A Matter of Considerable Gravity: On the Purported Detection of Gravitational Waves and Cosmic Inflation
Editor's note: Dr. Gordon is a Senior Fellow with the Center for Science & Culture and Associate Professor of the History and Philosophy of Science at Houston Baptist University. He is the co-editor with William Dembski of The Nature of Nature: Examining the Role of Naturalism in Science (Intercollegiate Studies Institute, 2011).
The world of science has been abuzz recently with the report that physicists involved in the BICEP2 project (Background Imaging of Cosmic Extragalactic Polarization 2), using a telescope at the South Pole to analyze the polarization of light from the early universe, had detected the imprint of gravitational waves that had been stretched by the process of cosmic inflation a trillion-trillion-trillionths of a second after the Big Bang 13.7 billion years ago. In view of all the excitement, some reflection on the nature of the alleged discovery, its reliability, and its significance is advisable.
One of the things that bothered Albert Einstein about Newton's theory of gravity was that gravitational force, in Newtonian conception, acted instantaneously across any distance without any discernible medium that carried the force. Two massive objects on opposite sides of the universe have an instantaneous effect on each other that is proportional to their respective masses and inversely proportional to the square of the distance between them. For instance, the motion of planets around the Sun in our solar system redistributes matter in a way that instantly changes the gravitational field on the other side of the universe. Einstein's 1915 theory of general relativity changed this. In 1905, with his special theory of relativity describing non-accelerated motion, he found that the speed of light was the limiting velocity at which any cause could have a spacetime effect. His theory of general relativity, which extended his analysis to accelerated motion and gave an account of the nature of gravity-induced motion in terms of the curvature of spacetime (roughly, matter tells spacetime how to curve and spacetime tells matter how to move), predicted the existence of gravitational waves that propagate at the speed of light. In other words, general relativity eliminated the action-at-a-distance in Newtonian gravity by describing gravitational effects as ripples in spacetime that propagated outward from massive objects at the speed of light.
Now, Big Bang theory has its theoretical basis in general relativity, which predicts that the universe is spatiotemporally expanding in the future direction and thus would be contracting if we were to reverse the direction of time. As Roger Penrose and Stephen Hawking showed in the late 1960s, no matter which general-relativistic model of our universe is chosen, this contraction leads to a beginning point in the finite past -- a singularity, to use the technical term -- from which not just matter and energy, but spacetime itself, emerged. This coming into existence of the universe from nothing (no space, no time, no matter, no energy, and hence no physical laws either) is what is known as the Big Bang. It is, as the agnostic astronomer Robert Jastrow once observed, startling evidence for the doctrine of creation ex nihilo. He famously put it this way:
For the scientist who has lived by his faith in the power of reason [editorial aside: Jastrow might better have said "faith in the sufficiency of materialist explanations" because the inference from the ex nihilo generation of the universe to a transcendent intelligent cause is eminently reasonable], the story ends like a bad dream. He has scaled the mountain of ignorance; he is about to conquer the highest peak; as he pulls himself over the final rock, he is greeted by a band of theologians who have been sitting there for centuries.
This having been established, as the physicist George Gamow demonstrated in 1948, one of the predictions of Big Bang theory is the existence of gravitational ripples and cosmic background radiation (CBR) that are an "echo of Creation," as it were, throughout the whole observable universe. This cosmic background electromagnetic radiation was discovered in 1965 by Robert Wilson and Arno Penzias, a discovery for which they were awarded the Nobel Prize. In this regard, the alleged detection of gravitational waves would serve as further confirmation of the correctness of Einstein's theory of general relativity and of the nature of the Big Bang itself. If corroborated by the scientific community, it would be a hugely important discovery, not just because of the evidence it provides for gravitational waves, but also because of the way this discovery is linked to another theory, namely, inflationary cosmology.
As implied in the opening paragraph, if gravitational waves have been detected by their effect on the polarization of light from the early universe, it is because this effect has been amplified to detectable size by cosmic inflation in the first 10-37 to 10-35 of a second after the universe exploded into existence. According to the hypothesis of cosmic inflation, during this incredibly small period of time, the universe expanded at a velocity exponentially faster than the speed of light (this would not violate special relativity because it is not describing motion within spacetime but rather the expansion of spacetime itself). I will say more about the justifications and implications of inflationary cosmology presently, but the first thing we need to address is the reliability of these recently reported results, and in this respect there are ample grounds for being tentative. Polarization of the CBR from the Big Bang is regularly observed and attributed to magnetic fields in space produced by intervening galaxies or intergalactic dust. The BICEP2 scientists attempted, to the best of their ability, to get a look at the CMB apart from such known polarizing factors and discovered that, insofar as they succeeded, the polarization was still there. The search for another source of this polarization yielded the suggestion that gravity-wave compression of matter in the early universe could have such a polarizing effect. However, in order for it to be large enough to match what was observed, it would require amplification that only something like cosmic inflation could provide. Further study revealed that if the dials on gravity-wave compression and inflationary expansion were tweaked in just the right way, and a reasonable guess at polarizing dust interference was accommodated, a moderately significant polarization signal remained above the noise that could be explained by carefully selected gravitational and inflationary causes. In short, there's a lot of room for doubt about the proposed explanation of the data and ample room for more conventional explanations to prove adequate to the task (for more on this, see Rob Sheldon's article referenced in the further reading suggested at the end of this post). Nonetheless, if these results hold up to extended critical scrutiny, some Nobel Prizes will likely be forthcoming.
With the tentativeness of these results firmly in view, we need to examine the reason that cosmic inflation was first proposed. Alan Guth suggested an inflationary mechanism in 1980 to explain why the temperature of the cosmic background radiation was the same throughout the observable universe to one part in a hundred thousand, and why the density of mass-energy resulting from the Big Bang yielded a universe that was flat to at least one part in a quadrillion (explanatory demands known respectively as the "horizon" and "flatness" problems). Inflation is therefore intended to explain away the fine-tuning of certain physical quantities intimately connected to the Big Bang origin of our universe, especially since this thermodynamic connectedness and homogeneity seems necessary if our universe is to be capable of supporting life. In short, inflation was invoked to provide a physical rather than a transcendent metaphysical explanation for our universe's fine-tuned life-supporting properties.
The irony of the proposal, at least in regard to the sensibilities of those inclined to scientific materialism, is that inflationary processes actually increase rather than decrease the required fine-tuning associated with our universe. For instance, the energy of the inflationary field has to be shut off with tremendous precision in order for a universe like ours to exist, with inflationary models requiring a shut-off energy precision of at least one part in 1053 and perhaps as much as one part in 10123. Furthermore, inflation is an entropy-increasing process (it increases the thermodynamic disorder of the cosmos), yet even without it, as Roger Penrose has shown, the universe's initial entropy was fine-tuned to one part in 10 to the 10123 power. In other words, adding an inflationary process to the already hyper-exponentially fine-tuned entropy required by the Big Bang exponentially increases its hyper-exponential fine-tuning. What is more, as theoretical cosmologists Sean Carroll and Heywood Tam demonstrated in 2010, the chance of an inflationary process producing a realistic cosmology is only one in 10660,000,000.
Of course, the inflationary mechanism is often regarded as generative of an unending and rapid succession of universes with the idea that, if enough universes are produced by such means, the improbabilities just mentioned don't matter. Several things need to be said about this "inflationary multiverse" proposal:
(1) First of all, as pointed out by one of the physicists involved in the BICEP2 project, Kent Irwin at Stanford University, the BICEP2 results do not address the truth or falsity of inflationary multiverse theories.
(2) Secondly, attempting to swamp the improbabilities intrinsic to inflation by multiplying the number of universes it generates to the point of compensation has consequences that undermine scientific rationality. In a materialist multiverse resting on the hypothesis of an undirected and irreducibly probabilistic quantum inflationary mechanism that lacks any principle of sufficient material causality, anything can happen for no reason at all. What is more, quantum-mechanically speaking, everything that can happen, no matter how improbable, does happen, and it happens with unlimited frequency. In this environment we can have no confidence that the future will resemble the past in a way that legitimates uniformitarian assumptions and the very inductive inferences that make science possible. In short, taken seriously, the inflationary multiverse proposal completely undermines scientific rationality.
(3) Thirdly, at least two paradoxes result from the inflationary multiverse proposal that suggest our place in such a multiverse must be very special: the "Boltzmann Brain Paradox" and the "Youngness Paradox." In brief, if the inflationary mechanism is autonomously operative in a way that generates a multiverse, then with probability indistinguishable from one (i.e., virtual necessity) the typical observer in such a multiverse is an evanescent thermal fluctuation with memories of a past that never existed (a Boltzmann brain) rather than an observer of the sort we take ourselves to be. Alternatively, by a second measure, post-inflationary universes should overwhelmingly have just been formed, which means that our existence in an old universe like our own has a probability that is effectively zero (i.e., it's nigh impossible). So if our universe existed as part of such a multiverse, it would not be at all typical, but rather infinitely improbable (fine-tuned) with respect to its age and compatibility with stable life-forms.
(4) Fourthly, a mechanism that generates universes ad infinitum must have stable characteristics that constrain its operation if it is to avoid breaking down and sputtering to a halt. In short, universe-generators have finely tuned design parameters that themselves require explanation. So postulating a universe-generator to explain away the appearance of first-order design in a single universe does not obviate the inference to design, it merely bumps it up to the next level. Avoiding an infinite regress of explanatory demands leads to the recognition of actual design terminating in an Intelligence that transcends spacetime, matter and energy, and which, existing timelessly logically prior to creating any universe or multiverse, must also therefore exist necessarily, and therefore require no further explanation of its own existence.
(5) Fifthly and finally, as demonstrated by Arvind Borde, Alan Guth, and Alexander Vilenkin in 2003 (see further reading suggestions below), any inflationary multiverse has a beginning in the finite past: while inflationary models can, in theory, be eternal into the future, it is mathematically impossible for them to be eternal into the past. This means that the inflationary multiverse entails creation ex nihilo in precisely the same manner as the Big Bang. The universe thus manifests dependence on a transcendent reality in respect of its origin, but what is more, in virtue of the manifest absence of sufficient material causation in many aspects of its persistence as a quantum-mechanical phenomenon, the material universe also manifests dependence on a transcendent reality in respect of its operation (for an extended argument to this effect, see my article on quantum-theoretic challenges to philosophical naturalism referenced in the suggested readings).
What all of this reveals, of course, is that it's intelligent design all the way through and all the way down and that theophobic scientific materialists, once they get past knee-jerk denials, must come to terms with what is, for them, a worldview-defeating fact.
Suggestions for Further Reading
Barnes, Luke. (2011) "The Fine-Tuning of the Universe for Intelligent Life."
Barrow, J.D., and Tipler, F.J. (1986) The Anthropic Cosmological Principle. Oxford: Oxford University Press.
Borde, A., Guth, A., and Vilenkin, A. (2003) "Inflationary spacetimes are not past-complete."
Carroll, S., and Tam, H. (2010) "Unitary Evolution and Cosmological Fine-Tuning."
Collins, Robin (1999) "A Scientific Argument for the Existence of God: The Fine-Tuning Design Argument," in Michael J. Murray, ed. Reason for the Hope Within. Grand Rapids: Eerdmans, pp.47-75.
_______. (2003) "Evidence for Fine-Tuning," in N. Manson, ed. God and Design: The Teleological Argument and Modern Science. New York: Routledge, pp.178-99.
_______. (2009) "The Teleological Argument: An Exploration of the Fine-Tuning of the Universe," in William L. Craig and J.P. Moreland, eds. The Blackwell Companion to Natural Theology. Oxford: Blackwell, pp.202-81.
_______. (2013) "The Fine Tuning Evidence is Convincing," in J. P. Moreland, Chad Meister, and Khaldoun A Sweis, eds. Debating Christian Theism. New York: Oxford University Press, pp. 35-46.
Copan, Paul, and William Lane Craig. (2004) Creation out of Nothing: A Biblical, Philosophical, and Scientific Exploration. Grand Rapids: Baker Academic.
Ellis, G.F.R. (2006) "Issues in the Philosophy of Cosmology."
Gordon, Bruce L. (2010) "Inflationary Cosmology and the String Multiverse," in Robert J. Spitzer, S.J. New Proofs for the Existence of God: Contributions of Contemporary Physics and Philosophy. Grand Rapids: Eerdmans, pp. 75-103.
_______. (2011a). "A Quantum-Theoretic Argument against Naturalism," in Bruce L. Gordon and William A. Dembski, eds., The Nature of Nature: Examining the Role of Naturalism in Science. Wilmington: ISI Books, pp.179-214.
_______. (2011b) "Balloons on a String: A Critique of Multiverse Cosmology," in Bruce L. Gordon and William A. Dembski, eds., The Nature of Nature: Examining the Role of Naturalism in Science. Wilmington: ISI Books, pp.558-601.
_______. (2013a) "In Defense of Uniformitarianism," Perspectives on Science and the Christian Faith, vol. 65, no. 2, pp.79-86.
Guth, Alan H. (1997) The Inflationary Universe: The Quest for a New Theory of Cosmic Origins. Reading: Perseus Books.
Holder, Rodney D. (2004) God, the Multiverse, and Everything: Modern Cosmology and the Argument from Design.Burlington: Ashgate.
Sheldon, Robert B. (2014) "Bang for the Buck: What the BICEP2 Consortium's Discovery Means," Evolution News & Views, March 19, 2014.
Steinhardt, Paul. (2011) "The Inflation Debate," Scientific American, v.34 (4), 36-43.