Anthropic principle
The anthropic principle (from Greek anthropos "man" ), short AP, says that the observable universe is observable only because it has all the properties that allow the observer a life. Would not it be suitable for the development of awareness enabled life, so no one would be there who could describe it.
- 7.1 Origin of Life
- 7.2 Fine-tuning of the fundamental constants
- 7.3 Anthropic Principle and infinite universes
- 7.4 Anthropic Principle and String Theory
- 7.5 Doomsday argument
- 7.6 Inverse gambler's fallacy
Development of the concept
The principle was introduced conceptually in 1973 by the cosmologist Brandon Carter during the celebrations in Nicolaus Copernicus ' 500th birthday in the scientific debate, although similar reasoning strategies were also previously used occasionally. It combines the properties of the observable universe with the necessity of the existence of a conscious observer who is also able to detect this universe. Anthropic principles, as discussed in physical science generally, are "natural" explanations for conditions in the universe offer, which therefore do not appear to an observer very unlikely, and by chance explain or make a goal or purposeful ( teleological ) impression.
Because of the ambiguous definition of the anthropic principle by Carter today there are dozens of different interpretations. While the " trivial" form, namely, that the necessity of the existence of an observer is to be considered in the interpretation of astronomical data, well recognized, some more versions will be discussed scientifically and philosophically. The existing today different formulations of the anthropic principle can be distinguished according to teleological and nichtteleologischen interpretations, which have an almost opposite intention. Here, as formulated by Carter weak anthropic principle is considered nichtteleologisch since it only describes effects that come into existence by selective observation, while the strong anthropic principle also allows teleological interpretations because of its ambiguous definition. In science prevail nichtteleologische interpretations, often only nichtteleologische interpretations are even considered scientifically reasonable and the anthropic principle even certified an almost anti-teleological thrust.
Some popular versions of the anthropic principle
Brandon Carter
As a first concrete formulation of the anthropic principle apply some passages in Carter's publication of 1974 ( from B. Carter, " Large Number Coincidences and the Anthropic Principle in Cosmology " IOUT 63 (1974 ) 291 translated):
- General AP: " .. what we can expect to observe must be restricted by the conditions which are necessary for our presence as observers ".
- Weak AP (English weak anthropic principle, WAP ): " .. we must be prepared to take into account the fact that our site is necessary privileged in the universe in the sense that it is compatible with our existence as observers ."
- Strong AP (English strong anthropic principle, SAP): " .. the universe ( and hence the fundamental parameters on which it depends ) must be such that it allows the creation of observers within it at some stages ."
Especially the uncertain meaning of the word "shall" in the strong AP is responsible for the unclear interpretation of this principle, because it can be interpreted both as a requirement of simple logical compatibility of the observational data with the observer existence as well as to a greater teleological sense. Because of this teleological interpretability of the strong AP in this Formulation him a speculative and unscientific character is accused often.
1983 Carter emphasized that the principle should be used in its original form only to warn astrophysicist and cosmologist from possible errors in the interpretation of astronomical and cosmological data if biological constraints of the observer would not be included.
John Leslie
John Leslie considered the anthropic principle as a tautology that can be just as logical inference rules, which are also tautologies used to draw inferences from empirical observations.
He formulated the anthropic principle in general:
- Every intelligent being which is, may find themselves only where intelligent life is possible.
The difference between weak and strong AP is according to Leslie only that the weak AP claims that intelligent life can find only in those areas within a given universe, where observers can exist at all, while the strong AP to several universes (or also refers to a single universe with causally independent regions) and claims that intelligent life can only find in such universes, in which the existence of observers is possible.
Nick Bostrom
Nick Bostrom asked in 2002: "Is it possible to combine the core idea of the effect of selective perception in a simple statement ," He concluded that it might be so, but that "many anthropic principles are simply confused? . Some, especially those that draw their inspiration from Brandon Carter's seminal work, sound reasonable ... but they are too weak to do real scientific work. In particular, I argue that it does not allow the existing methodology to derive any observable consequences of current cosmological theories, despite the fact that these theories can be tested quite easily and also be tested empirically by astronomers. What is needed to bridge this methodological gap, is a more suitable determination on how the effects of selective perception must be involved " to implement his views, he defines the self - selection hypothesis (Self -Sampling Assumptions ). :
- Self Sampling Assumption ( SSA): One should conclude, as if one were a random selection from the set of all observers in its reference class.
- Strong Self Sampling Assumption ( SSSA ): One should conclude, as if the current observation time would be a random selection from the set of all observer moments in its reference class.
The SSA and SSSA allow, unlike other anthropic principles, assign the potential in the observable universe observations a chance; usually, those universes in which conscious observer can not exist, excluded from the observation without considering this. It is therefore not really a pure anthropic principle more, but has in this respect similar to a proposed by astrophysicist Richard Gott synthesis of anthropischem and kopernikanischem principle, the Copernican anthropic principle -.
This self- selection hypotheses Bostrum extended to a model of " anthropic bias " ( anthropic bias) and anthropischem Close ( anthropic reasoning ). It takes into account the uncertainty about the significance of the observation at a given time of observation in the universe. The model attempts to overcome existing limits by human cognitive biases. Since the exact determination of the reference class, ie the class of all entities from which an observer can reasonably selected as random, but in many cases is uncertain Bostrum holds especially those evidence with the aid of anthropic principles for credible, whose results are possible regardless of the choice of the reference class.
John Archibald Wheeler
From the physicist John Archibald Wheeler, a version of the AP, which is often associated with the subjective idealism of George Berkeley comes (J. Wheeler in The nature of scientific discovery Owen Gingerich (editor) Washington Smithsonian Press, 1975. J. Wheeler in Foundational problem in special sciences RE Butts, J. Hintikka ( editors ), Dordrecht, Reidel ).
- Participatory anthropic principle (PAP ): Observers are necessary to create the universe.
Especially when PAP a quantum mechanical phenomenon, the so-called reduction of the wave function in the measurement in connection with an observer is placed. Roughly speaking, a measurement is interpreted as an observation of a conscious being, and the associated reduction of the wave function is interpreted as a " realization " of the world in a definite state. The observer therefore would therefore be an integral part of the physical description of the world; only by his observation the world would accept "reality."
The PAP is closely related to the interpretation of quantum mechanics, in particular the so-called Copenhagen interpretation, which represents the reduction of the wave function in the measurement. Thus, recent developments in the interpretation of quantum mechanics that allow an objective description of the quantum mechanical measurement process in purely quantum mechanical terms, ie no reference to a classical laws obeying measuring apparatus as in the Copenhagen interpretation company, also relevant for the assessment of the PAPs.
This principle, an unscientific teleological character is accused in general. A critical review of the PAP are also J. Eearman.
Barrow and Tipler
In 1986, the controversial book The Anthropic Cosmological Principle by John D. Barrow and Frank J. Tipler has been published. This paved the cosmologist John Barrow a so-called anthropic principle from him the way. It was his intention to find a way of dealing with the incredible coincidences that led to our presence in a universe that seems perfectly adjusted to our existence. All of the exact energy state of the electron up to the expression of the weak interaction seems tailor-made to allow our existence. We seem to live in a universe that depends on a number of independent variables for which sufficient a tiny change to make it uninhabitable for any form of life. And yet we exist. The anthropic principle states that the reason why we are here and these questions at all considering, it follows from the fact that exactly have the correct values for the variables.
- Weak anthropic principle (English weak anthropic principle (WAP ) ): " The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirements for the existence of places at which carbon- based life forms can develop, and by the requirement that the universe must be old enough that this process has already occurred. "
- Strong anthropic principle (English strong anthropic principle (SAP) ): " The universe must be such that the development of life is possible at a certain stage of its history in it ."
In addition, Barrow and Tipler also postulated yet another Final Anthropic Principle (FAP ) called, principle, according to which the universe is constructed so that it should be possible in the future with technological means to achieve eternal life.
- Final anthropic principle (Final Anthropic Principle ): " Intelligent information-processing must occur in the universe, and, once it is created, it will never die ."
Tipler 1994 extended this concept in his book The Physics of Immortality to the Omega Point Theory. However, both the book and the theory initiated in the art world in general because of the many extremely questionable and highly speculative assumptions with harsh criticism and rejection.
Anti-teleological interpretation
The nichtteleologische interpretation has the intention to explain perceived as improbabilities conditions in cosmology by selection effects in possible observations which are caused by the conditions necessary for the existence of the observer. In particular, together with many-worlds models or a universe is assumed to be infinite ( or at least sufficiently large) is the anthropic principle, be able to explain such improbabilities seemingly teleological acting nichtteleologisch, and thus has a pronounced antiteleologischen character. For example, in an infinite universe, an observer only in such areas exist with spatially varying physical constants, and therefore locally observe only those areas in which these constants allow conscious life. Even a universe that is largely hostile to life, could thus appear as "made" for an observer for life.
The current state of development of string theory includes the possibility to probability of side-by- Existierens very many natural laws of different universes ( typical estimates indicate the astronomical figure of approx 10500 ). Should this still speculative possibility substantiated, would constitute a strong argument for the nichtteleologische interpretation, one of these many worlds is contingent, " life friendly".
Teleological interpretation
The teleological interpretation of nature emerged since the 1970s again sporadically in some scientific and popular publications, but is propagated mainly in the more religious environment. Teleological modes of explanation try the universe through goal or purpose- principles or mechanisms directed or planned and directed by a divine being to represent. As an example of a teleological anthropic principle is often called the Participatory Anthropic Principle controversial by John Archibald Wheeler.
Sometimes it is nowadays equated in some popular science publications, actually incorrect and contrary to the original intention of this principle, anthropic principle and teleological mode of explanation. Especially in creationist circles, the anthropic principle is usually narrowed inadmissible to the teleological interpretation. In his teleological interpretation as it was about also spread by John D. Barrow and Frank J. Tipler, the principle goes back to deep historical roots. So the world was aligned before Darwin for most philosophers and theologians to humans. Only by Charles Darwin's theory of evolution, the currently prevailing non- teleological view prevailed.
Criticism and defense of the Anthropic Principle
Criticized the anthropic principle for its tautological character, since it must always be true according to the rules of logic. This will usually replies that the purpose of the anthropic principle and is not to express their own content, but only that it is used as evidence, including tautologies are valid and useful. Despite its original intention of the anthropic principle antiteleologischen a teleological character and was accused of being unscientific, especially in its strong form. Even the naming is " anthropic " criticized as " conscious observer " includes not only human observer, but any kind of intelligent observers.
Proponents of the anthropic principle suggest that the universe so finely tuned to appear to allow the existence of life as we know it, and that - would also only one of the fundamental physical constants of their value vary - this life is not possible would be. It works were written, who argue that the anthropic principle was able to explain physical constants such as the fine structure constant, the number of dimensions of the universe and the cosmological constant. The advocates point out that these constants have no "obvious" values . The universe we observe has to be suitable for the development of intelligent life, because otherwise we would not be here to observe it. Whether this fine tuning and thus the anthropic principle is absolutely necessary for the explanation of life, however, is controversial. Opponents argue that this fine tuning is only necessary if one assumes that equipped with consciousness of life only, so, as we know it possible. If you drop this not been justifiable restriction, therefore, the fine-tuning would not be necessary.
A further criticism of the anthropic principle is that theories which allow the anthropic principle as an argument, often were not falsifiable. For example, would in an infinite universe, obeying quantum mechanical laws actually happen all possible operations anywhere, so rare they may be. Specifically, would be due to quantum mechanical fluctuations, the sudden emergence of so-called "Freak Observer" that could learn all sorts of actual or even hallucinated observations inevitable. In principle we could therefore not even be sure that we ourselves are not a freak Observer. There would therefore no possible observation, with which one could refute such a theory. This problem can, however, escape by going on to a statistical argument, as in natural science is anyway customary in practice. Although all observations are possible, but not all are equally common, and some events, such as the emergence of a Freak Observer, are so extremely rare that you can exclude them practically.
Although not really a fundamental critique of the validity of the anthropic principle is, however, often argued that it often takes more of a stopgap role by providing a possible explanation for circumstances in which the science has stronger declarations missing.
Anthropic and Copernican principle
It is interesting to look at because of the imprecise definition of the anthropic principle, the relationship of the anthropic principle to the Copernican principle, which denies an excellent position of man in the cosmos is. Even the naming of the anthropic principle, though often criticized as misleading seems to point to a contradiction between the two principles.
In his interpretation nichtteleologischen the anthropic principle is not necessarily in contradiction to the Copernican principle, since there may be applications of the anthropic principle here, which presuppose a universe that is homogeneous throughout and the Copernican principle is the same. The weak anthropic principle, for example, but also be applied to universes that are predominantly hostile to life, and only in small life-friendly "islands" allow the existence of intelligent life forms such as humans. Here the weak anthropic principle can be used to in order to explain the fact that intelligent observers can only observe habitable islands within the universe as selective observation. Since people could observe only those specific areas, and have therefore an epistemological special position in such a universe. You would be so contrary to the Copernican principle at least excellent observer, even if the person does not occupy a special position in the sense here is that the universe would be specifically geared to its existence through. The astrophysicist R. God has proposed the anthropic - Copernican principle in his exposition of the Doomsday argument, which forms a synthesis of the two principles.
It is different with teleological interpretations of the anthropic principle. Here is a " mechanism " or a principle is ultimately adopted, align the universe to a particular goal. Depending on how strong this goal is aligned specifically to the existence of the people out are those anthropic principles therefore also contrary to the Copernican principle, if this is interpreted strictly antiteleologisch. If the Copernican principle "only" in the epistemological sense defined, that is, only a special position of man is denied as observers in the existing universe, the principles must certainly not here basically contradict each other.
Application of anthropic principles
Origin of life
The anthropic principle is only required for the formation of ( intelligent ) life in our universe given as argument, if one assumes that some steps that are essential to the formation of ( intelligent ) life on a given planet with suitable conditions very are unlikely. This is currently still controversial scientifically, which must inevitably arise from extremely unlikely ( for the development of an intelligent civilization ), to the opposite position, after the life given reasonably appropriate environmental conditions, there is a wide spectrum of opinions.
Taking the origin of life on a given planet is highly unlikely, so the weak anthropic principle is often considered with the assumption of an infinite ( or very large ) universe as a way to explain the origin of life, despite some possibly locally likely evolutionary steps. In such an infinite ( or very large ) universe, the pure number of suitable planets would the improbability of the evolution of life on a planet considered individually outweigh life and would therefore have virtually inevitably arise. This is particularly interesting because current astronomical observation data can be interpreted with an infinite, or at least very large universe.
Conversely, can be inferred from the fact of terrestrial intelligent life and the Anthropic Principle to draw conclusions on some properties of the evolution. For example, Carter concluded in 1983 that in the interpretation of evolutionary history also astrophysics constraints of the process are observed. Carter assumes that the earthly life came to be in accordance with the theory of evolution, and continue from the remarkable coincidence that the duration of the origin of life to the development of terrestrial intelligent life ( ≈ 4 billion years ) is of the same order of magnitude as the lifetime of the Sun-like stars. This would be after Carter a very big coincidence if the typical development time of intelligent life would be much shorter than the lifetime of the Sun ( ≈ 10 billion years), but on the weak anthropic principle ( self- selection principle) could be easily explained if the typical development time intelligent life (a lot) would be larger than the sun life. To explain the long development time, there must be at least an unlikely evolutionary step in the development of intelligent life. Further, Carter points out that the development time terrestrial intelligent life indeed is of the same order of magnitude as the lifetime of the sun, but on the other hand also has a difference. From this difference estimates Carter from a limit of at most about two unlikely evolutionary stages. This result is often used to estimate the possibility of extraterrestrial intelligence in the visible universe. Feoli Antonio and Salvatore Rampone argued that, if the estimated size of our visible universe and the number of planets is involved is a higher probability for the development of extraterrestrial intelligence in this visible universe is possible, as it implies the result of Carter's.
Fine-tuning of the fundamental constants
Also, the broader question of why the laws of nature and the natural constants of the observable universe ever have the qualities and values to allow life, is often answered with the anthropic principle. In this case, however, strong anthropic principles and frequent world theories are used, so that the arguments have predominantly speculative investments. Again, the question arises to what extent does not have to be given in most logically possible universes from the outset the possibility of life. It is not clear whether ultimately there ever a need for explanation and therefore a reason for the application of the anthropic principle.
Barrow and Tipler write about the fine-tuning, which means that the fundamental constants of the universe seem perfectly matched to each other so that they make life possible:
The anthropic principle is able, together with multi- world theories ( multiverse ) a statement of the alleged by some cosmologists fine-tuning of the universe - what life thus makes it all possible - to give. Thus the anthropic principle contradict the need for an intelligent planning of creation to explain this fine-tuning, as it is, for example, by proponents of intelligent design hypothesis about the religious philosopher Richard Swinburne, is proposed. On the other hand, the existence of virtually infinite number of parallel universes for other reasons is proposed, and the anthropic principle gives this theory additional support. Assuming that a number of possible universes would be able to produce intelligent life, there must be actual universes that actually do this, and our obviously belongs to them.
The alleged fine-tuning was as " argument from lack of imagination " criticized for the assumption that no other forms of life are possible. Moreover, it could be that the area of the fundamental constants that allows the evolution of carbon-based life, much less subject to restrictions, as has been claimed ( Stenger, "Timeless Reality ").
Anthropic Principle and infinite universes
Is the universe infinite, or is there an infinite number of universes, perhaps also with other natural constants or even other laws of nature, then any physically possible process must occur infinitely often, was his relative probability, no matter how low on the visible universe. For example, the formation of ( intelligent ) life would inevitably, no matter how unlikely some stages of development would have been.
One criticism is that this reasoning is speculative; of a radical positivist point of view it does not make sense to draw from a unverifiable property of the universe as " infinity " conclusions, since such properties are rejected as metaphysical and transcendent. In today's analytic philosophy, however, such a transcendent sizes are certainly allowed as long as they play a role in an empirical theory, which provides a total of testable ( falsifiable ) predictions. Theistic world explanations that involve inextricably speculative and transcendental ideas, the above argument can not refuse for this reason, without being inconsistent anyway.
Anthropic Principle and String Theory
String theory says that there could be a large number of possible universes with different conditions: multiverse hypothesis. Some physicists see in this finding confirms the anthropic principle, as thus multiple universes are possible, in which intelligent life can not exist and therefore never conscious observer will ask questions about their properties. See other physicists in the multiverse hypothesis is an alternative to teleological interpretation of the Anthropic Principle, from the religious fundamentalists derive the need for a creator being. This thesis is still currently discussed controversially in science.