Monthly Archives: January 2023

What Is the James Webb Space Telescope?

The James Webb Space Telescope is the largest, most powerful space telescope ever built.

NASA Activity Books

Become a NASA Space Place Explorer with these printable activity books.

Color Your Universe: Find the Hidden Objects

Can you find all the NASA and space-themed hidden objects?

What Are Constellations?

Learn more about what these groups of stars can (and cant) tell us about our place in the universe.

How Scary Is Space?

Check out these nine unearthly nightmares that could be happening right now in our own galaxy. Eek!

Is Time Travel Possible?

Airplanes and satellites can experience changes in time! Read on to find out more.

What Powers a Spacecraft?

It all depends on what the spacecraft will do! Read on to learn more.

What Is a Transit?

A transit is when one object in space crosses in front of another object in space. The Moon transits the Sun during an eclipse, but did you know that other objects can transit, too? Learn more in this article.

How Old Are Galaxies?

Most galaxies formed more than 10 billion years ago! Learn about how we find the age of galaxies using light.

What Is a Light-Year?

A light-year is the distance light travels in one Earth year. Learn about how we use light-years to measure the distance of objects in space.

What Is a Nebula?

A nebula is a cloud of dust and gas in space.

How Many Solar Systems Are in Our Galaxy?

Astronomers have discovered 2,500 so far, but there are likely to be many more!

What Is a Supernova?

Learn more about these exploding stars!

What Is a Gravitational Wave?

How do gravitational waves give us a new way to learn about the universe?

What Is an Exoplanet?

What is an exoplanet? And how do we know they're out there?

Searching for Other Planets Like Ours

Exoplanets are far away and hard to see. How do we look for them?

Types of Galaxies

Explore the different types of galaxies!

What Is a Barycenter?

And how does it help us find new planets?

Make Stretchy Universe Slime!

Make the universe stretch and expand!

Dark Matter

and dark energy, too!

Make a Pinwheel Galaxy Pinwheel

A galaxy in the palm of your hand

What Is a Galaxy?

How many are there?

What Is the Big Bang?

Why do we call it that?

Where Does Interstellar Space Begin?

Interstellar space begins where the suns magnetic field stops affecting its surroundings.

What Is a Satellite Galaxy?

What are they and what will become of them?

Build your own spacecraft!

Become a NASA engineer!

What Is a Black Hole?

Space Place in a Snap tackles this fascinating question!

A Planet Without a Sun?

Astronomers may have found a planet without a sun!

What Is a Planet?

The answer isn't so simple...

Make a Galactic Mobile

Let the beauty of the galaxies shine in your room.

Write your own zany adventure story!

Write your own zany adventure story!

Gallery of NASA Universe Images

Galaxies, nebulae, and supernova remnants to view or print.

What Is Gravity?

Gravity is the force by which a planet or other body draws objects toward its center.

What's in Space?

What is out there that you cannot see with your bare eyes?

Lucy's Planet Hunt . . .

A story about a girl's search for another Earth.

NASA Pumpkin Stencils

Paint pumpkins with space and Earth science designs

Printable Space Valentines

Share these with your friends and family!

Explore the Electromagnetic Spectrum

The windows show the Universe in all its colors.

Make colorful star cookies!

Find out why stars aren't all the same color.

A real shooting star!

Is Mira the zippiest star in the galaxy?

Build a physics machine!

And learn about conservation of oomph!

Make a Galaxy Montage

Make a colorful work of galactic art.

Roman Space Observer

Catch as many astrophysical objects and phenomena as possible in this game! This link takes you away from NASA Space Place.

Build a model spacecraft to explore the universe!

Paper models of the great space observatories and explorers of the universe. This link takes you away from NASA Space Place.

StarChild

A learning center for young astronomers. This link takes you away from NASA Space Place.

Read more:
Universe | NASA Space Place NASA Science for Kids

We often refer to our expanding universe with one simple word: space. But where does space begin and, more importantly, what is it?

Space is an almost perfect vacuum, nearly void of matter and with extremely low pressure. In space, sound doesn't carry because there aren't molecules close enough together to transmit sound between them. Not quite empty, bits of gas, dust and other matter floats around "emptier" areas of the universe, while more crowded regions can host planets, stars and galaxies.

From our Earth-bound perspective, outer space is most often thought to begin about 62 miles (100 kilometers) above sea level at what is known as the Krmn line. This is an imaginary boundary at an altitude where there is no appreciable air to breathe or scatter light. Passing this altitude, blue starts to give way to black because oxygen molecules are not in enough abundance to make the sky blue.

Related: Where DOES Space Begin? Virgin Galactic Flies Right into the Debate

No one knows exactly how big space is. It's difficult to determine because of what we can see in our detectors. We measure long distances in space in "light-years," representing the distance it takes for light to travel in a year (roughly 5.8 trillion miles (9.3 trillion kilometers)).

From the light that is visible in our telescopes, we have charted galaxies reaching almost as far back as the Big Bang, which is thought to have started our universe about 13.8 billion years ago. This means we can "see" into space at a distance of almost 13.8 billion light-years. But the universe continues to expand, making "measuring space," even more challenging.

Additionally, astronomers are not totally sure if our universe is the only one that exists. This means that space could be a whole lot bigger than we even think.

The majority of space is relatively empty, with just stray bits of dust and gas floating around. This means that when humans send a probe to a distant planet or asteroid, the craft will not encounter "drag" in the same way that an airplane does as it sails through space.

In fact, the vacuum environment in space and on the moon, is one reason why the lunar lander of the Apollo program was designed to have an almost spider-like appearance, as it was described by the Apollo 9 crew. Because the spacecraft was designed to work in a zone with no atmosphere, it didn't need to have smooth edges or an aerodynamic shape.

In addition to the bits of debris that speckle the "emptier" regions of space, research has shown that these areas are also home to different forms of radiation. In our own solar system, the solar wind charged particles that stream from the sun emanate throughout the solar system and occasionally cause auroras near Earth's poles. Cosmic rays also fly through our neighborhood, stemming from supernovas outside of the solar system.

In fact, the universe as a whole is inundated with what is known as the cosmic microwave background (CMB), which is essentially the leftover radiation from the explosion mostly commonly known as the Big Bang. The CMB is the oldest radiation that our instruments can detect.

Infographic: Cosmic Microwave Background Explained

There remain two giant mysteries about space: dark matter and dark energy.

While scientists have provided extensive evidence for the existence of dark matter and dark energy, they are each still poorly understood as, so far, scientists cannot directly observe them and can only observe their effects.

Roughly 80% of all of the mass in the universe is made up of what scientists have dubbed "dark matter," but it's not known what it actually is or if it is even matter by our current definition. However, while dark matter doesn't emit light or energy and cannot, therefore, be directly observed, scientists have found overwhelming evidence that it makes up the vast majority of the matter in the cosmos.

Dark energy might have a similar name to dark matter, but it's a whole different component entirely.

Thought to make up nearly 75% of the universe, dark energy is a mysterious and unknown force or entity that scientists think is responsible for the universe's ongoing expansion.

Smaller black holes can form from the gravitational collapse of a gigantic star, which forms a singularity from which nothing can escape not even light, hence the name of the object. No one is quite sure what lies within a black hole, or what would happen to a person or object who fell into it but research is ongoing.

An example is gravitational waves, or ripples in space-time that come from interactions between black holes. This was first predicted by Albert Einstein at the turn of the last century, when he showed that time and space are linked; time speeds up or slows down when space is distorted.

As of mid-2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration has announced three black-hole interactions and mergers detected through gravitational waves, in just two years.

The team found these three events in about two years, indicating that when LIGO is implemented at full sensitivity, the observatory may be able to find these sorts of events frequently, scientists said in May 2017. Should a bunch of these black hole events be detected, it could help scientists learn how black holes of a certain size (several tens of sun masses) are born, and later merge into new black holes.

Stars (like our own sun) are immense balls of gas that produce their own radiation. They can range from red supergiants to cooling white dwarfs that are the leftovers of supernovas, or star explosions that occur when a big one runs out of gas to burn. These explosions spread elements throughout the universe and are the reason that elements such as iron exist. Star explosions can also give rise to incredibly dense objects called neutron stars. If these neutron stars send out pulses of radiation, they are called pulsar stars.

Planets are objects whose definition came under scrutiny in 2006, when astronomers were debating whether Pluto could be considered a planet or not. At the time, the International Astronomical Union (the governing body on Earth for these decisions) ruled that a planet is a celestial body that orbits the sun, is massive enough to have a nearly round shape, and has cleared its orbit of debris. Under this designation, Pluto and similar small objects are considered "dwarf planets," although not everyone agrees with the designation. After the New Horizons spacecraft flew by Pluto in 2015, principal investigator Alan Stern and others again opened up the debate, saying the diversity of terrain on Pluto makes it more like a planet.

The definition of extrasolar planets, or planets outside the solar system, is still not firmed up by the IAU, but essentially astronomers understand it to mean objects that behave like planets in our neighborhood. The first such planet was found in 1992 (in the constellation Pegasus) and since that time, thousands of alien planets have been confirmed with many more suspected. In solar systems that have planets under formation, these objects are often called "protoplanets" because they aren't quite the maturity of those planets we have in our own solar system.

Asteroids are rocks that are not quite big enough to be dwarf planets. We've even found asteroids with rings around them, such as 10199 Charilko. Their small size often leads to the conclusion that they were remnants from when the solar system was formed. Most asteroids are concentrated in a belt between the planets Mars and Jupiter, but there are also many asteroids that follow behind or ahead of planets, or can even cross in a planet's path. NASA and several other entities have asteroid-searching programs in place to scan for potentially dangerous objects in the sky and monitor their orbits closely.

In our solar system, comets (sometimes called dirty snowballs) are objects believed to originate from a vast collection of icy bodies called the Oort Cloud. As a comet approaches the sun, the heat of our star causes ices to melt and stream away from the comet. The ancients often associated comets with destruction or some sort of immense change on Earth, but the discovery of Halley's Comet and related "periodic" or returning comets showed that they were ordinary solar system phenomena.

Among the biggest cosmic structures we can see are galaxies, which essentially are vast collections of stars. Our own galaxy is called the Milky Way, and is considered a "barred spiral" shape. There are several types of galaxies, ranging from spiral to elliptical to irregular, and they can change as they come close to other objects or as stars within them age.

Often galaxies have supermassive black holes embedded in the center of their galaxies, which are only visible through the radiation that each black hole emanates as well as through its gravitational interactions with other objects. If the black hole is particularly active, with a lot of material falling into it, it produces immense amounts of radiation. This kind of a galactic object is called a quasar (just one of several types of similar objects.)

Large groups of galaxies can form in clusters that are groups as large as hundreds or thousands of galaxies bound together gravitationally. Scientists consider these the largest structures in the universe.

This page was updated in Jan. 2022 by Space.com senior writer Chelsea Gohd.

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What Is Space? - A Definition of Our Universe and Beyond | Space

Framework of distances and directions

Space is the boundless three-dimensional extent in which objects and events have relative position and direction.[1] In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime. The concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework.

Debates concerning the nature, essence and the mode of existence of space date back to antiquity; namely, to treatises like the Timaeus of Plato, or Socrates in his reflections on what the Greeks called khra (i.e. "space"), or in the Physics of Aristotle (Book IV, Delta) in the definition of topos (i.e. place), or in the later "geometrical conception of place" as "space qua extension" in the Discourse on Place (Qawl fi al-Makan) of the 11th-century Arab polymath Alhazen.[2] Many of these classical philosophical questions were discussed in the Renaissance and then reformulated in the 17th century, particularly during the early development of classical mechanics. In Isaac Newton's view, space was absolutein the sense that it existed permanently and independently of whether there was any matter in the space.[3] Other natural philosophers, notably Gottfried Leibniz, thought instead that space was in fact a collection of relations between objects, given by their distance and direction from one another. In the 18th century, the philosopher and theologian George Berkeley attempted to refute the "visibility of spatial depth" in his Essay Towards a New Theory of Vision. Later, the metaphysician Immanuel Kant said that the concepts of space and time are not empirical ones derived from experiences of the outside worldthey are elements of an already given systematic framework that humans possess and use to structure all experiences. Kant referred to the experience of "space" in his Critique of Pure Reason as being a subjective "pure a priori form of intuition".

In the 19th and 20th centuries mathematicians began to examine geometries that are non-Euclidean, in which space is conceived as curved, rather than flat. According to Albert Einstein's theory of general relativity, space around gravitational fields deviates from Euclidean space.[4] Experimental tests of general relativity have confirmed that non-Euclidean geometries provide a better model for the shape of space.

Galilean and Cartesian theories about space, matter, and motion are at the foundation of the Scientific Revolution, which is understood to have culminated with the publication of Newton's Principia in 1687.[5] Newton's theories about space and time helped him explain the movement of objects. While his theory of space is considered the most influential in Physics, it emerged from his predecessors' ideas about the same.[6]

As one of the pioneers of modern science, Galileo revised the established Aristotelian and Ptolemaic ideas about a geocentric cosmos. He backed the Copernican theory that the universe was heliocentric, with a stationary sun at the center and the planetsincluding the Earthrevolving around the sun. If the Earth moved, the Aristotelian belief that its natural tendency was to remain at rest was in question. Galileo wanted to prove instead that the sun moved around its axis, that motion was as natural to an object as the state of rest. In other words, for Galileo, celestial bodies, including the Earth, were naturally inclined to move in circles. This view displaced another Aristotelian ideathat all objects gravitated towards their designated natural place-of-belonging.[7]

Descartes set out to replace the Aristotelian worldview with a theory about space and motion as determined by natural laws. In other words, he sought a metaphysical foundation or a mechanical explanation for his theories about matter and motion. Cartesian space was Euclidean in structureinfinite, uniform and flat.[8] It was defined as that which contained matter; conversely, matter by definition had a spatial extension so that there was no such thing as empty space.[5]

The Cartesian notion of space is closely linked to his theories about the nature of the body, mind and matter. He is famously known for his "cogito ergo sum" (I think therefore I am), or the idea that we can only be certain of the fact that we can doubt, and therefore think and therefore exist. His theories belong to the rationalist tradition, which attributes knowledge about the world to our ability to think rather than to our experiences, as the empiricists believe.[9] He posited a clear distinction between the body and mind, which is referred to as the Cartesian dualism.

Following Galileo and Descartes, during the seventeenth century the philosophy of space and time revolved around the ideas of Gottfried Leibniz, a German philosophermathematician, and Isaac Newton, who set out two opposing theories of what space is. Rather than being an entity that independently exists over and above other matter, Leibniz held that space is no more than the collection of spatial relations between objects in the world: "space is that which results from places taken together".[10] Unoccupied regions are those that could have objects in them, and thus spatial relations with other places. For Leibniz, then, space was an idealised abstraction from the relations between individual entities or their possible locations and therefore could not be continuous but must be discrete.[11]Space could be thought of in a similar way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people.[12]Leibniz argued that space could not exist independently of objects in the world because that implies a difference between two universes exactly alike except for the location of the material world in each universe. But since there would be no observational way of telling these universes apart then, according to the identity of indiscernibles, there would be no real difference between them. According to the principle of sufficient reason, any theory of space that implied that there could be these two possible universes must therefore be wrong.[13]

Newton took space to be more than relations between material objects and based his position on observation and experimentation. For a relationist there can be no real difference between inertial motion, in which the object travels with constant velocity, and non-inertial motion, in which the velocity changes with time, since all spatial measurements are relative to other objects and their motions. But Newton argued that since non-inertial motion generates forces, it must be absolute.[14] He used the example of water in a spinning bucket to demonstrate his argument. Water in a bucket is hung from a rope and set to spin, starts with a flat surface. After a while, as the bucket continues to spin, the surface of the water becomes concave. If the bucket's spinning is stopped then the surface of the water remains concave as it continues to spin. The concave surface is therefore apparently not the result of relative motion between the bucket and the water.[15] Instead, Newton argued, it must be a result of non-inertial motion relative to space itself. For several centuries the bucket argument was considered decisive in showing that space must exist independently of matter.

In the eighteenth century the German philosopher Immanuel Kant developed a theory of knowledge in which knowledge about space can be both a priori and synthetic.[16] According to Kant, knowledge about space is synthetic, in that statements about space are not simply true by virtue of the meaning of the words in the statement. In his work, Kant rejected the view that space must be either a substance or relation. Instead he came to the conclusion that space and time are not discovered by humans to be objective features of the world, but imposed by us as part of a framework for organizing experience.[17]

Euclid's Elements contained five postulates that form the basis for Euclidean geometry. One of these, the parallel postulate, has been the subject of debate among mathematicians for many centuries. It states that on any plane on which there is a straight line L1 and a point P not on L1, there is exactly one straight line L2 on the plane that passes through the point P and is parallel to the straight line L1. Until the 19th century, few doubted the truth of the postulate; instead debate centered over whether it was necessary as an axiom, or whether it was a theory that could be derived from the other axioms.[18] Around 1830 though, the Hungarian Jnos Bolyai and the Russian Nikolai Ivanovich Lobachevsky separately published treatises on a type of geometry that does not include the parallel postulate, called hyperbolic geometry. In this geometry, an infinite number of parallel lines pass through the point P. Consequently, the sum of angles in a triangle is less than 180 and the ratio of a circle's circumference to its diameter is greater than pi. In the 1850s, Bernhard Riemann developed an equivalent theory of elliptical geometry, in which no parallel lines pass through P. In this geometry, triangles have more than 180 and circles have a ratio of circumference-to-diameter that is less than pi.

Although there was a prevailing Kantian consensus at the time, once non-Euclidean geometries had been formalised, some began to wonder whether or not physical space is curved. Carl Friedrich Gauss, a German mathematician, was the first to consider an empirical investigation of the geometrical structure of space. He thought of making a test of the sum of the angles of an enormous stellar triangle, and there are reports that he actually carried out a test, on a small scale, by triangulating mountain tops in Germany.[19]

Henri Poincar, a French mathematician and physicist of the late 19th century, introduced an important insight in which he attempted to demonstrate the futility of any attempt to discover which geometry applies to space by experiment.[20] He considered the predicament that would face scientists if they were confined to the surface of an imaginary large sphere with particular properties, known as a sphere-world. In this world, the temperature is taken to vary in such a way that all objects expand and contract in similar proportions in different places on the sphere. With a suitable falloff in temperature, if the scientists try to use measuring rods to determine the sum of the angles in a triangle, they can be deceived into thinking that they inhabit a plane, rather than a spherical surface.[21] In fact, the scientists cannot in principle determine whether they inhabit a plane or sphere and, Poincar argued, the same is true for the debate over whether real space is Euclidean or not. For him, which geometry was used to describe space was a matter of convention.[22] Since Euclidean geometry is simpler than non-Euclidean geometry, he assumed the former would always be used to describe the 'true' geometry of the world.[23]

In 1905, Albert Einstein published his special theory of relativity, which led to the concept that space and time can be viewed as a single construct known as spacetime. In this theory, the speed of light in a vacuum is the same for all observerswhich has the result that two events that appear simultaneous to one particular observer will not be simultaneous to another observer if the observers are moving with respect to one another. Moreover, an observer will measure a moving clock to tick more slowly than one that is stationary with respect to them; and objects are measured to be shortened in the direction that they are moving with respect to the observer.

Subsequently, Einstein worked on a general theory of relativity, which is a theory of how gravity interacts with spacetime. Instead of viewing gravity as a force field acting in spacetime, Einstein suggested that it modifies the geometric structure of spacetime itself.[24] According to the general theory, time goes more slowly at places with lower gravitational potentials and rays of light bend in the presence of a gravitational field. Scientists have studied the behaviour of binary pulsars, confirming the predictions of Einstein's theories, and non-Euclidean geometry is usually used to describe spacetime.

In modern mathematics spaces are defined as sets with some added structure. They are frequently described as different types of manifolds, which are spaces that locally approximate to Euclidean space, and where the properties are defined largely on local connectedness of points that lie on the manifold. There are however, many diverse mathematical objects that are called spaces. For example, vector spaces such as function spaces may have infinite numbers of independent dimensions and a notion of distance very different from Euclidean space, and topological spaces replace the concept of distance with a more abstract idea of nearness.

Space is one of the few fundamental quantities in physics, meaning that it cannot be defined via other quantities because nothing more fundamental is known at the present. On the other hand, it can be related to other fundamental quantities. Thus, similar to other fundamental quantities (like time and mass), space can be explored via measurement and experiment.

Today, our three-dimensional space is viewed as embedded in a four-dimensional spacetime, called Minkowski space (see special relativity). The idea behind spacetime is that time is hyperbolic-orthogonal to each of the three spatial dimensions.

Before Albert Einstein's work on relativistic physics, time and space were viewed as independent dimensions. Einstein's discoveries showed that due to relativity of motion our space and time can be mathematically combined into one objectspacetime. It turns out that distances in space or in time separately are not invariant with respect to Lorentz coordinate transformations, but distances in Minkowski space along spacetime intervals arewhich justifies the name.

In addition, time and space dimensions should not be viewed as exactly equivalent in Minkowski space. One can freely move in space but not in time. Thus, time and space coordinates are treated differently both in special relativity (where time is sometimes considered an imaginary coordinate) and in general relativity (where different signs are assigned to time and space components of spacetime metric).

Furthermore, in Einstein's general theory of relativity, it is postulated that spacetime is geometrically distorted curved near to gravitationally significant masses.[25]

One consequence of this postulate, which follows from the equations of general relativity, is the prediction of moving ripples of spacetime, called gravitational waves. While indirect evidence for these waves has been found (in the motions of the HulseTaylor binary system, for example) experiments attempting to directly measure these waves are ongoing at the LIGO and Virgo collaborations. LIGO scientists reported the first such direct observation of gravitational waves on 14 September 2015.[26][27]

Relativity theory leads to the cosmological question of what shape the universe is, and where space came from. It appears that space was created in the Big Bang, 13.8billion years ago[28] and has been expanding ever since. The overall shape of space is not known, but space is known to be expanding very rapidly due to the cosmic inflation.

The measurement of physical space has long been important. Although earlier societies had developed measuring systems, the International System of Units, (SI), is now the most common system of units used in the measuring of space, and is almost universally used.

Currently, the standard space interval, called a standard meter or simply meter, is defined as the distance traveled by light in a vacuum during a time interval of exactly 1/299,792,458 of a second. This definition coupled with present definition of the second is based on the special theory of relativity in which the speed of light plays the role of a fundamental constant of nature.

Geography is the branch of science concerned with identifying and describing places on Earth, utilizing spatial awareness to try to understand why things exist in specific locations. Cartography is the mapping of spaces to allow better navigation, for visualization purposes and to act as a locational device. Geostatistics apply statistical concepts to collected spatial data of Earth to create an estimate for unobserved phenomena.

Geographical space is often considered as land, and can have a relation to ownership usage (in which space is seen as property or territory). While some cultures assert the rights of the individual in terms of ownership, other cultures will identify with a communal approach to land ownership, while still other cultures such as Australian Aboriginals, rather than asserting ownership rights to land, invert the relationship and consider that they are in fact owned by the land. Spatial planning is a method of regulating the use of space at land-level, with decisions made at regional, national and international levels. Space can also impact on human and cultural behavior, being an important factor in architecture, where it will impact on the design of buildings and structures, and on farming.

Ownership of space is not restricted to land. Ownership of airspace and of waters is decided internationally. Other forms of ownership have been recently asserted to other spacesfor example to the radio bands of the electromagnetic spectrum or to cyberspace.

Public space is a term used to define areas of land as collectively owned by the community, and managed in their name by delegated bodies; such spaces are open to all, while private property is the land culturally owned by an individual or company, for their own use and pleasure.

Abstract space is a term used in geography to refer to a hypothetical space characterized by complete homogeneity. When modeling activity or behavior, it is a conceptual tool used to limit extraneous variables such as terrain.

Psychologists first began to study the way space is perceived in the middle of the 19th century. Those now concerned with such studies regard it as a distinct branch of psychology. Psychologists analyzing the perception of space are concerned with how recognition of an object's physical appearance or its interactions are perceived, see, for example, visual space.

Other, more specialized topics studied include amodal perception and object permanence. The perception of surroundings is important due to its necessary relevance to survival, especially with regards to hunting and self preservation as well as simply one's idea of personal space.

Several space-related phobias have been identified, including agoraphobia (the fear of open spaces), astrophobia (the fear of celestial space) and claustrophobia (the fear of enclosed spaces).

The understanding of three-dimensional space in humans is thought to be learned during infancy using unconscious inference, and is closely related to hand-eye coordination. The visual ability to perceive the world in three dimensions is called depth perception.

Space has been studied in the social sciences from the perspectives of Marxism, feminism, postmodernism, postcolonialism, urban theory and critical geography. These theories account for the effect of the history of colonialism, transatlantic slavery and globalization on our understanding and experience of space and place. The topic has garnered attention since the 1980s, after the publication of Henri Lefebvre's The Production of Space . In this book, Lefebvre applies Marxist ideas about the production of commodities and accumulation of capital to discuss space as a social product. His focus is on the multiple and overlapping social processes that produce space.[29]

In his book The Condition of Postmodernity, David Harvey describes what he terms the "time-space compression." This is the effect of technological advances and capitalism on our perception of time, space and distance.[30] Changes in the modes of production and consumption of capital affect and are affected by developments in transportation and technology. These advances create relationships across time and space, new markets and groups of wealthy elites in urban centers, all of which annihilate distances and affect our perception of linearity and distance.[31]

In his book Thirdspace, Edward Soja describes space and spatiality as an integral and neglected aspect of what he calls the "trialectics of being," the three modes that determine how we inhabit, experience and understand the world. He argues that critical theories in the Humanities and Social Sciences study the historical and social dimensions of our lived experience, neglecting the spatial dimension.[32] He builds on Henri Lefebvre's work to address the dualistic way in which humans understand spaceas either material/physical or as represented/imagined. Lefebvre's "lived space"[33] and Soja's "thirdspace" are terms that account for the complex ways in which humans understand and navigate place, which "firstspace" and "Secondspace" (Soja's terms for material and imagined spaces respectively) do not fully encompass.

Postcolonial theorist Homi Bhabha's concept of Third Space is different from Soja's Thirdspace, even though both terms offer a way to think outside the terms of a binary logic. Bhabha's Third Space is the space in which hybrid cultural forms and identities exist. In his theories, the term hybrid describes new cultural forms that emerge through the interaction between colonizer and colonized.[34]

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Space - Wikipedia

Watch the Space Station over the First Coast Saturday evening with a rocket launch Sunday  FirstCoastNews.com WTLV-WJXX

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Watch the Space Station over the First Coast Saturday evening with a rocket launch Sunday - FirstCoastNews.com WTLV-WJXX