The public's attitude toward scientists has always been ambivalent -- witness the near reverence for Einstein and yet the consistently negative portrayals of scientists in films like Frankenstein, Dr. Strangelove, Jurassic Park, etc. While the public admires scientific achievement, people often recoil from the archetypal scientist's "superiority," limited perspective and cold objectivity. The public is less aware of another, more subtle, scientific shortcoming that belies the notion of objectivity. The problem is that scientists often present an excessively rosy picture of their knowledge to the public, while amongst themselves they reveal far more uncertainty over what is known and what is assumed. It reminds me of Janus, the ancient Roman god of polarities, whose head has two opposing faces, one smiling and one frowning.
An exemplar field for exploring this Janus-faced behavior is cosmology -- a field that millions of people find fascinating enough to follow in the media, or to lay out $24.95 for Stephen Hawking's nearly incomprehensible book A Brief History of Time. A recent review of the Big Bang model, written by well-respected cosmologists and published in Scientific American, provides a typical case of scientific salesmanship. The authors clearly state that several predictions of the model have been verified, and that all observations are consistent with the Standard Big Bang model (SBB). This sounds pretty impressive, but how can one reconcile this assessment with the fact that cosmological discussions at scientific conferences and in technical journals become quite heated over at least 5 major areas of disagreement between nature and the SBB.
These problem areas include the dark matter problem (90%-99% of the universe is mystery stuff), the causality problem (no explanation for why the universe popped out of its initially collapsed state), the age problem (finding stars that appear to be older than the universe), and so on. In the world's premier astrophysics journal, I have seen one article by a leading expert in nucleosynthesis (primordial formation of atomic nuclei) saying that the amount of helium must be within a certain range or the SBB is "falsified," while another paper in the same issue reports helium observations that lie outside that range. Since the public is regularly told that successful nucleosynthesis predictions are an evidential cornerstone for the Big Bang theory, the actual uncertainty in nucleosynthesis studies must come as a surprise to many.
It is easy to find similar examples of conflicting scientific assessments that are highly correlated with the intended audience. As an explanation, some cosmologists might argue that the level of technical difficulty and detail in their presentations must be appropriately tailored to the needs and abilities of each audience. This is surely a valid concern, but the take-home messages for both public and academic presentations should be the same. The Big Bang theory should not be described as "correct" to one audience and "in trouble" to another.
So has the Big Bang paradigm been "proven" or "falsified"? Perhaps the best answer is that the SBB, like all scientific paradigms, is an approximation and approximations either accurately model our limited knowledge or have shortcomings that indicate the need for a superseding paradigm. Approximations, by definition, cannot be completely correct. The question is not so much whether a paradigm is right or wrong, but whether or not it offers the best, i.e., most accurate and comprehensive, explanation for our observational knowledge.
It is correct to say that Newton's theory of gravity is a relic (even though it is preferentially used for space flight calculations), but it is not correct to say that Einstein's newer theory is the final answer on gravitation. Both are approximations, with Einstein's approach to space, time, matter and gravitation being far more accurate, mathematically difficult and conceptually exquisite. One can envision a time when a broader and deeper theory marries gravity to other "forces" and Einstein's theory is subsumed as a more limited approximation.
So how does one account for the confident smile that the cosmologist shows to the public and the furrowed brow shown to colleagues? Well, for one thing the public pays the scientist, and it is natural to assure your patron that everything is under control. For another, the scientist likes to be viewed as a brilliant thinker who has the answers. A third reason is that everything is hyped these days. Moreover, as T.S. Kuhn implies in his scientific classic The Structure of Scientific Revolutions, there is a more subtle psychological component to the Janus-faced behavior. The science student is gradually steeped in the prevailing paradigm until it becomes common sense -- other ideas sound and feel misguided. Still, the scientist secretly questions everything. While his professional status is linked to the status of the prevailing paradigm, his most cherished goal is to discover something radically new. Such is the intellectual split-personality of the scientist.
What I wish to argue here is that in the long run scientific forthrightness is crucial to scientists and to the broader community. Whereas all parties benefit when theoretical assumptions and observational uncertainties are kept in clear view, sugar-coated presentations mislead the public and stifle scientific progress. Cosmologists, science writers and editors should scrupulously treat the Big Bang model as an approximation. Even if the model is reasonably accurate for the observable portion of the universe, our sphere of observation may still represent only the tiniest of blips in an unimaginably larger and more intricate universe. We are not Masters of the Universe. We are, at best, perpetual students of nature. We should not feel the least bit embarrassed about this, but rather be proud of the human struggle to comprehend. Wondrous discoveries have been made since Galileo turned his telescope toward the night sky. As Einstein put it:
"All our science, measured against reality, is primitive
and childlike -
and yet it is the most precious thing we have."
The characteristics of the microwave background radiation, the apparent expansion of our galactic scale environment, and abundances of light elements suggest that the Big Bang model is a good approximation, far better than many previous models. But let's hold it there for now. Scientists do not struggle towards a "final theory." We have seen the folly and/or horror of "absolute certainty" often enough to know better. Cosmologists should remain restless, questioning, unsatisfied -- openly admitting current weaknesses. Good scientific theories, like the Big Bang model, are stepping stones in a widening and deepening understanding of the cosmos. Undoubtedly there are exciting new paradigms that have yet to be dreamt of or explored. Science evolves.