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Encyclopedia > Anthropic principle

In physics and cosmology, the anthropic principle states that we should take into account the constraints that our existence as observers imposes on the sort of universe that we could observe. Originally proposed as a rule of reasoning, the term has since been extended to cover supposed "superlaws" that in various ways require the universe to support intelligent life, usually assumed to be carbon-based, and occasionally to be specifically human beings. Anthropic reasoning involves assessing these constraints by analyzing the properties of universes with different fundamental parameters or laws of physics from ours, and has frequently concluded that essential structures, from atomic nuclei to the whole universe, depend, for stability, on delicate balances between different fundamental forces; balances which occur only in a small minority of possible universes — so that ours seems to be fine-tuned for life. Anthropic reasoning also attempts to explain and quantify this fine tuning. Within the scientific community the usual approach is to invoke selection effects from a real ensemble of alternate universes, which cause an anthropic bias in what can be observed; competing strategies, occasionally also called anthropic, include intelligent design. A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... Cosmology, from the Greek: κοσμολογία (cosmologia, κόσμος (cosmos) order + λογια (logia) discourse) is the study of the Universe in its totality, and by extension, humanitys place in it. ... For other uses, see Universe (disambiguation). ... Fundamental physical constant redirects here. ... A physical law or a law of nature is a scientific generalization based on empirical observations. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... The deepest visible-light image of the cosmos. ... This article does not cite any references or sources. ... Selection bias is a distortion of evidence or data that arises from the way that the data are collected. ... For other uses, see Multiverse (disambiguation). ... For other uses, see Intelligent design (disambiguation). ...


The anthropic principle has led to more than a little confusion and controversy, partly because several distinct ideas carry this label. All versions of the principle have been accused of providing simplistic explanations which undermine the search for a deeper physical understanding of the universe. The invocation of either multiple universes or an intelligent designer are highly controversial, and both ideas have been criticized by some as being presently untestable, and therefore not within the purview of contemporary science. The idea that the universe that we can observe is only part of the whole physical reality led to the definition of multiverse, the set of multiple possible universes. ... Falsifiability (or refutability or testability) is the logical possibility that an assertion can be shown false by an observation or a physical experiment. ...

Contents

Anthropic coincidences

Main article: fine-tuned universe

Robert Dicke[1] noted that the age of the universe as seen by living observers is not random, but is constrained by biological factors that require it to be roughly a "golden age".[2] Ten times younger, and there would not have been time for sufficient interstellar levels of carbon to build up by Nucleosynthesis; but ten times older, and the golden age of main sequence stars and stable planetary systems would have already come to an end. This explained away a rough coincidence between large dimensionless numbers constructed from the constants of physics and the age of the universe, which had inspired Dirac's varying-G theory. The deepest visible-light image of the cosmos. ... Robert Henry Dicke (May 6, 1916 – March 4, 1997) was an American physicist and astrophysicist. ... The age of the universe, in Big Bang cosmology, refers to the time elapsed between the Big Bang and the present day. ... Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ... The Dirac large numbers hypothesis refers to an observation made by Paul Dirac in 1937 relating ratios of size scales in the universe to that of force scales. ...


Later, Dicke reasoned that the density of matter in the universe must be almost exactly the critical density needed to stop the universe from recollapsing (the "Dicke coincidences" argument, see article on Dicke). It seems he was wrong: latest estimates are that matter has about 30% of the critical density, with the rest contributed by a cosmological constant. Steven Weinberg[3] gave an anthropic explanation: he noted that the cosmological constant has a remarkably low value, some 120 orders of magnitude smaller than expected from particle physics (often described as the worst prediction in physics). However, if the cosmological constant was more than about 10 times the observed value, the universe would suffer catastrophic inflation, preventing the formation of stars, and, presumably, life. The Friedmann equations relate various cosmological parameters within the context of general relativity. ... Robert Henry Dicke (May 6, 1916 – March 4, 1997) was an American experimental physicist, who made important contributions to the fields of astrophysics, atomic physics, cosmology and gravity. ... In physical cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ... Steven Weinberg (born May 3, 1933) is an American physicist. ...


The observed values of the dimensionless parameters (such as the fine-structure constant) that govern the four forces of nature are finely balanced. A slight increase in the strong nuclear force would bind the dineutron and the diproton and all the hydrogen in the early universe would have been converted to helium. There would be no water or the long-lived stable stars that are essential for the development of life. Similar relationships are evident in each of the four force strengths. If they are modified sufficiently the universe's structure and capacity for life is greatly affected. A list of cosmological, chemical and physical "anthropic coincidences" is given by Hugh Ross[4]. The fine-structure constant or Sommerfeld fine-structure constant, usually denoted , is the fundamental physical constant characterizing the strength of the electromagnetic interaction. ... A fundamental interaction or fundamental force is a mechanism by which particles interact with each other, and which cannot be explained in terms of another interaction. ... The deepest visible-light image of the cosmos. ... The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... Hugh Ross Hugh N. Ross (born 1945) is a Canadian-born Old Earth Creationist. ...


One of the best known examples of anthropic reasoning used in the prediction of cosmological phenomena was by Fred Hoyle. He calculated and then reasoned that there must be an excited state at an energy of 7.6 million electron volts in the nucleus of carbon-12 since he, Fred Hoyle, a life form based upon carbon molecules, existed, then the resonance must also exist to create the carbon. [5] [6] Sir Frederick Hoyle, FRS, (born on June 24, 1915 in Gilstead, Yorkshire, England – August 20, 2001 in Bournemouth, England)[1] was a British astronomer, he was educated at Bingley Grammar School and notable for a number of his theories that run counter to current astronomical opinion, and a writer of...


Origin of the anthropic principle

The phrase "anthropic principle" was coined by the theoretical astrophysicist Brandon Carter, in his contribution to a 1973 Kraków symposium honouring Copernicus's 500th birthday. Carter articulated the Anthropic Principle as a reaction to overuse of the Copernican Principle, which states that we are not at a special position in the Universe. As Carter says, "Although our situation is not necessarily central, it is inevitably privileged to some extent".[7] Carter was particularly reacting against the use of the Copernican principle to justify the Perfect Cosmological Principle, that all large regions and times in the universe must be statistically identical. This principle underlay the steady-state theory which had recently been proved wrong by unequivocal evidence for radical changes in the Universe with time (starting with the Big Bang). Brandon Carter is a theoretical physicist, most famous for his work on the properties of black holes and for introducing the anthropic principle. ... For other uses, see Krakow (disambiguation). ... Symposium originally referred to a drinking party (the Greek verb sympotein means to drink together) but has since come to refer to any academic conference, whether or not drinking takes place. ... Nicolaus Copernicus (in Latin; Polish Mikołaj Kopernik, German Nikolaus Kopernikus - February 19, 1473 – May 24, 1543) was a Polish astronomer, mathematician and economist who developed a heliocentric (Sun-centered) theory of the solar system in a form detailed enough to make it scientifically useful. ... In cosmology, the Copernican principle, named after Nicolaus Copernicus, states [1] More recently, the principle is generalised to the relativistic concept that humans are not privileged observers of the universe. ... The Perfect Cosmological Principle is an extension of the Cosmological Principle stating that the Universe is not only homogeneous and isotropic in space, but also in time. ... For alternative meanings see steady state (disambiguation). ... For other uses, see Big Bang (disambiguation). ...


Carter defined two forms of the Anthropic principle, a "weak" one which referred only to anthropic selection of privileged space-time locations in the universe, and a more controversial "strong" form which referred to the fundamental parameters of physics.


Roger Penrose explains the weak form: Sir Roger Penrose, OM, FRS (born 8 August 1931) is an English mathematical physicist and Emeritus Rouse Ball Professor of Mathematics at the Mathematical Institute, University of Oxford and Emeritus Fellow of Wadham College. ...

The argument can be used to explain why the conditions happen to be just right for the existence of (intelligent) life on the earth at the present time. For if they were not just right, then we should not have found ourselves to be here now, but somewhere else, at some other appropriate time. This principle was used very effectively by Brandon Carter and Robert Dicke to resolve an issue that had puzzled physicists for a good many years. The issue concerned various striking numerical relations that are observed to hold between the physical constants (the gravitational constant, the mass of the proton, the age of the universe, etc.). A puzzling aspect of this was that some of the relations hold only at the present epoch in the earth's history, so we appear, coincidentally, to be living at a very special time (give or take a few million years!). This was later explained, by Carter and Dicke, by the fact that this epoch coincided with the lifetime of what are called main-sequence stars, such as the sun. At any other epoch, so the argument ran, there would be no intelligent life around in order to measure the physical constants in question-so the coincidence had to hold, simply because there would be intelligent life around only at the particular time that the coincidence did hold!

The Emperor's New Mind, Chapter 10 The Emperors New Mind: Concerning Computers, Minds and The Laws of Physics is a 1989 book by mathematical physicist Roger Penrose. ...

One reason this is plausible is that there are plenty of other places and other times in which we can imagine finding ourselves. But when applying the strong principle, we only have one Universe, with one set of fundamental parameters, so what exactly is the point being made? Carter offers two possibilities: first, we can use our own existence to make "predictions" about the parameters. But second, "as a last resort", we can convert these predictions into explanations by assuming that there is more than one Universe, in fact a large or infinite collection of universes; what is now called a multiverse ("world ensemble" is Carter's term), in which the parameters (and perhaps the laws of physics) do vary from universe to universe. The strong principle then becomes an example of a selection effect, exactly analogous to the weak principle. Postulating a multiverse is certainly a radical step, but as a pay-off it offers at least a partial answer to a question which seem to be out of the reach of normal science: "why do the fundamental laws take that particular form and not another?" For other uses, see Multiverse (disambiguation). ... A selection effect is seen in experiments or observations where there is a bias in the underlying methodology that leads to results that preferentially include or exclude certain kinds of results. ...


Since Carter's original paper, the term "Anthropic Principle" has been extended to cover a number of ideas which are different in important ways from the ones he espoused. Particular confusion was caused by the influential book The Anthropic Cosmological Principle by John D. Barrow and Frank Tipler,[8] which makes a very different distinction between "weak" and "strong" anthropic principle, as discussed in the next section. John David Barrow FRS (born November 29, 1952, London) is an English cosmologist, theoretical physicist, and mathematician. ... Frank J. Tipler is a professor of mathematical physics at Tulane University, New Orleans, physicist, theologian and cornucopian philosopher. ...


Brandon Carter was not the first to invoke some form of the anthropic principle. For instance, Dicke wrote in 1957 that: "The age of the Universe 'now' is not random but conditioned by biological factors ... [changes in the values of the fundamental constants of physics] would preclude the existence of man to consider the problem."[9] Alfred Russel Wallace anticipated the anthropic principle as long ago as 1903: "Such a vast and complex universe as that which we know exists around us, may have been absolutely required ... in order to produce a world that should be precisely adapted in every detail for the orderly development of life culminating in man."[10] The anthropic principle is perhaps even echoed by Karl Marx's theory of historical materialism: "The first premise of all human history is, of course, the existence of living human individuals. Thus the first fact to be established is the physical organization of these individuals and their consequent relation to the rest of nature."[11] For the Cornish painter, see Alfred Wallis. ... Karl Heinrich Marx (May 5, 1818 – March 14, 1883) was a 19th century philosopher, political economist, and revolutionary. ... Historical materialism is the methodological approach to the study of society, economics, and history which was first articulated by Karl Marx (1818-1883), although Marx himself never used the term (he referred it as philosophical materialism, a term he used to distinguish it from what he called popular materialism). Historical...


Variants of the anthropic principle

  • Carter's Weak anthropic principle (WAP): "we must be prepared to take account of the fact that our location in the universe is necessarily privileged to the extent of being compatible with our existence as observers." Note that for Carter, "location" is a space-time position.
  • Carter's Strong anthropic principle (SAP): "the Universe (and hence the fundamental parameters on which it depends) must be such as to admit the creation of observers within it at some stage. To paraphrase Descartes, 'cogito ergo mundus talis est'." The Latin tag ("I think, therefore the world is such [as it is]") makes it clear that "must" indicates a deduction from the fact of our existence; the statement is thus a truism.

Quite different definitions of these terms were offered by Barrow[12], and variants of these were used in his book with Tipler[13]: Fundamental physical constant redirects here. ... A truism is a claim that is so obvious or self-evident as to be hardly worth mentioning, except as a reminder or as a rhetorical or literary device. ...

  • Barrow and Tipler's Weak anthropic principle: "The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the Universe be old enough for it to have already done so."[14] Unlike Carter they restrict the principle to carbon-based life, rather than just "observers". A more important difference is that they apply the WAP to the fundamental physical constants, such as the fine structure constant, the number of dimensions in the universe, and the cosmological constant — just the topics that Carter reserves for the SAP.
  • Barrow and Tipler's Strong anthropic principle: "The Universe must have those properties which allow life to develop within it at some stage in its history."[15] This looks very similar to Carter's SAP, but for Barrow and Tipler, unlike Carter, the "must" is an imperative, as shown by their three possible elaborations of the SAP:[16]
    • "There exists one possible Universe 'designed' with the goal of generating and sustaining 'observers.' " This can be seen as simply the classic design argument dressed in the garb of contemporary cosmology. It implies that the purpose of the universe is to give rise to intelligent life, with the laws of nature and their fundamental constants set to ensure that life as we know it will emerge and evolve.
    • "Observers are necessary to bring the Universe into being." Barrow and Tipler believe that this can be validly inferred from quantum mechanics, as has long been suggested by John Archibald Wheeler (his "participatory universe").
    • "An ensemble of other different universes is necessary for the existence of our Universe." Contrast this with Carter, who merely says that an ensemble of universes is necessary for the SAP to count as an explanation.

The first of these has of course been welcomed by proponents of intelligent design. Carter has protested that such teleological readings "are quite different from, and even contradictory with, what I intended".[17] The Barrow and Tipler SAP has also been rejected as a fundamental misreading of Carter by the philosophers John Leslie[18] and Nick Bostrom.[19] For Bostrom, Carter's anthropic principle just warns us to make allowance for anthropic bias, that is, the bias created by anthropic selection effects (called "observation" selection effects by Bostrom) — the necessity for observers to exist in order to get a result. He writes: Carbon forms the backbone of biology for all life on Earth. ... The fine-structure constant or Sommerfeld fine-structure constant, usually denoted , is the fundamental physical constant characterizing the strength of the electromagnetic interaction. ... For other uses of this term, see Spacetime (disambiguation). ... In physical cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ... The deepest visible-light image of the cosmos. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... John Archibald Wheeler (born July 9, 1911) is an eminent American theoretical physicist. ... For other uses, see Intelligent design (disambiguation). ... Teleology (telos: end, purpose) is the philosophical study of design, purpose, directive principle, or finality in nature or human creations. ... For other individuals named John Leslie, see John Leslie (disambiguation). ... Nick Bostrom (Boström in the original Swedish) is a philosopher at the University of Oxford, and known for his work on the anthropic principle. ... A selection effect is seen in experiments or observations where there is a bias in the underlying methodology that leads to results that preferentially include or exclude certain kinds of results. ...

Many 'anthropic principles' are simply confused. Some, especially those drawing inspiration from Brandon Carter's seminal papers, are sound, but... they are too weak to do any real scientific work. In particular, I argue that existing methodology does not permit any observational consequences to be derived from contemporary cosmological theories, though these theories quite plainly can be and are being tested empirically by astronomers. What is needed to bridge this methodological gap is a more adequate formulation of how observation selection effects are to be taken into account.

Anthropic Bias, Introduction. [20]

  • Bostrom's Strong Self-Sampling Assumption (SSSA): Each observer-moment should reason as if it were randomly selected from the class of all observer-moments in its reference class. Analysing an observer's experience into a sequence of "observer-moments" helps avoid certain paradoxes; but the main ambiguity is the selection of the appropriate "reference class": for Carter's WAP this might correspond to all real or potential observer-moments in our universe; for the SAP, to all in the multiverse. Bostrom's mathematical development shows that choosing either too broad or too narrow a reference class leads to counter-intuitive results; but he is not able to prescribe a perfect choice.
  • Playwright and Novelist Michael Frayn describes a position which expresses one form of the Strong Anthropic Principle in his 2006 book "The Human Touch", which explores what he characterises as "the central oddity of the Universe":

It's this simple paradox. The Universe is very old and very large. Humankind, by comparison, is only a tiny disturbance in one small corner of it - and a very recent one. Yet the universe is only very large and very old because we are here to say it is... And yet, of course, we all know perfectly well that it is what it is whether we are here or not.[21] Michael Frayn (born 8 September 1933) is an English playwright and novelist. ...

Character of Anthropic reasoning

Much confusion has been caused by Carter's decision to focus on a rather tautological component of his ideas. In fact anthropic reasoning is of interest to scientists mainly for what is only implicit in the formal definitions, namely that we should consider seriously universes with different values of the "fundamental parameters" — that is, the dimensionless physical constants and the dimensionless initial conditions at the Big Bang. Carter (and others) argue that life as we know it would not be possible in most of these; in other words, that the universe is fine tuned. Collins & Hawking (1973) characterise Carter's then-unpublished big idea as the postulate that "there is not one universe but a whole infinite ensemble of universes with all possible initial conditions".[22] If this is granted, the anthropic principle provides a plausible explanation for the fine tuning of our universe: typical universes are not fine-tuned, but, if there are enough universes, a small proportion will be capable of supporting intelligent life: ours must be one of these, and so the observed fine tuning should be no cause for wonder. In this sense it is in direct opposition to design arguments. Fundamental physical constant redirects here. ... For other uses, see Big Bang (disambiguation). ... The deepest visible-light image of the cosmos. ...


But how seriously can we take the multiverse? And which specific multiverse should we assume? — this question must be answered before any quantitative anthropic predictions can be made. Although philosophers have discussed related concepts for centuries, in the early 1970s the only genuine physical theory giving a multiverse of sorts was the many worlds interpretation of quantum mechanics. This would allow variation in initial conditions, but not in truly fundamental constants. Since that time a number of mechanisms for producing a multiverse have been suggested: see the review by Max Tegmark[23], and the multiverse (science) article. An important development in the 1980s was the combination of inflation theory with the idea that some parameters are determined by symmetry breaking in the early universe, which allows parameters previously thought of as "fundamental constants" to vary over very large distances, eroding the distinction between Carter's weak and strong principles. At the beginning of the 21st century, the concept of the string landscape gave a mechanism for varying essentially all the constants, including the number of spatial dimensions.[24] This article may be too technical for most readers to understand. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Max Tegmark Max Tegmark born 1967 in Sweden to Karin Tegmark and Harold S Shapiro, is a cosmologist formerly at the University of Pennsylvania and now at the Massachusetts Institute of Technology as an Associate Professor. ... A multiverse (or meta-universe) is the hypothetical set of multiple possible universes (including our universe) that together comprise all of physical reality. ... Inflation is the idea—first proposed by Alan Guth (1981)—that the nascent universe passed through a phase of exponential expansion (the inflationary epoch) that was driven by a negative pressure vacuum energy density. ... Promotional picture Symmetry Breaking is a rock band from Northern New Jersey, in the United States. ... The string landscape is an idea to implement the anthropic principle, in particular Steven Weinbergs proposal for anthropic selection of the vacuum density, in string theory. ...


The anthropic idea that fundamental parameters are selected from a multitude of different possibilities (each actual in some universe or other) contrasts with the traditional hope of physicists for a theory of everything with no free parameters: as Einstein said, "What really interests me is whether God had any choice in the creation of the world". Quite recently, proponents of the leading candidate "theory of everything", String theory, proclaimed "the end of the anthropic principle"[25] since there would be no free parameters to select. Ironically, string theory now seems to offer no hope of predicting fundamental parameters, and some of its exponents have resorted to invoking the anthropic principle (see below). This article or section is in need of attention from an expert on the subject. ... Einstein redirects here. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point...


Opponents of intelligent design are not limited to hypothesizing the existence of alternate universes: they may argue anti-anthropically that the universe is less fine-tuned than often claimed, or that accepting fine tuning as a brute fact is less astonishing than the idea of an intelligent creator. Furthermore, even accepting fine tuning, Sober (2005)[26] and Ikeda and Jefferys[27] argue that the Anthropic Principle as conventionally stated actually undermines intelligent design. This is discussed in more detail in fine-tuned universe. The deepest visible-light image of the cosmos. ...


Paul Davies has discussed fine-tuning at length, and in his book The Goldilocks Enigma (2006) he summarises the current state of the debate in detail. He concludes by enumerating the alternative responses: For the member of the National Assembly for Wales, see Paul Davies (Welsh politician). ...

  • A - The absurd universe - It just happens to be that way.
  • B - The unique universe - There is a deep underlying unity in physics which necessitates the universe being this way. Some 'Theory of Everything' will explain why the various features of the Universe must have exactly the values that we see.
  • C - The multiverse - Multiple Universes exist which have all possible combinations of characteristics, and we naturally find ourselves within the one that supports our existence.
  • D - Intelligent Design - An intelligent Creator designed the Universe specifically to support complexity and the emergence of Intelligence.
  • E - The life principle - There is an underlying principle that constrains the universe to evolve towards life and mind.
  • F - The self-explaining universe - A closed explanatory or causal loop: 'perhaps only universes with a capacity for consciousness can exist'.
  • G - The fake universe - We are living in a virtual reality simulation.

Omitted here is Lee Smolin's model of cosmological natural selection, also known as fecund universes, which proposes that universes have "offspring" which are more plentiful if they happen to have features common to our universe. Also see Gardner (2005).[28] Lee Smolin at Harvard. ... Cosmological natural selection is a hypothesis proposed by Lee Smolin intended as a scientific alternative to the anthropic principle. ...


Clearly all of these resolve some aspects of the puzzle, and leave other questions unanswered. Followers of Carter would allow only option C as an anthropic explanation, whereas C through F are covered by different versions of Barrow and Tipler's SAP (and also G if considered a variant on D).


The anthropic principle, at least as conceived by Carter, can be applied on scales much smaller than the whole universe. For instance Carter (1983)[29] inverted the usual line of reasoning and pointed out that in interpreting the evolutionary record, one must take into account cosmological and astrophysical considerations. With this in mind, Carter concluded that, given the best estimates of the age of the universe, the evolutionary chain probably can allow only one or two low probability links. This conclusion has been disputed.[30] The age of the universe, in Big Bang cosmology, refers to the time elapsed between the Big Bang and the present day. ...


Observational evidence

Can observational evidence be obtained for the anthropic principle, or rather for any particular version? Certainly not for Carter's WAP, which is merely good advice to the scientist and makes no debatable assertions. The obvious way to test Barrow's SAP, which says that the Universe is required to support life, is to check a number of different universes to see if they all supported life; but such a test is impossible because other universes are unobservable by definition.


John Leslie[31] makes a number of predictions from the point of view of the Carter SAP (with multiverse): For other individuals named John Leslie, see John Leslie (disambiguation). ...

  • Developments in physics will strengthen the idea that early phase transitions occur probabilistically rather than deterministically [so there will not be a deep physical reason for the values of fundamental constants].
  • Various methods for generating multiple universes will survive theoretical investigation.
  • Claims of fine tuning will be borne out.
  • Attempts to discover exotic (non-carbon-based) life will repeatedly fail.
  • Mathematical studies of galaxy formation will confirm that it does depend delicately on expansion rate.

Hogan[32] has emphasised that it would be very strange if all fundamental constants were strictly determined, since this would leave us with no ready explanation for apparent fine tuning. In fact we might have to resort to something like Barrow and Tipler's SAP: there would be no option for such a universe not to support life.


Probabilistic predictions of parameter values can be made given (i) a particular multiverse with a "measure", i.e. a well defined "density of universes" (so, for parameter X, one can calculate the prior probability P(X0) dX that X is in the range X0 < X < X0 + dX), and (ii) an estimate of the number of observers in each universe, N(X) (e.g. this might be taken as proportional to the number of stars). The probability of observing value X is then proportional to N(X) P(X). (A more sophisticated analysis is offered by Nick Bostrom[33]). A generic feature is that the expected values should not be "over tuned", i.e. if there is some perfectly tuned value (e.g. zero) we don't expect to be much closer to it than needed to allow life. The small but (apparently) finite value of the cosmological constant is often regarded as a successful prediction in this sense. Nick Bostrom (Boström in the original Swedish) is a philosopher at the University of Oxford, and known for his work on the anthropic principle. ... In physical cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ...


One thing that would not count as evidence for the Anthropic principle is anti-Copernican evidence that the Earth or the Solar System were literally in a special position in the universe (for possible hints of this see Copernican principle), unless there was some reason to think that said position was a necessary condition for our existence as observers. In cosmology, the Copernican principle, named after Nicolaus Copernicus, states [1] More recently, the principle is generalised to the relativistic concept that humans are not privileged observers of the universe. ...


The Anthropic Cosmological Principle

The most thorough extant study of the anthropic principle is the controversial book The Anthropic Cosmological Principle by John D. Barrow, a cosmologist, and Frank J. Tipler, a mathematical physicist. This book contains an extensive review of the relevant history of ideas, because its authors believe that the anthropic principle has important antecedents in the notions of intelligent design, the philosophies of Fichte, Hegel, Bergson, and Alfred North Whitehead, and the omega point cosmology of Teilhard de Chardin. Barrow and Tipler carefully distinguish teleological reasoning from eutaxiological reasoning; the former asserts that order must have a consequent purpose; the latter asserts more modestly that order must have a planned cause. They attribute this important but nearly always overlooked distinction to Hicks (1883).[34] This is a list of controversial non-fiction books aimed at the general reader which discuss controversial issues, or are (or were at the time of writing) controversial for other reasons. ... John David Barrow FRS (born November 29, 1952, London) is an English cosmologist, theoretical physicist, and mathematician. ... Frank J. Tipler (born in 1947 in Andalusia, Alabama) is a professor of mathematical physics at Tulane University in New Orleans, Louisiana. ... The history of ideas is a field of research in history that deals with the expression, preservation, and change of human ideas over time. ... For other uses, see Intelligent design (disambiguation). ... Johann Gottlieb Fichte Johann Gottlieb Fichte (May 19, 1762 - January 27, 1814) has significance in the history of Western philosophy as one of the progenitors of German idealism and as a follower of Kant. ... Georg Wilhelm Friedrich Hegel (August 27, 1770 - November 14, 1831) was a German philosopher born in Stuttgart, Württemberg, in present-day southwest Germany. ... Henri Bergson Henri-Louis Bergson (October 18, 1859 _ January 4, 1941) was a French philosopher, influential in France, but out of the main currents of his time. ... Alfred North Whitehead, OM (February 15, 1861 Ramsgate, Kent, England – December 30, 1947 Cambridge, Massachusetts, USA) was an English-born mathematician who became a philosopher. ... Omega point is a term invented by French Jesuit Pierre Teilhard de Chardin to describe the ultimate maximum level of complexity-consciousness, considered by him the aim towards which consciousness evolves. ... This article needs cleanup. ... Teleology (telos: end, purpose) is the philosophical study of design, purpose, directive principle, or finality in nature or human creations. ...


Barrow and Tipler set out in great detail the numerous anthropic coincidences and constraints which have been derived over the years, including many of their own original results. While the book is primarily a work of theoretical physics, it also discusses a variety of related topics in chemistry and earth science. They also use the anthropic principle to reject the possibility of extraterrestrial intelligence. For other uses, see Chemistry (disambiguation). ... Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. ... Extraterrestrial life refers to forms of life that may exist and originate outside of the planet Earth. ...


Seeing little sense in a principle that requires intelligent life to arise but then lets it go extinct, they propose yet another version:

  • Final anthropic principle (FAP): "Intelligent information-processing must come into existence in the Universe, and, once it comes into existence, it will never die out."[35]

They state that while the FAP is a valid physical statement, it is also "closely connected with moral values". FAP places strong constraints on the structure of the Universe, developed further in Tipler's The Physics of Immortality.[36] One such constraint is that the universe must end in a big crunch, which seems unlikely in view of the more recent discovery of dark energy. In his review[37] of Barrow and Tipler, Martin Gardner ridiculed the FAP by quoting the last two sentences of their book as defining a Completely ridiculous anthropic principle (CRAP): "At the instant the Omega Point is reached, life will have gained control of all matter and forces not only in a single universe, but in all universes whose existence is logically possible; life will have spread into all spatial regions in all universes which could logically exist, and will have stored an infinite amount of information, including all bits of knowledge which it is logically possible to know. And this is the end."[38] The final anthropic principle (FAP) is defined by physicists John D. Barrow and Frank J. Tiplers 1986 book The Anthropic Cosmological Principle as a generalization of the anthropic principle as follows: Final anthropic principle (FAP): Intelligent information-processing must come into existence in the Universe, and, once it comes... This article is about the cosmological theory. ... In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. ... Martin Gardner (b. ... Omega point is a term invented by French Jesuit Pierre Teilhard de Chardin to describe the ultimate maximum level of complexity-consciousness, considered by him the aim towards which consciousness evolves. ...


In fairness, the authors warn at the start that it should not be assumed that they are committed to the ideas they describe, and they specifically call their SAP and FAP "quite speculative".


Criticisms

A common criticism of Carter's SAP is that it is an easy get-out which discourages searches for physical explanations. To quote Penrose again: "it tends to be invoked by theorists whenever they do not have a good enough theory to explain the observed facts."[39]


Some applications of the anthropic principle have been criticized as an argument by lack of imagination for assuming that the only possible chemistry of life is one based on carbon compounds and liquid water (sometimes called "carbon chauvinism", see also alternative biochemistry).[40] The range of fundamental physical constants allowing evolution of carbon-based life may also be much less restrictive than proposed.[41] For instance, Harnik et al.[42] propose a Weakless Universe in which the Weak nuclear force is eliminated apparently without significant effect, provided some adjustments are made in the other forces. However, some of the fine-tuned details of our universe would rule out complex structures of any kind — stars, planets, galaxies etc — if violated. The argument from ignorance, also known as argumentum ad ignorantium or argument by lack of imagination, is the assertion that because something is currently inexplicable, it did not happen, or that because one cannot conceive of something, it cannot exist. ... Carbon chauvinism is the viewpoint in xenobiology that carbon is necessarily the basis of all life on other planets, as carbons chemical and thermodynamic properties render it far superior to all other elements. ... Alternative biochemistry is the speculative biochemistry of alien life forms that differ radically from those on Earth. ... In physics, fundamental physical constants are, in the strictest sense, physical constants that are independent of systems of units and hence are dimensionless numbers. ... The Weakless Universe is a hypothetical universe that contains no weak interactions, but is otherwise very similar to our own universe. ... The weak nuclear force or weak interaction is one of the four fundamental forces of nature. ...


Carter's SAP and Barrow and Tipler's WAP are truisms or tautologies, stating something not obvious to everyone yet trivially true. As such they are often criticised as an elaborate way of saying "if things were different, they would be different", which explains nothing. But discussion of anthropic principles implicitly posits that our ability to ponder cosmology at all is contingent on one or more fundamental physical parameters having numerical values falling within quite a narrow range, which is not a tautology, and neither is the postulate of an actual multiverse. Moreover, working out the consequences of a change in the fundamental parameters for our existence is far from trivial, and, as we have seen, can lead to quite unexpected constraints. A truism is a claim that is so obvious or self-evident as to be hardly worth mentioning, except as a reminder or as a rhetorical or literary device. ... Look up tautology in Wiktionary, the free dictionary. ...


Critics of the Barrow and Tipler SAP claim that it is neither testable nor falsifiable, and thus is not science. The same criticism has been leveled against the multiverse idea, although we have seen that proponents argue that it does make falsifiable predictions, albeit not very strong ones. A modified version of this criticism is that such calculations are in practice impossible because we understand so little about the emergence of life, especially intelligent life, that it is effectively impossible to calculate the number of observers in each universe; moreover the prior distribution of universes as a function of parameters is too easy to modify to get any desired result.[43] Scientific method is a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. ...


Carter himself[44] has frequently regretted his own choice of the word anthropic as conveying the misleading impression that the principle involves humans specifically, rather than intelligent observers in general. Others[45] have criticised the word principle as too grandiose for a relatively straightforward application of selection effects. Selection bias is a distortion of evidence or data that arises from the way that the data are collected. ...


Steven Jay Gould [46] [47], Michael Schermer [48] and others have observed that known causes and effects seem to have been reversed in the Anthropic Principle. Dr. Gould compared the claim that the universe is fine-tuned for the benefit of our kind of life to claiming that hotdogs were originally made long and narrow so that they would fit modern hotdog buns, or that ships had been invented to provide homes for barnacles. These critics cite the vast store of physical and evolutionary evidence which shows that life has been fine-tuned by the universe, through natural selection, to match the conditions in which life exists. Fossil, genetic and other biological evidence abundantly supports the observation that life adapts to physics, not the other way around.


The paleophysicist Caroline Miller has said: [49]

The Anthropic Principle is based on the underlying belief that the universe was created for our benefit. Unfortunately for its adherents, all of the reality-based evidence at our disposal contradicts this belief. In a non-anthropocentric universe, there is no need for multiple universes or supernatural entities to explain life as we know it.

Paul Davies contends (http://www.abc.net.au/science/bigquestions/) that this criticism incorrectly characterises the claim being made. He argues that the claim is that the physical nature of the universe has to be fine tuned in a number of ways to permit any sort of life to exist, which can then adapt to its conditions - as one example, 'for life to exist there must be atoms'; and that if any one of several physical constants were different by small amounts atoms would not exist.


Anthropic principle in cosmic inflation

Main article: Cosmic Inflation

A critique of cosmic inflation, questioning the very premise of the theory, was offered by Don N. Page[50] who emphasized the point that initial conditions which made it possible that a thermodynamic arrow of time in a Big Bang type of theory must necessarily include a low entropy initial state of the Universe and therefore to be extremely improbable. The critique was rebutted by Paul Davies[51] who used an inflationary version of the anthropic principle. While accepting the premise that the initial state of the visible Universe (originally a microscopic amount of space before the inflation) had to possess a very low entropy value — due to random quantum fluctuations — to account for the observed thermodynamic arrow of time, he deemed it not a problem of the theory but an advantage. That the tiny patch of space from which our observable Universe grew had to be extremely orderly, to allow inflation resulting in a universe with an arrow of time, makes it unnecessary to adopt any ad-hoc hypotheses about the initial entropy state which are necessary in other Big Bang theories. In physical cosmology, cosmic inflation is the idea that the nascent universe passed through a phase of exponential expansion that was driven by a negative-pressure vacuum energy density. ... This article or section does not cite its references or sources. ... For other uses, see Big Bang (disambiguation). ... For a less technical and generally accessible introduction to the topic, see Introduction to entropy. ... For the member of the National Assembly for Wales, see Paul Davies (Welsh politician). ...


Anthropic principle in string theory

String theory predicts a large number of possible universes, called the backgrounds or vacua. The set of these universes or vacua is often called the "multiverse" or "anthropic landscape" or "string landscape". Leonard Susskind has argued that the existence of a large number of vacua puts the anthropic reasoning on firm ground; only universes with the remarkable properties sufficient to allow observers to exist are beheld while a possibly much larger set of universes without such properties go utterly unnoted. Steven Weinberg[52] refers to the Anthropic Principle as a "turning point" in modern science since, applied to the string landscape, it "may explain how the constants of nature that we observe can take values suitable for life without being fine-tuned by a benevolent creator." Others, most notably David Gross but also Lubos Motl, Peter Woit and Lee Smolin, argue that this is not predictive. Max Tegmark,[53] Mario Livio and Martin Rees[54] respond that various ingredients of well-accepted theories will never be testable, and that the test of a physical theory is not that every aspect of it should be observable and/or testable, but rather that enough is observable and testable to give confidence in the theory's correctness. The string theory landscape or anthropic landscape refers to the large number of different false vacua in string theory. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point... A multiverse (or meta-universe) is the hypothetical set of multiple possible universes (including our universe) that together comprise all of physical reality. ... The string theory landscape or anthropic landscape refers to the large number of different false vacua in string theory. ... Leonard Susskind (born 1940[1]) is the Felix Bloch professor of theoretical physics at Stanford University in the field of string theory and quantum field theory. ... Steven Weinberg (born May 3, 1933) is an American physicist. ... David Jonathan Gross (born February 19, 1941 in Washington, D.C.) is an American particle physicist and string theorist (although hes stated to the Brazilian newspaper Folha de São Paulo, on 09/27/2006, that the second area is included in the first one). ... Lubo&#353; Motl in a restaurant Lubo&#353; Motl (born 1973) is a Czech theoretical physicist who works on string theory and conceptual problems of quantum gravity. ... Peter Woit at Harvard University Peter Woit is a mathematician at Columbia University. ... Lee Smolin at Harvard. ... Max Tegmark Max Tegmark born 1967 in Sweden to Karin Tegmark and Harold S Shapiro, is a cosmologist formerly at the University of Pennsylvania and now at the Massachusetts Institute of Technology as an Associate Professor. ... Mario Livio (born 1945) is an astrophysicist and an author of works that popularize science and mathematics. ... The Right Honourable Martin John Rees, Baron Rees of Ludlow, FRS (born 23 June 1942) is a professor of astronomy. ...


See also

This article does not cite any references or sources. ... The Doomsday argument (DA) is a probabilistic argument that claims to predict the future lifetime of the human race given only an estimate of the total number of humans born so far. ... The inverse gamblers fallacy is a tempting mistake in judgments of probability, comparable to the gamblers fallacy whence its name derives. ... Metaphysical naturalism is any worldview in which nature is all there is and all things supernatural (which stipulatively includes as well as spirits and souls, non-natural values, and universals as they are commonly conceived) do not exist. ... The mediocrity principle is the notion in the philosophy of science that there is nothing special about Earth, and by implication the human race. ... The Rare Earth hypothesis is a hypothesis in planetary astronomy and astrobiology which argues that the emergence of complex multicellular life (metazoa) on Earth required an extremely unlikely combination of astrophysical and geological events and circumstances. ... Nick Bostrom (Boström in the original Swedish) is a philosopher at the University of Oxford, and known for his work on the anthropic principle. ...

Footnotes

  1. ^ Dicke, R. H. (1961). "Dirac's Cosmology and Mach's Principle". Nature 192: 440-441. 
  2. ^ Davies, P. (2006). The Goldilocks Enigma. Allen Lane. ISBN 0713998830. 
  3. ^ Weinberg, S. (1987). "Anthropic bound on the cosmological constant". Physical Review Letters 59: 2607-2610. 
  4. ^ Ross, H., web site: Design and the Anthropic Principle, section "The Universe as a Fit Habitat"
  5. ^ University of Birmingham [Bent Chains and the Anthropic Principle]
  6. ^ Rev. Mod. Phys. 29 (1957) 547
  7. ^ Carter, B. (1974). "Large Number Coincidences and the Anthropic Principle in Cosmology". IAU Symposium 63: Confrontation of Cosmological Theories with Observational Data: 291-298, Dordrecht: Reidel. 
  8. ^ Barrow J. D. and Tipler, F. J. (1986). The Anthropic Cosmological Principle. Oxford Univ. Press. ISBN 0-19-282147-4. 
  9. ^ Dicke, R. H. (1957). "Gravitation without a Principle of Equivalence". Reviews of Modern Physics 29: 363–376. 
  10. ^ Wallace, A. R. (1904). Man's place in the universe: a study of the results of scientific research in relation to the unity or plurality of worlds, 4th ed. London: George Bell & Sons, 256-7. 
  11. ^ Marx, Karl (1845). The German Ideology, Chapter 1. 
  12. ^ Barrow, J.. "Anthropic Definitions". Quarterly Journal of the Royal Astronomical Society 24: 146-153. 
  13. ^ Barrow & Tipler's section on definitions is quoted verbatim at Genesis of Eden Diversity Encyclopedia
  14. ^ Barrow and Tipler 1986: 16
  15. ^ Barrow and Tipler 1986: 21
  16. ^ Barrow and Tipler 1986: 22
  17. ^ Carter, B. 2004, "Anthropic Principle in Cosmology." Paper presented at the conference "Cosmology: Facts and Problems," hosted by the College de France.
  18. ^ Leslie, J. (1986). "Probabilistic Phase Transitions and the Anthropic Principle". Origin and Early History of the Universe: LIEGE 26: 439-444, Knudsen. 
  19. ^ Bostrom, N. (2002). Anthropic Bias: Observation Selection Effects in Science and Philosophy. Routledge. ISBN 0-415-93858-9.  5 chapters available online.
  20. ^ Bostrom, N. (2002), op. cit.
  21. ^ The Human Touch Michael Frayn Faber & Faber ISBN 0571232175
  22. ^ Collins C. B., Hawking, S. W. (1973). "Why is the universe isotropic?". Astrophysical Journal 180: 317-334. 
  23. ^ Tegmark, M. (1998). "Is 'the theory of everything' merely the ultimate ensemble theory?". Annals of Physics 270: 1-51. 
  24. ^ strictly, the number of non-compact dimensions, see String theory.
  25. ^ Kane, Gordon L., Perry, Malcolm J., and Zytkow, Anna N. (2002). "The Beginning of the End of the Anthropic Principle". New Astronomy 7: 45–53. arXiv:astro-ph/0001197. 
  26. ^ Sober, Elliott, 2005, "The Design Argument" in Mann, W. E., ed., The Blackwell Guide to the Philosophy of Religion. Blackwell Publishers.
  27. ^ Ikeda, M. and Jeffreys, W. (2006). Unpublished "FAQ" The Anthropic Principle Does Not Support Supernaturalism
  28. ^ Gardner, James N., 2005, "The Physical Constants as Biosignature: An anthropic retrodiction of the Selfish Biocosm Hypothesis," International Journal of Astrobiology.
  29. ^ Carter, B. (1983). "The anthropic principle and its implications for biological evolution". Philosophical Transactions of the Royal Society A310: 347-363. 
  30. ^ Feoli, A. and Rampone, S. (1999). "Is the Strong Anthropic Principle too weak?". Nuovo Cim. B114: 281–289. arXiv:gr-qc/9812093. 
  31. ^ Leslie, J. (1986) op. cit.
  32. ^ Hogan, Craig (2000). "Why is the universe just so?". Reviews of Modern Physics 72: 1149-1161. 
  33. ^ Bostrom (2002), op. cit.
  34. ^ Hicks, L. E. (1883). A Critique of Design Arguments. New York: Scribner's. 
  35. ^ Barrow and Tipler 1986: 23
  36. ^ Tipler, F. J. (1994). The Physics of Immortality. DoubleDay. ISBN 0385467982. 
  37. ^ Gardner, M., "WAP, SAP, PAP, and FAP," The New York Review of Books 23, No. 8 (May 8, 1986): 22-25.
  38. ^ Barrow and Tipler 1986: 677
  39. ^ Penrose, R. (1989). The Emperor's New Mind. Oxford University Press. ISBN 0198519737.  Chapter 10.
  40. ^ e.g. Carr, B. J., Rees, M. J. (1979). "The anthropic principle and the structure of the physical world". Nature 278: 605–612. 
  41. ^ Stenger, Victor J (2000). Timeless Reality: Symmetry, Simplicity, and Multiple Universes. Prometheus Books. ISBN 1-57392-859-3. 
  42. ^ Harnik, R., Kribs, G., Perez, G. (2006). "A Universe without Weak interactions". Physical Review D74: 035006.  preprint
  43. ^ Starkman, G. D., Trotta, R. (2006). "Why Anthropic Reasoning Cannot Predict Λ". Physical Review Letters 97: 201301.  See also this physics news story
  44. ^ e.g. Carter (2004) op. cit.
  45. ^ e.g. message from Martin Rees presented at the Kavli-CERCA conference (see video in External links)
  46. ^ Gould, Steven Jay. "Clear Thinking in the Sciences". Lectures at Harvard University. 
  47. ^ Gould, Steven Jay (2002). Why People Believe Weird Things: Pseudoscience, Superstition, and Other Confusions of Our Time. 
  48. ^ Schermer, Michael (2007). Why Darwin Matters. 
  49. ^ Miller, Caroline. "The Confusion of Cause and Effect in Bad Science". Lecture at Piffard University. 
  50. ^ Page, D.N. (1983). "Inflation does not explain time asymmetry". Nature 304: 39. 
  51. ^ Davies, P.C.W. (1984). "Inflation to the universe and time asymmetry". Nature 312: 524. 
  52. ^ Weinberg, S. (2007). "Living in the multiverse". B. Carr (ed) Universe or multiverse?, Cambridge University Press.  preprint
  53. ^ Tegmark (1998) op. cit.
  54. ^ Livio, M. and Rees, M. J. (2003). "Anthropic reasoning". Science 309: 1022. 

Robert Henry Dicke (May 6, 1916 &#8211; March 4, 1997) was an American physicist and astrophysicist. ... For the member of the National Assembly for Wales, see Paul Davies (Welsh politician). ... Steven Weinberg (born May 3, 1933) is an American physicist. ... Brandon Carter is a theoretical physicist, most famous for his work on the properties of black holes and for introducing the anthropic principle. ... John David Barrow FRS (born November 29, 1952, London) is an English cosmologist, theoretical physicist, and mathematician. ... Frank J. Tipler (born in 1947 in Andalusia, Alabama) is a professor of mathematical physics at Tulane University in New Orleans, Louisiana. ... Alfred Russel Wallace For the Cornish painter, see Alfred Wallis. ... Karl Heinrich Marx (May 5, 1818 – March 14, 1883) was a 19th century philosopher, political economist, and revolutionary. ... The Coll ge de France is a higher education teaching and research establishment located in Paris, France. ... For other individuals named John Leslie, see John Leslie (disambiguation). ... Nick Bostrom (Boström in the original Swedish) is a philosopher at the University of Oxford, and known for his work on the anthropic principle. ... Stephen William Hawking, CH, CBE, FRS, FRSA, (born 8 January 1942) is a British theoretical physicist. ... Max Tegmark Max Tegmark born 1967 in Sweden to Karin Tegmark and Harold S Shapiro, is a cosmologist formerly at the University of Pennsylvania and now at the Massachusetts Institute of Technology as an Associate Professor. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... Frank J. Tipler is a professor of mathematical physics at Tulane University, New Orleans, physicist, theologian and cornucopian philosopher. ... Martin Gardner (b. ... Sir Roger Penrose, OM, FRS (born 8 August 1931) is an English mathematical physicist and Emeritus Rouse Ball Professor of Mathematics at the Mathematical Institute, University of Oxford and Emeritus Fellow of Wadham College. ... Bernard J. Carr is a professor of mathematics and astronomy at Queen Mary, University of London (QMUL). ... The Right Honourable Martin John Rees, Baron Rees of Ludlow, FRS (born 23 June 1942) is a professor of astronomy. ... Victor J. Stenger (born January 29, 1935) is emeritus professor of physics and astronomy at the University of Hawaii and adjunct professor of philosophy at the University of Colorado. ... The Right Honourable Martin John Rees, Baron Rees of Ludlow, FRS (born 23 June 1942) is a professor of astronomy. ... For the member of the National Assembly for Wales, see Paul Davies (Welsh politician). ... Steven Weinberg (born May 3, 1933) is an American physicist. ...

References

  • Cirkovic, M. M. (2002). "On the First Anthropic Argument in Astrobiology". Earth, Moon, and Planets 91: 243-254. 
  • Cirkovic, M. M. (2004). "The Anthropic Principle and the Duration of the Cosmological Past". Astronomical and Astrophysical Transactions 23: 567-597. 
  • Conway Morris, Simon (2003). Life's Solution: Inevitable Humans in a Lonely Universe. Cambridge University Press. 
  • Craig, William Lane (1987). "Critical review of The Anthropic Cosmological Principle". International Philosophical Ouarterly 27: 437- 47. 
  • Hawking, Stephen W. (1988). A Brief History of Time. New York: Bantam Books, p.174. ISBN 0-553-34614-8. 
  • Stenger, Victor J. (1999), "Anthropic design," The Skeptical Inquirer 23 (August 31 1999): 40-43
  • Taylor, Stuart Ross (1998). Destiny or Chance: Our Solar System and Its Place in the Cosmos. Cambridge University Press. ISBN 0521785219. 
  • Tegmark, Max (1997). "On the dimensionality of spacetime". Classical and Quantum Gravity 14: L69-L75.  A simple anthropic argument for why there are 3 spatial and 1 temporal dimensions.
  • Tipler, F. J. (2003). "Intelligent Life in Cosmology". International Journal of Astrobiology 2: 141-48. 
  • Walker, M. A., and Cirkovic, M. M. (2006). "Anthropic Reasoning, Naturalism and the Contemporary Design Argument". International Studies in the Philosophy of Science 20: 285-307.  Shows that some of the common criticisms of AP based on its relationship with numerology or the theological Design Argument are wrong.
  • Ward, P. D., and Brownlee, D. (2000). Rare Earth: Why Complex Life is Uncommon in the Universe. Springer Verlag. ISBN 0-387-98701-0.. 
  • Vilenkin, Alex (2006). Many Worlds in One: The Search for Other Universes. Hill and Wang. ISBN 978-0809095230. 

Simon Conway Morris is a British paleontologist. ... William Lane Craig William Lane Craig (born August 23, 1949) is an American philosopher, theologian, New Testament historian, and Christian apologist. ... Stephen William Hawking, CH, CBE, FRS, FRSA, (born 8 January 1942) is a British theoretical physicist. ... Victor J. Stenger (born January 29, 1935) is emeritus professor of physics and astronomy at the University of Hawaii and adjunct professor of philosophy at the University of Colorado. ... Max Tegmark Max Tegmark born 1967 in Sweden to Karin Tegmark and Harold S Shapiro, is a cosmologist formerly at the University of Pennsylvania and now at the Massachusetts Institute of Technology as an Associate Professor. ... Frank J. Tipler (born in 1947 in Andalusia, Alabama) is a professor of mathematical physics at Tulane University in New Orleans, Louisiana. ... The Rare Earth hypothesis is a hypothesis in planetary astronomy and astrobiology which argues that the emergence of complex multicellular life (metazoa) on Earth required an extremely unlikely combination of astrophysical and geological events and circumstances. ... Alexander Vilenkin is Professor of Physics and Director of the Institute of Cosmology at Tufts University. ...

External links


  Results from FactBites:
 
Anthropic principle - Wikipedia, the free encyclopedia (2179 words)
The term "anthropic principle" was first proposed in 1973 by theoretical physicist Brandon Carter in his contribution to a symposium titled "Confrontation of Cosmological Theories with Observational Data" honouring Copernicus's 500th birthday.
He took this opportunity to articulate the anthropic principle as the contrary of what has come to be called the Copernican principle (which Copernicus did not articulate), which denies that the position of human beings in the cosmological order is in any way privileged.
Proponents of the anthropic principle suggest that we live in a universe that appears to be "fine-tuned" to allow the existence of life as we know it because otherwise we would not be there to observe this universe, cf.
  More results at FactBites »

 
 

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