This program unpacks Playstation 3 Theme files (.p3t) so that you can touch-up an existing theme to your likings or use a certain wallpaper from it (as many themes have multiple). But remember, if you use content from another theme and release it, be sure to give credit!
Download p3textractor.zip from above. Extract the files to a folder with a program such as WinZip or WinRAR. Now there are multiple ways to extract the theme.
The first way is to simply open the p3t file with p3textractor.exe. If you don’t know how to do this, right click the p3t file and select Open With. Alternatively, open the p3t file and it will ask you to select a program to open with. Click Browse and find p3textractor.exe from where you previously extracted it to. It will open CMD and extract the theme to extracted.[filename]. After that, all you need to do for any future p3t files is open them and it will extract.
The second way is very simple. Just drag the p3t file to p3textractor.exe. It will open CMD and extract the theme to extracted.[filename].
For the third way, first put the p3t file you want to extract into the same folder as p3textractor.exe. Open CMD and browse to the folder with p3extractor.exe. Enter the following: p3textractor filename.p3t [destination path]Replace filename with the name of the p3t file, and replace [destination path] with the name of the folder you want the files to be extracted to. A destination path is not required. By default it will extract to extracted.filename.
The world is the totality of entities, the whole of reality, or everything that exists.[1] The nature of the world has been conceptualized differently in different fields. Some conceptions see the world as unique while others talk of a "plurality of worlds". Some treat the world as one simple object while others analyze the world as a complex made up of parts.
In scientific cosmology, the world or universe is commonly defined as "[t]he totality of all space and time; all that is, has been, and will be". Theories of modality talk of possible worlds as complete and consistent ways how things could have been. Phenomenology, starting from the horizon of co-given objects present in the periphery of every experience, defines the world as the biggest horizon or the "horizon of all horizons". In philosophy of mind, the world is contrasted with the mind as that which is represented by the mind. Theology conceptualizes the world in relation to God, for example, as God's creation, as identical to God or as the two being interdependent. In religions, there is a tendency to downgrade the material or sensory world in favor of a spiritual world to be sought through religious practice. A comprehensive representation of the world and our place in it, as is found in religions, is known as a worldview. Cosmogony is the field that studies the origin or creation of the world while eschatology refers to the science or doctrine of the last things or of the end of the world.
In various contexts, the term "world" takes a more restricted meaning associated, for example, with the Earth and all life on it, with humanity as a whole or with an international or intercontinental scope. In this sense, world history refers to the history of humanity as a whole and world politics is the discipline of political science studying issues that transcend nations and continents. Other examples include terms such as "world religion", "world language", "world government", "world war", "world population", "world economy", or "world championship".
The corresponding word in Latin is mundus, literally 'clean, elegant', itself a loan translation of Greek cosmos 'orderly arrangement'. While the Germanic word thus reflects a mythological notion of a "domain of Man" (compare Midgard), presumably as opposed to the divine sphere on the one hand and the chthonic sphere of the underworld on the other, the Greco-Latin term expresses a notion of creation as an act of establishing order out of chaos.[4]
Different fields often work with quite different conceptions of the essential features associated with the term "world".[5][6] Some conceptions see the world as unique: there can be no more than one world. Others talk of a "plurality of worlds".[4] Some see worlds as complex things composed of many substances as their parts while others hold that worlds are simple in the sense that there is only one substance: the world as a whole.[7] Some characterize worlds in terms of objective spacetime while others define them relative to the horizon present in each experience. These different characterizations are not always exclusive: it may be possible to combine some without leading to a contradiction. Most of them agree that worlds are unified totalities.[5][6]
Monism is a thesis about oneness: that only one thing exists in a certain sense. The denial of monism is pluralism, the thesis that, in a certain sense, more than one thing exists.[7] There are many forms of monism and pluralism, but in relation to the world as a whole, two are of special interest: existence monism/pluralism and priority monism/pluralism. Existence monism states that the world is the only concrete object there is.[7][8][9] This means that all the concrete "objects" we encounter in our daily lives, including apples, cars and ourselves, are not truly objects in a strict sense. Instead, they are just dependent aspects of the world-object.[7] Such a world-object is simple in the sense that it does not have any genuine parts. For this reason, it has also been referred to as "blobject" since it lacks an internal structure like a blob.[10] Priority monism allows that there are other concrete objects besides the world.[7] But it holds that these objects do not have the most fundamental form of existence, that they somehow depend on the existence of the world.[9][11] The corresponding forms of pluralism state that the world is complex in the sense that it is made up of concrete, independent objects.[7]
Scientific cosmology can be defined as the science of the universe as a whole. In it, the terms "universe" and "cosmos" are usually used as synonyms for the term "world".[12] One common definition of the world/universe found in this field is as "[t]he totality of all space and time; all that is, has been, and will be".[13][5][6] Some definitions emphasize that there are two other aspects to the universe besides spacetime: forms of energy or matter, like stars and particles, and laws of nature.[14] World-conceptions in this field differ both concerning their notion of spacetime and of the contents of spacetime. The theory of relativity plays a central role in modern cosmology and its conception of space and time. A difference from its predecessors is that it conceives space and time not as distinct dimensions but as a single four-dimensional manifold called spacetime.[15] This can be seen in special relativity in relation to the Minkowski metric, which includes both spatial and temporal components in its definition of distance.[16]General relativity goes one step further by integrating the concept of mass into the concept of spacetime as its curvature.[16]Quantum cosmology uses a classical notion of spacetime and conceives the whole world as one big wave function expressing the probability of finding particles in a given location.[17]
The world-concept plays a role in many modern theories of modality, sometimes in the form of possible worlds.[18] A possible world is a complete and consistent way how things could have been.[19] The actual world is a possible world since the way things are is a way things could have been. There are many other ways things could have been besides how they actually are. For example, Hillary Clinton did not win the 2016 US election, but she could have won them. So there is a possible world in which she did. There is a vast number of possible worlds, one corresponding to each such difference, no matter how small or big, as long as no outright contradictions are introduced this way.[19]
Possible worlds are often conceived as abstract objects, for example, in terms of non-obtaining states of affairs or as maximally consistent sets of propositions.[20][21] On such a view, they can even be seen as belonging to the actual world.[22] Another way to conceive possible worlds, made famous by David Lewis, is as concrete entities.[4] On this conception, there is no important difference between the actual world and possible worlds: both are conceived as concrete, inclusive and spatiotemporally connected.[19] The only difference is that the actual world is the world we live in, while other possible worlds are not inhabited by us but by our counterparts.[23] Everything within a world is spatiotemporally connected to everything else but the different worlds do not share a common spacetime: They are spatiotemporally isolated from each other.[19] This is what makes them separate worlds.[23]
It has been suggested that, besides possible worlds, there are also impossible worlds. Possible worlds are ways things could have been, so impossible worlds are ways things could not have been.[24][25] Such worlds involve a contradiction, like a world in which Hillary Clinton both won and lost the 2016 US election. Both possible and impossible worlds have in common the idea that they are totalities of their constituents.[24][26]
Within phenomenology, worlds are defined in terms of horizons of experiences.[5][6] When we perceive an object, like a house, we do not just experience this object at the center of our attention but also various other objects surrounding it, given in the periphery.[27] The term "horizon" refers to these co-given objects, which are usually experienced only in a vague, indeterminate manner.[28][29] The perception of a house involves various horizons, corresponding to the neighborhood, the city, the country, the Earth, etc. In this context, the world is the biggest horizon or the "horizon of all horizons".[27][5][6] It is common among phenomenologists to understand the world not just as a spatiotemporal collection of objects but as additionally incorporating various other relations between these objects. These relations include, for example, indication-relations that help us anticipate one object given the appearances of another object and means-end-relations or functional involvements relevant for practical concerns.[27]
In philosophy of mind, the term "world" is commonly used in contrast to the term "mind" as that which is represented by the mind. This is sometimes expressed by stating that there is a gap between mind and world and that this gap needs to be overcome for representation to be successful.[30][31][32] One problem in philosophy of mind is to explain how the mind is able to bridge this gap and to enter into genuine mind-world-relations, for example, in the form of perception, knowledge or action.[33][34] This is necessary for the world to be able to rationally constrain the activity of the mind.[30][35] According to a realist position, the world is something distinct and independent from the mind.[36] Idealists conceive of the world as partially or fully determined by the mind.[36][37]Immanuel Kant's transcendental idealism, for example, posits that the spatiotemporal structure of the world is imposed by the mind on reality but lacks independent existence otherwise.[38] A more radical idealist conception of the world can be found in Berkeley's subjective idealism, which holds that the world as a whole, including all everyday objects like tables, cats, trees and ourselves, "consists of nothing but minds and ideas".[39]
Different theological positions hold different conceptions of the world based on its relation to God. Classical theism states that God is wholly distinct from the world. But the world depends for its existence on God, both because God created the world and because He maintains or conserves it.[40][41][42] This is sometimes understood in analogy to how humans create and conserve ideas in their imagination, with the difference being that the divine mind is vastly more powerful.[40] On such a view, God has absolute, ultimate reality in contrast to the lower ontological status ascribed to the world.[42] God's involvement in the world is often understood along the lines of a personal, benevolent God who looks after and guides His creation.[41]Deists agree with theists that God created the world but deny any subsequent, personal involvement in it.[43]Pantheists reject the separation between God and world. Instead, they claim that the two are identical. This means that there is nothing to the world that does not belong to God and that there is nothing to God beyond what is found in the world.[42][44]Panentheism constitutes a middle ground between theism and pantheism. Against theism, it holds that God and the world are interrelated and depend on each other. Against pantheism, it holds that there is no outright identity between the two.[42][45]
In philosophy, the term world has several possible meanings. In some contexts, it refers to everything that makes up reality or the physical universe. In others, it can mean have a specific ontological sense (see world disclosure). While clarifying the concept of world has arguably always been among the basic tasks of Western philosophy, this theme appears to have been raised explicitly only at the start of the twentieth century,[46]
Plato is well known for his theory of forms, which posits the existence of two different worlds: the sensible world and the intelligible world. The sensible world is the world we live in, filled with changing physical things we can see, touch and interact with. The intelligible world is the world of invisible, eternal, changeless forms like goodness, beauty, unity and sameness.[47][48][49] Plato ascribes a lower ontological status to the sensible world, which only imitates the world of forms. This is due to the fact that physical things exist only to the extent that they participate in the forms that characterize them, while the forms themselves have an independent manner of existence.[47][48][49] In this sense, the sensible world is a mere replication of the perfect exemplars found in the world of forms: it never lives up to the original. In the allegory of the cave, Plato compares the physical things we are familiar with to mere shadows of the real things. But not knowing the difference, the prisoners in the cave mistake the shadows for the real things.[50]
Two definitions that were both put forward in the 1920s, however, suggest the range of available opinion. "The world is everything that is the case", wrote Ludwig Wittgenstein in his influential Tractatus Logico-Philosophicus, first published in 1921.[51]
Martin Heidegger, meanwhile, argued that "the surrounding world is different for each of us, and notwithstanding that we move about in a common world".[52]
"World" is one of the key terms in Eugen Fink's philosophy.[53] He thinks that there is a misguided tendency in western philosophy to understand the world as one enormously big thing containing all the small everyday things we are familiar with.[54] He sees this view as a form of forgetfulness of the world and tries to oppose it by what he calls the "cosmological difference": the difference between the world and the inner-worldly things it contains.[54] On his view, the world is the totality of the inner-worldly things that transcends them.[55] It is itself groundless but it provides a ground for things. It therefore cannot be identified with a mere container. Instead, the world gives appearance to inner-worldly things, it provides them with a place, a beginning and an end.[54] One difficulty in investigating the world is that we never encounter it since it is not just one more thing that appears to us. This is why Fink uses the notion of play or playing to elucidate the nature of the world.[54][55] He sees play as a symbol of the world that is both part of it and that represents it.[56] Play usually comes with a form of imaginary play-world involving various things relevant to the play. But just like the play is more than the imaginary realities appearing in it so the world is more than the actual things appearing in it.[54][56]
The concept of worlds plays a central role in Nelson Goodman's late philosophy.[57] He argues that we need to posit different worlds in order to account for the fact that there are different incompatible truths found in reality.[58] Two truths are incompatible if they ascribe incompatible properties to the same thing.[57] This happens, for example, when we assert both that the earth moves and that the earth is at rest. These incompatible truths correspond to two different ways of describing the world: heliocentrism and geocentrism.[58] Goodman terms such descriptions "world versions". He holds a correspondence theory of truth: a world version is true if it corresponds to a world. Incompatible true world versions correspond to different worlds.[58] It is common for theories of modality to posit the existence of a plurality of possible worlds. But Goodman's theory is different since it posits a plurality not of possible but of actual worlds.[57][5] Such a position is in danger of involving a contradiction: there cannot be a plurality of actual worlds if worlds are defined as maximally inclusive wholes.[57][5] This danger may be avoided by interpreting Goodman's world-concept not as maximally inclusive wholes in the absolute sense but in relation to its corresponding world-version: a world contains all and only the entities that its world-version describes.[57][5]
Hinduism constitutes a family of religious-philosophical views.[61] These views present perspectives on the nature and role of the world. Samkhya philosophy, for example, is a metaphysical dualism that understands reality as comprising 2 parts: purusha and prakriti.[62] The term "purusha" stands for the individual conscious self that each of "us" possesses. Prakriti, on the other hand, is the 1 world inhabited by all these selves.[63] Samkhya understands this world as a world of matter governed by the law of cause and effect.[62] The term "matter" is understood in a sense in this tradition including physical and mental aspects.[64] This is reflected in the doctrine of tattvas, according to which prakriti is made up of 23 principles or elements of reality.[64] These principles include physical elements, like water or earth, and mental aspects, like intelligence or sense-impressions.[63] The relation between purusha and prakriti is conceived as 1 of observation: purusha is the conscious self aware of the world of prakriti and does not causally interact with it.[62]
A conception of the world is present in Advaita Vedanta, the monist school among the Vedanta schools.[61] Unlike the realist position defended in Samkhya philosophy, Advaita Vedanta sees the world of multiplicity as an illusion, referred to as Maya.[61] This illusion includes impression of existing as separate experiencing selfs called Jivas.[65] Instead, Advaita Vedanta teaches that on the most fundamental level of reality, referred to as Brahman, there exists no plurality or difference.[65] All there is is 1 all-encompassing self: Atman.[61] Ignorance is seen as the source of this illusion, which results in bondage to the world of mere appearances. Liberation is possible in the course of overcoming this illusion by acquiring the knowledge of Brahman, according to Advaita Vedanta.[65]
Contemptus mundi is the name given to the belief that the world, in all its vanity, is nothing more than a futile attempt to hide from God by stifling our desire for the good and the holy.[66] This view has been criticised as a "pastoral of fear" by historian Jean Delumeau.[67]
In Islam, the term "dunya" is used for the world. Its meaning is derived from the root word "dana", a term for "near".[69] It is associated with the temporal, sensory world and earthly concerns, i.e. with this world in contrast to the spiritual world.[70] Religious teachings warn of a tendency to seek happiness in this world and advise a more ascetic lifestyle concerned with the afterlife.[71] Other strands in Islam recommend a balanced approach.[70]
In Mandaean cosmology, the world or earthly realm is known as Tibil. It is separated from the World of Light (alma d-nhūra) above and the World of Darkness (alma d-hšuka) below by aether (ayar).[72][73]
A worldview is a comprehensive representation of the world and our place in it.[74] As a representation, it is a subjective perspective of the world and thereby different from the world it represents.[75] All higher animals need to represent their environment in some way in order to navigate it. But it has been argued that only humans possess a representation encompassing enough to merit the term "worldview".[75] Philosophers of worldviews commonly hold that the understanding of any object depends on a worldview constituting the background on which this understanding can take place. This may affect not just our intellectual understanding of the object in question but the experience of it in general.[74] It is therefore impossible to assess one's worldview from a neutral perspective since this assessment already presupposes the worldview as its background. Some hold that each worldview is based on a single hypothesis that promises to solve all the problems of our existence we may encounter.[76] On this interpretation, the term is closely associated to the worldviews given by different religions.[76] Worldviews offer orientation not just in theoretical matters but also in practical matters. For this reason, they usually include answers to the question of the meaning of life and other evaluative components about what matters and how we should act.[77][78] A worldview can be unique to one individual but worldviews are usually shared by many people within a certain culture or religion.
The idea that there exist many different worlds is found in various fields. For example, theories of modality talk about a plurality of possible worlds and the many-worlds interpretation of quantum mechanics carries this reference even in its name. Talk of different worlds is also common in everyday language, for example, with reference to the world of music, the world of business, the world of football, the world of experience or the Asian world. But at the same time, worlds are usually defined as all-inclusive totalities.[5][6][15][14] This seems to contradict the very idea of a plurality of worlds since if a world is total and all-inclusive then it cannot have anything outside itself. Understood this way, a world can neither have other worlds besides itself or be part of something bigger.[5][57] One way to resolve this paradox while holding onto the notion of a plurality of worlds is to restrict the sense in which worlds are totalities. On this view, worlds are not totalities in an absolute sense.[5] This might be even understood in the sense that, strictly speaking, there are no worlds at all.[57] Another approach understands worlds in a schematic sense: as context-dependent expressions that stand for the current domain of discourse. So in the expression "Around the World in Eighty Days", the term "world" refers to the earth while in the colonial[79] expression "the New World" it refers to the landmass of North and South America.[15]
Cosmogony is the field that studies the origin or creation of the world. This includes both scientific cosmogony and creation myths found in various religions.[80][81] The dominant theory in scientific cosmogony is the Big Bang theory, according to which both space, time and matter have their origin in one initial singularity occurring about 13.8 billion years ago. This singularity was followed by an expansion that allowed the universe to sufficiently cool down for the formation of subatomic particles and later atoms. These initial elements formed giant clouds, which would then coalesce into stars and galaxies.[16] Non-scientific creation myths are found in many cultures and are often enacted in rituals expressing their symbolic meaning.[80] They can be categorized concerning their contents. Types often found include creation from nothing, from chaos or from a cosmic egg.[80]
Eschatology refers to the science or doctrine of the last things or of the end of the world. It is traditionally associated with religion, specifically with the Abrahamic religions.[82][83]
In this form, it may include teachings both of the end of each individual human life and of the end of the world as a whole. But it has been applied to other fields as well, for example, in the form of physical eschatology, which includes scientifically based speculations about the far future of the universe.[84] According to some models, there will be a Big Crunch in which the whole universe collapses back into a singularity, possibly resulting in a second Big Bang afterward. But current astronomical evidence seems to suggest that our universe will continue to expand indefinitely.[84]
World history studies the world from a historical perspective. Unlike other approaches to history, it employs a global viewpoint. It deals less with individual nations and civilizations, which it usually approaches at a high level of abstraction.[85] Instead, it concentrates on wider regions and zones of interaction, often interested in how people, goods and ideas move from one region to another.[86] It includes comparisons of different societies and civilizations as well as considering wide-ranging developments with a long-term global impact like the process of industrialization.[85] Contemporary world history is dominated by three mai
This article is about the general framework of distance and direction. For the space beyond Earth's atmosphere, see Outer space. For the writing separator, see Space (punctuation). For other uses, see Space (disambiguation).
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 khôra (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 polymathAlhazen.[4] 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.
Isaac Newton viewed space as absolute, existing permanently and independently of whether there was any matter in the.[5] In contrast, other natural philosophers, notably Gottfried Leibniz, thought 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 metaphysicianImmanuel Kant said that the concepts of space and time are not empirical ones derived from experiences of the outside world—they 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".
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 Mathematica in 1687.[6] 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.[7]
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 planets—including the Earth—revolving 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 idea—that all objects gravitated towards their designated natural place-of-belonging.[8]
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 structure—infinite, uniform and flat.[9] 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.[6]
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.[10] 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 philosopher–mathematician, 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".[11] 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.[12]
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.[13]
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.[14]
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.[15] 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.[16] 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 published his theory of space as "a property of our mind" by which "we represent to ourselves objects as outside us, and all as in space" in the Critique of Pure Reason[17] On his view the nature of spatial predicates are "relations that only attach to the form of intuition alone, and thus to the subjective constitution of our mind, without which these predicates could not be attached to anything at all."[18] This develops his theory of knowledge in which knowledge about space itself can be both a priori and synthetic.[19]
According to Kant, knowledge about space is synthetic because any proposition about space cannot be true merely in virtue of the meaning of the terms contained in the proposition. In the counter-example, the proposition "all unmarried men are bachelors" is true by virtue of each term's meaning. Further, space is a priori because it is the form of our receptive abilities to receive information about the external world. For example, someone without sight can still perceive spatial attributes via touch, hearing, and smell. Knowledge of space itself is a priori because it belongs to the subjective constitution of our mind as the form or manner of our intuition of external objects.
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.[20] Around 1830 though, the Hungarian János 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.[21]
Henri Poincaré, 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.[22] 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.[23] In fact, the scientists cannot in principle determine whether they inhabit a plane or sphere and, Poincaré 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.[24] 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.[25]
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 vacuum is the same for all observers—which 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.[26] 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.
This program unpacks Playstation 3 Theme files (.p3t) so that you can touch-up an existing theme to your likings or use a certain wallpaper from it (as many themes have multiple). But remember, if you use content from another theme and release it, be sure to give credit!
Download p3textractor.zip from above. Extract the files to a folder with a program such as WinZip or WinRAR. Now there are multiple ways to extract the theme.
The first way is to simply open the p3t file with p3textractor.exe. If you don’t know how to do this, right click the p3t file and select Open With. Alternatively, open the p3t file and it will ask you to select a program to open with. Click Browse and find p3textractor.exe from where you previously extracted it to. It will open CMD and extract the theme to extracted.[filename]. After that, all you need to do for any future p3t files is open them and it will extract.
The second way is very simple. Just drag the p3t file to p3textractor.exe. It will open CMD and extract the theme to extracted.[filename].
For the third way, first put the p3t file you want to extract into the same folder as p3textractor.exe. Open CMD and browse to the folder with p3extractor.exe. Enter the following: p3textractor filename.p3t [destination path]Replace filename with the name of the p3t file, and replace [destination path] with the name of the folder you want the files to be extracted to. A destination path is not required. By default it will extract to extracted.filename.
This program unpacks Playstation 3 Theme files (.p3t) so that you can touch-up an existing theme to your likings or use a certain wallpaper from it (as many themes have multiple). But remember, if you use content from another theme and release it, be sure to give credit!
Download p3textractor.zip from above. Extract the files to a folder with a program such as WinZip or WinRAR. Now there are multiple ways to extract the theme.
The first way is to simply open the p3t file with p3textractor.exe. If you don’t know how to do this, right click the p3t file and select Open With. Alternatively, open the p3t file and it will ask you to select a program to open with. Click Browse and find p3textractor.exe from where you previously extracted it to. It will open CMD and extract the theme to extracted.[filename]. After that, all you need to do for any future p3t files is open them and it will extract.
The second way is very simple. Just drag the p3t file to p3textractor.exe. It will open CMD and extract the theme to extracted.[filename].
For the third way, first put the p3t file you want to extract into the same folder as p3textractor.exe. Open CMD and browse to the folder with p3extractor.exe. Enter the following: p3textractor filename.p3t [destination path]Replace filename with the name of the p3t file, and replace [destination path] with the name of the folder you want the files to be extracted to. A destination path is not required. By default it will extract to extracted.filename.
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This program unpacks Playstation 3 Theme files (.p3t) so that you can touch-up an existing theme to your likings or use a certain wallpaper from it (as many themes have multiple). But remember, if you use content from another theme and release it, be sure to give credit!
Download p3textractor.zip from above. Extract the files to a folder with a program such as WinZip or WinRAR. Now there are multiple ways to extract the theme.
The first way is to simply open the p3t file with p3textractor.exe. If you don’t know how to do this, right click the p3t file and select Open With. Alternatively, open the p3t file and it will ask you to select a program to open with. Click Browse and find p3textractor.exe from where you previously extracted it to. It will open CMD and extract the theme to extracted.[filename]. After that, all you need to do for any future p3t files is open them and it will extract.
The second way is very simple. Just drag the p3t file to p3textractor.exe. It will open CMD and extract the theme to extracted.[filename].
For the third way, first put the p3t file you want to extract into the same folder as p3textractor.exe. Open CMD and browse to the folder with p3extractor.exe. Enter the following: p3textractor filename.p3t [destination path]Replace filename with the name of the p3t file, and replace [destination path] with the name of the folder you want the files to be extracted to. A destination path is not required. By default it will extract to extracted.filename.
The full set of rings, imaged as Saturn eclipsed the Sun from the vantage of the Cassini orbiter, 1.2 million km (¾ million miles) distant, on 19 July 2013 (brightness is exaggerated). Earth appears as a dot at 4 o'clock, between the G and E rings.
The rings of Saturn are the most extensive and complex ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometers to meters,[1] that orbit around Saturn. The ring particles are made almost entirely of water ice, with a trace component of rocky material. There is still no consensus as to their mechanism of formation. Although theoretical models indicated that the rings were likely to have formed early in the Solar System's history,[2] newer data from Cassini suggested they formed relatively late.[3]
Although reflection from the rings increases Saturn's brightness, they are not visible from Earth with unaided vision. In 1610, the year after Galileo Galilei turned a telescope to the sky, he became the first person to observe Saturn's rings, though he could not see them well enough to discern their true nature. In 1655, Christiaan Huygens was the first person to describe them as a disk surrounding Saturn.[4] The concept that Saturn's rings are made up of a series of tiny ringlets can be traced to Pierre-Simon Laplace,[4] although true gaps are few – it is more correct to think of the rings as an annular disk with concentric local maxima and minima in density and brightness.[2] On the scale of the clumps within the rings there is much empty space.
The rings have numerous gaps where particle density drops sharply: two opened by known moons embedded within them, and many others at locations of known destabilizing orbital resonances with the moons of Saturn. Other gaps remain unexplained. Stabilizing resonances, on the other hand, are responsible for the longevity of several rings, such as the Titan Ringlet and the G Ring.
Well beyond the main rings is the Phoebe ring, which is presumed to originate from Phoebe and thus share its retrograde orbital motion. It is aligned with the plane of Saturn's orbit. Saturn has an axial tilt of 27 degrees, so this ring is tilted at an angle of 27 degrees to the more visible rings orbiting above Saturn's equator.
Voyager 2 view of Saturn casting a shadow across its rings. Four satellites, two of their shadows, and ring spokes are visible.
In September 2023, astronomers reported studies suggesting that the rings of Saturn may have resulted from the collision of two moons "a few hundred million years ago".[5][6]
Detail of Galileo's drawing of Saturn in a letter to Belisario Vinta (1610)
Galileo Galilei was the first to observe the rings of Saturn in 1610 using his telescope, but was unable to identify them as such. He wrote to the Duke of Tuscany that "The planet Saturn is not alone, but is composed of three, which almost touch one another and never move nor change with respect to one another. They are arranged in a line parallel to the zodiac, and the middle one (Saturn itself) is about three times the size of the lateral ones."[7] He also described the rings as Saturn's "ears". In 1612 the Earth passed through the plane of the rings and they became invisible. Mystified, Galileo remarked "I do not know what to say in a case so surprising, so unlooked for and so novel."[4] He mused, "Has Saturn swallowed his children?" — referring to the myth of the TitanSaturn devouring his offspring to forestall the prophecy of them overthrowing him.[7][8] He was further confused when the rings again became visible in 1613.[4]
Early astronomers used anagrams as a form of commitment scheme to lay claim to new discoveries before their results were ready for publication. Galileo used the anagram "smaismrmilmepoetaleumibunenugttauiras" for Altissimum planetam tergeminum observavi ("I have observed the most distant planet to have a triple form") for discovering the rings of Saturn.[9][10][11]
In 1657 Christopher Wren became Professor of Astronomy at Gresham College, London. He had been making observations of the planet Saturn from around 1652 with the aim of explaining its appearance. His hypothesis was written up in De corpore saturni, in which he came close to suggesting the planet had a ring. However, Wren was unsure whether the ring was independent of the planet, or physically attached to it. Before Wren's hypothesis was published Christiaan Huygens presented his hypothesis of the rings of Saturn. Immediately Wren recognised this as a better hypothesis than his own and De corpore saturni was never published. Robert Hooke was another early observer of the rings of Saturn, and noted the casting of shadows on the rings.[12]
Huygens' ring hypothesis and later developments[edit]
Huygens' ring hypothesis in Systema Saturnium (1659)
Huygens began grinding lenses with his father Constantijn in 1655 and was able to observe Saturn with greater detail using a 43× power refracting telescope that he designed himself. He was the first to suggest that Saturn was surrounded by a ring detached from the planet, and famously published the anagram: "aaaaaaacccccdeeeeeghiiiiiiillllmmnnnnnnnnnooooppqrrstttttuuuuu".[13] Three years later, he revealed it to mean Annulo cingitur, tenui, plano, nusquam coherente, ad eclipticam inclinato ("[Saturn] is surrounded by a thin, flat, ring, nowhere touching [the body of the planet], inclined to the ecliptic").[14][4][15] He published his ring hypothesis in Systema Saturnium (1659) which also included his discovery of Saturn's moon, Titan, as well as the first clear outline of the dimensions of the Solar System.[16]
In 1675, Giovanni Domenico Cassini determined that Saturn's ring was composed of multiple smaller rings with gaps between them;[17] the largest of these gaps was later named the Cassini Division. This division is a 4,800-kilometre-wide (3,000 mi) region between the A ring and B Ring.[18]
In 1787, Pierre-Simon Laplace proved that a uniform solid ring would be unstable and suggested that the rings were composed of a large number of solid ringlets.[19][4][20]
In 1859, James Clerk Maxwell demonstrated that a nonuniform solid ring, solid ringlets or a continuous fluid ring would also not be stable, indicating that the ring must be composed of numerous small particles, all independently orbiting Saturn.[21][20] Later, Sofia Kovalevskaya also found that Saturn's rings cannot be liquid ring-shaped bodies.[22][23] Spectroscopic studies of the rings which were carried out independently in 1895 by James Keeler of the Allegheny Observatory and by Aristarkh Belopolsky of the Pulkovo Observatory showed that Maxwell's analysis was correct.[24][25]
Four robotic spacecraft have observed Saturn's rings from the vicinity of the planet. Pioneer 11's closest approach to Saturn occurred in September 1979 at a distance of 20,900 km (13,000 mi).[26]Pioneer 11 was responsible for the discovery of the F ring.[26]Voyager 1's closest approach occurred in November 1980 at a distance of 64,200 km (39,900 mi).[27] A failed photopolarimeter prevented Voyager 1 from observing Saturn's rings at the planned resolution; nevertheless, images from the spacecraft provided unprecedented detail of the ring system and revealed the existence of the G ring.[28]Voyager 2's closest approach occurred in August 1981 at a distance of 41,000 km (25,000 mi).[27]Voyager 2's working photopolarimeter allowed it to observe the ring system at higher resolution than Voyager 1, and to thereby discover many previously unseen ringlets.[29]Cassini spacecraft entered into orbit around Saturn in July 2004.[30]Cassini's images of the rings are the most detailed to-date, and are responsible for the discovery of yet more ringlets.[31]
The rings are named alphabetically in the order they were discovered[32] (A and B in 1675 by Giovanni Domenico Cassini, C in 1850 by William Cranch Bond and his son George Phillips Bond, D in 1933 by Nikolai P. Barabachov and B. Semejkin, E in 1967 by Walter A. Feibelman, F in 1979 by Pioneer 11, and G in 1980 by Voyager 1). The main rings are, working outward from the planet, C, B and A, with the Cassini Division, the largest gap, separating Rings B and A. Several fainter rings were discovered more recently. The D Ring is exceedingly faint and closest to the planet. The narrow F Ring is just outside the A Ring. Beyond that are two far fainter rings named G and E. The rings show a tremendous amount of structure on all scales, some related to perturbations by Saturn's moons, but much unexplained.[32]
In September 2023, astronomers reported studies suggesting that the rings of Saturn may have resulted from the collision of two moons "a few hundred million years ago".[5][6]
Simulated appearance of Saturn as seen from Earth over the course of one Saturn year
Saturn's axial tilt is 26.7°, meaning that widely varying views of the rings, of which the visible ones occupy its equatorial plane, are obtained from Earth at different times.[33] Earth makes passes through the ring plane every 13 to 15 years, about every half Saturn year, and there are about equal chances of either a single or three crossings occurring in each such occasion. The most recent ring plane crossings were on 22 May 1995, 10 August 1995, 11 February 1996 and 4 September 2009; upcoming events will occur on 23 March 2025, 15 October 2038, 1 April 2039 and 9 July 2039. Favorable ring plane crossing viewing opportunities (with Saturn not close to the Sun) only come during triple crossings.[34][35][36]
Saturn's equinoxes, when the Sun passes through the ring plane, are not evenly spaced. The sun passes south to north through the ring plane when Saturn's heliocentric longitude is 173.6 degrees (e.g. 11 August 2009), about the time Saturn crosses from Leo to Virgo. 15.7 years later Saturn's longitude reaches 353.6 degrees and the sun passes to the south side of the ring plane. On each orbit the Sun is north of the ring plane for 15.7 Earth years, then south of the plane for 13.7 years.[a] Dates for north-to-south crossings include 19 November 1995 and 6 May 2025, with south-to-north crossings on 11 August 2009 and 23 January 2039.[38] During the period around an equinox the illumination of most of the rings is greatly reduced, making possible unique observations highlighting features that depart from the ring plane.[39]
Simulated image using color to present radio-occultation-derived particle size data. The attenuation of 0.94-, 3.6-, and 13-cm signals sent by Cassini through the rings to Earth shows abundance of particles of sizes similar to or larger than those wavelengths. Purple (B, inner A Ring) means few particles are < 5 cm (all signals similarly attenuated). Green and blue (C, outer A Ring) mean particles < 5 cm and < 1 cm, respectively, are common. White areas (B Ring) are too dense to transmit adequate signal. Other evidence shows rings A to C have a broad range of particle sizes, up to m across.The dark Cassini Division separates the wide inner B Ring and outer A ring in this image from the HST's ACS (March 22, 2004). The less prominent C Ring is just inside the B Ring.Cassini mosaic of Saturn's rings on August 12, 2009, a day after equinox. With the rings pointed at the Sun, illumination is by light reflected off Saturn, except on thicker or out-of-plane sections, like the F Ring.Cassini space probe view of the unilluminated side of Saturn's rings (May 9, 2007).
The dense main rings extend from 7,000 km (4,300 mi) to 80,000 km (50,000 mi) away from Saturn's equator, whose radius is 60,300 km (37,500 mi) (see Major subdivisions). With an estimated local thickness of as little as 10 metres (32' 10")[40] and as much as 1 km (1093 yards),[41] they are composed of 99.9% pure water ice with a smattering of impurities that may include tholins or silicates.[42] The main rings are primarily composed of particles smaller than 10 m.[43]
Cassini directly measured the mass of the ring system via their gravitational effect during its final set of orbits that passed between the rings and the cloud tops, yielding a value of 1.54 (± 0.49) × 1019 kg, or 0.41 ± 0.13 Mimas masses.[3] This is around two-thirds the mass of the Earth's entire Antarctic ice sheet, spread across a surface area 80 times larger than that of Earth.[44][45] The estimate is close to the value of 0.40 Mimas masses derived from Cassini observations of density waves in the A, B and C rings.[3] It is a small fraction of the total mass of Saturn (about 0.25 ppb). Earlier Voyager observations of density waves in the A and B rings and an optical depth profile had yielded a mass of about 0.75 Mimas masses,[46] with later observations and computer modeling suggesting that was an underestimate.[47]
Although the largest gaps in the rings, such as the Cassini Division and Encke Gap, can be seen from Earth, the Voyager spacecraft discovered that the rings have an intricate structure of thousands of thin gaps and ringlets. This structure is thought to arise, in several different ways, from the gravitational pull of Saturn's many moons. Some gaps are cleared out by the passage of tiny moonlets such as Pan,[48] many more of which may yet be discovered, and some ringlets seem to be maintained by the gravitational effects of small shepherd satellites (similar to Prometheus and Pandora's maintenance of the F ring). Other gaps arise from resonances between the orbital period of particles in the gap and that of a more massive moon further out; Mimas maintains the Cassini Division in this manner.[49] Still more structure in the rings consists of spiral waves raised by the inner moons' periodic gravitational perturbations at less disruptive resonances.[citation needed]
Data from the Cassini space probe indicate that the rings of Saturn possess their own atmosphere, independent of that of the planet itself. The atmosphere is composed of molecular oxygen gas (O2) produced when ultraviolet light from the Sun interacts with water ice in the rings. Chemical reactions between water molecule fragments and further ultraviolet stimulation create and eject, among other things, O2. According to models of this atmosphere, H2 is also present. The O2 and H2 atmospheres are so sparse that if the entire atmosphere were somehow condensed onto the rings, it would be about one atom thick.[50] The rings also have a similarly sparse OH (hydroxide) atmosphere. Like the O2, this atmosphere is produced by the disintegration of water molecules, though in this case the disintegration is done by energetic ions that bombard water molecules ejected by Saturn's moon Enceladus. This atmosphere, despite being extremely sparse, was detected from Earth by the Hubble Space Telescope.[51]
Saturn shows complex patterns in its brightness.[52] Most of the variability is due to the changing aspect of the rings,[53][54] and this goes through two cycles every orbit. However, superimposed on this is variability due to the eccentricity of the planet's orbit that causes the planet to display brighter oppositions in the northern hemisphere than it does in the southern.[55]
In 1980, Voyager 1 made a fly-by of Saturn that showed the F ring to be composed of three narrow rings that appeared to be braided in a complex structure; it is now known that the outer two rings consist of knobs, kinks and lumps that give the illusion of braiding, with the less bright third ring lying inside them.[citation needed]
New images of the rings taken around the 11 August 2009 equinox of Saturn by NASA's Cassini spacecraft have shown that the rings extend significantly out of the nominal ring plane in a few places. This displacement reaches as much as 4 km (2.5 mi) at the border of the Keeler Gap, due to the out-of-plane orbit of Daphnis, the moon that creates the gap.[56]
Estimates of the age of Saturn's rings vary widely, depending on the approach used. They have been considered to possibly be very old, dating to the formation of Saturn itself. However, data from Cassini suggest they are much younger, having most likely formed within the last 100 million years, and may thus be between 10 million and 100 million years old.[3][57] This recent origin scenario is based on a new, low mass estimate, modeling of the rings' dynamical evolution, and measurements of the flux of interplanetary dust, which feed into an estimate of the rate of ring darkening over time.[3] Since the rings are continually losing material, they would have been more massive in the past than at present.[3] The mass estimate alone is not very diagnostic, since high mass rings that formed early in the Solar System's history would have evolved by now to a mass close to that measured.[3] Based on current depletion rates, they may disappear in 300 million years.[58][59]
There are two main theories regarding the origin of Saturn's inner rings. A theory originally proposed by Édouard Roche in the 19th century, is that the rings were once a moon of Saturn (named Veritas, after a Roman goddess who hid in a well). According to the theory the moon's orbit decayed until it was close enough to be ripped apart by tidal forces (see Roche limit).[60] Numerical simulations carried out in 2022 support this theory; the authors of that study proposed the name "Chrysalis" for the destroyed moon.[61] A variation on this theory is that this moon disintegrated after being struck by a large comet or asteroid.[62] The second theory is that the rings were never part of a moon, but are instead left over from the original nebular material from which Saturn formed.[citation needed]
A 2007 artist impression of the aggregates of icy particles that form the 'solid' portions of Saturn's rings. These elongated clumps are continually forming and dispersing. The largest particles are a few meters across.
A more traditional version of the disrupted-moon theory is that the rings are composed of debris from a moon 400 to 600 km (200 to 400 miles) in diameter, slightly larger than Mimas. The last time there were collisions large enough to be likely to disrupt a moon that large was during the Late Heavy Bombardment some four billion years ago.[63]
A more recent variant of this type of theory by R. M. Canup is that the rings could represent part of the remains of the icy mantle of a much larger, Titan-sized, differentiated moon that was stripped of its outer layer as it spiraled into the planet during the formative period when Saturn was still surrounded by a gaseous nebula.[64][65] This would explain the scarcity of rocky material within the rings. The rings would initially have been much more massive (≈1,000 times) and broader than at present; material in the outer portions of the rings would have coalesced into the moons of Saturn out to Tethys, also explaining the lack of rocky material in the composition of most of these moons.[65] Subsequent collisional or cryovolcanic evolution of Enceladus might then have caused selective loss of ice from this moon, raising its density to its current value of 1.61 g/cm3, compared to values of 1.15 for Mimas and 0.97 for Tethys.[65]
The idea of massive early rings was subsequently extended to explain the formation of Saturn's moons out to Rhea.[66] If the initial massive rings contained chunks of rocky material (>100 km; 60 miles across) as well as ice, these silicate bodies would have accreted more ice and been expelled from the rings, due to gravitational interactions with the rings and tidal interaction with Saturn, into progressively wider orbits. Within the Roche limit, bodies of rocky material are dense enough to accrete additional material, whereas less-dense bodies of ice are not. Once outside the rings, the newly formed moons could have continued to evolve through random mergers. This process may explain the variation in silicate content of Saturn's moons out to Rhea, as well as the trend towards less silicate content closer to Saturn. Rhea would then be the oldest of the moons formed from the primordial rings, with moons closer to Saturn being progressively younger.[66]
The brightness and purity of the water ice in Saturn's rings have also been cited as evidence that the rings are much younger than Saturn,[57] as the infall of meteoric dust would have led to a darkening of the rings. However, new research indicates that the B Ring may be massive enough to have diluted infalling material and thus avoided substantial darkening over the age of the Solar System. Ring material may be recycled as clumps form within the rings and are then disrupted by impacts. This would explain the apparent youth of some of the material within the rings.[67] Evidence suggesting a recent origin of the C ring has been gathered by researchers analyzing data from the Cassini Titan Radar Mapper, which focused on analyzing the proportion of rocky silicates within this ring. If much of this material was contributed by a recently disrupted centaur or moon, the age of this ring could be on the order of 100 million years or less. On the other hand, if the material came primarily from micrometeoroid influx, the age would be closer to a billion years.[68]
The Cassini UVIS team, led by Larry Esposito, used stellar occultation to discover 13 objects, ranging from 27 metres (89') to 10 km (6 miles) across, within the F ring. They are translucent, suggesting they are temporary aggregates of ice boulders a few meters across. Esposito believes this to be the basic structure of the Saturnian rings, particles clumping together, then being blasted apart.[69]
Research based on rates of infall into Saturn favors a younger ring system age of hundreds of millions of years. Ring material is continually spiraling down into Saturn; the faster this infall, the shorter the lifetime of the ring system. One mechanism involves gravity pulling electrically charged water ice grains down from the rings along planetary magnetic field lines, a process termed 'ring rain'. This flow rate was inferred to be 432–2870 kg/s using ground-based Keck telescope observations; as a consequence of this process alone, the rings will be gone in ~292+818 −124 million years.[70] While traversing the gap between the rings and planet in September 2017, the Cassini spacecraft detected an equatorial flow of charge-neutral material from the rings to the planet of 4,800–44,000 kg/s.[71] Assuming this influx rate is stable, adding it to the continuous 'ring rain' process implies the rings may be gone in under 100 million years.[70][72]
Subdivisions and structures within the rings[edit]
The densest parts of the Saturnian ring system are the A and B Rings, which are separated by the Cassini Division (discovered in 1675 by Giovanni Domenico Cassini). Along with the C Ring, which was discovered in 1850 and is similar in character to the Cassini Division, these regions constitute the main rings. The main rings are denser and contain larger particles than the tenuous dusty rings. The latter include the D Ring, extending inward to Saturn's cloud tops, the G and E Rings and others beyond the main ring system. These diffuse rings are characterised as "dusty" because of the small size of their particles (often about a μm); their chemical composition is, like the main rings, almost entirely water ice. The narrow F Ring, just off the outer edge of the A Ring, is more difficult to categorize; parts of it are very dense, but it also contains a great deal of dust-size particles.
Natural-color mosaic of Cassini narrow-angle camera images of the unilluminated side of Saturn's D, C, B, A and F rings (left to right) taken on May 9, 2007 (distances are to the planet's center).
