Reports that physicists are nearing the final frontier of knowledge have been greatly exaggerated.
The success of known physical laws to explain the world around us has consistently bred some confident and cocky attitudes toward the state of human knowledge, especially when the holes in our knowledge of objects and phenomena are perceived to be small and insignificant. Nobel laureates and other esteemed scientists are not immune from this stance, and in some cases have made especially embarrassing proclamations about the end of science.
A famous end-of-science prediction came in 1894, during the speech given by the soon-to-be Nobel laureate Albert A. Michelson on the dedication of the Ryerson Physics Lab, at the University of Chicago.
The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote…Future discoveries must be looked for in the sixth place of decimals.
One of the most brilliant astronomers of the time, Simon Newcomb, who was also co-founder of the American Astronomical Society, shared Michelson’s views in 1888 when he noted,
We are probably nearing the limit of all we can know about astronomy. Even the great physicist Lord Kelvin, who had the absolute temperature scale named after him, fell victim to his own confidence in 1900 with the claim,
There is nothing new to be discovered in physics now. All that remains is more and more precise measurement. These comments were expressed at a time when the luminiferous ether was still the presumed medium in which light propagated through space, and when the slight difference between the observed and predicted path of Mercury around the Sun was real and unsolved. These unsolved problems were perceived at the time to be small, requiring perhaps only small adjustments to the known physical laws to account for them.
Fortunately, Max Planck, one of the founders of quantum mechanics, had more foresight than his academic advisor. Here, in a 1924 lecture, he reflects on the advice given to him in 1874, when he began his studies in physics.
When I began my physical studies and sought advice from my venerable teacher Philipp von Jolly…he portrayed to me physics as a highly developed, almost fully matured science…Possibly in one or another nook there would perhaps be a dust particle or a small bubble to be examined and classified, but the system as a whole stood there fairly secured, and theoretical physics approached visibly that degree of perfection which, for example, geometry has had already for centuries.
Initially Planck had no reason to doubt his teacher’s views. But when our classical understanding of how matter radiates energy could not be reconciled with experiment, Planck became a reluctant revolutionary in 1900 by suggesting the existence of the quantum, an indivisible unit of energy that heralded an era of new physics. The next thirty years would see the discovery of the special and general theories of relativity, quantum mechanics, and the expanding universe.
With all this myopic precedence you would think that the brilliant and prolific physicist Richard Feynman would have known better. In his 1965 book The Character of Physical Law he declares,
We are very lucky to be living in an age in which we are still making discoveries…The age in which we live is the age in which we are discovering the fundamental laws of nature, and that day will never come again. It is very exciting, it is marvelous, but this excitement will have to go.
I claim no special knowledge of when the end of science will come, or where the end might be found, or whether an end exists at all. What I do know is that our species is dumber than we normally admit to ourselves. This limit of our mental faculties, and not necessarily of science itself, ensures to me that we have only just begun to figure out the universe.
Let’s assume, for the moment, that human beings are the smartest species on Earth. If, for the sake of discussion, we define “smart” as the capacity of a species to do abstract mathematics then one might further assume that human beings are the only smart species to have ever lived.
What are the chances that this first and only smart species in the history of life on Earth has enough smarts to completely figure out how the universe works? Chimpanzees are an evolutionary hair’s-width from us yet I think we can agree that no amount of tutelage will ever leave a chimp fluent in trigonometry. Now imagine a species on Earth, or anywhere else, as smart compared with humans as humans are compared with chimpanzees. How much of the universe might they figure out?
Tic-tac-toe fans know that the game’s rules are sufficiently simple that it’s possible to win or tie every game—if you know which first-moves to make. But young children play the game as though the outcome were remote and unknowable. The rules of engagement are also clear and simple for the game of chess, but the challenge of predicting your opponent’s upcoming sequence of moves grows exponentially as the game proceeds. So adults—even smart and talented ones—are challenged by the game and play it as though the end were a mystery.
Let’s go to Isaac Newton, who leads my list of the smartest people who ever lived. (I am not alone here. A memorial inscription on a bust of him in Trinity College, England, proclaims Qui genus humanum ingenio superavit, which loosely translates from the Latin, “of all humans, there is no greater intellect.”) What did Newton observe about his state of knowledge?
I do not know what I appear to the world; but to myself I seem to have been only like a boy playing on a seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay undiscovered before me.
The chessboard that is our universe has revealed some of its rules, but much of the cosmos still behaves mysteriously—as though there remain secret, hidden regulations to which it abides. These would be rules not found in the rulebook we have thus far written.
The distinction between knowledge of objects and phenomena, which operate within the parameters of known physical laws, and knowledge of the physical laws themselves is central to any perception that science might be coming to an end. The discovery of life on the planet Mars, or beneath the floating ice sheets of Jupiter’s moon Europa, would be the greatest discovery of any kind ever. You can bet, however, that the physics and chemistry of its atoms will be the same as the physics and chemistry of atoms here on Earth. No new laws necessary.
But let’s peek at a few unsolved problems from the underbelly of modern astrophysics and expose the breadth and depth of our contemporary ignorance, the solutions of which, for all we know, await the discovery of entirely new branches of physics.
While our confidence in the big bang description of the origin of the universe is very high, we can only speculate what lies beyond our cosmic horizon, 13 billion light years from us. We can only guess what happened before the big bang or why there should have been a big bang in the first place. Some predictions, from the limits of quantum mechanics, allow our expanding universe to be the result of just one fluctuation from a primordial space-time foam, with countless other fluctuations spawning countless other universes.
Shortly after the big bang, when we try to get our computers to make the universe’s hundred billion galaxies, we have trouble simultaneously matching the observational data from early and late times in the universe. A coherent description of the formation and evolution of the large-scale structure of the universe continues to elude us. We seem to be missing some important pieces of the puzzle.
Newton’s laws of motion and gravity looked good for hundreds of years, until they needed to be modified by Einstein’s theories of motion and gravity—the relativity theories. Relativity now reigns supreme. Quantum mechanics, the description of the atomic and nuclear universe, also reigns supreme, except that, as conceived, it is irreconcilable with Einstein’s theory of gravity. They each predict different phenomena for the domain in which they might overlap. Something’s got to surrender. Either there’s a missing part of Einstein’s gravity that enables it to accept the tenets of quantum mechanics, or there’s a missing part of quantum mechanics that enables it to accept Einstein’s gravity.
Perhaps there’s a third option: the need for a larger, inclusive theory that supplants them both. Indeed, string theory has been invented and called upon to do just that. It attempts to reduce the existence of all matter, energy, and their interactions to the simple existence of higher dimensional vibrating strings of energy. Different modes of vibration would reveal themselves in our measly dimensions of space and time as different particles and forces. Although string theory has had its adherents for more than twenty years, its claims continue to lie outside our current experimental capacity to verify its formalisms. Skepticism is rampant, but many are nonetheless hopeful.
We still do not know what forces enabled inanimate matter to assemble into life as we know it. Is there some mechanism or law of chemical self-organization that escapes our awareness because we have nothing with which to compare our Earth-based biology, and so we cannot evaluate what is essential and what is irrelevant to the formation of life?
We’ve known since Edwin Hubble’s seminal work during the 1920s that the universe is expanding, but we’ve only just learned that the universe is also accelerating, by some anti-gravity pressure dubbed dark energy for which we have no working theory to understand.
At the end of the day, no matter how confident we are in our observations, our experiments, our data, or our theories, we must go home knowing that ninety percent of all the gravity in the cosmos comes from some unknown, mysterious source. This source remains completely undetected by all means we have ever devised to observe the universe. As far as we can tell, it’s not made of ordinary stuff such as electrons, protons, and neutrons, or any form of matter or energy that interacts with them. We call this offending substance, dark matter, which remains the greatest enigma of modern times.
Does any of this sound like the end of science? Does any of this sound like we are on top of the situation? Does any of this sound like it’s time to congratulate ourselves? To me it sounds like we are all stupid helpless idiots, not unlike like our kissing cousin, the chimpanzee, trying to learn the Pythagorean theorem.
Maybe I’m being a little hard on Homo sapiens and have carried the chimpanzee analogy a little too far. Perhaps the question is not how smart is an individual of a species, but how smart is the collective brain-power of the entire species. Among humans, discoveries made by some are routinely shared with others through conferences, books, other media, and of course the Internet. While natural selection drives Darwinian evolution, the growth of human culture is largely Lamarckian, where new generations of humans inherit the acquired discoveries of generations past, allowing cosmic insight to accumulate without limit.
Each discovery of science therefore adds a rung to a ladder of knowledge whose end is not in sight because we are building the ladder as we go along. As far as I can tell, as we assemble and ascend this ladder, we will forever uncover the secrets of the universe—one by one.