December 2014 | Status: Second Draft
String theory gets flak again for not being sciencey enough. According to Ellis and Silk, the apparently highly annoyed authors of this paper, a lot of theories that float around in the cosmology department nowadays have no right to be called science.
In our view, the issue boils down to clarifying one question: what potential observational or experimental evidence is there that would persuade you that the theory is wrong and lead you to abandoning it? If there is none, it is not a scientific theory.
And of course, the implication is that such evidence should be produced right now — or at the very latest, by the date of an important conference (or is it an inquisition?) that the authors argue should be convened next year to discuss the matter.
To be honest, I have no horse in this race. It doesn’t matter to me whether the universe is made of strings, wires, or wireless dongles. Multiverse? Cool! Call me again when you have a working time machine. But one thing about this controversy bugs me like hell:
Why so impatient?
The Earth goes around the Sun, not the other way around. Copernicus realized this for the first time in the early 16th century. By the end of the 17th century, almost every scientist in Europe were convinced that Copernicus was right. Why? It was elegant (no epicycles), it was politically exciting (it went against the doctrine of the Roman Catholic Church and therefore looked especially sexy to reformers), and some of its followers (ever heard of Isaac Newton?) had come up with some really interesting equations.
In other words, heliocentrism in the late 17th century had all the features that a popular programming language today might have. It was hip, elegant, and supported by some of the rockstar scientists of the age. (The lack of epicycles was a particularly attractive feature because of the newly discovered moons of Jupiter. Too many levels of epicycles made the Ptolemaic model look rather inelegant.) But as a scientific theory, it remained unconfirmed, and its rival geocentrism remained unfalsified, even as the world embraced it as the truth.
Conclusive falsification of geocentrism, and thus compelling confirmation of heliocentrism, only arrived in 1838 with the first observation of parallax. That was almost 300 years after Copernicus first advocated heliocentrism, and over 100 years after almost everyone accepted it. For all those decades and centuries, people had been believing in heliocentrism without having tested it — all because it was so elegant.
The history of science is rife with examples like this. Some theories are inherently difficult to test, so it can take a few decades, or even centuries, to collect conclusive experimental evidence. Sometimes you have to wait for others to develop the technology you need, just as heliocentrism had to wait for highly accurate telescopes to measure parallax. Gravitational waves, for example, have been predicted for almost a century, but still hasn’t been experimentally confirmed. Because it costs a lot of time and money to develop the required technologies, a theory without a critical mass of highly motivated followers is at risk of fizzling out before it can ever be tested.
Every major advance in science happens this way, as famously observed by Thomas Kuhn. Baby theories are never testable on their first day outside of a scientist’s mind, but after a while, they grow up, and begin to resemble the shape of an adult specimen that Popper described.
This is an inevitable consequence of the fact that science depends on a bunch of hairless bipedal monkeys for its existence. When falsification takes a long time, humans tend to be influenced by political, philosophical, aesthetic, and even religious factors. And this isn’t a Totally Evil Thing™, because if we weren’t influenced by such factors, much fewer theories would ever make it to falsification. They would just fizzle out for lack of support, like a baby lost in an adult world without anyone to care for her.
How long has string theory been around? 50 years? And we’re already being impatient with it? Remember how long we had to wait for Darwin’s theory of evolution to become mainstream and well-supported by evidence? Remember how long it took for “driftists” (those who supported plate tectonics) and “fixists” (those who opposed it) to reach a consensus?
50 years is about as long as it takes for the scientific community to settle a dispute about the distant history of this planet using recent technology. How much longer do you think it will take to test a theory about the fundamental structure of the universe, when we can’t even imagine the kind of technology we’d need in order to test it?
Copernicus waited 300 years. String theorists should expect to wait 500-1000 years, if not more. And we, the rest of the society, should strive to support such long-term endeavors to the best of our abilities. It’s not as if string theorists are asking us to build expensive underground facilities for them. All they’re asking of us is to let some professors engage in geeky speculation for a few more centuries.
If we as a society can afford to throw money at SF films and number-puzzle games with a high “geek factor”, surely we can afford to give a bit of respect to the most creative physicists of our time whose conjectures unfortunately cannot be tested within their lifetime. Acknowledge that a small fraction of our scientific workforce needs to be engaged in such long-term projects, and take comfort in the fact that this fraction will always remain small.
Or have we become so insecure, narrow-minded, and short-sighted that we cannot stand the sight of as-yet-unfalsified theories occupying the precious pages of our journals?