The anthropic
principle: science, philosophy or guesswork ?
(1)
Mariano Artigas
Department of Philosophy, University of Navarra,
Pamplona (Spain)
Lecture in "The Impact of the Humanities on the
Development of European Science"
Summer School, 10-15 June 2004, Venice (Italy)
Istituto Veneto di Scienze, Lettere ed Arti, and
The Galileo Chair of History of Science of the
University of Padua
Unpublished text.
- 1. Constants of
nature and natural units
-
- 1.1. The
Constants of Nature
- 1.2. Natural
Units: George Stoney (1874)
- 1.3. Natural
Units: Max Planck (1899-1900)
- 2. The
dimensionless constants of nature
-
- 2.1.
Einstein’s Search for the Ultimate Theory of
Physics
- 2.2.
Dimensionless Constants and Other Worlds
- 3. Dimensionless
constants and large numbers
-
- 3.1. Constants of
Nature and Large Numbers: Sir Arthur Eddington
(1935f)
- 3.2. Large
Number’s Coincidences Are Not Accidental: Paul
Dirac (1937)
- 4. The formulation
of the anthropic principle
-
- 4.1. Introducing
Anthropic Reasoning: Gerald Whitrow (1955)
- 4.2. More
Anthropic Reasoning: Robert Dicke (1961)
- 4.3. The
principle is almost there: Collins and Hawking
(1973)
- 4.4. The Birth
of the Anthropic Principle: Brandon Carter
(1973)
- 5. The anthropic
principle comes of age
-
- 5.1. Life
Depends on Delicate Coincidences: Carr & Rees
(1979)
- 5.2. A Meeting
of the Royal Society (1983)
- 5.3. Carter
Revisited by Carter (1983)
- 5.4. John D.
Barrow and Frank J. Tipler on the Anthropic Principle
(1986)
- 6. Fine-tuning,
teleology, and other worlds
-
- 6.1.
Fine-Tuning
- 6.2. The
Teleological Argument
- 6.3. Many
Worlds
- 6.4. Observation
Selection Effects
- 7. Science,
philosophy, or gueswork?
- Bibliography
- Notes
“Basic science, at its most innovative, merges
into philosophy”.
Ernan McMullin 1
(2)
“It is well known that carbon is required to make
physicists”.
Robert H. Dicke 2
(3)
“A total of over thirty anthropic principles have
been formulated and many of them have been defined
several times over — in nonequivalent ways —
by different authors, and sometimes even by the same
authors on different occasions. Not surprisingly, the
result has been some pretty wild confusion concerning
what the whole thing is about”.
Nick Bostrom 3
(4)
One of the main characteristics of our age is the
dichotomy between the objective world of empirical
science, possessing an intersubjective character, and the
subjective world of the knowing being, i.e. ourselves,
which would remain forever alienated from the rational
level of objective scientific discussion. The anthropic
principle can be considered as a bridge between science,
philosophy and theology. Apparently it enables us to
introduce the human being, under the label of «the
observer», in the otherwise impersonal scientific
world, and to find a meaning to the world. This explains
the interest this principle has raised.
Nevertheless, it is not easy to define the status of
the anthropic principle. Some philosophically or
theologically minded people like it, while many people
think that its weaker form is a tautology, and its
stronger form is untenable. In any case, it is linked
with a host of interesting scientific and humanistic
problems, and can serve to illustrate the interaction
between the sciences and wider human problems.
The anthropic principle says, roughly, that the
existence of life (specifically, human or
«anthropic» life) in the Universe can set
constraints on the way the Universe is now, and how it
got to be the way it is now. An example. In order for us
to exist, there has to be one star (the Sun), orbited at
the appropriate distance by one planet (the Earth), made
of the right mixture of chemical elements (particularly
including carbon, nitrogen, oxygen and hydrogen: four
elements that play a key role in life processes). At
first sight, the existence of the vast Universe
containing millions of galaxies would be irrelevant for
us. But the elements of which we and the Earth are made
have been manufactured within the stars. The Big Bang
only produced hydrogen, helium and traces of a few light
elements. Carbon and other heavier elements are made as a
consequence of the nuclear processes within the stars.
Stars have their life cycle, and eventually explode and
liberate those elements, which congregate in planets like
the Earth. A very long time has been necessary for
galaxies and stars having been formed, for stars to have
completed their life cycle and have exploded, for a
planet like the Earth to be formed containing the
elements necessary for the evolution of life. Thus, we
are led to think that perhaps, for us to be here, the
Universe must have existed for billions of years. Our
existence may help to “explain” why so much
years have elapsed since the Big Bang until now. At the
same time, our existence imposes constraints upon many
features of the natural world: as we are here, the
natural world must possess the characteristics necessary
to make possible our existence, which include a striking
number of coincidences between distant branches of
physics. For instance, if the gravitational constant
(G) were slightly larger, stars would have burned
too hot and much too quickly to support the needs of
life; if it were slightly smaller, the intrastellar
process of nuclear fusion would have never initiated, and
life would have been incapable of arising on the Earth.
Something similar happens with the expansion rate of the
nascent universe, and other quantities of the physical
world.
One first interesting thing is that, contrary to what
we could expect, the anthropic principle was not proposed
in a humanist context. We can trace back its origin and
development to some speculations by physicists of a good
reputation in the scientific ambit. We are going to
examine the prehistory of the principle, how it was
formulated for the first time, the variety of
formulations that came afterwards, and their main
interpretations.
The speculations that would lead to the anthropic
principle begun with some reflections on the so-called
«constants of nature».
Physicist use to describe the world using mathematical
equations where we find two kinds of magnitude: the
«variables» that take different values
depending on the particular phenomena under
consideration, and the «constants», whose
value is the same for some kinds of bodies or phenomena.
Some constants have always the same value, and serve to
define the basic characteristics of our world. These are
called «universal constants» or
«constants of nature».
Also called «fundamental» or
«universal» constants, they are those
quantities that appear in the equations and do not change
throughout the universe. In some way they define the
basic physical characteristic of the world, they define
how our world is. If they were different, the world would
also be different: there would be no trees, or even
atoms, because even though their components were
assembled, they would not be stable. Five of these
constants are the following:
The charge of an electron (e), is the natural
unit of electric charge. It is equal but opposite in
effect to the positive charge of the proton = 1.602 x
10-19 coulombs
The speed of light in a vacuum (c), is the speed
at which electromagnetic radiation travels = 2.99792458
x 108 m s-1 (roughly 300,000
kilometers per second)
The Planck constant (h). Equal to the ratio of
the energy E of a quantum of energy to its
frequency ν (E = h ν) = 6.626 176 x
10-34 Js. In quantum-mechanical calculations
the Dirac constant is frequently used: ħ = h
/ 2π = 1.054589 x 10-34 Js
The gravitational constant (G). The constant that
appears in Newton’s law of gravitation = 6.67259 x
10-11 N m2 kg-2
(m3 kg-1 s-2)
Fine structure constant (α). The coupling constant
of the electromagnetic interaction in quantum field
theory. It is a dimensionless quantity and has a value
of approximately 1 /137. In terms of fundamental
constants, α =
e2/2ε0 hc
(Fine structure: closely spaced optical spectral lines
arising from transitions between energy levels; are
visible only at high resolution)
Some 19 universal constants are known. Besides the 5
listed above, others are: the Boltzmann constant, the
mass of an electron, the mass of a proton,
Avogadro’s number, the gas constant, the Rydberg
constant.
Physicists know quite well the values of these
universal constants, and refine them with ever increasing
accuracy. But at present there is no theory that explains
why they have the values they really have. Physicists
find this inconvenient, and would like to deduce their
value from a theory that would explain them. Instead,
they are sheer facts, they can only be measured. John
Barrow, one of the physicists that have worked more on
the anthropic principle, expresses the situation this
way:
This is the Holy Grail of fundamental physics and it
means the numerical calculation of one of the constants
of Nature. This has never been done. So far, the only
way we can know their values is by measuring them. This
seems unsatisfactory. It allows the constants that
appear in our theories to have a huge range of different
possible values without overthrowing the theory 4.
(8)
In this line, some attempts were made in the last
decades of the 19th century to reduce the
degree of arbitrariness in the universal constants,
defining some «natural units» based on basic
phenomena of the natural world.
In 1874 an Irish physicist, George Johnstone Stoney
(1826-1911), was searching a way to avoid the
conventional units used in measurements, and to find
“natural” units given by Nature itself. For
this purpose he turned to the constants of Nature known
at the time, specifically three of them: the speed of
light c, the unity of electric charge e,
and the constant of gravity G. Using the values
known at the time, he derived from these constants new
values for “natural units” of mass, length
and time:
M = (e2 / G)1/2 =
10-7 gram
L = (Ge2 / c4)1/2 =
10-37 meters
T = (Ge2 / c6)1/2 = 3
x10-46 seconds
These units are useless in practice. If we call them
Stoneys, instead of asking for 100 grams of peanuts, we
should ask for one billion Stoney-mass, and instead of
speaking of 45 minutes, we should speak of 9
x10-44 Stoney-time! Nevertheless, they paved
the way for further speculation that has proved extremely
fruitful in our time.
Max Plack (1858-1947) rediscovered Stoney’s idea
in a slightly different form in 1899. He was a central
figure in physics of his time,. He discovered the quantum
nature of energy, won the Nobel prize for physics in
1918, and died in 1947 aged 89. He was deeply religious
and greatly admired by his younger contemporaries like
Einstein and Bohr.
Planck’s conception of Nature placed great
emphasis upon its intrinsic rationality and independence
of human thought: he was a realist. Unlike Einstein, he
did not believe in any attainable all-encompassing theory
of physics which would explain all the constants of
Nature, for if this theory arrived then physics would
cease to be an inductive science. Here we perceive how
philosophical ideas can influence the scientific agenda
of the most prominent physicists.
Planck was suspicious of attributing fundamental
significance to quantities that had been created as a
result of the “accident” of our situation. He
wanted to see the establishment of
units of length, mass, time and temperature which are
independent of special bodies or substances, which
necessarily retain their significance for all times and
for all environments, terrestrial and human or otherwise
5.
Using G, c, his new constant of action
h (Planck’s constant), and also
Boltzman’s constant k (converts units of
energy into units of temperature), Planck obtained the
only combinations of them which can be formed with the
dimensions of mass, length, time and temperature. Their
values are not very different from Stoney’s:
m = (hc / G)1/2 = 5,56 x 10-5
gram
l = (Gh / c3)1/2 = 4,13 x
10-33 centimeters
t = (Gh / c5)1/2 = 1,38
x10-43 seconds
T = k-1(hc5 / G)1/2 =
3,5 x1032 Kelvin
There is something strange about the extremely big or
small values of these units (especially of length, time
and temperature). Again, in Planck’s time nobody
found them useful, but they acquired new meaning many
years later, at the end of the 20th century,
when physicist were searching for theories that unify
gravitation with quantum physics, a very difficult task.
Quantum theory and gravitation govern different kingdoms
that have little cause to talk to one another. No one
knows how to join the theories together. When the
Universe is smaller than the Planck length in size
(10-33 cm), less than the Planck time in age
(10-43 secs), and hotter than the Planck
temperature (1032 degrees), the known laws of
physics cease to work. John Barrow says:
Planck’s units mark the boundary of applicability
of our current theories. The constants of Nature mark
out the frontiers of our existing knowledge and show us
where our theories start to overreach themselves 6.
(12)
Stoney and Planck were searching for
“natural” units, based on fundamental
phenomena of the physical world. But even those natural
units had to be expressed in terms of some units which
involve human conventions. The speed of light, for
instance, must be expressed in terms of a unit of
longitude per unit of time, say 300,000 kilometers per
second. This is an inconvenient in some practical
affairs, and theoretical physicists also feel the
attraction of pure numbers, and want to find out the
characteristics of the world expressed in pure numbers.
Thus the real characteristics of the world would be
better appraised. Albert Einstein’s dream was to
find out a final theory that would encompass the whole
world and leave no room for conventions: the constants
should be derived from the final theory, and there could
exist only one such final theory.
The influence of extra-scientific ideas was evident in
Einstein’s case. He was deeply religious, but his
religion was a kind of pantheism where there was no place
for accidental coincidences or chance, as expressed by
his famous phrase, “God does not play
dice”.
In the second half of his life Albert Einstein
(1879-1955) tried to find an “ultimate
theory” of physics. The more we approach to it, the
less “free constants” would contain, i. e.
constants which can only be found by experiment. At
present in our theories there are a number of constants
of Nature which we just have to measure. According to
Einstein:
There are two kinds of constants: apparent and real
ones. The apparent ones are simply the outcome of the
introduction of arbitrary units, but are eliminable. The
real [true] ones are genuine numbers which God had to
choose arbitrarily, as it were, when He deigned to
create this world 7.
(15)
Einstein’s dream was that there could only be
one choice of them, so that the universe could only be as
it is.
One of Einstein’s clues was to build up
dimensionless numbers which result as a combination of
ordinary constants of Nature. Those dimensionless numbers
would be established through the logical foundation of
the final theory:
“Or one could put it like this: In a reasonable
theory there are no dimensionless numbers whose values
are only empirically determinable.
Of course, I cannot prove this. But I cannot imagine a
unified and reasonable theory which explicitly contains
a number which the whim of the Creator might just as
well have chosen differently, whereby a qualitatively
different lawfulness of the world would have resulted.
Or one could put it like this: A theory which in its
fundamental equations explicitly contains a non-basic
constant would have to be somehow constructed from bits
and pieces which are logically independent of each
other; but I am confident that this world is not such
that so ugly a construction is needed for its
theoretical comprehension” 8.
(16)
Even though we have advanced a lot towards the
unification of the fundamental theories of physics,
Einstein’s dream continues to be a dream. It is
difficult to establish that a unique world could exist.
If one believes in a personal creator God, obviously God
can create so many different words as He chooses. The
opposite idea was condemned by the archbishop of Paris in
1277 as posing limits to God’s omnipotence. The
French physicist Pierre Duhem saw this condemnation as
the founding date of modern empirical science, always in
need of experiments to contact with the real physical
world.
An approach quite different from Einstein’s is
possible. Instead of considering one unique possible
world, we could consider many different possible worlds,
each one of then defined by a set of dimensionless
constants. Talk of many worlds has become one of the
favorite topics today.
Let us consider, for instance, the fine structure
constant α, and another similar constant referred
to gravity called αG:
α = 2π e2 / hc
≈ 1 / 137 (fine structure constant)
αG =
Gmpr2 / hc ≈
10-38
In this context, John Barrow has written:
“The identification of dimensionless constants of
Nature like α and αG , along with
the numbers that play the same defining role for the
weak and strong forces of Nature encourages us to think
for a moment about worlds others than our own. These
other worlds may be defined by laws of Nature which are
the same as those which govern the Universe as we know
it but they will be characterised by different values of
dimensionless constants. These numerical shifts will
alter the whole fabric of our imaginary worlds. The
balances between their forces will be different from
those in our world. Atoms may have different properties.
Gravity may play a role in the small-scale world. The
quantum nature of reality may enter in unexpected
places” 9.
(17)
“The last important lesson we learn from the way
that pure numbers like α define the world is what
it really means for world to be different. The pure
number that we call the fine structure constant and
denote by á is a combination of the electron
charge, e, the speed of light, c, and
Planck’s constant, h. At first we might be
tempted to think that a world in which the speed of
light was slower would be a different world. But this
would be a mistake. If c, h and e
were changed so that the values they have in metric (or
any other) units were different when we looked them up
in our tables of physical constants, but the value of
α remained the same, this new world could be
observationally indistinguishable from our
world. The only thing that counts in the definition of
the world are the vales of the dimensionless constants
of Nature. If all masses are doubled in value you cannot
tell because all the pure numbers defined by the ratios
of any pair of masses are unchanged” 10.
(18)
We have seen that, searching for natural units, Planck
found out very large or small numbers. Other numbers of
this kind appear when dealing in other ways with the
constants of nature. The appearance of such large numbers
had been a source of amazement ever since they were first
noticed by Hermann Weyl in 1919. Further speculation was
carried out in this line by Sir Arthur Eddington and by
the Nobel prize winner Paul Dirac.
Arthur Stanley Eddington (1882-1944) was one of the
most prominent astrophysicists of his time. He always
kept to his Quaker religion, was a pacifist, and never
took part in active conflicts (such as the upcoming First
World War: as a conscientious objector, he avoided active
war service and was able to continue his research at
Cambridge during the war years of 1914-1918). Since 1913
he held a position as an astronomy professor at
Cambridge. In 1914, he became director of the Cambridge
Observatory and a full member of the Royal Society.
He made several significant contributions to the area
concerning general relativity and astrophysics. Eddington
can be called the “Father of Modern Theoretical
Astrophysics”. He studied the properties of a solar
eclipse on various expeditions around the world. This
research eventually confirmed Albert Einstein’s
general theory of relativity (that as light passes a very
massive star, its path is bent due to gravity: eclipse
expedition to Principe Island in West Africa in 1919).
Eddington spent a great amount of time researching the
internal makeup of stars. In spite of some of his
mistakes, Arthur Eddington made a great deal of valuable
additions to the scientific community.
Eddington wrote several philosophical works such as
The Nature of the Physical World (1928), New
Pathways of Science (1935), and The Philosophy of
Physical Science (1939). He considered that
epistemology is at the basis of physics, that physical
laws and physical constants are the consequences of the
condition of observation. He believed that pure though
could succeed in arriving at a complete description of
the physical world: laws of nature and constants of
nature could be deduced from epistemological
considerations. Eddington had a fascination with the
fundamental constants of nature and produced some
surprising numerical coincidences most of which were
published after his death in his posthumous book
Fundamental Theory (Cambridge University Press,
1946). The Fundamental Theory would explain the numerical
values of the constants of Nature. He did not finish his
plan.
He published parts of his results many years before.
When he did this work in the 1920s, there was no good
understanding of the nuclear forces, so he limited to the
constants defining the gravitational and electromagnetic
forces. He arranged them into three pure dimensionless
numbers, and added his cosmological number
NEdd.
Ratio of the masses of the proton and electron:
mpr / me ≈ 1840
The inverse of the fine structure constant: 2πh /
e2 ≈ 137
Ratio of the gravitational force to the
electromagnetic force between and electron and a proton:
e2 / Gmprme ≈
1040
Number of protons in the visible universe:
NEdd ≈ 1080
These he called “the ultimate constants”.
In 1935 he posed a question that continues to be posed
today:
Are these four constants irreducible, or will a further
unification of physics show that some or all of them can
be dispensed with? Could they have been different from
what they actually are?... the question arises whether
the above ratios can be assigned arbitrarily or whether
they are inevitable. In the former case we can only
learn their values by measurement; in the latter case it
is possible to find them by theory... I think the
opinion now widely prevails that the [above four]
constants... are not arbitrary but will ultimately be
found to have a theoretical explanation; though I have
also heard the contrary view expressed 11.
(21)
We have those dimensionless numbers which result from
combinations of the fundamental constants. Some of them
have an “strange” appearance as related with
1040, its squares and cubes
(22):
total number of protons in the observable universe:
1080
ratio of the strengths of electromagnetic and
gravitational forces between two protons:
1040
“action” of the observable universe in
units of the fundamental Planck units of action:
10120
cosmological constant in units of the square of the
Planck length: 10-120
John Barrow notes:
Eddington had tried to build a theory that made their
[large numbers] appearance understandable. But he failed
to convince a significant body of cosmologists that he
was on the right track. Yet Eddington succeeded in
persuading people that there was something that needed
explaining. Completely unexpectedly, it was one of his
famous neighbours in Cambridge who wrote the short
letter to the journal Nature which succeeded in
fanning interest in the problem with an idea that
remains a viable possibility even to this day [Paul
Dirac] 12.
(23)
Paul Dirac (1902-1984) was the Lucasian Professor of
Mathematics at the University of Cambridge, and one of
the greatest physicists in the 20th century.
In Cambridge he coincided for some time with Eddington.
He received the 1933 Nobel prize in physics jointly with
Erwin Schrödinger “for the discovery of new
productive forms of atomic theory”. His main
contribution was the formulation of a theory that
combined quantum mechanics with relativity.
Dirac can hardly be considered as promoting loose
speculation. In a biographical note we read, “There
is a standard folklore of Dirac stories, mostly revolving
around Dirac saying exactly what he meant and no more.
Once when someone, making polite conversation at dinner,
commented that it was windy, Dirac left the table and
went to the door, looked out, returned to the table and
replied that indeed it was windy. It has been said in
jest that his spoken vocabulary consisted of
’Yes’, ’No’, and ’I
don’t know.’ 13
In 1937, Dirac published his first paper on large
numbers and cosmological matters 14. Years later, in
an interview, he was asked, Could you summarize your
thinking on the large numbers hypothesis? In his
answer he referred to the coincidences between several
large number of the same order of magnitude, about
1040, and he added:
Now, you might say, this is a remarkable coincidence.
But it is rather hard to believe that. One feels that
there must be some connection between these very large
numbers, a connection which we cannot explain at present
but which we shall be able to explain in the future when
we have a better knowledge both of atomic theory and of
cosmology.
Let us assume that these two numbers are connected. Now
one of these numbers is not a constant. The age of the
universe, of course, gets bigger and bigger as the
universe gets older. So the other one must be increasing
also in the same proportion. 15
Dirac relied on the work on large numbers done by
Eddington, specifically three large numbers:
N1 = (size of the observable universe) /
(electron radius) = ct / (e2 / me
c2) ≈ 1040
N2 = electromagnetic-to-gravitational force
between proton and electron = e2 /
Gmempr) ≈ 1040
N3 = number of protons in the observable
universe = c3t / Gmpr ≈
1080
Dirac’s Large Numbers Hypothesis was that
Any two of the very large dimensionless numbers
occurring in Nature are connected by a simple
mathematical relation, in which the coefficients are of
the order of magnitude unity 16.
(25)
This is the final Summary of Dirac’s paper:
It is proposed that all the very large dimensionless
numbers which can be constructed from the important
natural constants of cosmology and atomic theory are
connected by simple mathematical relations involving
coefficients of the order of magnitude unity. The main
consequences of this assumption are investigated and it
is found that a satisfactory theory of cosmology can be
built up from it 17
Eddington and others had written down such hypothesis,
but Eddington did not distinguish between the entire
universe and the observable universe (a sphere with
radius equal to the speed of light times the present age
of the universe). This has as a consequence that some
constants of Nature must be changing as the universe
ages. Dirac chose to abandon the constancy of
Newton’s gravitational constant. This provoked much
discussion: pages in the journal Nature with
arguments for and against.
Dirac’s hypothesis about the variable character
of the gravitational constant did not survive for long,
as it was shown that it was incompatible with the past
conditions necessary for life to emerge (oceans boiling
in the pre-Cambrian era, 200-300 million years ago, and
life had existed on Earth for at least 500 million
years).
But the general idea survived that the coincidences of
the large numbers were seen as consequences of a deeper
set of relationships. Very large dimensionless numbers
amongst the constants of Nature, taking values as
1040 and 1080, are not independent
accidents: there must be consequences rather than
coincidences.
By 1950 a lot of work had been done about the
constants of nature and the relations existing among
them, specially when very large numbers were involved. In
the 1950s, this begun to be related to the conditions
necessary for the existence of human beings. This was the
beginning of anthropic reasoning that, some years later,
would lead to the formulation of the anthropic
principle.
Gerald Whitrow (1912-2000), a cosmologist and
philosopher of science who served as vice-president of
the Royal Astronomical Society in England, published in
1955 an article where he introduced a characteristic
anthropic reasoning. The title was, “Why physical
space has three dimensions” 18. Whitrow’s
article begins quoting the beginning of Galileo’s
Dialogue, where Salviati introduces a discussion
of Aristotle’s arguments on this topic. After a
historical sketch of different aspects of the problem,
Whitrow writes:
I suggest that a possible clue to the elucidation of
this problem is provided by the fact that physical
conditions on the Earth have been such that the
evolution of Man has been possible. 19
In his argument, Whitrow does not use the term
«anthropic», but his reasoning has the
characteristic flavor of what would later on be placed
under that label, as he concludes:
A new attempt to throw light on the question indicates
that this fundamental topological property of the world
may possibly be regarded as partly contingent and partly
necessary, since it could be inferred as the
unique natural concomitant of certain other contingent
characteristics associated with the evolution of the
higher forms of terrestrial life, in particular of Man,
the formulator of the problem 20.
Robert Henry Dicke (1916-1997) was a physicist from
Princeton. He was elected to the National Academy of
Sciences in 1967. Among his many prizes and awards were
the National Medal of Science (1971), the Comstock Prize
of the National Academy of Sciences (1973), and the NASA
Medal for Exceptional Scientific Achievement (1973). He
was a member of the National Science Board from 1970 to
1976. He was appointed to the Princeton University
Department of Physics in 1946.
It was Dicke who explained in 1964 to the astronomers,
Arno Penzias and Robert Wilson, that they had discovered
the cosmic microwave background radiation that was
predicted by an important cosmological model, the big
bang model. Both groups submitted papers on the subject
to The Astrophysical Journal. Dicke’s group
presented the theoretical explanation of the radiation;
Wilson and Penzias described its observation. Thirteen
years later, the Nobel Prize in physics was awarded to
Penzias and Wilson for their discovery. The discovery of
cosmic microwave background radiation provided decisive
support for the big bang model of cosmic origins, which
has become the dominant paradigm in cosmology today.
In 1961 Dicke related the large numbers coincidence to
biological factors 21. The age of the universe must
be large enough for the production of the chemical
factors that are necessary for the existence of observers
like us. This can be given a quantitative estimate. Even
though he did not use the name “anthropic,”
the core of what would be called later on
“anthropic principle” was already there.
In his very short 1961 paper, Dicke refers first of
all to Eddington’s and Dirac’s attempts at
relating the dimensionless constants, and then to
Dirac’s suggestion that “all the large
numbers vary with time”. Dicke refers to three
dimensionless constants that are related to values of the
order of 1040 :
(1) Gmp2 / ħ ≈
10-39 (gravitational coupling constant)
(2) T mpc / ħ ≈ 1042
(T = Hubble age of the universe)
(3) M / mp ≈ 1080 (mass of
the universe to its visible limits)
After some reflections, Dicke writes:
It will be shown that, with the assumption of an
evolutionary universe, T [the Hubble age of the
universe] is not permitted to take one of an enormous
range of values, but is somewhat limited by the
biological requirements to be met during the epoch of
man.
The first of these requirements is that the universe,
hence galaxy, shall have aged sufficiently for there to
exist elements other than hydrogen. It is well known
that carbon is required to make physicists.
It is known that the galaxy was formed initially from
hydrogen only. Hence, the minimum time for the start of
the epoch of man is set by the age of the shortest-lived
stars, for elements, other than hydrogen, are formed in
the interior, and distributed at the death, of the star.
An upper limit for the epoch of man is set by the
requirement that he has an hospitable home in the form
of a planet circling a luminous star. This time is set
by the maximum age of a star capable of producing energy
by nuclear reactions...
... Thus, contrary to our original supposition, T
is not a “random choice” from a wide range
of possible choices, but is limited by the criteria for
the existence of physicists 22.
After some more reflections, Dicke’s final
paragraph concludes:
The statistical support for Dirac’s cosmology is
found to be missing. However, the existence of
physicists now and the assumption of the validity of
Mach’s Principle are sufficient to demand that the
order-of magnitude relations between the three numbers,
given by equations (1), (2) and (3), be satisfied
23.
The anthropic reasoning is explicit in Dicke’s
article, and is used to draw consequences about the age
of the universe, and also to relate large dimensionless
physical numbers, rejecting Dirac’s assumption that
large numbers vary with time. This is why Barrow and
Tipler consider Dicke as the formulator of the weak
anthropic principle.
Dicke published his anthropic ideas in 1961. Other
anthropic ideas were proposed by Brandon Carter, and
circulated in proofs in Cambridge around 1967, and were
presented at Princeton in 1970. These ideas were echoed
by an article published by two other physicists from
Cambridge, C. B. Collins and Stephen W. Hawking in 1973
24. They explained the isotropy of the
universe using an anthropic reasoning: only a certain
kind of models of the universe are compatible with our
own existence as observers. The universe is isotropic
because we are here: it is a consequence of our own
existence.
Here we have an anthropic reasoning, expressed in a
provocative form that would make of it the center of so
much discussion in the following years.
In 1973 a meeting was celebrated at Cracow on the
occasion of the 500th anniversary of
Copernicus’ birth. Brandon Carter, then lecturer at
the Department of Applied Mathematics and Theoretical
Physics, University of Cambridge, contributed with the
paper «Large Number Coincidences and the Anthropic
Principle in Cosmology» 25. There he used
from the first time, in the very title, the expression
«anthropic principle», and also the
distinction, which soon became a standard practice,
between two versions of the principle, a
«weak» version and a «strong»
one.
Carter begins his paper saying:
Prof. Wheeler has asked me to say something for the
record about some ideas that I once suggested (at the
Clifford Memorial meeting in Princeton in 1970) and to
which Hawking and Collins have referred (The
Astrophys.J., 180, 317, 1973). This concerns
a line of thought which I believe to be potentially
fertile, but which I did not write up at the time
because I felt (as I still feel) that it needs further
development. However, it is not inappropriate that this
matter should have cropped up again on the present
occasion, since it consists basically of a reaction
against exaggerated subservience to the
“Copernican principle” 26.
This (1974) is the first official presentation of the
“anthropic principle”, and a quite modest
presentation: Carter feels uncertain, and he says that
the thing needs further development. He feels justified
because they are celebrating a Copernicus meeting, and
there has been an exaggeration in interpreting the
Copernican principle. It is true, Carter reminds us, that
“we must not assume gratuitously that we occupy a
privileged central position in the
Universe”, but:
Unfortunately there has been a strong (not always
subconscious) tendency to extend this to a most
questionable dogma to the effect that our situation
cannot be privileged in any sense. This dogma (which in
its most extreme form led to the “perfect
cosmological principle” on which the steady state
theory was based) is clearly untenable, as was pointed
out by Dicke (Nature 192, 440, 1961), if one
accepts (a) that specially favourable conditions (of
temperature, chemical environment, etc.) are
prerequisite for our existence, and (b) that the
Universe evolves and is by no means spatially
homogeneous on a local site 27.
It is worth noticing that here there is a natural
explanation of the use of the term
«principle» to refer to the «anthropic
principle». This is important because one of the
main objections refers to the allegedly improper use of
the term, as in this case we do not deal with a physical
principle in the usual sense of the term (as in the
«principle of conservation of energy», or the
«principles of conservation», or the
«principle of least action», which refer to
well formulated physical laws of a very general
character). Carter speaks of «anthropic
principle» in opposition of the so-called
«Copernican principle»: even «perfect
cosmological principle», which Carter considers a
false dogma).
Carter goes on by saying that his interest in that
matter arose from reading Bondi’s book
Cosmology (1959), where certain “large
numbers coincidences” are listed as evidence
justifying the introduction of exotic theories that
depart from accepted physical laws. He is convinced that
the opposite is true: conventional physics and cosmology
could in principle been used to predict those
coincidences in advance of their observation. so
that:
However these predictions do require the use of what may
be termed the anthropic principle to the effect
that what we can expect to observe must be restricted by
the conditions necessary for our presence as observers.
(Although our situation is not necessarily
central, it is inevitably privileged to some
extent.) 28.
(30)
With this paragraph, the anthropic principle was born.
Notice also that Carter introduces it speaking of
«predictions» that we can make using it. One
of the main criticisms is that this principle does not
lead to any prediction. So much so that in the following
three sections of his article Carter examines orderly
three classes of theoretical prediction of Bondi’s
coincidences that can be made by using: (a)
«Prediction of the Traditional Kind»; (b)
«Prediction Based on the Weak Anthropic
Principle»; and (c) «Prediction Based on the
Strong Anthropic Principle».
Prediction of the first kind (Prediction of the
Traditional Kind) refers to the order of magnitude of the
mass of stars.
Prediction of the second kind (Prediction Based on the
Weak Anthropic Principle) refers to the coincidence (in
order of magnitude) of Hubble’s fractional
expansion rate of the Universe and the gravitational
coupling constant. Following Dicke, this could be
predicted taking into account that the present age of the
Universe is constrained by anthropic limits. In this
context Carter writes:
This prediction provides a good illustration of the use
of the “weak”anthropic
principle to the effect that 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
29.
(31)
With this paragraph, the «weak anthropic
principle» was born. And it was born as related to
a specific prediction.
It is also important to notice that Carter’s
original version of the «weak» principle
refers to «our location in the universe». The
whole thing originated in contrast with the so-called
«Copernican principle», i. e. that we do not
occupy any privileged location in the universe. In
contrast, Carter stated that our location is privileged
at least in one respect, namely that it must lead us to
observe precisely what we really observe. Our own
existence poses some conditions to the result of our
observation and, therefore, to our theories. We cannot
admit observations or theories that are incompatible with
«our existence as observers».
Prediction of the third kind (Prediction Based on the
Strong Anthropic Principle) refers to a relationship
between constants related to the age of the Universe.
Carter writes:
Condition [8] is a good example of a prediction based on
what may be termed the “strong”
anthropic principle stating that 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”
30.
(32)
The «strong anthropic principle» was born.
Further reasoning shows that it makes possible to predict
the third of the large numbers coincidences listed by
Bondi, the one that relates the number of particles in
the visible universe to the gravitational coupling
constant.
The «strong» principle refers to the
Universe and its fundamental characters in relation with
our existence, whilst the «weak» principle
refers to our location in the Universe as related to our
quality of observers. Carter notices that there is no
reason to abandon conventional theories, and adds that
the character of the predictions is different in both
cases:
whereas a prediction based only on the weak
anthropic principle (as used by Dicke) can amount to a
complete physical explanation, on the other hand even an
entirely rigorous prediction based on the strong
principle will not be completely satisfying from a
physicist’s point of view since the possibility
will remain of finding a deeper underlying theory
explaining the relationships that have been predicted
31.
Carter entitled the last section of his article
«World Ensembles and the Gravitational
Constant». It begins with this words:
It is of course always philosophically possible —
as a last resort, when no stronger physical argument is
available - to promote a prediction based on the
strong anthropic principle to the status of an
explanation by thinking in terms of a
“world ensemble”... The existence of any
organism describable as an observer will only be
possible for certain restricted combinations of the
parameters, which distinguish within the world-ensemble
an exceptional cognizable subset. A prediction
based on the strong anthropic principle may be regarded
as a demonstration that the feature under consideration
is common to all members of the cognizable subset
32.
(33)
Carter provides further details about possible
predictions (of the weakness of the gravitational
constant, restrictions on the fundamental parameters of
nuclear physics). Clearly his paper is centered around
the predictive value of the anthropic principle. Then he
concludes:
The acceptability of predictions of this kind as
explanations depends on one’s attitude to the
world ensemble concept. Although the idea that there may
exist many universes, of which only one can be known to
us, may at first sight seem philosophically undesirable,
it does not really go very much further than the Everett
doctrine (see B. S. De Witt: 1967, Phys. Rev.
160, 113) to which one is virtually forced by the
internal logic of quantum theory. According to the
Everett doctrine the Universe, or more precisely the
state vector of the Universe, has many branches of which
only one can be known to any well defined observer
(although all are equally “real”). This
doctrine would fit very naturally with the world
ensemble philosophy that I have tried to describe.
Even though I would personally be happier with
explanations of the values of the fundamental coupling
constants etc. based on a deeper mathematical structure
(in which they would no longer be fundamental but would
be derived), I think it is worthwhile in the meanwhile
to make a systematic exploration of the a priori limits
that can be placed on these parameters (so long as they
remain fundamental) by the strong anthropic principle.
If it were to turn out that strict limits could
always be obtained in this way, while attempts to derive
them from more fundamental mathematical structures
failed, this would be able to be construed as evidence
that the world ensemble philosophy should be taken
seriously — even if one did not like it 33.
(34)
Once the anthropic principle was formulated in 1974 by
Brandon Carter, it developed its own life. Different
authors interpreted the principle in diverse ways, and
proposed new extensions. Until 1974 the discussions
remained confined within the scientific ambit, even
though they were sometimes in the borderline with
philosophy. Since 1974 the discussion trespassed those
frontiers, and other very different issues entered the
scene. Three of them are specially important: the
so-called fine-tuning of the Universe; its
philosophical consequences for teleological
arguments, including the design argument to prove the
existence of God; and talks about other worlds.
The three items are related. We are going to see some of
the main events that contributed to the expansion of the
anthropic principle.
Two other astronomers from Cambridge, Carr and Rees,
echoed the interest on the anthropic principle in an
article published in Nature in 1979 34. On the
one hand, apparently they endorsed the principle. In the
entry of the article we read:
several aspects of our Universe — some of which
seem to be prerequisites for the evolution of any form
of life — depend rather delicately on apparent
’coincidences’ among the physical constants
35.
(36)
In the conclusion, they highlighted the same idea:
The possibility of life as we know it evolving in the
Universe depends on the values of a few basic physical
constants — and is in some respects remarkably
sensitive to their numerical values 36.
(37)
Later on in the conclusion, however, they showed that
the anthropic principle did not reach the status of a
physical theory, even though they pointed out that the
principle expresses a remarkable fact:
These arguments [Wheeler’s and Everett’s
ensembles of universes] go a little way towards giving
the anthropic principle the status of a physical theory
but only a little: it may never aspire to being much
more than a philosophical curiosity. One day, we may
have a more physical explanation for some of the
relationships discussed here that now seem genuine
coincidences... However, even if all apparently
anthropic coincidences could be explained in this way,
it would still be remarkable that the relationships
dictated by physical theory happened also to be those
propitious for life 37.
(38)
On 25 and 26 May 1983 a Discussion Meeting of the
Royal Society was held in London, with the purpose of
studying the issues related with the constants of
physics. Martin Rees was also involved in it. The
discovery of a close relationship between progress in
particle physics and the concept of the very early
Universe fuelled a new study of the classical problems
about the relationship between the constants, their
unique character, other worlds, etc. 38.
In the Introductory remarks by one of the
editors of the Proceedings we are told that, out of the
16 topics discussed,
interest in [three of them] in recent times originally
instigated the proposal to hold this Discussion.
However, because of their speculative character and of
their inability as yet to produce new predictions, it
was considered that the main emphasis ought to be upon
the study of the constants themselves rather than the
role of the constants in these applications 39.
(39)
A prudent reservation is, therefore, placed on those
three topics, which were the last ones: «The origin
and significance of certain ’cosmological
numbers’: possible relation to the constants of
physics» (number 13, by Rees) 40 ;
«The dependence upon the values of the constants of
physics of macro-phenomena on the Earth and in the
cosmos» (number 14, by Press and Lightman) 41 ;
and «The anthropic principle and the significance
for physical and biological theory of the values of the
constants of physics» (number 16, by Carter)
42. Though not signaled by the editor,
the missing number was obviously connected with these
three: «Dependence of physics upon the basic
constant of dimensionality» (number 15, by Barrow)
43.
We continue to find out the same kind of problems
treated, as ever before, within a scientific ambit, and a
very illustrious one: The Royal Society of London (Carter
being a fellow of it). Also, the problems were treated
with some reservation, «because of their
speculative character and of their inability as yet to
produce new predictions» (as already seen, several
predictions had been produced, but referring to
previously known phenomena, and without the precision
characteristic of mature physics).
It is worth noting also that, besides Carter, two
other among the participants (Martin Rees and John
Barrow) were playing already or would play a very
important role in further developments and discussions of
the anthropic principle. Rees notes that
The masses and lifetimes of stars can be expressed in
term of fundamental constants. Such expressions always
involve powers of the number
ħ/Gmp2 [the gravitational
coupling constant: ≈10-38], whose huge
magnitude stems from the weakness of gravity on
microphysical levels. Our physical understanding of what
determines galactic dimensions is not yet,
however, on the same firm footing. Observational
cosmology gives us three basic numbers that characterize
our Universe... We are unsure how (or, indeed, whether)
these cosmological numbers can be derived from known
physics 44.
Rees ends his paper with an interesting remark:
Insofar as the aim of physics is to erode the number of
independent underivable constants, it is gratifying that
there is a serious chance of calculating the quantities
listed above in terms of microphysical parameters
45.
In their contribution, Press and Lightman review the
manner in which the fundamental constants affect our
daily lives.
Barrow examines the role played by the dimensions of
space-time in determining the form of various physical
laws and constants of Nature, and suggests a formulation
of the anthropic principle. In fact, the title of the
8th and final section of his paper is
«The anthropic principle», a prelude of the
big book that he (jointly with Frank Tipler) would
publish a few years later (which is quoted as «in
press» in this paper). He refers to the previous
publications on related subjects by Whitrow, Dicke,
Carter and others, and says that it is difficult to
determine if small changes in the values of some
fundamental constants could not be compensated by changes
in other constants 46 : also a prelude of vast
discussions that were going to grow around the anthropic
principle.
Since 1975, Carter worked at the Paris-Meudon
Observatory in France. In the 1983 Meeting of the Royal
Society, Carter reflected on the principle he had
formulated ten years before.
In the Introduction to his paper Carter provides some
explanation of his anthropic principle. He describes the
extreme antithesis between the ancient anthropocentric
outlook and the (dangerous) perfect cosmological
principle (Bondi & Gold, 1948) that the Universe is
entirely homogeneous apart from minor local fluctuations,
and he comments on the formulation of the «weak
anthropic principle»:
It was in an attempt to draw attention to the need for a
more balanced intermediate attitude, between primitive
anthropocentrism and its equally unjustifiable
antithesis that I came to introduce the term
anthropic principle (Carter 1974) to express the
notion that ’although our situation is not
necessarily central is necessarily privileged to some
extent’, in so much as special conditions are
necessary for our very existence. The practical
scientific utility of this principle arises from its
almost tautological corollary to the effect that in
making general inferences from what we observe in the
Universe, we must allow for the fact that our
observations are inevitably biased by selection effects
arising from the restriction that our situation should
satisfy the conditions that are necessary a
priori, for our existence. The term
self-selection principle would be an alternative
and perhaps more appropriate description for this hardly
questionable but easily overlooked precept. (If I had
guessed that the term ’anthropic principle’
would come to be so widely adopted I would have been
more careful in my original choice of words. The
imperfection of this now standard terminology is that it
conveys the suggestion that the principle applies only
to mankind. However, although this is indeed the case as
far as we can apply it ourselves, it remains true that
the same self-selection principle would be applicable by
any extraterrestrial civilization that may exist.)
47
(40)
(41)
Carter comments three applications of the «weak
(selection) anthropic principle», using Bayesian
probabilities to discriminate between the probabilities
of theories in the light of a given evidence. Afterwards
he introduces a digression on the strong anthropic
principle, rewriting it, and almost (as will become
apparent in the following) rejecting it:
As I originally formulated it (Carter 1974) this
’strong’ principle consisted in the remark
that our mere existence as intelligent observers imposes
restrictions not just on our situation but even on the
general properties of the Universe, including the values
of the fundamental parameters that are the subject of
the present meeting. Although this
’principle’ has aroused considerable
enthusiasm in certain quarters, it is not something that
I would be prepared to defend with the same degree of
conviction as is deserved by its ’weak’
analogue 48.
(42)
Carter’s doubts arise from our ignorance about
the unified theories towards which we are progressing,
and our ignorance of alternative life forms and,
therefore, on the restrictions we should assume. Carter
finds even the name inappropriate:
Even the choice of the term ’anthropic’ is
less judicious in the ’strong’ than in the
’weak’ case: in retrospect, I regret not
having used an expression, such for example as
’the cognition principle’, having a more
transcendent connotation 49.
Immediately, Carter vigorously rejects the view of the
philosopher Gale who has proposed to promote the
principle to the status of a “reality”
principle, and he includes a quite long appreciation on
science, reality and realism, which has a phenomenist and
instrumentalist flavour. He adds that applications of the
strong anthropic principle should be judged by the
standards of a humble, merely explicative rather than
predictive, category. And notes that in the rest of his
article he will deal only with the «weak»
anthropic principle, whose genuinely predictive power
should become apparent.
The rest of the article (sections 3-6) is concerned
with a very specific issue, which is the new significant
point Carter wants to make: the remarkable coincidence
between the timescale of past biological evolution on
Earth and the future life expectancy of the Sun. Carter
concludes that civilizations comparable with our own are
likely to be extremely rare. His conclusions seem highly
disputable, and his last moral is that
one should try to steer a moderate course between the
Scylla of excessive anthropocentrism and the Charybdis
of unjustifiable neglect of anthropic selection effects
50.
Shortly afterwards, in 1986, John Barrow and Frank
Tipler published their influential work on the anthropic
principle 51. They provided the versions of the
anthropic principle that prevailed in posterior
discussion. The formulation of the weak anthropic
principle is the following:
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
requirement that the Universe be old enough for it to
have already done so 52.
(43)
And the formulation of the strong anthropic principle
is the following:
The Universe must have those properties which allow life
to develop within it at some stage in its history.
53
(44)
Both formulations present remarkable differences with
Carter’s original ones. Carter’s strong
version is quite similar to the version usually presented
as the weak principle, and Carter’s weak version is
even weaker. This is important, if only because many
discussions usually consider the strongest version as the
central one, and conclude that the anthropic principle is
nonsense. We have also seen that Carter was very
cautious, to the extreme of nearly repudiating it, with
his strong version (to say nothing with even stronger
versions).
As a representative of the usual presentation of the
anthropic principle in the two versions, and also of the
confusions associated with it, we can take the following
text:
Carter was not, however, claiming that the Universe was
our own personal playground, made specifically with
humanity in mind. The version of the Anthropic Principle
that he proposed that day, which is now referred to as
the Weak Anthropic Principle (WAP) stated only that by
our very existence as carbon-based intelligent
creatures, we impose a sort of selection effect on the
Universe. For example, in a Universe where just one of
the fundamental constants that govern nature was changed
- say, the strength of gravity - we wouldn’t be
here to wonder why gravity is the strength it is. The
following is the official definition of the WAP:
“Weak Anthropic Principle (WAP): the observed
values of all physical and cosmological quantities are
not equally probable but they take on the values
restricted by the requirement that there exist sites
where carbon-based life can evolve and by the
requirement that the Universe be old enough for it to
have already done so.” (The Anthropic Cosmological
Principle by John Barrow and Frank Tipler, p. 16).
Later, Carter also proposed the Strong Anthropic
Principle (SAP), which states that the Universe had to
bring humanity into being. This version is much more
teleological, if not theological, and is of a highly
speculative nature. Nonetheless, Carter had scientific
reasons to propose it. The definition of the SAP is as
follows: “Strong Anthropic Principle (SAP): the
Universe must have those properties which allow life to
develop within it at some stage in it’s
history.” (The Anthropic Cosmological Principle,
p. 21) 54.
(45)
The examples of confusion could be easily multiplied.
On the other hand, we have seen that Carter himself
extended his original ideas (1973) in the Meeting of the
Royal Society (1983), and to some extent changed them.
Also, in 2003, working as director of research in the
observatory of Paris-Meudon, in a paper on the anthropic
interpretation of quantum theory, Carter proposed to
introduce an «entropy principle» that would
supersede the weak anthropic principle 55. In
another paper also from 2003, Carter stated that
«the only reality of which we have a direct
knowledge is that of a subjective mental
perception», concluding in a kind of
«sollipsism without sollipsism» 56
(which is not an easy idea to assimilate).
In 1986, the new book by Barrow and Tipler considered
the anthropic principle as a contemporary continuation of
teleological reasoning. It begins with a historical
overview of design arguments, and continues with modern
ideas about teleology where Bergson, Whitehead and
Teilhard de Chardin find their place. Then, after more
than 200 pages, we arrive to Dirac, Dicke and Carter, in
a chapter entitled «The Rediscovery of the
Anthropic Principle», as though this principle had
always been there, changing only its formulation
according to the state of science in the different
times.
Barrow and Tipler provide an interesting overview of
the many aspects of the anthropic principle, and examine
in detail its manifestations in physics, astrophysics,
cosmology, quantum mechanics, and biochemistry, carrying
their analysis until the search for extraterrestrial
intelligent life. One may wonder, however, whether they
really clarify the issues, or rather make them even more
complex than they previously were. This holds especially
for the meaning of the anthropic principle, which is the
central issue.
In any case, ever since 1986, discussion on the
anthropic principle has extended enormously and has
produced an immense amount of bibliography. We are going
to consider some of the latest and more impressive
discussions, which place the whole discussion on new
feet.
Discussions on the anthropic principle usually centers
now on three closely related issues: fine-tuning,
teleology, and other worlds.
A number of relationships between the universal
constants are «fine-tuned», which means that
they are fine-tuned for human life. If their values were
slightly different, human life could not exist. As Nick
Bostrom puts it,
One aspect of anthropic reasoning that has attracted
plenty of attention from both philosophers and
physicists, is its use in cosmology to explain the
apparent fine-tuning of our universe.
“Fine-tuning” refers to the supposed fact
that there is a set of cosmological parameters or
fundamental physical constants that are such that had
they been very slightly different, the universe would
have been void of intelligent life. For example, in the
classical big bang model, the early expansion speed
seems fine-tuned. Had it been very slightly greater, the
universe would have expanded too rapidly and no galaxies
would have formed. There would only have been a very low
density hydrogen gas getting more and more dispersed as
time went by. In such a universe, presumably, life could
not evolve. Had the early expansion speed been very
slightly less, then the universe would have recollapsed
very soon after the big bang, and again there would have
been no life. Our universe, having just the right
conditions for life, appears to be balancing on a
knife’s edge ( Leslie 1989). A number of other
parameters seem fine-tuned in the same sense —
e.g. the ratio of the electron mass to the proton mass,
the magnitudes of force strengths, the smoothness of the
early universe, the neutron-proton mass difference,
perhaps even the metric signature of spacetime ( Tegmark
1997) 57.
(47)
It is tempting to relate this fine-tuning with
teleological arguments. If one believes in the existence
of a provident God who governs the world, it is easy to
interpret the fine-tuning of the universe as the result
of the providence of God: the universe is fine-tuned
because God prepared it to make possible the appearance
and the life of the humankind. Then the anthropic
principle would be related to the teleological
argument.
The teleological argument is usually presented in the
English-speaking world as the «argument from
design». It is worth noting, however, that the
«argument from design» is only one of the
formulations of the teleological argument. For instance,
one of the most important formulations of the
teleological argument is the famous «fifth
way» of Thomas Aquinas. This is Aquinas’
text:
The fifth way is taken from things’ being
directed. We see that there are things that have no
knowledge, like physical bodies, but which act for the
sake of an end. This is clear in that they always, or
for the most part, act in the same way, and achieve what
is best. This shows that they reach their end not by
chance but in virtue of some tendency. But things which
have no knowledge do not have a tendency to an end
unless they are directed by something that does have
knowledge and understanding. An example is an arrow
directed by an archer. Therefore there is some being
with understanding which directs all things to their
end, and this, we say, is God 58.
(48)
Here there is no reference to design. The fifth way is
based on the existence of finality (tendencies) in the
natural world, and on the fact that the result of these
natural tendencies is «what is best» (id
quod est optimum). The argument assumes this
«fact». The obvious objection is that there
is evil in the world, and Thomas Aquinas answers
theologically: God permits the existence of evil because
He is able to produce good out from evil. This shows that
we are not here in front of an argument that intends to
prove the existence of God beginning from a zero point.
This argument, as usually any argument to prove the
existence of God, is a reflection that believers make to
provide a rational basis for their beliefs, or to help
other people to grasp the rationality of believing in
God.
There is another version of the teleological argument,
also in the works of Thomas Aquinas, centered on the
order of the cosmos, where different parts contribute to
a unitary result. This argument is more similar to the
«argument from design»:
It is impossible for things contrary and discordant to
fall into one harmonious order always or for the most
part, except under some one guidance, assigning to each
and all a tendency to a fixed end. But in the world we
see things of different natures falling into harmonious
order, not rarely and fortuitously, but always or for
the most part. Therefore there must be some Power by
whose providence the world is governed; and that we call
God 59.
(49)
The «argument from design» is
characteristic of the modern age, when the development of
modern empirical science showed that the natural world is
governed by laws, and God was seen as a supreme Architect
who has designed those laws that determine the
characteristics of the world, which, in turn, was seen as
a marvelous machine full of intelligent contrivances.
This argument received a strong blow when Darwin proposed
his theory of the formation of the living beings (the
beings where design is more apparent) as the result of
the combination of chance mutations and natural
selection. As a result, some claim that the theory of
evolution has shown that there is no need of a divine
designer: natural causes would be sufficient to explain
the working of the natural world.
In this context, fine-tuning is sometimes seen as
providing new strength to the argument from design.
An alternative explanation of the fine-tuning of the
universe has been proposed, consisting on the existence
of many different worlds. If many worlds exist that have
different characteristics governed by different universal
constants, then it is no surprise that there may exist
one like ours, with those constants so fine-tuned that
they appear as the result of a plan. Divine design and
many worlds are seen as opposed explanations. But there
are not really opposed. Nick Bostrom has written:
Some philosophers and physicists take fine-tuning to be
an explanandum that cries out for an explanans. Two
possible explanations are usually envisioned: the design
hypothesis and the ensemble hypothesis. Although these
explanations are compatible, they tend to be viewed as
competing. If we knew that one of them were correct,
there would be less reason to accept to the other
60.
(50)
In spite of this, Bostrom presents them as rival,
disqualifies the design explanation, and adds:
In contrast to some versions of the design hypothesis,
the meaningfulness of the ensemble hypothesis is not
much in question. Only those subscribing to a very
strict verificationist theory of meaning would deny that
it is possible that the world might contain a large set
of causally fairly disconnected spacetime regions with
varying physical parameters 61.
(51)
But the existence of a divine plan should not be
considered as an alternative explanation to the
many-worlds hypotheses. The divine plan can operate
through natural causes. Theconfusion between the
scientific and the metaphysical or religious levels of
explanation is crucial and very frequent.
John Leslie, one of the most active philosophers in
this field, has listed a whole collection of many-worlds
theories. He writes that
Cosmologists have suggested numerous ways in which
greatly many, greatly varied universes could be
generated 62.
(52)
Then he lists four types of such argument: oscillating
universes where Big Bangs are succeeded by Big Collapses,
each cycle counting as a new universe; a gigantic or
infinite space divided into domains or regions with very
different properties; many-worlds quantum mechanics; and
quantum-fluctuational universes 63. The main idea
is:
In short, modern theorists find it easy to invent
mechanisms for making apparent physics and
overt properties differ from one universe to
another even when the underlying physics and the most
fundamental properties remain always the same 64.
Quantum fluctuations are specially popular in this
line. Our universe, and other universes, would be the
result of quantum fluctuations in empty space. The
quantum world would made possible the production of
universes out of a physical state that, even though it
cannot by identified with the metaphysical
«nothingness», would be practically
«nothing» (and is presented very often as
produced «ex nihilo»). Thus, Edward P. Tryon
wrote in a famous seminal paper published in
Nature in 1973:
In my model, I assume that our Universe did indeed
appear from nowhere about 1010 yr ago.
Contrary to widespread belief, such an event need not
have violated any of the conventional laws of physics.
The laws of physics merely imply that a Universe which
appears from nowhere must have certain specific
properties. In particular, such a Universe must have a
zero net value for all conserved quantities 65.
(53)
Tryon added:
I offer the modest proposal that our Universe is simply
one of those things which happen from time to time
66.
Of course it is very difficult (to say the least) to
control empirically such ideas, and Tryon himself
acknowledged at the end of his article that his model was
admittedly speculative. Nevertheless, there is no reason
to deny, in the name of philosophy or theology, the
possibility of such «mechanisms» provided we
do not identify the vacuum with nothingness, even though
it is surprising how easily many different of them are
found, and how easily they seem to be accepted without
empirical support.
Nevertheless, the main point is not this. What is
relevant from the philosophical and theological point of
view is to notice that those mechanisms are not a real
alternative to the divine creation of the world, and that
divine action should not be presented as an alternative
explanation of the fine tuning of the universe.
God’s action as the First Cause extends to
everything in the universe, in any moment of its
existence, from the very beginning until the present
time. Only a self-sufficient Being can be the source of
limited, changeable, finite beings. Empirical science
deals with secondary causes or natural mechanisms, which
always depend ultimately on the action of God. As it is
nonsense opposing evolution to creation, it is also
nonsense opposing any physical theory about the origin of
the universe to God’s action. It is irrelevant for
metaphysics and for theology that the universe may have
originated from a fluctuation of the quantum vacuum, or
that there are many universes. What is impossible is that
the material world may be completely self-sufficient, not
needing a metaphysical transcendent Cause.
There is now a great amount of literature, including
TV films whose protagonists are well known physicists and
even Nobel prize winners, to the effect that the
existence of many, even infinite universes is a
triviality. We could be surrounded by them here and now.
Superstring theories provides us with 11 dimensions, 7 of
them not manifest in our ordinary experience, and they
would be real and could contain items similar and even
identical with those of the visible universe. In the May
2003 issue of Scientific American an article by
Max Tegmark begins with these words
(54):
Not just a staple of science fiction, other universes
are a direct implication of cosmological observations.
And then he goes on saying:
Is there a copy of you reading this article? A person
who is not you but who lives on a planet called Earth,
with misty mountains, fertile fields and sprawling
cities, in a solar system with eight other planets? The
life of this person has been identical to yours in every
respect. But perhaps he or she now decides to put down
this article without finishing it, while you read on.
The idea of such an alter ego seems strange and
implausible, but it looks as if we will just have to
live with it, because it is supported by astronomical
observations. The simplest and most popular cosmological
model today predicts that you have a twin in a galaxy
about 10 to the 1028 meters from here. This
distance is so large that it is beyond astronomical, but
that does not make your doppelgänger any less real.
The estimate is derived from elementary probability and
does not even assume speculative modern physics, merely
that space is infinite (or at least sufficiently large)
in size and almost uniformly filled with matter, as
observations indicate. In infinite space, even the most
unlikely events must take place somewhere. There are
infinitely many other inhabited planets, including not
just one but infinitely many that have people with the
same appearance, name and memories as you, who play out
every possible permutation of your life choices 67.
(55)
Tegmark proposes a kind of «postulate of
reality» that runs thus:
One of the many implications of recent cosmological
observations is that the concept of parallel universes
is no mere metaphor. Spare appears to be infinite in
size. If so, then somewhere out there, everything that
is possible becomes real, no matter how improbable it
is...
... And this is fairly solid physics 68.
(56)
Tegmark follows a line of thought that begun with Alan
Guth
(57), who proposed in the early 1980s the idea of
«inflation» (derived from this we have the
«inflationary universe»). The universe, in
its first moments after the Big Bang (actually, in a very
tine fraction of the first second) would have experienced
a tremendous «inflation»: from a very small
beginning, its volume would have expanded to a much
greater size. This is a respectful scientific idea that
explains several features of the very early universe, and
provides us with predictions that have been successfully
tested by the WMAP (Wilkinson Microwave Anisotropy
Probe):
One of the intriguing consequences of inflation is that
quantum fluctuations in the early universe can be
stretched to astronomical proportions, providing the
seeds for the large scale structure of the universe. The
predicted spectrum of these fluctuations was calculated
by Guth and others in 1982. These fluctuations can be
seen today as ripples in the cosmic background
radiation, but the amplitude of these faint ripples is
only about one part in 100,000. Nonetheless, these
ripples were detected by the COBE satellite in 1992, and
they have now been measured to much higher precision by
the WMAP satellite and other experiments. The properties
of the radiation are found to be in excellent agreement
with the predictions of the simplest models of inflation
69.
(58)
Inflation has been re-elaborated by the Russian
physicist Andrei Linde
(59) (now in the USA), who has proposed a theory
named «Self-Reproducing Inflationary
Universe» (the title of an article published by
Linde in Scientific American, November 1994, pp.
48-55):
Initially, inflation was considered as an intermediate
stage of the evolution of the universe, which was
necessary to solve many cosmological problems. At the
end of inflation the scalar field decayed, the universe
became hot, and its subsequent evolution could be
described by the standard big bang theory. Thus,
inflation was a part of the big bang theory. Gradually,
however, the big bang theory became a part of
inflationary cosmology. Recent versions of inflationary
theory assert that instead of being a single, expanding
ball of fire described by the big bang theory, the
universe looks like a huge growing fractal. It consists
of many inflating balls that produce new balls, which in
turn produce more new balls, ad infinitum. Therefore the
evolution of the universe has no end and may have no
beginning. After inflation the universe becomes divided
into different exponentially large domains inside which
properties of elementary particles and even dimension of
space-time may be different 70.
(60)
Today we can find physicists who speak of creating
universes in our garden, of self-reproducing eternal
universes, and so on. Some of them explicitly say that
these theories change our ideas about man’s place
in the cosmos.
But the theistic perspective is not altered by any of
these theories. Inflation is a scientific respectable
idea, and, as already said, natural mechanisms belong to
the level of the actions of created beings that are
compatible with God’s action and need it to exist
and operate. Once said this, we can add that
Tegmark’s reasoning about identical parallel
universes, as well as the idea of infinitely
self-reproducing universes, belong much more to mere
fancy than to serious thinking, however they may be
presented as linked to scientific data (even in our
universe, nothing is repeated exactly in the same way:
much less should we admit that our lives are repeated
identically in other places). One can have the impression
that these ideas try to counterbalance theological
reasoning about divine action, but leaving aside that
they sound quite strange from the scientific and the
logical point of view, the main fact is that, as far as
they belong to scientific reasoning about the natural
world, they cannot oppose the metaphysical and
theological reasoning about divine action, which is fully
compatible with natural causes and provides the
foundation for their action.
The anthropic principle was first formulated as a
borderline aspect of cosmological issues. Gradually it
has shifted to the ambit of teleology. Then a kind of
antagonism emerged between many worlds and the theistic
idea, as competitors to explain the fact that our
universe is fine-tuned for human life. Now a respectable
idea (inflation), proposed first in order to solve
problems of the big bang model, is used to speculate
about parallel universes and eternally self-reproducing
universes. Whatever may be of those theories in the
future, one can safely assume that the theistic
perspective, and the Christian view of the human being,
are quite independent from those speculations.
Recognizing that around the anthropic principle
«confusion reigns supreme» 71 , Nick
Bostrom has attemped to clarify the problem, formulating
a theory of anthropic reasoning. He devoted to this aim
his doctoral dissertation, which has been published in
book format (see footnote 57). Bostrom says that, in
spite of the confusion, some interesting and useful
insights can be found in anthropic reasoning, and gives
as a reason to hope so that «it is used and taken
seriously by a range of leading physicists and
cosmologists» 72.
Bostrom explains anthropic reasoning as a kind of
«observation selection effect» or
«anthropic bias», namely a situation where
limitations on our ability to observe something can
spuriously affect the distribution or type of the
observed data. A selection effect is a bias introduced by
limitations in one’s data collection process. A
classical example is the method of telephone polling used
by the Literary Digest in the 1936 U.S.
presidential election. The Literary Digest had
harvested the addresses of the people they sent the
survey to mainly from telephone books and motor vehicle
registries. The poor of the depression era, a group where
Roosevelt was especially strong, often did not have a
phone or a car. The poll was biased against Roosevelt
supporters. An observational selection effect is a
selection effect that arises from the very preconditions
of observership. Another example, taken from Sir Arthur
Eddington: suppose you are trying to catch fish with a
net that doesn’t catch fish that are shorter than
20 cm. If you use such a net to catch a hundred fish and
they all turn out to be 20 cm or longer, then obviously
you are not allowed to regard this as evidence that the
minimum length of fish in the lake is 20 cm.
(61)
According to Bostron, the anthropic principle,
especially in its strong version, is heavily based upon
observational selection effects. Observational selection
effect theory states that conclusions developed from
selective or limited data cannot be used to generate
conclusions which transcend the scope of the
observations. Bostron develops a model to deal with
observation selection effects, and applies it to a
variety of problems in science and philosophy.
The anthropic principle originated within a scientific
context, fueled by scientists with interests that were in
the borderline with philosophy, and expanded rapidly,
including problems about teleology and many worlds.
In spite of the usual name, the anthropic principle
obviously is not a «principle» in the usual
scientific sense, as the principle of conservation of
energy or the principle of minimal action are. Neither is
it clear that it has an explanatory or predictive power.
From the very beginning Brandon Carter tried to show that
it really has predictive power. The principal prediction
attributed to anthropic reasoning is the existence of a
long-lived excited state of the nucleus of carbon 12, the
effect of which is to delay the conversion of carbon 12
into oxigen 16 (by combination with helium 4 nuclei),
thus providing enough carbon in the cosmic mix to support
carbon-based life. This process is fundamental for the
existence of life as we know it, and was successfully
predicted by Fred Hoyle in 1953, searching the conditions
that would made the production of carbon, and therefore
the existence of life on Earth, easily available.
It has often been said that the anthropic principle is
tautological, even though sometimes it is added that, as
mathematical tautologies enter into the physical sciences
when applied to factual issues, also the anthropic
principle, combined with factual problems, can be useful
in the sciences. Probably this is true. The version of
the anthropic principle that nobody would dispute is the
usually called «weak principle», stating
merely that, given our existence as scientists, the
preconditions for human life must obtain. This refers to
the necessary conditions for our life. This can be
applied to specific issues. Although usually it will be
difficult to arrive at precise conclusions, we can
sometimes arrive at some interesting clues, because the
«principle» may point out towards some limits
in the possible explanations.
It must also be said that the recognition, in the
light of observational data, that Einstein’s
infamous cosmological constant might not be zero has
recently changed the attitude towards anthropic thinking
among some scientists, even though it is not clear what
they might think of the anthropic principle:
perhaps the most significant change in cosmological
thinking involves a new willingness to discuss what used
to be an idea that was not normally mentioned in polite
company: the anthropic principle... The realization that
an extremely small, but non-zero, cosmological constant
might exist has changed physicists’ interest in
anthropic explanation of nature precisely because the
value it seems to take is otherwise so inexplicable...
In the end as with so many anthropic arguments, it is
hard to know what to make of this result, especially in
the absence of any fundamental theory 73.
(63)
On the other hand, as a speculative philosophical
issue, the interest of the principle is evident, even
though it is difficult to consider it as a real
«principle». In the context of teleology, it
points out towards a number of issues that are worth
considering as a factual basis for further reasoning. The
«fine tuning» of the universe for
carbon-based life, and specifically for human life,
should not be taken as a logical proof of the existence
of a divine plan; nevertheless, it is most coherent with
this plan, and reinforces the teleological and
theological reasoning.
The anthropic principle has contributed to the
development of a number of new scientific ideas on the
existence of worlds other than the one we know, sometimes
as a result of the opposition to the teleological
interpretations that the principle apparently suggests.
The interaction between science and philosophy (and
theology) in this case can be summarized in the following
sequence. In the first place, several philosophically
minded scientists have tried to solve problems regarding
the basic features of the world, in the limits of the
science of their time. Then other scientists have used
anthropic reasoning that eventually led to the
formulation of the anthropic principle, always in a
scientific context and trying to apply the principle to
scientific problems. Then, also in the hands of other
scientists, the issue exploded and merged with problems
on telelology and theology. In its turn, this has
provoked further speculation about other worlds and their
origin. Also, the so-called fine-tuning of the universe
has enlarged the perspectives for teleological
reasoning.
Barrow, John D. “Dimensionality”, in:
The Constants of Physics, W. H. McCrea and M. J.
Rees, eds. (The Royal Society: London, 1983), pp.
127-136.
Barrow, John D. and Tipler, Frank J. The Anthropic
Cosmological Principle (Oxford: Clarendon Press,
1986).
Barrow, John D. The Constants of Nature. From Alpha
to Omega — the Numbers That Encode the Deepest
Secrets of the Universe (New York: Vintage Books,
2002).
Bostrom, Nick. Anthropic Bias. Observation
Selection Effects in Science and Philosophy (New York
& London: Routledge, 2002).
Bostrom, Nick. Observational Selection Effects and
Probability, doctoral dissertation, London School of
Economics, Department of Philosophy, 3 July 2000: http://www.anthropic-principle.com/phd/phdhtml.html
Carr, B. J. & Rees, M. J. “The anthropic
principle and the structure of the physical world”,
Nature, vol. 278 (12 April 1979), pp. 605-612.
Carter, Brandon. “Large Number Coincidences and
the Anthropic Principle in Cosmology”, in:
Confrontation of Cosmological Theories with
Observational Data, M. S. Longair, ed. (Dordrecht:
Reidel, 1974), pp. 291-298. Reprinted in: Modern
Cosmology & Philosophy, J. Leslie ed.,
2nd ed. (Amherst, NY: Prometheus Books, 1998),
pp. 131-139.
Carter, Brandon. “The anthropic principle and
its implications for biological evolution”, in:
The Constants of Physics, W. H. McCrea and M. J.
Rees, eds. (The Royal Society: London, 1983), pp.
137-153.
Carter, Brandon. Anthropic interpretation of
quantum theory (News about that cat!), July 2003, pp.
11 and 16, in: http://luth2.obspm.fr/~carter/
Carter, Brandon. Anthropic interpretation of
quantum theory, July 2003: http://arxiv.org/PS_cache/hep-th/pdf/0403/0403008.pdf
Collins, C. B. and Hawking, S. W. “Why is the
universe isotropic?”, The Astrophysical
Journal, vol. 180 (1973), pp. 317-334.
Dicke, R. H. “Dirac’s Cosmology and
Mach’s Principle”, Nature, vol. 192,
No. 4801, 4 November 1961, pp. 440-441. Reprinted in:
Modern Cosmology & Philosophy, John Leslie
ed., 2nd ed. (Amherst, NY: Prometheus Books,
1998), pp. 127-130.
Dicke, Robert H. “Dirac’s Cosmology and
Mach’s Principle”, Nature, vol. 192,
No. 4801 (4 November 1961), pp. 440-441 [followed in p.
441 by a comment by P. A. M. Dirac]. Reprinted in:
Modern Cosmology & Philosophy, J. Leslie ed.,
2nd ed. (Amherst, NY: Prometheus Books, 1998),
pp. 127-130.
Dirac, Paul A. M. “A New Basis for
Cosmology”, Proceedings of the Royal Society of
London. Series A, vol. 165, No. 921 (5 April 1938),
pp. 199-208. [See also: Nature, 139, 323
(1937)].
Dirac, Paul. (interview with): http://www.fdavidpeat.com/interviews/dirac.htm
Eddington, Arthur S. New Pathways in Science
(Cambridge: Cambridge University Press, 1935).
Krauss, Lawrence M. “A just-so story”,
Nature, vol. 423 (15 May 2003), pp. 230-231.
Leslie, J. “The Anthropic Principle
Today”, in: Modern Cosmology &
Philosophy, J. Leslie ed. (Amherst, NY: Prometheus
Books, 1998), pp. 289-310.
McCrea, W. H. “Introductory remarks”, in:
The Constants of Physics, W. H. McCrea and M. J.
Rees, eds. (The Royal Society: London, 1983), pp.
1-3.
McMullin, Ernan. “Is Philosophy Relevant to
Cosmology?”, in: Modern Cosmology &
Philosophy, John Leslie, ed. (Amherst, NY: Prometheus
Books, 1998), pp. 35-56.
Press, W. H. and Lightman, A. P. “Dependence of
macrophysical phenomena on the values of the fundamental
constants”, in: The Constants of Physics, W.
H. McCrea and M. J. Rees, eds. (The Royal Society:
London, 1983), pp. 113-126.
Rees, M. J. “Large numbers and ratios in
astrophysics and cosmology”, in: The Constants
of Physics, W. H. McCrea and M. J. Rees, eds. (The
Royal Society: London, 1983), pp. 101-112.
Tegmark, M. “Parallel Universes”,
Scientific American, volume 288, number 5, pp.
41-51.
The Constants of Physics, W. H. McCrea and M.
J. Rees, eds. (The Royal Society: London, 1983). Original
publication: Philosophical Transactions of the Royal
Society of London, series A, volume 310 (no. 1512),
pages 209-363 (1983).
Tryon, E. P. “Is the universe a Vacuum
Pluctuation?”, Nature, vol. 246, No. 5433
(14 December 1973), pp. 396-397. Reprinted in (and quoted
by): Modern Cosmology & Philosophy, J. Leslie
ed. (Amherst, NY: Prometheus Books, 1998), pp.
222-225.
Whitrow, Gerald. “Why physical space has three
dimensions”, The British Journal for the
Philosophy of Science, Vol. 6, No. 21. (May, 1955),
pp. 13-31.
(1)
Ernan McMullin, “Is Philosophy Relevant to
Cosmology?”, in: Modern Cosmology &
Philosophy , John Leslie, ed. (Amherst, NY:
Prometheus Books, 1998), p. 42.
(2) R.
H. Dicke, “Dirac’s Cosmology and Mach’s
Principle”, Nature, vol. 192, No. 4801, 4
November 1961, pp. 440-441. Reprinted in: Modern
Cosmology & Philosophy , J. Leslie ed.,
2nd ed. (Amherst, NY: Prometheus Books, 1998),
p. 128.
(3) N.
Bostrom, Anthropic Bias. Observation Selection Effects
in Science and Philosophy (New York & London:
Routledge, 2002), p. 6.
(4)
John D. Barrow, The Constants of Nature. From Alpha to
Omega — the Numbers That Encode the Deepest Secrets
of the Universe (New York: Vintage Books, 2002), p.
65.
(5)
Quoted by: Barrow, The Constants of Nature , p.
25.
(6)
Barrow, The Constants of Nature , pp. 42-43.
(7)
Letter by Albert Einstein to Ilse Rosenthal-Schneider,
Princeton, 11 May 1945: quoted by Barrow, The
Constants of Nature , p. 35.
(8)
Letter by Albert Einstein to Ilse Rosenthal-Schneider,
Princeton, 13 October 1945: quoted by Barrow, The
Constants of Nature, p. 40.
(9)
Barrow, The Constants of Nature , cit., p. 48.
(10)
Ibid., p. 49.
(11)
A. S. Eddington, New Pathways in Science
(Cambridge: Cambridge University Press, 1935), p. 233 and
234.
(12)
Barrow, The Constants of Nature, cit., pp. 99.
(13)
Article by J. J. O’Connor and E. F. Robertson:
http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Dirac.html
(visited 3 May 2004). On Dirac and large numbers, see:
Barrow, The Constants of Nature, cit., pp.
99-103.
(14)
P. A. M. Dirac, “A New Basis for Cosmology”,
Proceedings of the Royal Society of London. Series
A, vol. 165, No. 921 (5 April 1938), pp. 199-208. [p]
[See also: Nature, 139, 323 (1937)].
(15)
Interview with Paul Dirac: http://www.fdavidpeat.com/interviews/dirac.htm
(visited 3 May 2004).
(16)
Dirac, “A New Basis for Cosmology”, cit., p.
201.
(17)
Ibid., p. 208.
(18)
Gerald Whitrow, “Why physical space has three
dimensions”, The British Journal for the
Philosophy of Science , Vol. 6, No. 21. (May, 1955),
pp. 13-31.
(19)
Ibid., p. 29.
(20)
Ibid., p. 31.
(21)
R. H. Dicke, “Dirac’s Cosmology and
Mach’s Principle”, Nature, vol. 192,
No. 4801, 4 November 1961, pp. 440-441. Reprinted in:
Modern Cosmology & Philosophy , J. Leslie ed.,
2nd ed. (Amherst, NY: Prometheus Books, 1998),
pp. 127-130.
(22)
Ibid., pp. 128-129.
(23)
Ibid., p. 130.
(24)
C. B. Collins and S. W. Hawking, “Why is the
universe isotropic?”, The Astrophysical
Journal, vol. 180 (1973), pp. 317-334.
(25)
B. Carter, “Large Number Coincidences and the
Anthropic Principle in Cosmology”, in:
Confrontation of Cosmological Theories with
Observational Data, M. S. Longair, ed. (Dordrecht:
Reidel, 1974), pp. 291-298. Reprinted in: Modern
Cosmology & Philosophy, J. Leslie ed.,
2nd ed. (Amherst, NY: Prometheus Books, 1998),
pp. 131-139.
(26)
Ibid., p. 131.
(27)
Ibid., pp. 131-132.
(28)
Ibid., p. 132.
(29)
Ibid., p. 133.
(30)
Ibid., p. 135.
(31)
Ibid., p. 136.
(32)
Ibid., p. 137.
(33)
Ibid., p. 139.
(34)
B. J. Carr & M. J. Rees, “The anthropic
principle and the structure of the physical world”,
Nature, vol. 278 (12 April 1979), pp. 605-612.
(35)
Ibid., p. 605.
(36)
Ibid., p. 612.
(37)
Ibid.
(38)
The Constants of Physics, W. H. McCrea and M. J.
Rees, eds. (The Royal Society: London, 1983), p. v.
Original publication: Philosophical Transactions of
the Royal Society of London , series A, volume 310
(no. 1512), pages 209-363 (1983). We will quote by the
separated volume, which has 153 pages
(39)
W. H. McCrea, “Introductory remarks”,
ibid., pp. 2-3.
(40)
M. J. Rees, “Large numbers and ratios in
astrophysics and cosmology”, ibid., pp.
101-112.
(41)
W. H. Press and A. P. Lightman, “Dependence of
macrophysical phenomena on the values of the fundamental
constants”, ibid., pp. 113-126.
(42)
B. Carter, “The anthropic principle and its
implications for biological evolution”,
ibid., pp. 137-153.
(43)
J. D. Barrow, “Dimensionality”, ibid.,
pp. 127-136.
(44)
Rees, “Large numbers and ratios in astrophysics and
cosmology”, cit., p. 101.
(45)
Ibid., p. 111.
(46)
Barrow, “Dimensionality”, ibid., p.
135.
(47)
Carter, “The anthropic principle and its
implications for biological evolution”, cit., pp.
137-138.
(48)
Ibid., p. 141.
(49)
Ibid., p. 142.
(50)
Ibid., p. 152.
(51)
J. D. Barrow and F. J. Tipler, The Anthropic
Cosmological Principle (Oxford: Clarendon Press,
1986).
(52)
Ibid., p. 16.
(53)
Ibid., p. 21.
(54)
This text is found in a web page entitled «The
Anthropic Principle»:
http://www.physics.sfsu.edu/~lwilliam/sota/anth/anthropic_principle_index.html
(visited on 4 May 2004).
(55)
Brandon Carter, Anthropic interpretation of quantum
theory, July 2003: http://arxiv.org/PS_cache/hep-th/pdf/0403/0403008.pdf
(visited 3 May 2004).
(56)
Brandon Carter, Anthropic interpretation of quantum
theory (News about that cat!), July 2003, pp. 11 and
16, in: http://luth2.obspm.fr/~carter/
(57)
Nick Bostrom, Anthropic Bias. Observation Selection
Effects in Science and Philosophy (New York &
London: Routledge, 2002), p. 15.
(58)
Thomas Aquinas, Summa Theologiae , part 1,
question 2, article 3, in the body of the article.
(59)
Thomas Aquinas, Summa contra Gentes , book 1,
chapter 13.
(60)
Bostrom, Anthropic Bias , cit., p. 11.
(61)
Ibid., p. 13.
(62)
J. Leslie, “The Anthropic Principle Today”,
in: Modern Cosmology & Philosophy, J. Leslie
ed. (Amherst, NY: Prometheus Books, 1998), p. 292.
(63)
Ibid., pp. 292-295.
(64)
Ibid., p. 293.
(65)
E. P. Tryon, “Is the universe a Vacuum
Pluctuation?”, Nature, vol. 246, No. 5433
(14 December 1973), pp. 396-397. Reprinted in (and quoted
by): Modern Cosmology & Philosophy, J. Leslie
ed. (Amherst, NY: Prometheus Books, 1998), p. 223.
(66)
Ibid., p.224.
(67)
M. Tegmark, “Parallel Universes”,
Scientific American , volume 288, number 5, p.
41.
(68)
Ibid., p. 42.
(69)
This and the following data are taken from the web page
of Alan Guth:
http://web.mit.edu/physics/facultyandstaff/faculty/alan_guth.html#inflationaryuniverse
.
(70)
This and the following data are taken from the web page
of Andrei Linde: http://www.stanford.edu/~alinde.
(71)
Nick Bostrom, Observational Selection Effects and
Probability, doctoral dissertation, London School of
Economics, Department of Philosophy, 3 July 2000: http://www.anthropic-principle.com/phd/phdhtml.html,
p. 8.
(72)
Ibid., p. 12.
(73)
Lawrence M. Krauss, “A just-so story”,
Nature , vol. 423 (15 May 2003), pp. 230-231.
Index of
slides
The Anthropic Principle: Science, Philosophy or Guesswork
?
Ernan McMullin (1981)
Robert Dicke (1961)
Nick Bostrom (2002)
Contents
1 Constants of Nature and Natural Units
1.1. The Constants of Nature
John Barrow on the Constants of Nature
1.2. Natural Units: George Stoney (1874) (1)
1.2. Natural Units: George Stoney (1874) (2)
1.3. Natural Units: Max Planck (1899-1900) (1)
1.3. Natural Units: Max Planck (1899-1900) (2)
2 The dimensionless Constants of Nature
2.1. Einstein’s Search for the Ultimate Theory of
Physics (1)
Albert Einstein (1945) (2)
Albert Einstein (1945) (3)
2.2. Dimensionless Constants and Other Worlds (John D.
Barrow) (1)
2.2. Dimensionless Constants and Other Worlds (John D.
Barrow) (2)
3 Dimensionless Constants and Large Numbers
3.1. Constants of Nature and Large Numbers: Sir Arthur
Eddington (1)
3.1. Constants of Nature and Large Numbers: Sir Arthur
Eddington (2)
Dimensionless numbers with an “strange”
appearance: related with 1040, its squares and
cubes
John D. Barrow on Eddington
3.2. Large Number’s Coincidences are not
accidental: Paul Dirac (1937) (1)
Paul Dirac (2)
4 The formulation of the Anthropic Principle
4.1. Introducing Anthropic Reasoning: Gerald Whitrow
(1955)
4.2. More Anthropic Reasoning: Robert Dicke
(1961)
4.3. The principle is Almost There: Collins and Hawking
(1973)
4.4. The Birth of the Anthropic Principle: Brandon Carter
(1973) (1)
4.4. The Birth of the Anthropic Principle: Brandon Carter
(1973) (2)
4.4. The Birth of the Anthropic Principle: Brandon Carter
(1973) (3)
Carter on Anthropic Principle, 1973 (1)
Carter on Anthropic Principle, 1973 (2)
5 The Anthropic Principle comes of Age
5.1. Life Depends on Delicate Coincidences: Carr &
Rees (1979) (1)
5.1. Life Depends on Delicate Coincidences: Carr &
Rees (1979) (2)
5.1. Life Depends on Delicate Coincidences: Carr &
Rees (1979) (3)
5.2. A Meeting of the Royal Society (1983)
5.3. Carter Revisited by Carter (1983) (1)
5.3. Carter Revisited by Carter (1983) (2)
5.3. Carter Revisited by Carter (1983) (3)
5.4. Barrow and Tipler on the Anthropic Principle (1986)
(1)
5.4. Barrow and Tipler on the Anthropic Principle (1986)
(2)
Confusion increases: an example
6 Fine-Tuning, Teleology, and Other Worlds
6.1. Fine-Tuning
6.2. The Teleological Argument (1)
6.2. The Teleological Argument (2)
6.3. Many Worlds (1)
6.3. Many Worlds (2)
6.3. Many Worlds (3)
6.3. Many Worlds (4)
6.3. Many Worlds (5) Max Tegmark
Max Tegmark (Scientific American, May 2003)
Max Tegmark (Scientific American, May 2003) The Reality
Postulate
Alan Guth
The inflationary universe
Andrei Linde
Eternal chaotic inflation
6.4. Observation Selection Effects
7 Science, Philosophy, or Gueswork?
In the end...
Full presentation
Note: Flash animation bigger than 1 Mb.
To pass the slides, clic on the image.
|
Grupo
de Investigación sobre Ciencia, Razón y Fe
(CRYF)