Star of the Star Wars universe) are typically not referred to as 'starships' (but see 'slower-than-light ships' above). Terms like may be considered to be more accurate. Space stations and other structures intended to orbit a celestial body or serve as a point of contact/maintenance/docking station for other ships are not usually called starships, even if they can move under their own power.

WHAT IS SPACE?

Space is a boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of the boundless four-dimensional field known as space-time. In mathematics spaces with different numbers of dimensions and with different underlying structures can be examined. The concept of space is measured to be of fundamental importance to an understanding of the universe although disagreement continues between philosopher over whether it is itself an entity, a relationship between entities, or part of a conceptual structure.

Many of the philosophical questions arose in the 17th century, during the early development of classical mechanics. In Isaac Newton's view, space was unconditional - in the sense that it existed permanently and independently of whether there were any matter in the space. Other natural philosophers, notably Gottfried Leibniz, thought instead that space was a collection of relationships between objects, given by their distance and direction from one another. In the 18th century, Immanuel Kant described space and time as elements of a systematic framework which humans use to structure their experience. In the 19th and 20th centuries mathematicians began to examine non-Euclidean geometries, in which space can be said to be curved, rather than flat. According to Albert Einstein's theory of general relativity, space around gravitational fields deviates from Euclidean space. Experimental tests of general relativity have established that non-Euclidean space provides a better model for explaining the existing laws of mechanics and optics.

Outer space comprises the relatively unfilled regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace and terrestrial locations. There is no apparent boundary between Earth's atmosphere and space as the density of the atmosphere gradually decreases as the altitude increases. Nevertheless, the Federation Aéronautique International has established the Kerman line at an altitude of 100 kilometers (62 mi)) as a working classification for the boundary between aeronautics and astronautics. This is used because above an altitude of roughly 100 kilometers (62 mi), as Theodore von Kerman calculated, a vehicle would have to travel faster than orbital velocity in order to derive sufficient aerodynamic lift from the environment to support itself. The United States designates people who travel above an altitude of 50 miles (80 km)) as astronauts. During re-entry, roughly 120 kilometers (75 mi) marks the boundary where atmospheric drag becomes noticeable, depending on the ballistic coefficient of the vehicle.

Contrary to popular sympathetic, outer space is not completely empty (i.e. a perfect vacuum,) but contains a low density of particles, principally hydrogen plasma, as well as electromagnetic radiation. Supposedly, it also contains dark matter and dark energy.

The term outer space was first recorded by H. G. Wells in his novel First Men in the Moon in 1901. The shorter term space is actually older, first used to mean the region beyond Earth's sky in John Milton's Paradise Lost in 1667.