Anthropic principle

The anthropic principle, also known as the "observation selection effect", is the hypothesis, first proposed in 1957 by Robert Dicke, that the range of possible observations that could be made about the universe is limited by the fact that observations could happen only in a universe capable of developing intelligent life. Proponents of the anthropic principle argue that it explains why the universe has the age and the fundamental physical constants necessary to accommodate conscious life, since if either had been different, no one would have been around to make observations. Anthropic reasoning is often used to deal with the idea that the universe seems to be finely tuned for the existence of life.

Quotes

 * Quotations listed alphabetically by author or work.

B

 * Whitrow... proposed an anthropic resolution of the venerable philosophical question Why physical space has three dimensions? (arguing that with a space of different dimensionality there would be no living being to pose the question) and, similarly to [Grigory Moiseevich] Idlis, alluded around 1955 to an anthropic explanation of the size of the observable universe. Anyway, he never published these last ideas, which were developed years later by Wheeler. The only reference to Whitrow’s argument that appeared in print during the 1950s seems to be that due to the philosopher of religion Eric Lionel Mascall, who attributed to the English’s mathematician that"it may be necessary for the universe to have the enormous size and complexity which modern astronomy has revealed, in order for the earth to be a possible habitation for living beings."
 * Stefano Bettini, "Anthropic Reasoning in Cosmology: A Historical Perspective" (2004)


 * The gap between a dumb and a clever person may appear large from an anthropocentric perspective, yet in a less parochial view the two have nearly indistinguishable minds.
 * Nick Bostrom, Superintelligence: Paths, Dangers, Strategies (2014), Ch. 4

C

 * To say that Nature displays intelligence doesn't make you a Christian fundamentalist. Einstein said as much, and a fascinating theory called the anthropic principle has been seriously considered by Stephen Hawking, among others.
 * Deepak Chopra, "Intelligent Design Without the Bible" in The Huffington Post (23 August 2005)

D

 * The really amazing thing is not that life on Earth is balanced on a knife-edge, but that the entire universe is balanced on a knife-edge. You see, even if you dismiss mankind as just a mere hiccup in the great scheme of things, the fact remains that the entire universe seems unreasonably suited to the existence of life — almost contrived — you might say a "put-up job".
 * Paul Davies, BBC Horizon documentary, "The Anthropic Principle," 1987.
 * Misquoted often: for example by Gerald Schroeder and by Dennis Prager in "Why Some Scientists Embrace the ‘Multiverse’: This universe’s evidence suggests a Designing Intelligence, so atheists resort to an idea with no evidence", National Review, 18 June 2013.


 * Matter in quantum mechanics is not an inert substance but an active agent, constantly making choices between alternative possibilities according to probabilistic laws. ...It appears that mind, as manifested by the capacity to make choices, is to some extent inherent in every electron. ...Our brains appear to be devices for the amplification of the mental component of the quantum choices made by molecules inside our heads. ...There is evidence from peculiar features of the laws of nature that the universe as a whole is hospitable to the growth of mind. ...an extension of the Anthropic Principle up to a universal scale.
 * Freeman Dyson, Infinite in All Directions: Gifford Lectures given at Aberdeen, Scotland April-November 1985 (1988) p. 297 (paperback edition).


 * Science does not accept Aristotelian styles of explanation, that a stone falls because of its nature... it likes to be on Earth... Within science, all causes must be local and instrumental. Purpose is not acceptable as an explanation... Action at a distance, either in space or time, is forbidden. Especially, teleological influences of final goals upon phenomena are forbidden. ...The choice of laws of nature, and the choice of initial conditions for the universe, are questions belonging to meta-science and not to science. Science is restricted to the explanation of phenomena within the universe. Teleology is not forbidden when explanations go beyond ...into meta-science. The most familiar example of a meta-scientific explanation is the so-called Anthropic Principle. ...It accords with the spirit of modern science that we have two complementary styles of explanation, the teleological style allowing a role for purpose in the universe at large, and the non-teleological style excluding purpose...
 * Freeman Dyson, Infinite in All Directions (1988) pp. 295-296 (paperback, 1989).

E

 * What we hear about eternal inflation or the string landscape, seems somehow unavoidably to lead to some kind of multiverse. However, it seems to me there is a fundamental problem there. Once of course you have the multiverse, then you can start playing around and try to find probability or getting to the anthropic principle, or whatever. But the point is that the picture is essentially a classical one, and it is difficult to see that if you have many universes, coming essentially with an inflationary state, that there would not be plenty of horizons in this. Now the quantum mechanics of horizons is, I think, perfectly not understood. The simplest example is the black hole, where after all nobody knows really if the problem lies in the singularity or if it lies really already in the horizon.
 * François Englert, as quoted in:

G

 * Why was there a Big Bang? What, if anything, came before? What mechanisms generated the exponential inflation of the early Universe? What are dark matter and dark energy, which dominate today's Universe? How did the first stars and galaxies form? Why are the fundamental constants of nature what they are? Must we depend on the Cosmic Anthropic Principle to 'answer' such questions? Is our Universe unique, or must we appeal to a Multiverse? What will be the ultimate fate of our Universe?
 * Sheldon Lee Glashow, "Beyond Darwin: from the elements to the Universe." Contributions to Science (2009): 133-139 (quote from p. 139)

H

 * I think the Anthropic Cosmological Principle brings to us an idea perhaps as old as humanity itself: that we are not at all just an accidental anomaly, the microscopic caprice of a tiny particle whirling in the endless depth of the universe. Instead, we are mysteriously connected to the entire universe, we are mirrored in it, just as the entire evolution of the universe is mirrored in us.
 * Václav Havel, The Need for Transcendence in the Postmodern World (1994)


 * Until recently, it might have seemed that we were an unhappy bit of mildew on a heavenly body whirling in space among many that have no mildew on them at all. this was something that classical science could explain. Yet, the moment it begins to appear that we are deeply connected to the entire universe, science reaches the outer limits of its powers. Because it is founded on the search for universal laws, it cannot deal with singularity, that is, with uniqueness. The universe is a unique event and a unique story, and so far we are the unique point of that story. But unique events and stories are the domain of poetry, not science. With the formulation of the Anthropic Cosmological Principle, science has found itself on the border between formula and story, between science and myth. In that, however, science has paradoxically returned, in a roundabout way, to man, and offers him — in new clothing — his lost integrity. It does so by anchoring him once more in the cosmos.
 * Václav Havel, The Need for Transcendence in the Postmodern World (1994)


 * What makes the Anthropic Principle and the Gaia Hypothesis so inspiring? One simple thing: Both remind us, in modern language, of what we have long suspected, of what we have long projected into our forgotten myths and perhaps what has always lain dormant within us as archetypes. That is, the awareness of our being anchored in the earth and the universe, the awareness that we are not here alone nor for ourselves alone, but that we are an integral part of higher, mysterious entities against whom it is not advisable to blaspheme. This forgotten awareness is encoded in all religions. All cultures anticipate it in various forms. It is one of the things that form the basis of man's understanding of himself, of his place in the world, and ultimately of the world as such.
 * Václav Havel, The Need for Transcendence in the Postmodern World (1994)


 * There ought to be something very special about the boundary conditions of the universe and what can be more special than that there is no boundary?
 * Stephen Hawking, as quoted in The Anthropic Cosmological Principle (1986) by John D. Barrow and Frank J. Tipler. p. 444

K

 * ... when non-perturbative phenomena are included, there is no problem from the string theory point of view in effecting continuous transitions between Calabi-Yau spaces of different topology. This shows that stringy ideas about geometry are really more general than those found in classical Riemannian geometry. The moduli space of Calabi-Yau manifolds should thus be regarded as a continuously connected whole, rather than a series of different ones individually associated with different topological objects ... Thus, questions about the topology of Calabi-Yau spaces must be treated on the same footing as questions about the metric on the spaces. That is, the issue of topology is another aspect of the the moduli fields. These considerations are relevant to understanding the ground state of the universe.
 * Gordon L. Kane, Malcolm J. Perry, and Anna N. Zytkow: ArXiv preprint

L

 * Many scientists are still ashamed of using the . Just as the friends of were afraid of using the name '', the opponents of the anthropic principle often say that they do not want to use the 'A' in their research.
 * Andrei Linde (2007). Chapter 8. "The inflationary multiverse". In: Bernard Carr (ed.), Universe or Multiverse? (pp. 127-150). Cambridge: Cambridge University Press. (quote from p. 128)


 * The theory of the inflationary multiverse changes the way we think about our place in the world. According to its most popular version, our world may consist of infinitely many exponentially large parts, exhibiting different sets of low-energy laws of physics. Since these parts are extremely large, the interior of each of them behaves as if it were a separate universe, practically unaffected by the rest of the world. This picture, combined with the theory of eternal inflation and anthropic considerations, may help to solve many difficult problems of modern physics, including the cosmological constant problem.
 * Andrei Linde 2017)

P

 * What the anthropic principle depends upon is the idea that whatever is the nature of the universe, or universe portion that we see about us, being subject to whatever dynamical laws govern its actions, this must be strongly favourable to our very existence.
 * Roger Penrose, The Emperor's New Mind (1989), Ch. 3, Fantasy, p. 311


 * Whereas originally the hopes for string theory, and its descendants, were that some kind of uniqueness would be arrived at, whereby the theory would supply mathematical explanations for the measured numbers of experimental physics, the string theorists were driven to find refugee in the strong anthropic argument in an attempt to narrow down an absolutely vast number of alternatives. In my own view, this a very sad and unhelpful place for a theory to find itself.
 * Roger Penrose, The Emperor's New Mind (1989), Ch. 3 Fantasy, p 322

R

 * In fact Sax was suspicious of all the current cosmology, placing humanity as it did right at the center of things, time after time. It suggested to Sax that all these formulations were artifacts of human perception only, the strong anthropic principle seeping into everything they saw, like color.
 * Kim Stanley Robinson, Blue Mars (1996), Chapter 13, “Experimental Procedures” (p. 641)

S

 * By inclination, Weinberg is an extreme reductionist. But he is also a realist and acknowledges when something is not working the way he might want it to. In 1987 the arch-reductionist concluded that certain facts seemed to be inconsistent with any explanation based on the usual kind of mathematical reasoning. Instead, it seemed they might be true only because if they were not, we observers could not be here to observe them. Weinberg undoubtedly disliked such anthropic-principle explanations. But when, to his disappointment, he found that the anthropic principle might explain the apparent vanishing of the cosmological constant, he said so loudly and clearly, despite the great hostility of the physics community toward the principle.
 * Leonard Susskind:

W

 * The old cosmological constant problem is to understand why the is so small; the new problem is to understand why it is comparable to the present mass density. ...  does not help with either; anthropic considerations offer a possibility of solving both. In theories with a  that takes random initial values, the anthropic principle may apply to the cosmological constant, but probably to nothing else.
 * Steven Weinberg,


 * We are participators in bringing into being not only the near and here but the far away and long ago. We are in this sense, participators in bringing about something of the universe in the distant past and if we have one explanation for what's happening in the distant past why should we need more?
 * John Archibald Wheeler, "The Anthropic Universe" (Feb 18, 2006) Australia's Science Show, with Martin Redfern moderating excerpts from several scientists, including Wheeler. Audio recording and transcript available. See also same show at WayBack Machine, Internet archive.org.


 * Once one starts to admit anthropic interpretations of fine-tuning problems like the cosmological constant, it is clear that such a proposal might be made for other fine-tuning problems, such as the problem of the Higgs boson mass. Certainly, we would not be here if the Higgs boson mass, and hence also the and  and  and  masses, were greatly bigger. If they were near the, for example, any collection of more than a few elementary particles would collapse into a Black Hole. More generally, if the elementary particle masses were scaled up by a factor N, the number of elementary particles in a star or planet would scale down like N–3, and for very modest N the stars would stop shining.
 * Edward Witten, (quote from p. 478) preprint