الهوامش
تمهيد وشكر وتقدير
(1)
Bernard Carr and Martin Rees, “The Anthropic Principle
and the Structure of the Physical World,” Nature, vol. 278 (1979), p. 605.
(2)
John Barrow and Frank Tipler, The
Anthropic Cosmological Principle (New York: Oxford University
Press, 1986).
(3)
Martin Gardner, “WAP, SAP, PAP, & FAP,” New York Review of Books, May 8, 1986.
(4)
Leonard Susskind, The Cosmic
Landscape: String Theory and the Illusion of Intelligent
Design (New York: Little, Brown, 2005), p. 138.
(5)
Bernard Carr (ed.), Universe or
Multiverse? (Cambridge, UK: Cambridge University Press,
2007).
(6)
Paul Davies, The Mind of
God (New York: Simon & Schuster, 1992).
الفصل الأول: الأسئلة الكبرى
(1)
I shall restrict my discussion to life as we know it. The possibility of
exotic forms of life based on other chemical elements, or other physical
processes entirely, is certainly fascinating but completely
speculative. If life is common, we have no reason to suppose
that our form of life is atypical. Readers interested in a less
conservative approach will find an up-to-date discussion in
Peter Ward, Life as We Do Not Know
It (New York: Viking, 2005).
(2)
Fred Hoyle, “The Universe: Past and Present
Reflections,” Annual Review of Astronomy and
Astrophysics, vol. 20 (1982), p. 16.
(3)
See, for example, David Park, The Grand Contraption: The World as Myth, Number, and
Chance (Princeton, NJ: Princeton University Press, 2005).
(4)
The term was popularized by the
physicist Heinz Pagels in The Cosmic Code
(New York: Simon & Schuster, 1982).
(5)
See, for example, Edward Craig, The Mind of God and the Works of Man (New
York: Oxford University Press, 1987).
(6)
See, for example, John W. Carroll, Laws of Nature (New York: Cambridge
University Press, 1994); and Alan Padgett, “The Roots of the Western
Concept of ‘Laws of Nature’: From the Greeks to Newton,”
Perspectives on
Science and Christian Faith, vol. 55, no. 3 (December 2003), p.
212.
(7)
Lucretius, De rerum
natura, edited by M. F. Smith (Indianapolis: Hackett
Publishing, 2001), p. 138.
(8)
Marcus Manilius, Astronomica, translated by G. P. Goold (Cambridge, MA:
Harvard University Press, 1977), p. 121.
(9)
Augustine, The Literal
Meaning of Genesis, vol. 2, translated by J. H. Taylor
(New York: Paulist Press, 1983), p. 92.
(10)
Stillman Drake, Discoveries
and Opinions of Galileo (New York: Doubleday-Anchor,
1957), p. 70.
(11)
James Jeans, The Mysterious
Universe (Cambridge, UK: Cambridge University Press,
1930), p. 140.
(12)
Unbeknownst to me, Lindsay’s naive question was being asked
at about the same time by one of the world’s leading theoretical
physicists, Eugene Wigner: see his “The Unreasonable Effectiveness of
Mathematics in the Natural Sciences,” Communications in Pure and Applied Mathematics, vol. 13,
no. 1 (1960), p. 1.
(13)
A minority school of thought says that this is all baloney, that the
laws of physics are just human inventions constructed for convenience, and
that there are no “real” laws at all. I am going to ignore this
dissenting position because I think it is totally wrong and does
not merit serious discussion.
(14)
Nancy Cartwright, How the
Laws of Physics Lie (New York: Oxford University Press,
1983).
(15)
David Mowaljarli and Jutta Malnic, Yorro Yorro (Rochester, VT: Inner
Traditions, 1993), chapter 23.
(16)
Richard Feynman, “The Meaning of It All,” 1963 John
Danz Lecture, published under the same title by Addison Wesley (Reading,
MA: 1998), p. 14.
(17)
Steven Weinberg, The First
Three Minutes (New York: Basic Books, 1977), p. 149.
الفصل الثاني: تفسير الكون
(1)
K is the symbol
for the unit of temperature
called the Kelvin. A temperature interval of one degree Kelvin is the same as an interval
of one degree Celsius, but the Kelvin scale starts from absolute zero, or about −273°C.
(2)
Roughly speaking, this is the final state into which a closed system
settles, following which no large-scale changes occur. For
a simple gas, it is a state of uniform pressure and density.
(3)
An ionized gas, also called a plasma, is
one in which the atoms are dissociated into electrons and nuclei, as
is caused by extreme heat. I shall describe the primordial
gas in more detail in Chapter
3.
(4)
The subsequent scattering of the CMB from early clumps of gas
produced subtle effects in the polarization of the radiation, effects that have
also been detected by WMAP.
(5)
Reproduced by kind permission of the correspondent.
(6)
Sometimes cosmologists refer to “the last
scattering surface,” the spherical shell of matter surrounding
Earth from which the radiation emanates at the moment of
transition from opaque to transparent. This transition
is technically termed the decoupling
of matter and radiation.
(7)
For a careful exposition of this point, see Tamara Davis and Charles
Lineweaver, “Misconceptions About the Big Bang,” Scientific American (March 2005), p.
36.
(8)
This issue is complicated by the theory of
inflation, which I shall describe in Chapter 3.
(9)
Analogously, when a ship disappears over the terrestrial horizon, we
do not infer that the Earth ends there.
(10)
This admirable term was suggested by Alan Guth, and I have decided
to adopt it here.
(11)
Time is not a dimension of space, but a dimension of spacetime.
(12)
This won’t apply if theories about “branes” turn out to be
correct—see Hiding Dimensions of Space.
(13)
To sound a note of caution, some cosmologists are concerned that the
largest features mapped by WMAP (technically, the lowest multipoles) display
some oddities not predicted by the conventional big bang model
of the universe. It is too soon to know whether this is due
to problems with the equipment and/or data analysis or if it
points to something significant and unexpected about the structure of the universe.
(14)
The limited accuracy of these observations
cannot establish that the universe is
exactly flat. What they tell
us is that if the universe is
shaped like Einstein’s hypersphere, then
the radius of the hypersphere is exceedingly large, so that within
the volume of space probed by our instruments
we cannot discern any curvature. Similar remarks apply
to any negative curvature.
(15)
Even if space is flat, it need not necessarily
be infinite. That is because Einstein’s theory says
nothing about the
topology of space. One possible topology
involves identifying points. Think of a sheet of paper on which
a particle enters from the left, traverses the
paper, and exits from the right. Now imagine rolling up the paper and
gluing the left and right edges together. The particle that previously
exited from the right would now reappear from the
left. Some cosmologists have suggested that space might be
like this and resemble a hall of mirrors. If we inhabited
such a universe, it might look to us
at first sight as if “the hall of mirrors” extended to infinity, but
on closer inspection we would discover that a finite volume of
space repeats itself, infinitely often. It is possible that the
universe consists of three-dimensional cells, repeated periodically, and
that light which we take to be from far away
is in fact wrapping around one or more times, creating the
illusion of distance. More complicated shapes, such
as the three-dimensional analogue of
the surface of a segmented soccer ball, have also been suggested.
(16)
I am being a little cavalier with my terminology. The word
matter here includes both dark matter and
dark energy, topics I shall discuss in Chapter
6.
(17)
Flatland: A Romance of Many
Dimensions by E. A. Abbott is now available in an edition
annotated by Ian Stewart (New York: Perseus Publishing, 2001).
(18)
See, for example, Lisa Randall, Warped Passages (New York: Harper-Collins,
2005).
(19)
Gerald Whitrow, “Why Space Has Three Dimensions,”
British Journal for the Philosophy of
Science, vol. 6, no. 21 (1955), p.
1.
الفصل الثالث: كيف بدأ الكون؟
(1)
The helium that is used to fill balloons comes not from the big bang,
but from the product of radioactive decay in the Earth’s interior.
(2)
This “happy medium” is related
to the fact that space is flat.
(3)
Inflation was originally invented by Guth to solve
a different problem—the absence of entities known as magnetic
monopoles. Alan Guth’s own
account can be read in his book The
Inflationary Universe: The Quest for a New Theory of Cosmic
Origins (New York: Perseus Publishing, 1998).
(4)
The word
scalar means that the field can
be described simply by specifying a single number
(the strength of the field) at each point in space. By contrast, an electric field
has both a magnitude and a direction at each point;
it is a so-called
vector field. Gravitation
is more complicated still—a
tensor field—requiring
even more numbers at each point to fully describe it.
(5)
Don’t confuse the mechanical
force exerted by the pressure, which is
huge and outward (though contained by Earth), with the gravitational force
that this pressure generates, which is tiny and inward.
(6)
Pressure and energy are normally measured in different units.
To discuss the correspondence between these quantities
you must divide the pressure by
c2,
which
then gives it the same units as energy density. This large
divisor explains why energy gravitates so much more strongly than pressure.
(7)
Mechanically, the scalar field sucks—fiercely;
gravitationally it repels—gently. You might be wondering why, if
this scalar field sucks so much, it doesn’t pull itself into a smaller and
smaller region. That is because
it is spread uniformly through space, so there is no
privileged place for it to converge: it is being sucked every
way at once, and there is no net force to
pull it to any particular place.
(8)
There is, however, a further issue about
the creation of matter, related
to the question of antimatter. I shall defer
this complication until the next chapter.
(9)
Good popular accounts have been written by some of the originators.
In addition to Guth’s book, see, for example, Andrei Linde, Inflation and Quantum Cosmology (San Diego,
CA: Academic Press, 1990).
(10)
The Born-Einstein Letters, translated
by Irene Born (London: Macmillan, 1971), p. 91.
(11)
Particle creation by the expansion
of the universe is a purely gravitational (and normally very weak)
process. It should not be confused with particle production
from the decay of the inflaton field, or from heat energy
(such as occurred at the end of inflation).
(12)
“Ex nihilo, nihil fit.” De
rerum natura in Lucretius, On the Nature of the Universe,
translated by R. E. Latham (New York: Penguin, 1951).
(13)
In Chapter 10, I shall consider the extremely
speculative idea of backward-in-time causation, where
the big bang could be said to have been
caused by later events retroactively.
(14)
City of God, Book xi.6, in Basic Writings of St. Augustine, edited by W. T. Oates
(New York: Random House, 1948).
(15)
It is sometimes conjectured that in the cyclic model the state of the
universe is somehow reset at the bounce (technically, the
entropy is reduced). However, this step is rather contrived. It either has to be imposed
by
hand or tied to a more complicated—and speculative—model of the sort I
explain in Chapter 10.
(16)
For the mathematically inclined, the Planck length
is given by (Gh/2 π c3)
1/2.
(17)
You may wonder why quantum effects of electromagnetism set in at
atomic dimensions, whereas quantum effects of gravitation are predicted to
be important only on much smaller scales of size. The reason stems in part
from the huge disparity in strength between the two forces, a topic I shall
discuss in the next chapter.
(18)
This is known technically as the “no-boundary” proposal.
(19)
Hawking’s own account can be found in his book A Brief History of Time (New York: Bantam,
1988).
(20)
John Leslie, Universes (New York: Routledge, 1989), p.
95.
(21)
This is a curious inversion of the usual
situation in quantum mechanics. In the inflating universe, the
most conspicuous consequences of quantum mechanics are
on the
largest
scale of size.
(22)
In this respect, eternal inflation is
reminiscent of the old steady-state
theory of cosmology, championed by Hoyle, in which
the universe has no beginning or end, but new matter
is continually created as the universe
expands so as to maintain an unchanging average
density. Where eternal inflation differs is that entire
universes are created rather than particles of
matter.
(23)
Andre Linde, “Inflation and Quantum Cosmology,” in
300 Years of Gravitation, edited
by S. W. Hawking & W. Israel (New York: Cambridge University Press,
1987), p. 618.
(24)
Leonard Susskind, The Cosmic
Landscape: String Theory and the Illusion of Intelligent
Design (New York: Little, Brown, 2005), chapter 11.
(25)
This is something of a simplification. When
using the theory of relativity, we have to remember
that distances, like times, are not absolute but
relative, so we must always specify the circumstances of the
observer when discussing a distance. Paradoxically, if the observer is located inside
one of
the bubbles (as we are within our pocket universe), it is possible for the size
of the bubble to be
infinite
relative to that observer, even though, viewed
from outside the bubble, it is finite.
(26)
David Hume, Dialogues
Concerning Natural Religion, edited by Martin
Bell (New York: Penguin, 1990), part V, p. 77.
الفصل الرابع: مِمَّ يتألف الكون؟ وكيف تترابط أجزاؤه؟
(1)
Even uranium plays a role in life on Earth. Its slow radioactive decay
over billions of years keeps the interior of our planet
hot, driving the convection currents that move the
continental crust around, an essential process
for recycling carbon and other substances used to maintain our ecosystem.
(2)
Positrons are today familiar from their role in medical imaging in the
form of positron emission tomography (PET) scans.
(3)
These decay schemes also involve neutrinos.
(4)
When heavy particles decay into lighter ones, the excess mass-energy
appears in the form of kinetic energy: the decay products are created moving
at high speed.
(5)
Why stop there? Perhaps quarks (and maybe leptons too) are made out
of yet smaller particles, which are in turn made of even smaller particles,
and so on. Such ideas have been tried. But most physicists think that quarks
and leptons are the bottom level, in terms of composite particle
combinations. They may not be the last word, however, as I shall discuss at the end
of
this chapter.
(6)
The masses of the neutrinos are still being worked out. They all seem
close to zero.
(7)
The stability of neutrinos is more complicated. They don’t decay as
such: instead, they keep rotating their identities between different neutrino flavors.
(8)
The word
recoil is a bit misleading here, because
if the charges were of
opposite sign, the deflection would be inward rather than
outward. As a result of Heisenberg’s uncertainty
principle, the momentum transfer can be negative in
quantum processes, causing an inward jerk rather
than an outward deflection. However, the general
picture in terms of virtual photon exchange is the same.
(9)
Mathematically speaking, one integrates
over a weighted set of possibilities.
(10)
This procedure is known as
perturbation theory.
(11)
This statement refers to the photon’s rest mass
(see Box 1).
الفصل الخامس: إغراء التوحيد الكامل
(1)
How might a process that takes on
average much longer than the age
of the universe show up in an experiment? The answer
lies with the statistical nature of quantum mechanics. There
is a certain probability that, from among a huge number
of protons (many tons of material), one or two protons
will decay in, say, a month. The experimenters looked
for such occasional isolated decay events, but saw nothing.
(2)
It is important to understand that the
particles emanating from high-energy collisions are not
just the constituents of the impacting bodies: many
of them are created ab initio from the energy of impact. For
example, physicists routinely create electron-positron pairs,
or proton-antiproton pairs.
(3)
The link between the spins of particles and the collective properties
of assemblages of them as governed by the Pauli exclusion principle is not
obvious, and has to do with certain abstract symmetries involved
in the quantum concept of spin.
(4)
This law has the same general form as
gravitation, as shown in Figure
1-1.
(5)
The technical term given to this difficulty is
non-renormalizability.
(6)
It does have something to say about the ultrahot, very early universe,
though, and it is not impossible that some stringy relic may be found by
cosmologists. But so far there is no sign of any.
(7)
The problem of multiplicity is greatly exacerbated by the existence in
the theory of so-called fluxes, analogous to lines of electric or magnetic
force, which can thread through the compactified spaces in
a colossal number of different ways.
(8)
Amazingly, the idea of “an extensible model of an electron” as a membrane
was introduced into theoretical physics as long ago as the 1960s,
by Paul Dirac. In the 1980s the class of extended objects was generalized
from strings and membranes to any number of higher dimensions that is less
than the dimensionality of the space in which they moved. This wider
class became known as p-branes. The
early history of branes is reviewed by Michael Duff in
“Benchmarks on the Brane” (hep-th/0407175v3; February 23, 2005).
(9)
Polchinski called these membranes D-branes, as
distinct from p-branes, and like p-branes they can be generalized
to three, four, and so on, dimensions.
(10)
Michio Kaku, “Unifying the Universe,” New Scientist, April 16, 2005.
الفصل السادس: قوى الكون المظلمة
(1)
Light elements is the
term used to mean the lowest-mass elements.
They include deuterium—which, confusingly, is also known as “heavy hydrogen.”
(2)
The word
massive here means “high mass”: it does
not mean large in physical size. WIMPs would be pointlike particles
but individually weighing more than the heaviest atoms.
(3)
An excellent account of dark matter in its different forms is given by
Joel Primack and Nancy Abrams, The View from the Center of
the Universe (New York: Riverhead,
2006).
(4)
Stephen Baxter, Time (New York: HarperCollins,
1999).
(5)
P.C.W. Davies, “Cosmological Event Horizons, Entropy
and Quantum Particles,” Annales de l’Institut
Henri Poincaré, vol. 49, no. 3 (1988), p. 297.
(6)
Robert R. Caldwell, Marc Kamionkowski, and Nevin N.
Weinberg, “Phantom Energy: Dark Energy With
w < −1
Causes a
Cosmic Doomsday,” Physical Review
Letters, vol. 91 (2003), 071301–1.
(7)
Freeman Dyson, “Time Without End: Physics and Biology
in an Open Universe,” Reviews of Modern
Physics, vol. 51, no. 3 (1979), p.
447.
(8)
It is possible that a supercivilization could
engineer a new “baby” universe as an escape route: see Chapter
8.
الفصل السابع: كون ملائم للحياة
(1)
Nicolaus Copernicus, De
revolutionibus orbium coelestium (“On the Revolutions of
the Heavenly Spheres”) (Amherst: Prometheus Books, 1995), p. 8.
Originally published in Nuremberg, 1543.
(2)
The anthropic principle has a large
literature. A comprehensive treatment with many references
is given by John Barrow and Frank Tipler, The Anthropic Cosmological Principle (New
York: Oxford University Press, 1986).
(3)
Brandon Carter, “Large Number Coincidences and the
Anthropic Principle in Cosmology,” in
Confrontation of Cosmological Theories with Observational
Data, IAU Symposium 63, edited by M. Longair (Dordrecht,
Netherlands: Reidel, 1974), p. 291.
(4)
See, for example, Paul Davies, The Fifth Miracle (New York: Simon & Schuster,
1998). Actually, it is rather more favorable for the transfer to occur
the other way—that is, for life to start on Mars and
come to Earth inside ejected rocks. Either way, one
would still be dealing with a single genesis event.
(5)
Some science fiction writers, and a few scientists, have speculated
about life based on very different chemical or physical processes, and it’s
true that scientists have no clear idea of what might
or might not be possible. Even harder to assess are
the possibilities for life based on radically different laws
of physics. I shall adopt the conservative position
that, in the absence of evidence to the contrary, life is
restricted to something close to what we know.
(6)
I shall discuss only a handful of examples. Readers
wanting a more complete treatment should refer to Barrow and Tipler, The Anthropic Cosmological
Principle.
(7)
As a result, neutrinos are emitted. The neutrino
flux from the sun has
been measured with very sensitive equipment. Neutrinos have extremely
low (rest) mass. If that were not the case, protons would lack
the necessary mass-energy to turn into neutrons inside stars, thus
preventing the sun from shining steadily and sustaining life.
(8)
For full details, see Richard Dawkins, The Ancestor’s Tale (New York: Houghton
Mifflin, 2005).
(9)
Lithium and beryllium get manufactured as by-products
of other reactions.
(10)
H. Oberhummer, A. Csótó, and H. Schlattl, “Stellar
Production Rates of Carbon and Its Abundance in the Universe,” Science, vol. 289 (2000), p. 88.
(11)
The word
ylem is an obsolete Middle English
word meaning the primordial substance
from which matter formed. Gamow used the term to
mean a mixture of protons and neutrons.
(12)
Tritium is an isotope of hydrogen with nuclei containing
two neutrons and one proton, so it is even heavier than deuterium.
(13)
By this, Gamow means a nucleus with either
two protons and three neutrons or three protons and two
neutrons. As I have mentioned, neither configuration is stable.
(14)
George Gamow, My
World Line: An Informal Biography (New York:
Viking, 1970), p. 127. Reprinted courtesy of the Gamow Family
Estate.
(15)
More familiar is the decay of a neutron
into a proton, with an attendant release of an antineutrino. The
reverse process I am discussing here,
with a proton turning into a neutron, can happen
in an imploding star because the intense gravitational
field that is created supplies the necessary energy.
(16)
There are other, less efficient, ways for stars to divest themselves of
carbon, so it is not clear how critical the neutrino interaction strength is to
the fine-tuning argument for this element.
(17)
Neutron decay is a statistical process subject to
quantum fluctuations. Half-life is defined as the average time it
takes for exactly half of a population of neutrons to decay.
(18)
Max Tegmark, Anthony Aguirre, Martin Rees, and Frank
Wilcek, “Dimensionless Constants, Cosmology and Other Dark Matters,”
Physical Review I, vol. 77
(2206), p. 23505.
(19)
That is, why is the model so wrong—I don’t
think we made a mistake in our sums!
(20)
Inflation requires dark energy to be non-zero for a very brief time just
after the big bang, but physicists still assumed that in the post-inflation
phase the dark energy would drop to precisely zero.
(21)
Leonard Susskind, The Cosmic
Landscape: String Theory and the Illusion of Intelligent
Design (New York: Little, Brown, 2005), p.
78.
(22)
As far as I know, Sidney Coleman of Harvard University, who helped
to pioneer the subject of symmetry-breaking in the early universe, was the
first person to use the phrase “the big fix” to describe the dramatic suppression
of dark energy.
(23)
Steven Weinberg, “Anthropic Bound on the Cosmological
Constant,”
Physical Review Letters, vol. 59 (1987), p.
2607.
(24)
The formation of galaxies depends delicately on the magnitudes of
both the dark energy and the primordial density fluctuations. In my
discussion I am assuming that the latter is held fixed while the former is allowed
to vary. If both quantities are allowed to vary together, the
analysis is more complicated. See, for example, Tegmark et al.,
“Dimensionless Constants, Cosmology
and Other Dark Matters.”
الفصل الثامن: هل تحل نظرية الكون المتعدد لغز جولديلوكس؟
(1)
That solitary individual was I. L. Rozenthal, who succeeded
in publishing a credible review paper (Soviet Physics Uspekhi,
vol. 23 [1980], p. 296). This was no mean feat in a regime that strongly discouraged
any discussion
that departed from the strict Marxist philosophy of dialectical materialism.
(2)
The various constants I have mentioned assume numerical values
that depend on the system of units used to express them. For example,
the speed of light is either (roughly) 300,000 km per second or 186,000 miles
per second. Constants may be combined to form dimensionless ratios, which
are pure numbers, independent of units. For example, the square of the
charge on the electron divided by Planck’s constant and the speed of light is
a pure number with a value close to 0.001617. When considering whether
the laws of physics contain free parameters that might vary from place to
place, it makes sense only to discuss variations of such dimensionless ratios.
(3)
Neutrinos fall outside this scheme. Experiments show that they do
have a tiny mass, but its explanation lies beyond the Standard Model.
(4)
The Higgs particle is a boson because it has spin 0.
(5)
James Watson, The Double
Helix (New York: Touchstone,
2001).
(6)
This example can be likened to the rule of the road. In some countries
people drive on the right; in others they drive on the left. Which
one is chosen is just a matter of historical accident. It doesn’t make any difference
so
long as everybody uses the same rule.
(7)
If you did the experiment
very precisely, the selection of the direction
could be traced back to chaotic molecular jiggles.
(8)
This example comes from Sidney Coleman.
(9)
By “low-temperature” and “low-energy” I mean low compared with
the temperature and energy of symmetry-breaking. As we shall see, that
may involve GUT or even Planck values. Given these
elevated scales, what physicists normally refer to as “high-energy physics”
is still very low-energy indeed. So the low-energy world
includes the world of subatomic accelerators
such as the LHC, as well as everyday experience.
(10)
The alert reader may notice that this is about the time when inflation
is supposed to have happened—which is no coincidence. It was
by considering the application of GUTs to the very early universe that Alan Guth got
the idea of the inflationary universe scenario in the first place, and
in fact a plausible candidate for the inflaton field is one of the GUT Higgs fields.
(11)
Actually, I’m making this up. Nobody knows because the theory is
too complicated. But there are lots of options.
(12)
Leonard Susskind, The Cosmic
Landscape: String Theory and the Illusion of Intelligent
Design (New York: Little, Brown, 2005), p.
21.
(13)
The existence of a landscape is based on a consideration of the five
“corners” of M theory representing the five original string theories, which
can be studied using an approximation method called perturbation theory.
Some theorists believe that the landscape is an artifact of this approximation
and predict that if the full underlying M theory could be properly
formulated and solved exactly, it would yield a single, unique
description—just one world. I shall
have more to say about the alternative view in Chapter 9.
(14)
The idea that eternal inflation might provide a natural mechanism to
generate large cosmic domains (pocket universes) with very different
low-energy physics, and with obvious anthropic consequences, dates from the
early 1980s. See A. D. Linde, “The New
Inflationary Universe Scenario,” in The Very
Early Universe, edited by G. W. Gibbons, S. W. Hawking,
and S. Siklos (New York: Cambridge University Press, 1983), p. 205. For
an up-to-date account of this “landscape exploration” process, see
Chapter 11 of Susskind’s book The Cosmic
Landscape.
(15)
The theories I have described here are by
no means the only ideas for a multiverse. A list of various
multiverse theories has been compiled by Nick Bostrom in
Anthropic Bias: Observations
and Selection Effects (New York: Routledge, 2002); see
also John Leslie, Universes (New
York: Routledge, 1989).
(16)
An excellent in-depth discussion and critique of these issues can be
found in Neil Manson (ed.), God and
Design (New York: Routledge,
2003).
(17)
The Edge annual question, 2006. See
www.edge.org.
(18)
This type of reasoning is fully convincing only
if one can assign precise statistical weights to different
universes, but we don’t know how to do
that yet. Another assumption is that there is no obvious minimum value of
the dark energy below which life would be impossible, unless
one considers negative values. A substantial amount of negative
dark energy would be life-threatening for a different
reason: it would add to the gravitational attraction
of the universe and cause rapid collapse to a big crunch.
(19)
More details of this work can be found in John
Barrow, The Constants of Nature (New
York: Random House, 2003).
(20)
Max Tegmark, “Parallel Universes,” Scientific American (May 2003), p. 31.
(21)
There is also a hidden assumption
that the systems being considered
have a finite, albeit very large, number of possible states. This
is the case for discrete variables, as arise from the
application of quantum mechanics, but
there is no logical reason why some physical variables
should not be continuous. If that were so, there would
be infinitely many “shades of gray,” and
the question of truly identical copies would be more subtle.
(22)
Nick Bostrom, “The Simulation Argument: Why the
Probability That You Are Living in a Matrix Is Quite High,” Times Higher Education Supplement, May 16,
2003. For a more scholarly analysis see Bostrom’s
“Are You Living in a Computer Simulation?”
Philosophical Quarterly, vol. 53,
no. 211 (2003), p. 243.
(23)
The assumption that all physical processes
can in principle be simulated by a universal computer rests
on an unproven but widely believed conjecture
called the Church-Turing thesis named after Alan
Turing and the American logician Alonzo Church).
See, for example, David Deutsch, The Fabric of Reality (New York: Viking,
1997), p. 134.
(24)
Cited in J. R. Newman, The World of
Mathematics (New York: Simon & Schuster,
1956).
(25)
A collection of essays on this topic can be found in
Daniel Dennett and Douglas Hofstadter, The Mind’s I (Brighton, UK: Harvester,
1981). See also David Chalmers, “The Matrix as Metaphysics,” in
Philosophers Explore the Matrix,
edited by Christopher Grau (Oxford, UK: Oxford University Press, 2005).
(26)
Alan Turing, “Computing Machinery and Intelligence,”
Mind, vol. 59 (1950), p. 433.
(27)
A classic being Isaac Asimov’s
I, Robot (New
York: Genome Press, 1950).
(28)
Roger Penrose, The Emperor’s
New Mind (New York: Oxford University Press,
1989).
(29)
Gordon Moore, cofounder of Intel, predicted
decades ago that computing power would double
about every one or two years. So far he has been
proved correct.
(30)
See, for example, Frank Tipler, The Physics of Immortality (New York:
Doubleday, 1994).
(31)
Interested readers can learn more by visiting Bostrom’s
Web site at www.simulation-argument.com.
(32)
Martin Rees, Our Final
Century (New York: Basic Books,
2004).
(33)
John Barrow, “Glitch,” New Scientist (June 7, 2003), p.
44. Reprinted courtesy of New Scientist.
(34)
Ibid.
(35)
The simulating system need not be an electronic
computer. If the assumption of computational universality
(see the next paragraph in the main
text), on which this entire discussion is based, is correct, then
the simulation could be performed using almost any objects, such as beer cans and
string, or even something as simple as a classical three-body chaotic system,
which is infinitely complex in its behavior. Also, “our” time and time
in the simulating system need not be the same. The simulation could be much
faster or much slower in its own time than our subjective experience of time
within the simulation.
(36)
Barrow, “Glitch.”
(37)
Paul Davies, “A Brief History of the Multiverse,”
New York Times, April 12, 2003.
(38)
Martin Rees, “In the Matrix,” Edge (www.edge.org), September 15,
2003.
الفصل التاسع: التصميم الذكي، والتصميم غير الذكي
(1)
Augustine, City of
God, XI, 4, 2,
in Basic Writings of St. Augustine, edited
by W. T. Oates (New York: Random House, 1948).
(2)
Aquinas is famous for his arguments for the existence of God, based
on “five ways” of reasoning. The five ways are contained in his
Summa Theologica,
edited by Timothy McDermott (Westminster, MD: Christian
Classics, 2000).
(3)
William Paley, Natural
Theology (1802), in Paley’s
Natural Theology with Illustrative Notes, edited by H.
Brougham and C. Bell (London, 1836), chapters 1 and 2.
(4)
Richard Dawkins, The Blind
Watchmaker (New York: Norton,
1987).
(5)
Henry Drummond, The
Lowell Lectures on the Ascent of Man (New York:
J. Pott & Co., 1894), pp. 427-28.
(6)
The term seems to have been coined by C. A. Coulson in
Science and
Christian Belief (London: Fontana, 1958), although
Drummond had already captured the basic idea in
The Ascent of Man.
(7)
A useful video demonstrating the details, featuring Dan-Erik Nilsson,
has been produced by WGBH Educational Foundation and Clear Blue Sky
Productions and can be found at
www.pbs.org/wgbh/evolution/library/01/1/1_011_01.htm.
(8)
Intelligent Design proponents are
(for political reasons) frustratingly
vague about the non-Darwinian mechanism whereby physical systems such
as the bacterial flagellum acquire their designlike structure. It does not have
to be an on-the-spot miracle, like a rabbit pulled out of a hat, although that is
apparently what their supporters prefer. There could be a designlike law of
nature that operates over evolutionary timescales. To establish the meaningfulness
of such a law, it is first necessary to provide a rigorous mathematical definition
of design. A heroic attempt at just that has been made by William Dembski: see his
book
No Free Lunch (Lanham, MD: Rowman & Littlefield,
2001).
(9)
A robust case for self-organization in biology is
made by Stuart Kauffman in his book At Home in the Universe
(New York: Oxford University Press, 1995).
(10)
Lee Smolin proposed a theory in which black
holes create “baby universes” that inherit laws
from their “parent universe,” with some random variation. In this
theory there is a sort of inheritance and variation, but no
selection. Details can be found in his book
Life of the Cosmos
(New York: Oxford University Press, 1997).
(11)
Christoph Schönborn, “Finding Design in
Nature,” New York Times, July
7, 2005.
(12)
See, for example, Nelson Pike, God and Timelessness (New York: Random House, 1970).
(13)
E. W. Harrison, “The Natural Selection of Universes
Containing Intelligent Life,” Quarterly Journal
of the Royal Astronomical Society, vol. 36, no. 3 (1995),
p. 193.
(14)
Remember, the landscape is not
a physical place or region, but a space
of possibilities—a parameter space. The superbeing
or supercivilization
could create a universe physically close by, but
a long way away in parameter space. If the universe
containing this being or civilization were already optimal
for life, we can imagine that it/they would choose to
create baby universes at a similar location in the landscape, to
make their product universes fit for life.
(15)
Olaf Stapledon, The Star
Maker (London: Methuen, 1937).
(16)
Fred Hoyle, The Intelligent
Universe (London: Michael Joseph, 1983), p. 249.
(17)
Andrei Linde, “Stochastic Approach to Tunneling and
Baby Universe Formation,” Nuclear
Physics, vol. B372 (1992), p. 421.
(18)
Heinz Pagels, The
Dreams of Reason (New York: Bantam, 1989), p. 156.
(19)
James Gardner, Biocosm (Maui, HI: Inner Ocean Publishing, 2003), p.
178.
(20)
A clear discussion is given by Richard Swinburne, The Coherence of Theism (New York:
Clarendon Press, 1977), part III.
(21)
That is, can a being that exists necessarily,
is good necessarily, is
omnipotent necessarily, and
so on, also not create necessarily? Can a necessary
being choose to not create?
(22)
Isaac Newton, who wrote more about theology than physics, used
this argument. He reasoned that space and time at least are necessary
because they emanate directly from God’s necessary being. This may have
been a factor in Newton’s view that space and time are absolute, universal,
and unchangeable. Of course, we now know that this is wrong.
(23)
A good place to start is Keith Ward,
God: A Guide for the Perplexed
(Oxford: Oneworld Publications, 2005).
(24)
The unique, no-free-parameters theory is indifferent about whether
there is only one representation of the universe or many. If there are many,
they will be in identical quantum states—the postulated unique vacuum
state of the theory. Because of the inherent uncertainty of quantum
mechanics, this does not require the universes to be precise
clones. So even the supposedly “unique” universe theory is consistent
with a limited form of multiverse.
(25)
The original idea for this analogy came
from Carl Sagan, who described it in his novel
Contact
(New York: Simon & Schuster, 1985). It has
been used in its present context by Rodney Holder in his
book
God, the Multiverse, and Everything
(Burlington, VT: Ashgate, 2004).
(26)
There is also a technical explanation, in terms of
the foundations of mathematics and logic, of why
a unique final theory is impossible. This has
to do with what is known as Gödel’s incompleteness theorem. For
a recent discussion of this theorem, see, for example, Gregory Chaitin,
Meta Math!
The Quest for Omega (New York: Pantheon Books, 2005). It
was partly in consideration of Gödel’s theorem that Stephen
Hawking, in a much publicized U-turn, recently repudiated the
existence of a unique theory of everything.
(27)
Stephen Hawking, A Brief
History of Time (New York: Bantam, 1988), p. 174.
(28)
Leibniz, who was a theist, considered this
problem and famously concluded that ours is the
best
of all possible worlds (for why would an all-good, perfect
God create something less than best?). Leibniz’s definition of
best refers not to maximum happiness for
humans, but more abstractly to mathematical
optimization: simplicity consistent with richness and diversity.
(29)
Anything that is logically self-consistent,
I mean. A round square, for example, could not exist anywhere.
(30)
Tegmark was certainly not the first to suggest
that all possible universes really exist. The idea was
embraced, for example, by the Princeton philosopher David Lewis.
(31)
Max Tegmark, “Parallel Universes,” Scientific American (May 2003), p. 31.
(32)
Ibid.
(33)
Benoît B. Mandelbrot, The
Fractal Geometry of Nature (New York: Freeman,
1982).
(34)
Tegmark calls it the “ultimate ensemble theory.”
(35)
See, for example, Chaitin, Meta Math!, p. 97.
(36)
The set of all sets that do not contain
themselves is not in fact a set, according
to the logical niceties of set theory.
(37)
Unless, that is, it can be demonstrated that there is a necessary being
that is necessarily unique.
(38)
For example, one axiom states that any
two points in space can be connected by a straight line.
(39)
This is perhaps a simplification. One
may have evidential reasons for believing in a particular
starting point. For example, support for a multiverse might
come from evidence of variations of the “constants” of
nature. Support for God might come from religious
experience or moral arguments.
(40)
Sometimes as “the only one,” but I have already
pointed out the dubiousness of that claim.
(41)
Martin Gardner, Are Universes
Thicker Than Blackberries? (New York: Norton, 2003), p.
3.
(42)
Richard Swinburne, The
Existence of God (New York: Oxford University Press,
1979), chapter 5.
(43)
Richard Dawkins, “The Improbability of God,”
Free Inquiry Magazine, vol. 18,
no. 3 (1998), p. 6.
(44)
Not the Tegmark multiverse:
that is
simple (well, maybe …).
الفصل العاشر: كيف أتى الوجود؟
(1)
Quoted by David Deutsch in The Fabric of
Reality (New York: Viking, 1997), pp. 177-78.
(2)
Brandon Carter, “Large Number Coincidences and the
Anthropic Principle in Cosmology,” in Confrontation of Cosmological Theories with Observational
Data, IAU Symposia No. 63, edited by M. S. Longair
(Dortrecht, Netherlands: Reidel, 1974), p. 291; “The Anthropic Principle
and Its Implications for Biological Evolution,” Philosophical Transactions of the Royal Society of London
A, vol. 310 1983, p. 347.
(3)
John Barrow and Frank Tipler, The Anthropic Cosmological Principle (New York: Oxford
University Press, 1986).
(4)
Freeman Dyson, Disturbing the
Universe (New York: Harper & Row, 1979), p. 250.
(5)
“Evolution’s Driving Force,” discussion between Robyn
Williams and Simon Conway Morris, ABC Radio National, December 3, 2005:
www.abc.net.au/rn/science/ss/stories/s1517968.htm.
(6)
Christian de Duve, Vital
Dust: Life as a Cosmic Imperative (New York: Basic Books,
1995), p. 300.
(7)
Stuart Kauffman, At Home in
the Universe (Oxford, UK: Oxford University Press,
1995).
(8)
Deutsch, The Fabric of
Reality, p. 181.
(9)
Ibid., p. 134. This statement is closely related to the Church-Turing
thesis, the claim that defines the basis for the concept of
a universal, or general-purpose, computer. Deutsch
proposes elevating this thesis to the status
of a fundamental principle of the universe.
(10)
Another example of an inconspicuous yet fundamental property of
quantum systems is entanglement, whereby two or more particles remain subtly linked
even though widely separated.
(11)
There is increasing evidence that some “junk” DNA, although not
part of the genetic coding system, may nevertheless play a role in the operation of
the cell.
(12)
The crucial and basic distinction between the “easy” and “hard”
problems of consciousness was first stressed by David Chalmers in a famous
essay, “Facing Up to the Problem of Consciousness,”
Journal of Consciousness Studies,
vol. 2 (1995), p. 200. Most, but
not all, philosophers have since accepted this distinction as valid.
(13)
Daniel Dennett, Consciousness
Explained (Boston: Little, Brown, 1991).
(14)
See, for example, David Chalmers, The Conscious Mind: The Search for a Fundamental
Theory (New York: Oxford University Press, 1997).
(15)
Just as Schrödinger’s cat is seemingly
in a state of “suspended animation” in the absence of an
observation, so the quantum universe as a whole remains
suspended in a superposition of vastly many “histories.” Readers
who want to know more about the disappearance of time in
quantum cosmology can find a detailed discussion
in The End of
Time by Julian Barbour (New York: Oxford University
Press, 2001).
(16)
Andrei Linde, “Inflation, Quantum Cosmology and the
Anthropic Principle,” in Science and Ultimate
Reality, edited by John Barrow, Paul Davies, and Charles
Harper (New York: Cambridge University Press, 2004), p. 426.
(17)
Quoted by Tim Folger, “Does the Universe Exist If We’re Not
Looking?” Discover Magazine, vol. 23,
no. 6 (June 2002), p. 43.
(18)
Some suggestions for how this may be achieved have been made by
Charles Lineweaver and myself: see P.C.W. Davies and Charles H. Lineweaver, “Finding
a
Second Sample of Life on Earth,” Astrobiology, vol. 5, no. 2 (April 2005), p. 154.
(19)
Physicists often refer to this as a Boltzmann
gas, after Ludwig Boltzmann, who studied how
gases approach thermodynamic equilibrium.
(20)
I’m referring here to the macroscopic state,
defined by averaging over
many molecules, not to the micro-states in which the
motions of individual molecules are specified.
(21)
This point is well recognized by
scientists, and attempts have been
made to provide a more precise definition of the elusive
quality of “organized complexity” that seems to characterize
life. One promising definition, introduced by Charles Bennett
of IBM, is in terms of the computational labor needed to
describe the system. Bennett calls this the “depth” of the
system. A related but more physics-based definition of depth was proposed by
Seth Lloyd and Heinz Pagels. A popular account of depth can be found in
Murray Gell-Mann, The
Quark and the Jaguar (New York: Freeman, 1994), pp.
100–105.
(22)
See, for example, Stuart Kauffman, Investigations (New York: Oxford University
Press, 2000); or Eric Chaisson, Epic of
Evolution: Seven Ages of the Cosmos (New York: Columbia
University Press, 2005).
(23)
Even professional biologists are not immune to backsliding
on this issue. In a recent article taking them to task, Charles
Lineweaver highlights what he calls the “planet of the apes fallacy.”
See Astrobiology, vol. 5, no. 5
(2005), p. 658.
(24)
See, for example, Daniel Dennett, Darwin’s Dangerous Idea (New York: Simon
& Schuster, 1996).
(25)
An interesting case in point is the Gaia theory of life on
Earth, according to which our planet’s ecology, geology, and climate
form an interconnected dynamic feedback system in which Earth and its
biosphere somehow cooperate to perpetuate life, for example, by
responding to external changes such as solar variability with
compensating climatic changes. In this popular form, the Gaia theory
looks decidedly teleological—Earth’s biosphere responds to internal and
external threats to secure its future—and it has been roundly criticized
as such.
(26)
Marx and Engels, Works, vol. 40 (Moscow, 1929), p. 550.
(27)
Murray Gell-Mann, “Nature Conformable to Herself,”
Complexity, vol. 1, no. 4 (1995),
p. 1126.
(28)
Gell-Mann, The Quark and the
Jaguar, p. 212. As an ironical aside, let me point out
that if the extended version of the multiverse theory is considered (the
one in which all possible laws are instantiated in a universe
somewhere), then included within this multiverse there must be universes with teleological laws.
One cannot banish teleological laws by fiat and at the same time argue
that all possible laws are permitted
in a universe somewhere. So if one embraces the extended multiverse
theory, the question then arises as to whether our universe is one of
those that actually has teleological
laws, or whether it hasn’t but is cunningly cooked up to mimic the
genuine article. If universes with teleological laws exist, ours would
be an excellent candidate. The universe certainly looks as if it
possesses teleological features. Well, perhaps it is teleological!
(29)
Heinz Pagels, Perfect
Symmetry (New York: Simon & Schuster, 1985), p. 347.
(30)
Časlav Bruckner and Anton Zeilinger, “Information and
Fundamental Elements of the Structure of Quantum Theory,” in Time, Quantum, and Information, edited by
Lutz Castell and Otfried Ischebeck (Berlin: Springer-Verlag, 2003), p.
323.
(31)
John Wheeler, “On Recognizing ‘Law Without Law,’”
American journal of Physics, vol.
51 (1983), p. 398.
(32)
This is not just the emergence of
low-energy effective laws via symmetry-breaking,
as discussed in Chapter 8. Wheeler proposes
that all laws
emerge from chaos after the origin of the universe.
(33)
John Wheeler, “Information, Physics, Quantum: The
Search for Links,” in Proceedings of the 3rd
International Symposium on the Foundations of Quantum
Mechanics, Tokyo, 1989, p. 354.
(34)
John Wheeler, “Frontiers of Time,” in Problems in the Foundations of Physics,
edited by G. Toraldo di Francia (Amsterdam: North-Holland, 1979), p.
395.
(35)
This is a general statement,
but in practice the bits are determined
by quantum mechanics, in the form of discrete yes/no
answers, such as whether an electron’s spin is up or down.
(36)
John Wheeler, At Home in the
Universe (New York: AIP Press, 1994), pp.
295–311. An attempt to build all of physics out of information has been
made by B. Roy Frieden in Physics from Fisher Information (New York:
Cambridge University Press, 1998) For up-to-date comment on “it from
bit,” see Science and Ultimate Reality, edited
by John Barrow, Paul Davies, and Charles Harper (New York: Cambridge
University Press, 2004), part IV. See also Wheeler, “Information,
Physics, Quantum.”
(37)
Two relevant papers by Rolf Landauer are “Wanted: A
Physically Possible Theory of Physics,” IEEE
Spectrum, vol. 4, no. 9 (1967), p. 105; and “Computation
and Physics: Wheeler’s Meaning Circuit?” Foundations of Physics, vol. 16, no. 6 (1986), p.
551.
(38)
Gregory Chaitin, Meta Math!
The Quest for Omega (New York: Pantheon Books, 2005), p.
115.
(39)
Seth Lloyd’s calculation is
described in his paper “Computational Capacity of
the Universe,” Physical Review
Letters, vol. 88 (2002), p. 237, 901. See also his book
The Computational
Universe (New York: Random House,
2006).
(40)
There may, however, be situations involving complex systems in
which the limit of 10120 does matter. See P.C.W. Davies, “Emergent Biological Principles and the Computational
Resources
of the Universe,” Complexity, vol.
10, no. 2 (2004), p. 1.
(41)
Paul Benioff, “Towards a Coherent Theory of Physics
and Mathematics,” Foundations of
Physics, vol. 32 (2002), p. 989.
(42)
Benioff’s proposed consistency criterion is that the theory
should maximally describe its own validity and sufficient strength.
(43)
Benioff, “Towards a Coherent Theory,” p.
1005.
(44)
I have given a popular account in my book About Time (New York: Simon &
Schuster, 1996).
(45)
F. Hoyle and J. V. Narlikar, Direct Inter-Particle Theories in Physics and Cosmology
(San Francisco: Freeman, 1974).
(46)
M. Gell-Mann and J. B. Hartle, “Time Symmetry and
Asymmetry in Quantum Mechanics and Quantum Cosmology,” in Physical Origins of Time Asymmetry,
edited by J. J. Halliwell, J. Pérez-Mercader, and W. H. Zurek (New York:
Cambridge University Press, 1994), p. 311.
(47)
S. W. Hawking, “The No Boundary Condition and the
Arrow of Time,” in Physical Origins of Time
Asymmetry, edited by J. J. Halliwell, J. Pérez-Mercader,
and W. H. Zurek (New York: Cambridge University Press, 1994), p. 346;
Hawking subsequently retracted the idea.
(48)
Light rays can be bent by material
obstacles, such as the edges of the
slit. Thus photons do not always travel in precisely straight lines.
(49)
Quantum mechanics requires that all particles have a wave aspect.
The two-slit experiment has, for example, been successfully carried out with electrons.
(50)
In a practical laboratory experiment the
photon would take only nanoseconds to pass from the
slits to the blind, and no human experimenter could make
a decision so finely judged as to take place after the
photon had traversed the slits but before it reached
the blind. But this is a minor quibble.
In principle one could make the distance
to the image screen as long as one likes.
(51)
W. C. Wickes, C. O. Alley, and O. Jakubowicz, “A
‘Delayed-Choice’ Quantum Mechanics Experiment,” in Quantum Theory and Measurement, edited by
John A. Wheeler and Wojciech H. Zurek (Princeton, NJ: Princeton
University Press, 1983), p. 457; see also T. Hellmuth,
H. Walther, A. Zajonc, and W. Schleich, “Delayed-Choice Experiments in Quantum
Interference,” in Physical Review A,
vol. 35 (1987), p. 2532.
(52)
There are lots of ingenious refinements
to this scenario and many actual experiments, including
some in which the accomplice can make a record and then
erase it. In all cases, no information can be sent back in time
by this sort of arrangement.
(53)
A rather natural way of considering the
delayed-choice experiment
comes from the so-called transactional interpretation of
quantum mechanics, due to John Cramer of the University
of Washington (see
Reviews of Modern Physics,
vol. 58 [1986], p. 647).
The essential idea is that a quantum
event, such as the scattering of an electron or the decay of
an atom, involves processes that go both forward and
backward in time at the speed of light. If
the transactional interpretation were applied to the universe as a whole, it
might yield a self-consistent description. The challenge would
then be to demonstrate that this description was unique.
(54)
Wheeler, “Information, Physics, Quantum,” p.
354.
(55)
The concept of a self-explanatory loop is reflected
in the ancient mystical symbol of the Ouroboros, represented
as a snake eating its own tail.
(56)
Wheeler’s more precise definition
was “a self-referential deductive
axiomatic system” (see “Information, Physics,
Quantum,” p. 357).
(57)
Barrow and Tipler, The
Anthropic Cosmological Principle; Frank Tipler, The Physics of Immortality (New York:
Doubleday, 1994).
(58)
“The Anthropic Universe,” a documentary
on the Australian Broadcasting Corporation’s Radio National,
The Science Show,
February 18, 2006, produced by Martin Redfern
and Pauline Newman. A transcript may be
found at
www.abc.net.au/rn/science/ss/stories/s1572643.htm.
(59)
John Wheeler, “World as a System Self-Synthesized by
Quantum Networking,” IBM Journal of Research and
Development, vol. 32, no. 1 (1988), p. 4.
(60)
Quoted by Folger, “Does the Universe Exist If We’re Not
Looking?”
(61)
Another way to avoid paradoxes is to
adopt the many-universes interpretation of quantum
mechanics. See Deutsch, The Fabric of
Reality, chapter 12.
(62)
If this skimpy discussion leaves the
reader more confused than before,
I can recommend my little book
How to Build a Time Machine (New
York: Viking, 2002) for more details.
(63)
Physicists will recognize this cumbersome
description as what is technically termed a closed time-like world line.
(64)
J. R. Gott III and L.-X. Li, “Can the Universe Create
Itself?” Physical Review D, vol. 58
(1998), p. 023501.
(65)
P. C. W. Davies, “Closed Time as an Explanation of the
Black Body Background Radiation,” Nature
Physical Science, vol. 240 (1972), p.
3.
(66)
Other scientists have had similar ideas. For
example, Fred Hoyle concluded that “the Universe is seen as
an inextricably linked loop … Everything exists at the courtesy
of everything else.” The Intelligent
Universe (London: Michael Joseph, 1983), p.
248.
(67)
Wheeler arrived at a similar
position. He insisted that the results of
quantum observations must
mean something
before the universe can be
said to be fully actualized. In this “meaning circuit” (depicted in
Figure 10-5,), the physical world gives rise to “observership”
and “meaning,” while observers and meaning loop back
and give rise to the physical world See, for example,
Wheeler, “World as a System.”
(68)
Landauer, “Computation and
Physics.”
(69)
S. W. Hawking and T. Herzog, “Populating the
Landscape: A Top Down Approach,” hep-th/0602091. A popular account is
Amanda Gefter, “Mr. Hawking’s Flexiverse,”
New Scientist (April 22, 2006),
p. 28.
(70)
Memes play the same role in human
culture that genes play in genetics. They
may be, for example, habits, fashions, or belief
systems. Memes replicate, spread within
the community, and compete.
خاتمة: التفسيرات الجوهرية
(1)
Broadcast in 1948 on the
Third Programme of
the BBC. Transcript reprinted in Bertrand Russell, Why I Am
Not a Christian (New York: Touchstone, 1957), p.
155.
(2)
Neil A. Manson, “Introduction,” in God and Design: The Teleological Argument and Modern
Science, edited by Neil Manson (New York: Routledge,
2003), p. 18.
(3)
Yes, according to the philosopher
John Leslie, who has championed
the theory that the universe exists because “it is good”
that it does so—an idea that goes back to Plato. The
challenge is to convince physicists that “ethical requiredness” has causal potency.
