Writing in the New York Times two physicists, Adam Frank of the University of Rochester and Marcelo Gleiser of Dartmouth College, explore the idea that physics has moved beyond the point at which empirical verification is possible or even necessary.  The debate, as they describe it, arises from suggestions by some physicists that we should “set aside the need for experimental confirmation of today’s most ambitious cosmic theories — so long as those theories are ‘sufficiently elegant and explanatory.’”

I understand this position.  I love a good theory.  But I don’t agree with it.

When I was a graduate student in theoretical astrophysics decades ago, my advisor would often decry the horror of “someone ruining a perfectly good theory by flying a spacecraft through it.”  That was his way of saying that, as theorists, we lived in fear of being disproven.  If too much data was collected, it might show that our theories were wrong or, at the very least, horribly incomplete.

I never knew if he was joking or serious, but I did get his point:  Without observational or experimental verification, you cannot take a theory very seriously.

Nevertheless, in accordance with the mantra of science, I delighted in ever more complete and mathematically elegant theories.  The mantra says that science explains why things work and that the goal of physics is to find the unifying theory of everything. Newton’s law of gravity explains why things fall. Einstein’s theory of relativity gives a better explanation. Combining relativity with quantum mechanics would produce the holy grail of physics—the Grand Unified Theory—which would explain everything.

Now older and, I hope, a bit wiser, I no longer believe that mantra.

Evidence of God

My rethinking of the mantra came from, of all places, a theologian. “The greatest evidence of God,” he said, “just might be the fact that the physical ‘laws’ of nature work so consistently.”

With this simple statement he blew wide open the underlying basis of physics.  The idea that the laws of nature work consistently, everywhere, and at all times is an a priori assumption of science. It is certainly borne out by observations of physical phenomena in the far reaches of the universe, and there is no reason to doubt its veracity.

But I had never stopped to ask why this consistency exists.

My theologian friend was suggesting that it exists because God made it that way and because God sustains it. Rocks don’t fall because of Newton’s law of gravity.  They fall because that is a facet of the way that God made the order of things.  Newton’s “law” of gravity merely describes, with great precision, how they fall.

Science, therefore, is not in the business of explaining why things work; it is in the business of describing how they work.  Our so-called “laws” of nature are nothing more than our best efforts to describe, codify, and quantify what things in nature naturally do. Observations and experiments are essential in order to discern which sets of descriptions—which theories—are accurate and which are not.

As our theories reveal patterns and regularities, and as the language of mathematics pushes the theories to ever-greater precision and predictability, we gain glimpses into the beauty of God’s creation.

Our theories are never perfect or complete.  There might be several different ways of describing the same set of phenomena, each with different limitations, but each one valid within its own limitations.  Ptolemy, Kepler, Newton, Einstein: Each has a different way of describing the motions of the planets; each has different limitations.

Though we no longer rely on his theoretical framework, Ptolemy was not wrong. As Frank and Geisler note, his epicycles do a very good job of describing and predicting the motions of planets as observed from Earth. Take apart a traditional analog planetarium projector and you will find gears upon gears intermeshed in deferents and epicycles. These gears replicate for planetarium audiences the motions of the planets as seen from the vantage point of being on Earth. Ptolemy’s description works.

Kepler’s ellipses provide a better description if you want to take a space traveler’s view of the solar system. It is commonly said that Kepler’s system is more “real,” meaning that planets actually move along ellipses rather than along epicycles.  It would be more accurate to say that Kepler’s system is more convenient if you want your vantage point to be from somewhere outside the solar system.

If you want to be a space traveler, then you need Newton.  Indeed, NASA uses Newtonian mechanics to navigate spacecraft traversing our solar system. And if you want to navigate exceedingly accurately, or if you want to investigate a black hole, then you need Einstein’s relativity.

Mathematically, you can reduce Einstein to Newton, Newton to Kepler, and Kepler to Ptolemy.  It must be that way because they all describe the same reality.  If you could ask God, how would he describe the physical world?

Dangers and Joys

There are dangers here. If we take our descriptions too seriously, we may fail to remember that they are just our own meager attempts to describe the reality that God has ordained.

If we decide that we do not need to validate our theories with observations and experiments, then we are in grave danger of becoming wedded to theories that do not actually describe anything real or that are limited to that which we can ourselves imagine. Who are we to infer that which God has ordained?

But there is also the possibility of joy: The quest to verify theories sometimes leads to genuine surprises. When our observations or experiments yield wholly unexpected results, we scientists tend to be elated. The true joy of science is discovering that which we had not even begun to imagine. To rule out observational and experimental verification is to rule out the possibility of surprises.

To insist on making the observations and doing the experiments is to keep the door open to the delight of finding the unexpected. In so doing, we open ourselves to those wonderful moments when we encounter the God of Surprises.