Updated: Oct 8
Author: Arpan Dey
Paul Halpern is a science writer and professor of physics at Saint Joseph's University, Philadelphia. He holds a Ph.D. in theoretical physics, and has authored numerous popular science books. The first Halpern book I read was Einstein's Dice And Schrödinger's Cat: How Two Great Minds Battled Quantum Randomness To Create A Unified Theory Of Physics. I loved reading this book. The great story of Einstein and Schrödinger's battle against quantum mechanics felt so much better in the words of Paul Halpern. Since then, I have explored some other works of Paul Halpern as well. A few days ago, I couldn't resist the urge to email him with a few questions, mainly about the philosophy of physics. Heartfelt thanks to Professor Halpern for not only taking some time out of his schedule to answer my questions, but also permitting me to publish this interview.
1. My philosophy about the universe can be roughly summed up by this statement: “Ordered complexity is a fortunate product of random processes.” In other words, I believe that the complexity we see around us can, in theory, be explained by random processes. We don’t need any higher being or God to explain that. But I’m not saying everything is random. Everything occurs according to certain rules; however, these rules were not made up by God, different rules apply in different realities, and we are in that reality where the rules permit the formation of life. What do you think about this? Is your philosophy about the universe similar?
First of all, may I applaud you, as a young thinker, for having a philosophy about the universe. I was challenged by a philosophy course myself at university, and did not find it easy. That [ordered complexity is a fortunate product of random processes] is a very interesting statement. I think there is a lot of truth in the idea that order might emerge from seeming randomness. I write "seeming" because, as chaos theory informs us, apparent randomness in certain cases stems from deterministic laws. Regarding religion, as a scientist I do not comment on such matters, and leave discussions of faith to theologians and individuals themselves as they grapple with their personal searches for meaning. What I would personally add to your statement is the importance of natural selection, also known as "survival-of-the-fittest," the Darwinian law of optimization. It quickly sorts through the mayhem of vying systems and judges which one is most effective. In physics, that is related to the least action principle, which finds the optimum path amongst contenders, which turns out to match classical reality.
Thanks to Professor Halpern for agreeing with me on this regard. And also, special thanks to him for adding the bit about natural selection to my statement. Darwin's theory of evolution is undoubtedly one of the greatest triumphs of science. It showed how complexity can arise spontaneously in Nature. And yes, the bit about the principle of least action is also a very interesting and important point. Just like my statement about ordered complexity, this succinct statement (in physics, that is related to the least action principle, which finds the optimum path amongst contenders, which turns out to match classical reality) actually holds a lot of information about the nature of the universe.
2. What are your thoughts about the future of theoretical physics? Could there be such a thing as a unified theory, and if yes, will we ever discover it? Or do you think there is a limit to how much we can know about the universe?
We are tantalizingly close to a unified theory, but frustratingly far away at the same time. Three of the four natural interactions - electromagnetism, and the weak and strong nuclear interactions - have been encapsulated by the Standard Model. In it, material ingredients are represented by quarks and leptons, each a part of the class of subatomic particles known as fermions. Agents of force, in contrast, are represented by exchange bosons, including photons, the W and Z particles, and gluons. On top of that the Higgs mechanism lends rest mass to the fermions. The Standard Model is remarkably predictive. Yet, despite its successes, it does not explain while neutrinos always coil (a property technically called "chirality") in the left-handed direction, and even more glaringly, how gravitation fits into the picture. Years of attempts to find a quantum theory of gravitation has produced only sketches of ideas, rather than a satisfyingly predictive theory. I do hope that a full unified theory will be found eventually.
There's nothing to add. I have written a lot on this subject (the theory of everything). But I would like to say that Halpern's statement, "We are tantalizingly close to a unified theory, but frustratingly far away at the same time," really resonates with me! Let's see what the future has in store for us!
3. Richard Feynman said, "If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis that all things are made of atoms - little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied." Do you agree with Feynman? What, according to you, should be the one sentence that should be passed on to the next generation, if all other knowledge is destroyed?
Feynman’s statement is excellent, but even more succinct and important would be an expression of Newton’s second law, something like "force (a push or pull or something similar) causes changes in motion, with the resulting acceleration (amount of change over time) being inversely proportional to the mass (quantity of material) the force acts on."
That is a very well-thought-out answer to my question. Of course, Newton's second law contains a lot of information. Much of mechanics can be formulated from this law, and mechanics is the foundation of so many other areas of physics. So of course, if you could pass on just one sentence to the next generation, Newton's second law would be a good contender. However, it seems extremely unlikely that all of physics can be derived just from this statement. But that's probably true for Feynman's statement as well. Also, another contender could probably be the law of increase of entropy and the tendency of systems to reach an equilibrium state, breaking symmetry in the process.
4. Is science a boon or curse to humanity? Has it done more good than harm, or is it the other way round? Also, what do you think about the future of humankind? In particular, which, among climate change, nuclear war, pandemics and artificial intelligence, do you think is currently the most serious threat to humankind?
Science has the potential to either save or destroy humanity. I sincerely believe nuclear weapons remain the biggest threat by far, with their potential to render Earth lifeless (at least advanced life) in a frighteningly brief period of time, but climate change also gravely threatens global health. I am more optimistic, in comparison to those dire calamities, about trying to avoid the effects of future pandemics, because of the astonishing recent progress in the development of vaccines and antiviral medications. Finally, for AI, perhaps its biggest threats are disinformation, which challenges democracies that rely on fact-based decision making, and rampant military use, such as autonomous drones. Our hope lies in strong, fact-based universal education, helping the public understand science and statistics to combat false claims - such as, for example, the unsupported claim that vaccines cause autism.
Well, that makes sense to me. Once again, thanks to Halpern for this beautifully-framed answer.
5. This question is a bit weird, but I think this question is linked to a lot of big questions we ask about the fundamental nature of reality. If some event (by “event,” I mean a fundamental metaphysical event, so we can’t use the usual rules of science and probability to this) has occurred, is it more likely to occur again or less likely? And why? According to some, it is more likely to occur again since it is a possible event (it has already occurred once). However, my point is that the first occurrence of the event might change the conditions that favored its occurrence, so that the second occurrence of the event is much less likely. What do you say about this?
The answer to your question depends on whether it is a closed system that conserves energy, in which case recurrence is likely, or an open thermodynamic system, in which case entropy builds up and recurrence is unlikely within a reasonable time frame.
Of course, that makes sense. The only thing I'd like to say is that the law of conservation of energy, or the law of entropy are scientific laws that seem to hold in our universe. I'm not sure if these laws would hold at a fundamental level.
6. What do you think about the relation between physics and metaphysics? Can metaphysics, like physics, really aid us in understanding the true nature of reality, or is metaphysics purely speculation?
I think metaphysics provides an excellent scaffold to build systematic science. It asks deep questions about the nature of reality that offer a structure for scientific inquiry. Yet ultimately the answers to these questions must be matched to empirical data. Where such data is lacking, however, I think there remains room for logical inference.
That's, again, a beautiful answer. This was not really the answer I was expecting, but it is a unique and logical answer. It's a new way to look at metaphysics. Of course, asking deep questions about the nature of reality is what really gave birth to science in the first place. The statement, "...metaphysics provides an excellent scaffold to build systematic science," makes sense. However, I would like to add that depending too much on metaphysics is probably not a good idea for a scientist. I have already written a lot about my arguments regarding this. But Halpern's reply really helped me look at the question from a different perspective.
7. What is the most important lesson that the history and development of physics has taught you? And what is your advice to aspiring physicists?
The history of physics teaches us that there are many false starts and dead ends, that scientists are manifestly human with ample faults as well as strengths, and that there are many open questions to challenge today’s aspiring physicists.
Indeed! I couldn't have put it better myself.