ORIGIN OF THE ORIGIN:
THE BIG BANG, SPECULATION, AND THE END OF SCIENCE
The well-known big bang theory of
our universe tells us that all we can physically observe came into being in
some unknown way about 13.5 billion years ago.
One of the most important pieces of observational evidence undergirding
the theory is the existence of the cosmic background radiation, originally very
hot but now reduced to the form of harmless, soft, cool microwaves just 3
degrees above absolute zero. The cosmic
microwave background (CMB) fills all space and partially penetrates Earth's
atmosphere to be absorbed by you and me.
I would like to focus on the discovery of the CMB as an example of how
ideas originally borne of theoretical speculation succeed in becoming serious
science. Then I will look at the
evolution of the big bang theory over the past 40 years, and share with you
what I believe are serious problems in how modern science is being practiced.
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Genesis of the CMB and its discovery
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| Figure 1: George Gamow in 1956. |
The story begins
in 1946, when the great physicist George Gamow (Figure 1) attempted to explain
the origin, and relative amounts, of different elements and concluded that an
expanding universe would have to be part of the picture. In 1948, Gamow's associate Ralph Alpher
predicted that the early universe should have been filled with hot radiation
that would limit the production of elements heavier than hydrogen (H) and
helium (He). Expansion of the universe
would cool the radiation, and shortly after, Alpher and Robert Herman predicted
that space should be filled today with the CMB radiation at a temperature of
about 5 degrees above absolute zero.
Predictions are one of the fruits of good theoretical physics, but until
the CMB was experimentally observed, the big bang theory remained in limbo.
A fascinating part
of the story is the 19-year delay in searching for the background
radiation. Stephen Weinberg, in his
famous book on the big bang, The First
Three Minutes, gives three reasons for the delay. First,
the primary goal of Gamow et al.'s big bang theory, explaining the origin of the
elements, was better-explained in 1957 by the more convincing theory that
elements heavier than helium could be synthesized in stars, which is what we
believe today. Second, there was a failure of communication: theorists were not
aware of what experimentalists were capable of measuring, and experimentalists
were unaware of the prediction of the background radiation. And third,
the very idea that we could know anything of significance and substance about
something so remote in time pervaded the scientific community—a real failure of
imagination!
The eventual discovery of the cosmic
background radiation was the academic equivalent of a masterful
Tinker-to-Evers-to-Chance triple play.
In 1965, a young theorist from Princeton, James Peebles, came to Johns
Hopkins University and gave a talk on the background radiation. (I was a JHU graduate student at the time and
vaguely remember Peebles' talk.) Peebles
was associated with the great physicist Robert Dicke who was searching for the
background radiation even though he had no recollection of Gamow et al's prediction. Dicke believed the most likely kind of
universe would be an infinitely old and oscillating one—a never-ending (and
never-beginning) cycle of an explosive big bang followed by a destructive big
crunch followed by an explosive big bang, etc., etc., reminiscent of Hindu
religious cosmology. Dicke knew that
background radiation would be associated with such an oscillating universe and
mounted an experimental effort to detect it.
But weeks before Dicke could do his experiment, which surely would have succeeded,
two scientists from Bell Labs, Robert Wilson and Arno Penzias, were
investigating radiation noise from outer space that might interfere with
microwave communication equipment manufactured by "Ma Bell." They discovered an annoying microwave noise,
but had no idea about its true origin or significance. As Weinberg tells it, Penzias contacted
Bernard Burke, a radio astronomer at MIT, about an unrelated matter. Burke just happened to have talked with
another physicist, Ken Turner, who attended Peebles' Johns Hopkins talk. Burke
asked Penzias about their search for extraterrestrial noise sources, and
Penzias said they discovered something but had no idea what the source could
be. Burke suggested they contact the
team at Princeton. Dicke must have known
immediately that they had been scooped, and informed the Bell Lab boys what
they had found. So there you have it: Peebles to Turner to Burke to Penzias to
Dicke and we have one of the biggest home runs in modern science! The Nobel Prize for the discovery went to the
clueless Penzias and Wilson and neglected the prescient work of Dicke, Peebles,
and others. If Burke had not talked to
Turner, the prize would undoubtedly have gone to Dicke and his Princeton
crew. In any case, the time was ripe for
the discovery.
Certain lessons can be drawn from
the discovery of the cosmic background radiation. First, discoveries can occur in a
serendipitous manner over a period of time, thus lending credence that even in
science, the historical beginning of a period can be fuzzy and hard grist for
the historian of science's mill. Second,
the most imaginative people don't always get the prize. And third, constant communication between
scholars is vital.
Successes of the Big Bang and Steady State
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Figure 2: "The
dots run away from one another when
the rubber balloon is expanding," Gamow’s own
drawing of a 2-dimensional analog of an expanding
3-dimensional
universe.
|
Any plausible
theory must explain the following: (1) the universe at large consists primarily
of hydrogen and helium in the mass ratio of about 3:1; (2) the Hubble law,
according to which distant galaxies race away from us with speeds proportional
to their distances; and (3) the spectral shape of the CMB, which according to
the big bang should have a special “black body” spectral shape. An illustration of (2), from Gamow's own
hand, is shown in Figure 2.
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FIGURE
3: The measurement errors are so small they are hidden behind
the thin
theoretical curve.
|
Figure 3 shows the spectacular agreement between
big bang prediction and observation of the cosmic background's spectral
shape. The data points are hidden in the
theoretical curve—it doesn’t get much better than this!
The big bang theory has had a constant competitor in the steady state theory of the universe, formulated
by the late great physicist Fred Hoyle and his associates. This theory, called
the quasi-steady state theory in its
latest form, envisions an infinitely old and infinitely large expanding
universe in which the constant creation of matter prevents the universe from
becoming largely empty space. Surprisingly,
both the big bang and the more recent quasi-steady
state theories provide explanations for the three observations.
I must admit to a philosophical predisposition for the quasi-steady
state theory, but like the great majority of physicists, I have given it up in
favor of the big bang. What is it about
the big bang that wins the day? In a
nutshell, it is that this theory, when combined with results from particle
physics, gives a more economical, indeed more beautiful, explanation of empirical observations than the
quasi-steady state and other theories.
What does beauty have to do with physics? Plenty!
Poetry and science
Some of you might remember the great poet Coleridge's definition of
beauty as unity in variety. An example I use in my conceptual physics
class is one line from Shakespeare's Romeo
and Juliet, discussed by Jacob Bronowski in his beautiful little book Science and Human Values. In the face of
Romeo's impending suicide, he ponders the death of his most beloved. Inspired by her beauty even in death, Romeo
refers to:
Death that hath suckt the honey of thy breath.
What a beautiful
phrase: the "sting of death" was a common saying at the time, but
when it comes to Juliet, Shakespeare conjures up the life-spreading activity of
the bee that pollinates flowers and in the process makes lovely, fragrant honey
from here breath. All these different
ideas are packed into that one short phrase.
And so it is in science: we yearn for theories which are economical in
structure because they tie together a large number of seemingly disconnected
phenomenal. An ad hoc theory, on the other hand, is one which is constantly
modified to explain new, unexpected empirical evidence. What's wrong with that? Ad hoc theories are not beautiful but are like Rube Goldberg
contraptions—comical and inefficient, as they add devices to explain new
experimental data. A good theory, on the
other hand, explains many observations with a bare minimum of assumptions.
Throughout the years, the
quasi-steady state theory came to consist of a number of ad hoc patches
and band aids to make it work. Quite a contrast to the big bang theory, which
for years predicted new results confirmed by experimental verification, and in
the process showed that ideas previously thought to be unconnected are really
unified—a good example of scientific
unity in variety, of scientific
beauty.
Evolution of the original big bang—art in science
Over the years, the simple theory Weinberg described in such
brilliant terms has been subject to many modifications, particularly one known
as inflation which is an
exceptionally rapid expansion in the first 10-32 of a second of the
universe's existence. So we should now
refer to the inflationary big bang theory
of the universe's origin. The inflationary big bang has been spectacularly
successful in explaining a number of puzzling facts, like why the universe’s
geometry is flat and why it is so uniform. Ironically, the inflationary theory
allows for the possibility of a universe infinite in time and space, similar to
the steady state theory, but we can observe only a small part of it.
One triumph of inflationary cosmology involves the CMB spectrum
shown earlier. In fact, the curve shown
in Figure 3 threatens to be too
perfect, because if there weren't small irregularities from the theoretical
curve, it would imply that the universe is too smooth. Just look around: the universe is lumpy, from
air, water, and solids to stars and galaxies.
Figure 4 shows a tremendous success of modern astrophysics: different
colors in the picture correspond to tiny temperature variations in the CMB
corresponding to irregularities in the universe about 300,000 years after the
big bang and from which lumpiness in the form of galaxies, stars, and planets originated. Inflation theory does an excellent job of
explaining the statistical properties of the irregularities. The lower part of the figure is the same
thing at a different scale and has recently been seen to indicate a so-called
"axis of evil" problem with the inflationary big bang. The significance of this problem, and how
serious a threat it is to the inflationary big bang, remains to be seen.
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| Islands light, Microwave satellite charted the big bang's afterglow in unprecedented detail. |
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| FIGURE 4: Temperature variations in the CMB tell us about variations in the density of matter 300,000 years after the big bang. |
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FIGURE 5: Max Ernst, Le monde des
naifs.
(Photo of cover of The
Undivided Universe:
An ontological interpretation of quantum theory,
by D.
Bohm and B.J. Hiley, Routledge, London, 1993.)
|
To my taste, Figure 4 is a beautiful piece of pointillist-abstract art. Figure 5 shows Max Ernst's Dadaist Le monde des naifs, parts of which are vaguely similar to Figure 4 and other parts of which conjure up thoughts of beautiful mathematics, physics, astronomy, and colorful observations.
Big bang problems and speculations
Modifications of the inflationary
big bang continue to the present day.
More precise observations of the cosmic background radiation, galaxy and
supernova counts, cosmic distances, and galactic recession speeds have
confirmed many predictions of the theory, but have also given rise to problems
that have led to wild theoretical speculations, such as the existence of exotic
forms of "dark" matter and energy and particles with whimsical names
like "wimps" and "machos." All
of these exotics should be right here in Earth’s environment, but have never
been observed.
The inflationary big bang, to my
mind, now threatens to become an ad hoc
theory lacking the important criterion of unity in variety, of beauty. An article in the 7 March 2003 issue of Science shows that the uncertainties in
crucial parameters of the theory allow the possibility that our universe might
be oscillatory, just like Dicke thought back in 1965, and not expanding as the
standard big bang implies; or might be accelerating outward due to dark energy,
threatening to rip the entire cosmos apart.
We just don't know. A more sober
view at this period of science history would, in my opinion, focus on these
uncertainties and give more serious consideration to ideas such as
"Modifications of Newtonian Dynamics" (MONDS) which might explain
rotation rates of stars around galaxies without the need for the hitherto
unobserved, exotic, and hypothetical dark matter and energy.
Why worry? Isn't this
normal science?
Speculation is vital to any science,
but it is a double-edged sword. It can be used to challenge existing
theories, but it can also lead to theoretical constructs too clever by half
that buttress established "doctrine" in an ad hoc manner.
Nowhere have the speculations run
more rampant than in the apparent coincidences implied by the big bang. Take, for example, the existence of life, and
in the case of higher animals, of conscious life. Looking back in time, it appears that the big
bang process must have been extremely fine-tuned to give us the life-friendly properties
of atoms, particularly carbon atoms.
These cosmic coincidences have led to all sorts of speculations about
the theological and philosophical implications of the big bang's cosmological
coincidences. I believe on the contrary
that coincidences are a sign of incomplete or incorrect understanding and will
disappear when a true view of the situation is obtained.
Why worry over the difficulties of
the inflationary big bang? This would
appear to be normal science: two steps forward, one step back, as challenges
brought by new observations are met. But
I do worry, because distance measurements, upon which the entire subject of
cosmology rests, suffer from serious problems that don't appear to be taken
sufficiently seriously. I worry that the
big bang's theoretical and observational structure is built on sand—not
quicksand, but nonetheless sand of uncertain support. I worry that the big bang has become a
procrustean bed to which new theories are twisted and pulled to fit. I have always firmly believed that one of the
most important sources of scientific progress is the appropriate admission that
"we don't know." Should we
start looking in an entirely different direction? Should we take alternative ideas more
seriously, such as the MOND explanation of galactic rotation curves?
I particularly worry that the normal
process of science is being affected by the kind of hype and exaggerated claims
that pervade our political, economic, and cultural life. The mainstream media love a story that has
violence, and the big bang has always fit the bill, all the more so now, since
it is possible that the universe could be ripped to shreds by a strange dark
energy.
Ironic science and the end of real science
At this point, the inflationary big bang theory reigns, but in my
opinion it is only a useful theory, not
a superb theory like quantum physics and relativity. It seems more and more ad hoc and I occasionally find myself drawn back to the
quasi-steady state theory, as I try to carry out the balancing act between two
vital scientific attitudes: skepticism of new ideas and open-mindedness to
them. But I am confident that sooner or
later the normal practices of science will triumph and decide the issue for the
inflationary big bang (most likely), the quasi steady state, or something
altogether different.
A fundamental tenet of science is that theoretical ideas should have
consequences that are testable. Dark matter and energy should be right under
our noses but so far appear to be unobservable. These speculations and other
aspects of the inflationary big bang are reminiscent of what John Horgan, in
his book The End of Science, calls ironic science, i.e., science so far out
that it is not testable. Ironic science is the end of real science. Verifiable theories that explain a variety of
phenomena in a unified way—intellectual beauty in Coleridge’s sense—are the
proper end of real science.
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