White hole

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/White_hole

In general relativity, a white hole is a hypothetical region of spacetime and singularity that cannot be entered from the outside, although energy-matter, light and information can escape from it. In this sense, it is the reverse of a black hole, from which energy-matter, light and information cannot escape. White holes appear in the theory of eternal black holes. In addition to a black hole region in the future, such a solution of the Einstein field equations has a white hole region in its past. This region does not exist for black holes that have formed through gravitational collapse, however, nor are there any observed physical processes through which a white hole could be formed.

Supermassive black holes (SMBHs) are theoretically predicted to be at the center of every galaxy and may be essential for their formation. Stephen Hawking and others have proposed that these supermassive black holes could spawn supermassive white holes.

Overview

Like black holes, white holes have properties such as mass, charge, and angular momentum. They attract matter like any other mass, but objects falling towards a white hole would never actually reach the white hole's event horizon (though in the case of the maximally extended Schwarzschild solution, discussed below, the white hole event horizon in the past becomes a black hole event horizon in the future, so any object falling towards it will eventually reach the black hole horizon). Imagine a gravitational field, without a surface. Acceleration due to gravity is the greatest on the surface of any body. But since black holes lack a surface, acceleration due to gravity increases exponentially, but never reaches a final value as there is no considered surface in a singularity.

In quantum mechanics, the black hole emits Hawking radiation and so it can come to thermal equilibrium with a gas of radiation (not compulsory). Because a thermal-equilibrium state is time-reversal-invariant, Stephen Hawking argued that the time reversal of a black hole in thermal equilibrium results in a white hole in thermal equilibrium (each absorbing and emitting energy to equivalent degrees).^{[4][further explanation needed]} Consequently, this may imply that black holes and white holes are reciprocal in structure, wherein the Hawking radiation from an ordinary black hole is identified with a white hole's emission of energy and matter. Hawking's semi-classical argument is reproduced in a quantum mechanical AdS/CFT treatment, where a black hole in anti-de Sitter space is described by a thermal gas in a gauge theory, whose time reversal is the same as itself.

History

A diagram of the structure of the maximally extended black hole spacetime. The horizontal direction is space and the vertical direction is time.

In the 1930s, physicists Robert Oppenheimer and Hartland Snyder introduced the idea of white holes as a solution to Einstein's equations of general relativity. These equations, the foundation of modern physics, describe the curvature of spacetime due to massive objects. Whereas black holes are born from the collapse of stars, white holes represent the theoretical birth of space, time, and potentially even universes. At the center, space and time do not end into a singularity, but continue across a short transition region where the Einstein equations are violated by quantum effects. From this region, space and time emerge with the structure of a white hole interior, a possibility already suggested by John Lighton Synge.

The possibility of the existence of white holes was put forward by cosmologist Igor Novikov in 1964, developed by Nikolai Kardashev. White holes are predicted as part of a solution to the Einstein field equations known as the maximally extended version of the Schwarzschild metric describing an eternal black hole with no charge and no rotation. Here, "maximally extended" implies that spacetime should not have any "edges". For any possible trajectory of a free-falling particle (following a geodesic) in spacetime, it should be possible to continue this path arbitrarily far into the particle's future, unless the trajectory hits a gravitational singularity like the one at the center of the black hole's interior. In order to satisfy this requirement, it turns out that in addition to the black hole interior region that particles enter when they fall through the event horizon from the outside, there must be a separate white hole interior region, which allows us to extrapolate the trajectories of particles that an outside observer sees rising up away from the event horizon. For an observer outside using Schwarzschild coordinates, infalling particles take an infinite time to reach the black hole horizon infinitely far in the future, while outgoing particles that pass the observer have been traveling outward for an infinite time since crossing the white hole horizon infinitely far in the past (however, the particles or other objects experience only a finite proper time between crossing the horizon and passing the outside observer). The black hole/white hole appears "eternal" from the perspective of an outside observer, in the sense that particles traveling outward from the white hole interior region can pass the observer at any time, and particles traveling inward, which will eventually reach the black hole interior region can also pass the observer at any time.

Just as there are two separate interior regions of the maximally extended spacetime, there are also two separate exterior regions, sometimes called two different "universes", with the second universe allowing us to extrapolate some possible particle trajectories in the two interior regions. This means that the interior black-hole region can contain a mix of particles that fell in from either universe (and thus an observer who fell in from one universe might be able to see light that fell in from the other one), and likewise particles from the interior white-hole region can escape into either universe. All four regions can be seen in a spacetime diagram that uses Kruskal–Szekeres coordinates (see figure).

In this spacetime, it is possible to come up with coordinate systems such that if you pick a hypersurface of constant time (a set of points that all have the same time coordinate, such that every point on the surface has a space-like separation, giving what is called a 'space-like surface') and draw an "embedding diagram" depicting the curvature of space at that time, the embedding diagram will look like a tube connecting the two exterior regions, known as an "Einstein-Rosen bridge" or Schwarzschild wormhole.^[9] Depending on where the space-like hypersurface is chosen, the Einstein-Rosen bridge can either connect two black hole event horizons in each universe (with points in the interior of the bridge being part of the black hole region of the spacetime), or two white hole event horizons in each universe (with points in the interior of the bridge being part of the white hole region). It is impossible to use the bridge to cross from one universe to the other, however, because it is impossible to enter a white hole event horizon from the outside, and anyone entering a black hole horizon from either universe will inevitably hit the black hole singularity.

Note that the maximally extended Schwarzschild metric describes an idealized black hole/white hole that exists eternally from the perspective of external observers; a more realistic black hole that forms at some particular time from a collapsing star would require a different metric. When the infalling stellar matter is added to a diagram of a black hole's history, it removes the part of the diagram corresponding to the white hole interior region. But because the equations of general relativity are time-reversible – they exhibit Time reversal symmetry – general relativity must also allow the time-reverse of this type of "realistic" black hole that forms from collapsing matter. The time-reversed case would be a white hole that has existed since the beginning of the universe, and that emits matter until it finally "explodes" and disappears. Despite the fact that such objects are permitted theoretically, they are not taken as seriously as black holes by physicists, since there would be no processes that would naturally lead to their formation; they could exist only if they were built into the initial conditions of the Big Bang. Additionally, it is predicted that such a white hole would be highly "unstable" in the sense that if any small amount of matter fell towards the horizon from the outside, this would prevent the white hole's explosion as seen by distant observers, with the matter emitted from the singularity never able to escape the white hole's gravitational radius.

Properties

Depending on the type of black hole solution considered, there are several types of white holes. In the case of the Schwarzschild black hole mentioned above, a geodesic coming out of a white hole comes from the "gravitational singularity" it contains. In the case of a black hole possessing an electric charge ψ ** Ώ ** ώ (Reissner-Nordström black hole) or an angular momentum, then the white hole happens to be the "exit door" of a black hole existing in another universe. Such a black hole – white hole configuration is called a wormhole. In both cases, however, it is not possible to reach the region "in" the white hole, so the behavior of it – and, in particular, what may come out of it – is completely impossible to predict. In this sense, a white hole is a configuration according to which the evolution of the universe cannot be predicted, because it is not deterministic. A "bare singularity" is another example of a non-deterministic configuration, but does not have the status of a white hole, however, because there is no region inaccessible from a given region. In its basic conception, the Big Bang can be seen as a naked singularity in outer space, but does not correspond to a white hole.

Physical relevance

In its mode of formation, a black hole comes from a residue of a massive star whose core contracts until it turns into a black hole. Such a configuration is not static: we start from a massive and extended body which contracts to give a black hole. The black hole therefore does not exist for all eternity, and there is no corresponding white hole.

To be able to exist, a white hole must either arise from a physical process leading to its formation, or be present from the creation of the universe. None of these solutions appears satisfactory: there is no known astrophysical process that can lead to the formation of such a configuration, and imposing it from the creation of the universe amounts to assuming a very specific set of initial conditions which has no concrete motivation.

In view of the enormous quantities radiated by quasars, whose luminosity makes it possible to observe them from several billion light-years away, it had been assumed that they were the seat of exotic physical phenomena such as a white hole, or a phenomenon of continuous creation of matter (see the article on the steady state theory). These ideas are now abandoned, the observed properties of quasars being very well explained by those of an accretion disk in the center of which is a supermassive black hole.

Big Bang/Supermassive White Hole

Main article: Big Bang

See also: Lee Smolin § Cosmological natural selection, and Shockwave cosmology

A view of black holes first proposed in the late 1980s might be interpreted as shedding some light on the nature of classical white holes. Some researchers have proposed that when a black hole forms, a Big Bang may occur at the core/singularity, which would create a new universe that expands outside of the parent universe.

The Einstein–Cartan–Sciama–Kibble theory of gravity extends general relativity by removing a constraint of the symmetry of the affine connection and regarding its antisymmetric part, the torsion tensor, as a dynamical variable. Torsion naturally accounts for the quantum-mechanical, intrinsic angular momentum (spin) of matter. According to general relativity, the gravitational collapse of a sufficiently compact mass forms a singular black hole. In the Einstein–Cartan theory, however, the minimal coupling between torsion and Dirac spinors generates a repulsive spin–spin interaction that is significant in fermionic matter at extremely high densities. Such an interaction prevents the formation of a gravitational singularity. Instead, the collapsing matter on the other side of the event horizon reaches an enormous but finite density and rebounds, forming a regular Einstein–Rosen bridge. The other side of the bridge becomes a new, growing baby universe. For observers in the baby universe, the parent universe appears as the only white hole. Accordingly, the observable universe is the Einstein–Rosen interior of a black hole existing as one of possibly many inside a larger universe. The Big Bang was a nonsingular Big Bounce at which the observable universe had a finite, minimum scale factor.

Shockwave cosmology, proposed by Joel Smoller and Blake Temple in 2003, has the “big bang” as an explosion inside a black hole, producing the expanding volume of space and matter that includes the observable universe. This black hole eventually becomes a white hole as the matter density reduces with the expansion. A related theory gives an alternative to dark energy.

A 2012 paper argues that the Big Bang itself is a white hole. It further suggests that the emergence of a white hole, which was named a "Small Bang", is spontaneous—all the matter is ejected at a single pulse. Thus, unlike black holes, white holes cannot be continuously observed; rather, their effects can be detected only around the event itself. The paper even proposed identifying a new group of gamma-ray bursts with white holes.

Various hypotheses

Unlike black holes for which there is a well-studied physical process, gravitational collapse (which gives rise to black holes when a star somewhat more massive than the sun exhausts its nuclear "fuel"), there is no clear analogous process that leads reliably to the production of white holes. Although some hypotheses have been put forward:

• White holes as a kind of "exit" from black holes, both types of singularities would probably be connected by a wormhole (note that, like white holes, wormholes have not yet been found); when quasars were discovered it was assumed that these were the sought-after white holes but this assumption has now been discarded.
• Another widespread idea is that white holes would be very unstable, would last a very short time and even after forming could collapse and become black holes.
• Astronomers Alon Retter and Shlomo Heller suggest that the GRB 060614 anomalous gamma-ray burst that occurred in 2006 was a "white hole".
• In 2014, the idea of the Big Bang being produced by a supermassive white hole explosion was explored in the framework of a five-dimensional vacuum by Madriz Aguilar, Moreno and Bellini.
• Finally, it has been postulated that white holes could be the temporal inverse of a black hole.

At present, very few scientists believe in the existence of white holes and it is considered only a mathematical exercise with no real-world counterpart.

In popular culture

• A white hole appears in the Red Dwarf episode of the same name, wherein the protagonists must find a way to deal with its temporal effects.
• A white hole serves as a major source of conflict in the Yu-Gi-Oh! GX anime, as the radiance it exudes is both sentient and evil, known as the Light of Destruction.
• A white hole serves as a very important location in the video game Outer Wilds. In this game, falling into the black hole in the center of the planet Brittle Hollow leads to this white hole.
• A white hole appears in the animated television series Voltron: Legendary Defender.

Evolutionary origin of religion

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Evolutionary_origin_of_religion

The evolutionary origin of religion and religious behavior is a field of study related to evolutionary psychology, the origin of language and mythology, and cross-cultural comparison of the anthropology of religion. Some subjects of interest include Neolithic religion, evidence for spirituality or cultic behavior in the Upper Paleolithic, and similarities in great ape behavior.

Nonhuman religious behavior

Main article: Religious behavior in animals

Humanity's closest living relatives are common chimpanzees and bonobos. These primates share a common ancestor with humans who lived between six and eight million years ago. It is for this reason that chimpanzees and bonobos are viewed as the best available surrogate for this common ancestor. Barbara King argues that while non-human primates are not religious, they do exhibit some traits that would have been necessary for the evolution of religion. These traits include high intelligence, a capacity for symbolic communication, a sense of social norms, and realization of "self" continuity.

Elephants perform rituals for their dead. They demonstrate long periods of silence and mourning at the point of death; later, elephants return to grave sites and caress the remains. Some evidence suggests that many species grieve death and loss.

Relevant prerequisites for human religion

Increased brain size

In this set of theories, the religious mind is one consequence of a brain that is large enough to formulate religious and philosophical ideas. During human evolution, the hominid brain tripled in size, peaking 500,000 years ago. Much of the brain's expansion took place in the neocortex. The cerebral neocortex is presumed to be responsible for the neural computations underlying complex phenomena such as perception, thought, language, attention, episodic memory and voluntary movement. According to Dunbar's theory, the relative neocortex size of any species correlates with the level of social complexity of the particular species. The neocortex size correlates with a number of social variables that include social group size and complexity of mating behaviors. In chimpanzees the neocortex occupies 50% of the brain, whereas in modern humans it occupies 80% of the brain.

Robin Dunbar argues that the critical event in the evolution of the neocortex took place at the speciation of archaic Homo sapiens about 500,000 years ago. His study indicates that only after the speciation event is the neocortex large enough to process complex social phenomena such as language and religion. The study is based on a regression analysis of neocortex size plotted against a number of social behaviors of living and extinct hominids.

Stephen Jay Gould suggests that religion may have grown out of evolutionary changes that favored larger brains as a means of cementing group coherence among savanna hunters, after that larger brain enabled reflection on the inevitability of personal mortality.

Tool use

Lewis Wolpert argues that causal beliefs that emerged from tool use played a major role in the evolution of belief. The manufacture of complex tools requires creating a mental image of an object that does not exist naturally before actually making the artifact. Furthermore, one must understand how the tool would be used, that requires an understanding of causality. Accordingly, the level of sophistication of stone tools is a useful indicator of causal beliefs. Wolpert contends use of tools composed of more than one component, such as hand axes, represents an ability to understand cause and effect. However, recent studies of other primates indicate that causality may not be a uniquely human trait. For example, chimpanzees have been known to escape from pens closed with multiple latches, which was previously thought could only have been figured out by humans who understood causality. Chimpanzees are also known to mourn the dead, and notice things that have only aesthetic value, like sunsets, both of which may be considered to be components of religion or spirituality. The difference between the comprehension of causality by humans and chimpanzees is one of degree. The degree of comprehension in an animal depends upon the size of the prefrontal cortex: the greater the size of the prefrontal cortex the deeper the comprehension.

Development of language

See also: Origin of language and Religion and mythology

Religion requires a system of symbolic communication, such as language, to be transmitted from one individual to another. Philip Lieberman states "human religious thought and moral sense clearly rest on a cognitive-linguistic base". From this premise science writer Nicholas Wade states:

"Like most behaviors that are found in societies throughout the world, religion must have been present in the ancestral human population before the dispersal from Africa 50,000 years ago. Although religious rituals usually involve dance and music, they are also very verbal, since the sacred truths have to be stated. If so, religion, at least in its modern form, cannot pre-date the emergence of language. It has been argued earlier that language attained its modern state shortly before the exodus from Africa. If religion had to await the evolution of modern, articulate language, then it too would have emerged shortly before 50,000 years ago."

Another view distinguishes individual religious belief from collective religious belief. While the former does not require prior development of language, the latter does. The individual human brain has to explain a phenomenon in order to comprehend and relate to it. This activity predates by far the emergence of language and may have caused it. The theory is, belief in the supernatural emerges from hypotheses arbitrarily assumed by individuals to explain natural phenomena that cannot be explained otherwise. The resulting need to share individual hypotheses with others leads eventually to collective religious belief. A socially accepted hypothesis becomes dogmatic backed by social sanction.

Language consists of digital contrasts whose cost is essentially zero. As pure social conventions, signals of this kind cannot evolve in a Darwinian social world—they are a theoretical impossibility. Being intrinsically unreliable, language works only if one can build up a reputation for trustworthiness within a certain kind of society—namely, one where symbolic cultural facts (sometimes called 'institutional facts') can be established and maintained through collective social endorsement. In any hunter-gatherer society, the basic mechanism for establishing trust in symbolic cultural facts is collective ritual.

Transcending the continuity-versus-discontinuity divide, some scholars view the emergence of language as the consequence of some kind of social transformation that, by generating unprecedented levels of public trust, liberated a genetic potential for linguistic creativity that had previously lain dormant. "Ritual/speech coevolution theory" exemplifies this approach. Scholars in this intellectual camp point to the fact that even chimpanzees and bonobos have latent symbolic capacities that they rarely—if ever—use in the wild. Objecting to the sudden mutation idea, these authors argue that even if a chance mutation were to install a language organ in an evolving bipedal primate, it would be adaptively useless under all known primate social conditions. A very specific social structure—one capable of upholding unusually high levels of public accountability and trust—must have evolved before or concurrently with language to make reliance on "cheap signals" (words) an evolutionarily stable strategy. The animistic nature of early human language could serve as the handicap-like cost that helped to ensure the reliability of communication. The attribution of spiritual essence to everything surrounding early humans served as a built-in mechanism that provided instant verification and ensured the inviolability of one's speech.

Animal vocal signals are, for the most part, intrinsically reliable. When a cat purrs, the signal constitutes direct evidence of the animal's contented state. The signal is trusted, not because the cat is inclined to be honest, but because it just cannot fake that sound. Primate vocal calls may be slightly more manipulable, but they remain reliable for the same reason—because they are hard to fake. Primate social intelligence is "Machiavellian"—self-serving and unconstrained by moral scruples. Monkeys and apes often attempt to deceive each other, while at the same time remaining constantly on guard against falling victim to deception themselves. Paradoxically, it is theorized that primates' resistance to deception is what blocks the evolution of their signalling systems along language-like lines. Language is ruled out because the best way to guard against being deceived is to ignore all signals except those that are instantly verifiable. Words automatically fail this test.

Morality and group living

Main articles: Evolution of morality and Morality § Evolution

Frans de Waal and Barbara King both view human morality as having grown out of primate sociality. Although morality awareness may be a unique human trait, many social animals, such as primates, dolphins and whales, have been known to exhibit pre-moral sentiments. According to Michael Shermer, the following characteristics are shared by humans and other social animals, particularly the great apes:

attachment and bonding, cooperation and mutual aid, sympathy and empathy, direct and indirect reciprocity, altruism and reciprocal altruism, conflict resolution and peacemaking, deception and deception detection, community concern and caring about what others think about you, and awareness of and response to the social rules of the group.

De Waal contends that all social animals have had to restrain or alter their behavior for group living to be worthwhile. Pre-moral sentiments evolved in primate societies as a method of restraining individual selfishness and building more cooperative groups. For any social species, the benefits of being part of an altruistic group should outweigh the benefits of individualism. For example, a lack of group cohesion could make individuals more vulnerable to attack from outsiders. Being part of a group may also improve the chances of finding food. This is evident among animals that hunt in packs to take down large or dangerous prey.

All social animals have hierarchical societies in which each member knows its own place. Social order is maintained by certain rules of expected behavior and dominant group members enforce order through punishment. Additionally, higher order primates also have a sense of fairness. 

Chimpanzees live in fission-fusion groups that average 50 individuals. It is likely that early ancestors of humans lived in groups of similar size. Based on the size of extant hunter-gatherer societies, recent Paleolithic hominids lived in bands of a few hundred individuals. As community size increased over the course of human evolution, greater enforcement to achieve group cohesion would have been required. Morality may have evolved in these bands of 100 to 200 people as a means of social control, conflict resolution and group solidarity. According to Dr. de Waal, human morality has two extra levels of sophistication that are not found in primate societies.

Psychologist Matt J. Rossano argues that religion emerged after morality and built upon morality by expanding the social scrutiny of individual behavior to include supernatural agents. By including ever-watchful ancestors, spirits and gods in the social realm, humans discovered an effective strategy for restraining selfishness and building more cooperative groups. The adaptive value of religion would have enhanced group survival. Rossano is referring here to collective religious belief and the social sanction that institutionalized morality. According to Rossano's teaching, individual religious belief is thus initially epistemological, not ethical, in nature.

Evolutionary psychology of religion

Main article: Evolutionary psychology of religion

Cognitive scientists underlined that religions may be explained as a result of the brain architecture that developed early in the genus Homo in the course of the evolutionary history of life. Nonetheless, there is disagreement on the exact mechanisms that drove the evolution of the religious mind. The two main schools of thought hold:

• either that religion evolved due to natural selection and has selective advantage
• or that religion is an evolutionary byproduct of other mental adaptations.

Stephen Jay Gould, for example, saw religion as an exaptation or a spandrel, in other words: religion evolved as byproduct of psychological mechanisms that evolved for other reasons.

Such mechanisms may include the ability to infer the presence of organisms that might do harm (agent detection), the ability to come up with causal narratives for natural events (etiology), and the ability to recognize that other people have minds of their own with their own beliefs, desires and intentions (theory of mind). These three adaptations (among others) allow human beings to imagine purposeful agents behind many observations that could not readily be explained otherwise, e.g. thunder, lightning, movement of planets, complexity of life. The emergence of collective religious belief identified such agents as deities that standardized the explanation.

Some scholars have suggested that religion is genetically "hardwired" into the human condition. One controversial proposal, the God gene hypothesis, states that some variants of a specific gene, the VMAT2 gene, predispose to spirituality.

Another view builds on the concept of the triune brain: the reptilian brain, the limbic system, and the neocortex, proposed by Paul D. MacLean. Collective religious belief draws upon the emotions of love, fear, and gregariousness and is deeply embedded in the limbic system through socio-biological conditioning and social sanction. Individual religious belief utilizes reason based in the neocortex and often varies from collective religion. The limbic system is much older in evolutionary terms than the neocortex and is, therefore, stronger than it – much in the same way as the reptilian is stronger than both the limbic system and the neocortex.

Yet another view is that the behavior of people who participate in a religion makes them feel better and this improves their biological fitness, so that there is a genetic selection in favor of people who are willing to believe in a religion. Specifically, rituals, beliefs, and the social contact typical of religious groups may serve to calm the mind (for example by reducing ambiguity and the uncertainty due to complexity) and allow it to function better when under stress. This would allow religion to be used as a powerful survival mechanism, particularly in facilitating the evolution of hierarchies of warriors, which if true, may be why many modern religions tend to promote fertility and kinship.

Still another view, proposed by Fred H. Previc, sees human religion as a product of an increase in dopaminergic functions in the human brain and of a general intellectual expansion beginning around 80 thousand years ago (kya). Dopamine promotes an emphasis on distant space and time, which can correlate with religious experience. While the earliest extant shamanic cave-paintings date to around 40 kya, the use of ocher for rock art predates this and there is clear evidence for abstract thinking along the coast of South Africa 80 kya.

Paul Bloom suggests that "certain early emergent cognitive biases ... make it natural to believe in Gods and spirits".

Prehistoric evidence of religion

See also: Paleolithic religion and Prehistoric religion

Although the exact time when humans first became religious remains unknown, research in evolutionary archaeology shows credible evidence of religious/ritualistic behavior from around the Middle Paleolithic era (45–200 thousand years ago).

Paleolithic burials

The earliest evidence of religious thought is based on the ritual treatment of the dead. Most animals display only a casual interest in the dead of their own species. Ritual burial thus represents a significant change in human behavior. Ritual burials represent an awareness of life and death and a possible belief in the afterlife. Philip Lieberman states "burials with grave goods clearly signify religious practices and concern for the dead that transcends daily life."

The earliest evidence for treatment of the dead comes from Atapuerca in Spain. At this location the bones of 30 individuals believed to be Homo heidelbergensis have been found in a pit. Neanderthals are also contenders for the first hominids to intentionally bury the dead. They may have placed corpses into shallow graves along with stone tools and animal bones. The presence of these grave goods may indicate an emotional connection with the deceased and possibly a belief in the afterlife. Neanderthal burial sites include Shanidar in Iraq and Krapina in Croatia and Kebara Cave in Israel.

The earliest known burial of modern humans is from a cave in Israel located at Qafzeh. Human remains have been dated to 100,000 years ago. Human skeletons were found stained with red ocher. A variety of grave goods were found at the burial site. The mandible of a wild boar was found placed in the arms of one of the skeletons. Philip Lieberman states:

Burial rituals incorporating grave goods may have been invented by the anatomically modern hominids who emigrated from Africa to the Middle East roughly 100,000 years ago

Matt Rossano suggests that the period between 80,000 and 60,000 years before present, following the retreat of humans from the Levant to Africa, was a crucial period in the evolution of religion.

Use of symbolism

The use of symbolism in religion is a universal established phenomenon. Archeologist Steven Mithen contends that it is common for religious practices to involve the creation of images and symbols to represent supernatural beings and ideas. Because supernatural beings violate the principles of the natural world, there will always be difficulty in communicating and sharing supernatural concepts with others. This problem can be overcome by anchoring these supernatural beings in material form through representational art. When translated into material form, supernatural concepts become easier to communicate and understand. Due to the association of art and religion, evidence of symbolism in the fossil record is indicative of a mind capable of religious thoughts. Art and symbolism demonstrates a capacity for abstract thought and imagination necessary to construct religious ideas. Wentzel van Huyssteen states that the translation of the non-visible through symbolism enabled early human ancestors to hold beliefs in abstract terms.

Some of the earliest evidence of symbolic behavior is associated with Middle Stone Age sites in Africa. From at least 100,000 years ago, there is evidence of the use of pigments such as red ocher. Pigments are of little practical use to hunter gatherers, thus evidence of their use is interpreted as symbolic or for ritual purposes. Among extant hunter gatherer populations around the world, red ocher is still used extensively for ritual purposes. It has been argued that it is universal among human cultures for the color red to represent blood, sex, life and death.

The use of red ocher as a proxy for symbolism is often criticized as being too indirect. Some scientists, such as Richard Klein and Steven Mithen, only recognize unambiguous forms of art as representative of abstract ideas. Upper paleolithic cave art provides some of the most unambiguous evidence of religious thought from the paleolithic. Cave paintings at Chauvet depict creatures that are half human and half animal.

Origins and diversification of organized religion

See also: Neolithic religion

Social evolution of humans

Period (years ago)	Society type	Number of individuals
100,000–10,000	Bands	10s–100s
10,000–5,000	Tribes	100s–1,000s
5,000–3,000	Chiefdoms	1,000s–10,000s
3,000–1,000	States	10,000s–100,000s
2,000*–present	Empires	100,000s–1,000,000s

Organized religion traces its roots to the Neolithic Revolution that began 11,000 years ago in the Near East, but may have occurred independently in several other locations around the world. The invention of agriculture transformed many human societies from a hunter-gatherer lifestyle to a sedentary lifestyle. The Neolithic Revolution led to a population explosion and an acceleration in the pace of technological development. The transition from foraging bands to states and empires precipitated more specialized and developed forms of religion that reflected the new social and political environment. While bands and small tribes possess supernatural beliefs, these beliefs do not serve to justify a central authority, justify transfer of wealth or maintain peace between unrelated individuals. Organized religion emerged as a means of providing social and economic stability through the following ways:

• Justifying the central authority, which in turn possessed the right to collect taxes in return for providing social and security services.
• Bands and tribes consist of small number of related individuals. States and nations are composed of many thousands of unrelated individuals. Jared Diamond argues that organized religion served to provide a bond between unrelated individuals who would otherwise be more prone to enmity. In his book Guns, Germs, and Steel he argues that the leading cause of death among hunter-gatherer societies is murder.
• Religions that revolved around moralizing gods may have facilitated the rise of large, cooperative groups of unrelated individuals.

The states born out of the Neolithic Revolution, such as those of Ancient Egypt and Mesopotamia, were theocracies with chiefs, kings and emperors playing dual roles of political and spiritual leaders.^[36] Anthropologists have found that virtually all state societies and chiefdoms from around the world have been found to justify political power through divine authority. This suggests that political authority co-opts collective religious belief to bolster itself.

Invention of writing

See also: History of writing

Following the Neolithic Revolution, the pace of technological development (cultural evolution) intensified due to the invention of writing 5,000 years ago. Symbols that became words later on made effective communication of ideas possible. Printing, invented only over a thousand years ago, rapidly increased the speed of communication and became the main spring of cultural evolution. Writing is thought to have been first invented in either Sumeria or Ancient Egypt, and was initially used for accounting. Soon after, writing was used to record myth. The first religious texts mark the beginning of religious history. The Pyramid Texts from ancient Egypt form one of the oldest known religious texts in the world, dating to between 2400 and 2300 BCE. Writing played a major role in sustaining and spreading organized religion. In pre-literate societies, religious ideas were based on an oral tradition, which was articulated by shamans and remained limited to the collective memories of the society's inhabitants. With the advent of writing, information that was not easy to remember could easily be stored in sacred texts that were maintained by a select group (clergy). Humans could store and process large amounts of information with writing that otherwise would have been forgotten. Writing therefore enabled religions to develop coherent and comprehensive doctrinal systems that remained independent of time and place. Writing also brought a measure of objectivity to human knowledge. Formulation of thoughts in words and the requirement for validation made possible the mutual exchange of ideas and the sifting of generally acceptable from unacceptable ideas. The generally acceptable ideas became objective knowledge reflecting the continuously evolving framework of human awareness of reality that Karl Popper calls 'verisimilitude' – a stage on the human journey to truth.

Trillion Tree Campaign

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Trillion_Tree_Campaign

 

Trillion Tree Campaign

Formation	2018
Founded at	Grimaldi Forum, Monaco
Fields	Reforestation nature conservation
Official language	English, German, Spanish, French, Portuguese
Parent organization	Plant-for-the-Planet
Affiliations	UNEP
Website	trilliontreecampaign.org
Formerly called	Billion Tree Campaign

The Trillion Tree Campaign is a project which aims to plant one trillion trees worldwide. It seeks to repopulate the world's trees and combat climate change as a nature-based solution. The project was launched at PlantAhead 2018 in Monaco by Plant-for-the-Planet. In the fall of 2018, the project's official website was published in order to register, monitor, and donate trees to reforestation projects around the world. The campaign is a continuation of the activities of the earlier Billion Tree Campaign, instigated by Wangari Maathai, who founded the Green Belt Movement in Africa in 1977.

As of 30 May 2021, 164 restoration projects participate in the campaign and 13.96 billion (1.396% of the goal) trees have been planted worldwide.

History

Billion Tree Campaign

The Green Belt Movement began its activity in Africa in 1977, eventually planting more than 30 million trees. The Billion Tree Campaign was inspired by Nobel Peace Prize laureate Wangari Maathai, founder of the Green Belt Movement. When an executive in the United States told Maathai their corporation was planning to plant a million trees, her response was: "That's great, but what we really need is to plant a billion trees."

The project was launched in 2006 by the United Nations Environment Programme (UNEP) under the patronage of Prince Albert II of Monaco and the World Agroforestry Centre-ICRAF as a response to the challenges of climate change, as well as to a wider array of sustainability challenges from water supply to biodiversity loss, and achieved the initial target of planting a billion trees in 2007. The billionth tree, commonly known as an African olive, was planted in Ethiopia in November 2007. In 2008, the campaign's objective was raised to 7 billion trees, a goal which was surpassed three months before its target of the climate change conference that was held in Copenhagen, Denmark, in December 2009.

The 2-billionth tree took root as part of the United Nations World Food Programme agroforestry initiative. The campaign's target was then raised to seven billion trees. In 2009, UNEP mobilized action across the globe through the "Twitter for Trees" campaign. UNEP pledged to plant one tree to feed into the Billion Tree Campaign for every follower who joined from 5 May 2009 to World Environment Day on 5 June 2009. The campaign was a success, with 10,300 people following the page by World Environment Day.

The World Organization of the Scout Movement also planted trees under the campaign, in line with its mandate to study and protect nature across several countries. United Nations Peacekeeping missions also joined the campaign and planted trees within their field missions in East Timor, Ivory Coast, Darfur, Lebanon, Haiti, Congo, and Liberia, among others.

After the campaign

Felix Finkbeiner addressed the United Nations in a speech to open the International Year of Forests 2011, saying: "It is now time that we work together. We combine our forces, old and young, rich and poor; and together, we can plant a trillion trees. We can start the Trillion Tree Campaign." In December 2011, after more than 12 billion trees had been planted, UNEP formally handed management of the program to the youth-led not-for-profit Plant-for-the-Planet Foundation (an organisation that had been participating in the Billion Tree Campaign since 2007), based in Tutzing, Germany. Momentum has since continued, with 40,000 young ambassadors spreading the message in over 100 countries.

In 2015, researcher Tom Crowther found that about 3 trillion trees exist in the world and later it was also estimated that planting 1.2 trillion more trees would counteract 10 years of anthropogenic CO₂ emissions.

In 2017, Pakistan's Billion Tree Tsunami restored 350,000 hectares of forests.

On 9 March 2018, the Trillion Tree Declaration was signed at the Grimaldi Forum in Monaco. Signatories include Prince Albert II of Monaco, Gyalwang Drukpa, Patricia Espinosa in collaboration with the WWF, WCS, and BirdLife International.

In September 2019, the Plant-for-the-Planet app was released under an open-source license. It allowed users to register planted trees or to plant trees by donating to different tree-planting organizations around the world. The foundation does not take any commissions for donations made through the campaign.

One Trillion Tree initiative

The 2020 World Economic Forum, held in Davos, announced the creation of the One Trillion Tree initiative platform for governments, businesses, and civil society to provide support to the UN Decade on Ecosystem Restoration (2020–2030), led by UNEP and FAO. Forum participant Donald Trump, then-president of the United States, announced that the government of the U.S. would commit to the initiative.

Principles

• Reducing fossil fuel emissions
• Conserving existing ecosystems
• Restoration must be socially and ecologically responsible

By country

China

Further information: Environmental issues in China

In the years 2011—2022, China restored more than 70 million hectares (700,000 km²) of forests. The nation committed to plant and conserve 70 billion trees by the year 2030 as part of the Trillion Tree Campaign.

US

Further information: Environmental issues in the United States

 

The United States has pledged to plant, grow, and restore around 51 billion trees by the year 2030. Currently, forests in the country absorb 15% of its carbon emissions. This can rise to 27% with responsible reforestation.

Sea level

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Sea_level

This marker indicating sea level is situated between Jerusalem and the Dead Sea.

Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead a long-term average of tide gauge readings at a particular reference location.

The term above sea level generally refers to the height above mean sea level (AMSL). The term APSL means above present sea level, comparing sea levels in the past with the level today.

Earth's radius at sea level is 6,378.137 km (3,963.191 mi) at the equator. It is 6,356.752 km (3,949.903 mi) at the poles and 6,371.001 km (3,958.756 mi) on average. This flattened spheroid, combined with local gravity anomalies, defines the geoid of the Earth, which approximates the local mean sea level for locations in the open ocean. The geoid includes a significant depression in the Indian Ocean, whose surface dips as much as 106 m (348 ft) below the global mean sea level (excluding minor effects such as tides and currents).

Measurement

Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 200 millimetres (7.9 in) during the 20th century (2 mm/year).

Precise determination of a "mean sea level" is difficult because of the many factors that affect sea level. Instantaneous sea level varies substantially on several scales of time and space. This is because the sea is in constant motion, affected by the tides, wind, atmospheric pressure, local gravitational differences, temperature, salinity, and so forth. The mean sea level at a particular location may be calculated over an extended time period and used as a datum. For example, hourly measurements may be averaged over a full Metonic 19-year lunar cycle to determine the mean sea level at an official tide gauge.

Still-water level or still-water sea level (SWL) is the level of the sea with motions such as wind waves averaged out. Then MSL implies the SWL further averaged over a period of time such that changes due to, e.g., the tides, also have zero mean. Global MSL refers to a spatial average over the entire ocean area, typically using large sets of tide gauges and/or satellite measurements.

One often measures the values of MSL with respect to the land; hence a change in relative MSL or (relative sea level) can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates, or both. In the UK, the ordnance datum (the 0 metres height on UK maps) is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921. Before 1921, the vertical datum was MSL at the Victoria Dock, Liverpool. Since the times of the Russian Empire, in Russia and its other former parts, now independent states, the sea level is measured from the zero level of Kronstadt Sea-Gauge. In Hong Kong, "mPD" is a surveying term meaning "metres above Principal Datum" and refers to height of 0.146 m (5.7 in) above chart datum and 1.304 m (4 ft 3.3 in) below the average sea level. In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and offers the longest collated data about the sea level. It is used for a part of continental Europe and the main part of Africa as the official sea level. Spain uses the reference to measure heights below or above sea level at Alicante, while the European Vertical Reference System is calibrated to the Amsterdam Peil elevation, which dates back to the 1690s.

Satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001 and the Ocean Surface Topography Mission on the Jason-2 satellite in 2008.

Height above mean sea level

Main article: Height above mean sea level

Height above mean sea level (AMSL) is the elevation (on the ground) or altitude (in the air) of an object, relative to a reference datum for mean sea level (MSL). It is also used in aviation, where some heights are recorded and reported with respect to mean sea level (contrast with flight level), and in the atmospheric sciences, and in land surveying. An alternative is to base height measurements on a reference ellipsoid approximating the entire Earth, which is what systems such as GPS do. In aviation, the reference ellipsoid known as WGS84 is increasingly used to define heights; however, differences up to 100 metres (328 feet) exist between this ellipsoid height and local mean sea level. Another alternative is to use a geoid-based vertical datum such as NAVD88 and the global EGM96 (part of WGS84). Details vary in different countries.

When referring to geographic features such as mountains, on a topographic map variations in elevation are shown by contour lines. A mountain's highest point or summit is typically illustrated with the AMSL height in metres, feet or both. In unusual cases where a land location is below sea level, such as Death Valley, California, the elevation AMSL is negative.

Difficulties in use

1. Ocean
2. Reference ellipsoid
3. Local plumb line
4. Continent
5. Geoid

It is often necessary to compare the local height of the mean sea surface with a "level" reference surface, or geodetic datum, called the geoid. In the absence of external forces, the local mean sea level would coincide with this geoid surface, being an equipotential surface of the Earth's gravitational field which, in itself, does not conform to a simple sphere or ellipsoid and exhibits gravity anomalies such as those measured by NASA's GRACE satellites. In reality, the geoid surface is not directly observed, even as a long-term average, due to ocean currents, air pressure variations, temperature and salinity variations, etc. The location-dependent but time-persistent separation between local mean sea level and the geoid is referred to as (mean) ocean surface topography. It varies globally in a typical range of ±1 m (3 ft).

Dry land

Sea level sign seen on cliff (circled in red) at Badwater Basin, Death Valley National Park

Several terms are used to describe the changing relationships between sea level and dry land.

• "relative" means change relative to a fixed point in the sediment pile.
• "eustatic" refers to global changes in sea level relative to a fixed point, such as the centre of the earth, for example as a result of melting ice-caps.
• "steric" refers to global changes in sea level due to thermal expansion and salinity variations.
• "isostatic" refers to changes in the level of the land relative to a fixed point in the earth, possibly due to thermal buoyancy or tectonic effects, disregarding changes in the volume of water in the oceans.

The melting of glaciers at the end of ice ages results in isostatic post-glacial rebound, when land rises after the weight of ice is removed. Conversely, older volcanic islands experience relative sea level rise, due to isostatic subsidence from the weight of cooling volcanos. The subsidence of land due to the withdrawal of groundwater is another isostatic cause of relative sea level rise.

On planets that lack a liquid ocean, planetologists can calculate a "mean altitude" by averaging the heights of all points on the surface. This altitude, sometimes referred to as a "sea level" or zero-level elevation, serves equivalently as a reference for the height of planetary features.

Change

See also: Past sea level and sea level rise

Local and eustatic

See also: Eustatic sea level

Water cycles between ocean, atmosphere and glaciers

Local mean sea level (LMSL) is defined as the height of the sea with respect to a land benchmark, averaged over a period of time long enough that fluctuations caused by waves and tides are smoothed out, typically a year or more. One must adjust perceived changes in LMSL to account for vertical movements of the land, which can occur at rates similar to sea level changes (millimetres per year).

Some land movements occur because of isostatic adjustment to the melting of ice sheets at the end of the last ice age. The weight of the ice sheet depresses the underlying land, and when the ice melts away the land slowly rebounds. Changes in ground-based ice volume also affect local and regional sea levels by the readjustment of the geoid and true polar wander. Atmospheric pressure, ocean currents and local ocean temperature changes can affect LMSL as well.

Eustatic sea level change (global as opposed to local change) is due to change in either the volume of water in the world's oceans or the volume of the oceanic basins. Two major mechanisms are currently causing eustatic sea level rise. First, shrinking land ice, such as mountain glaciers and polar ice sheets, is releasing water into the oceans. Second, as ocean temperatures rise, the warmer water expands.

Short-term and periodic changes

The Last Glacial Period caused a much lower global sea level.

Warming temperatures and melting glaciers are currently raising the sea level.

Many factors can produce short-term changes in sea level, typically within a few metres, in timeframes ranging from minutes to months:

Periodic sea level changes
Diurnal and semidiurnal astronomical tides	12–24 h P	0.1–10+ m
Long-period tides	2-week to 1-year P	<0.1 m
Pole tides (Chandler wobble)	14-month P	5 mm
Meteorological and oceanographic fluctuations
Atmospheric pressure	Hours to months	−0.7 to 1.3 m
Winds (storm surges)	1–5 days	Up to 5 m
Evaporation and precipitation (may also follow long-term pattern)	Days to weeks	<0.1m
Ocean surface topography (changes in water density and currents)	Days to weeks	Up to 1 m
El Niño/southern oscillation	6 mo every 5–10 yr	Up to 0.6 m
Seasonal variations
Seasonal water balance among oceans (Atlantic, Pacific, Indian)	6 months
Seasonal variations in slope of water surface	6 months
River runoff/floods	2 months	1 m
Seasonal water density changes (temperature and salinity)	6 months	0.2 m
Seiches
Seiches (standing waves)	Minutes to hours	Up to 2 m
Earthquakes
Tsunamis (catastrophic long-period waves)	Hours	0.1–10+ m
Abrupt change in land level	Minutes	Up to 10 m

Recent changes

Further information: Ocean heat content and Effects of climate change on oceans

Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s. This was faster than the sea level had ever risen over at least the past 3,000 years. The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022. Climate change due to human activities is the main cause. Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise, with another 42% resulting from thermal expansion of water.

Sea level rise lags behind changes in the Earth's temperature by many decades, and sea level rise will therefore continue to accelerate between now and 2050 in response to warming that has already happened. What happens after that depends on human greenhouse gas emissions. If there are very deep cuts in emissions, sea level rise would slow between 2050 and 2100. It could then reach by 2100 slightly over 30 cm (1 ft) from now and approximately 60 cm (2 ft) from the 19th century. With high emissions it would instead accelerate further, and could rise by 1.0 m (3+1⁄3 ft) or even 1.6 m (5+1⁄3 ft) by 2100. In the long run, sea level rise would amount to 2–3 m (7–10 ft) over the next 2000 years if warming stays to its current 1.5 °C (2.7 °F) over the pre-industrial past. It would be 19–22 metres (62–72 ft) if warming peaks at 5 °C (9.0 °F).

Rising seas affect every coastal and island population on Earth. This can be through flooding, higher storm surges, king tides, and tsunamis. There are many knock-on effects. They lead to loss of coastal ecosystems like mangroves. Crop yields may reduce because of increasing salt levels in irrigation water. Damage to ports disrupts sea trade. The sea level rise projected by 2050 will expose places currently inhabited by tens of millions of people to annual flooding. Without a sharp reduction in greenhouse gas emissions, this may increase to hundreds of millions in the latter decades of the century.

Local factors like tidal range or land subsidence will greatly affect the severity of impacts. For instance, sea level rise in the United States is likely to be two to three times greater than the global average by the end of the century. Yet, of the 20 countries with the greatest exposure to sea level rise, twelve are in Asia, including Indonesia, Bangladesh and the Philippines. The resilience and adaptive capacity of ecosystems and countries also varies, which will result in more or less pronounced impacts. The greatest impact on human populations in the near term will occur in the low-lying Caribbean and Pacific islands. Sea level rise will make many of them uninhabitable later this century.

Societies can adapt to sea level rise in multiple ways. Managed retreat, accommodating coastal change, or protecting against sea level rise through hard-construction practices like seawalls are hard approaches. There are also soft approaches such as dune rehabilitation and beach nourishment. Sometimes these adaptation strategies go hand in hand. At other times choices must be made among different strategies. Poorer nations may also struggle to implement the same approaches to adapt to sea level rise as richer states.

Aviation

Main article: Altitude in aviation

 

Pilots can estimate height above sea level with an altimeter set to a defined barometric pressure. Generally, the pressure used to set the altimeter is the barometric pressure that would exist at MSL in the region being flown over. This pressure is referred to as either QNH or "altimeter" and is transmitted to the pilot by radio from air traffic control (ATC) or an automatic terminal information service (ATIS). Since the terrain elevation is also referenced to MSL, the pilot can estimate height above ground by subtracting the terrain altitude from the altimeter reading. Aviation charts are divided into boxes and the maximum terrain altitude from MSL in each box is clearly indicated. Once above the transition altitude, the altimeter is set to the international standard atmosphere (ISA) pressure at MSL which is 1013.25 hPa or 29.92 inHg.