Paul Davies is a world-renowned theoretical physicist, cosmologist, and astrobiologist. He has published over 30 best-selling science books and hundreds of research papers across a wide range of scientific fields. His research interests have focused mainly on quantum gravity, early universe cosmology, the theory of quantum black holes, and the nature of time. He has also made important contributions to the field of astrobiology, and was an early advocate of the theory that life on Earth may have originated on Mars. For several years he has also been running a major cancer research project and developed a new theory of cancer based on tracing its deep evolutionary origins. Among his many awards are the 1995 Templeton Prize and the Faraday Prize from The Royal Society. In addition, the asteroid 6870 Pauldavies is named after him. In this exchange, we attempt to connect his most recent book, “What’s Eating the Universe? And Other Cosmic Questions” to the current war in Ukraine.
* The following text is an excerpt from the full interview, which may be viewed below.
Is there a connection between What’s Eating the Universe and what’s eating Europe?
I set about writing the book before the current war in Ukraine, although just after I had visited Ukraine I spent a week there in the middle of 2019 before the pandemic hit. I visited Lviv, Kyiv, and Odesa. Everything seemed completely normal and just like any other European country, though one of my colleagues in Phoenix said to be sure to leave before the Russians arrive, so I think many of us did fear that this was going to happen. In terms of relating it to the book, well of course, now this is a bit of a stretch but if I can paint a really big picture there are really two conflicting views about the nature of the universe: one is that it’s getting better and better the other is that it’s getting worse and worse.
So for a hundred years our understanding of cosmology was dominated by the second law of thermodynamics that’s the law that says left to itself everything naturally degenerates and runs down and the universe is no exception and although it may endure for billions or trillions of years at the end things will sort of grind or halt an interesting activity will cease but set against that when we look back at the big bang at the condition of the universe in the early stages after the big bang it was really extraordinarily simple and bland and the complexity that we see all around us from galaxies galactic structure stars planets and life and all of these things have emerged since and so alongside this degenerative arrow of time this running down of things we see something an arrow going in the opposite direction a buildup of complexity and richness and diversity and of course we like to position human life as part of that positive arrow that life on earth began simple it’s evolved to greater complexity and that the emergence of life and mind and beings who cannot just observe the world but comprehend it as part of this sort of upward directionality.
What are your impressions of the current situation in Europe?
A mistake now in the current international situation could be catastrophic and we just have to hope that there is some sort of inherent wisdom that pervades the planet. That means no one individual can doom us all and I believe that is, in fact, the case so I’m going to take the positive view that we will get through this dark time, though I never expected to see another war in Europe, which looks from all its features like a recapitulation of World War II something which I’ve studied in great detail and we all thought that that type of conflict where one country thinks well I think I’ll grab another because it’s going to be good for me… that that was all over and so this looks like an anachronism to me.
Where does the title of your book come from?
There are one or two anomalies on the largest scale of size in the universe and these have become increasingly passing over the last decade or so, one of these, which is where I get the title of the book from, is that there is a big cold patch in the Southern hemisphere. When I say big, even from our perspective it’s bigger than the size of the full moon and so it’s a big part of the universe. It’s almost as if a cosmic giant has taken a bite out of it. It’s like a super void nobody really knows what has caused this. That is, you know what it is. Is something actually eating that part of the universe? Is it a neighboring universe that sort of bumped into ours? Is it a blemish left over from the birth pangs of the universe because it wasn’t as smooth and quantum-driven as I have suggested? Is there some other explanation we don’t know? This is one example of how there’s unfinished business in cosmology.
Can you talk about the role that symmetry has played through the big questions that you ask in your book?
There is a chapter on symmetry because it deals with the question of where matter comes from. In the lab we can make matter… for example, at the large hadron collider at Cern you make particles but when you do that, you always make the same number of antiparticles. There’s a symmetry between matter and antimatter. Okay, what are antiparticles? Well, we know about the electron. There’s a sort of mirror image particle called the positron which has the same mass as the electron but a positive electric charge. And if the two come together they explode and cancel each other out and just turn into photons. So somehow the universe, when the big bang went bang, it made only matter and not antimatter. Something broke that symmetry and we don’t really know what is, but there are plenty of ideas around, plenty of models, that people have looked at but nothing has quite nailed it at the moment. So that symmetry has been broken and had it not been broken we wouldn’t be here discussing it. In addition, the symmetry between matter and antimatter connects with some other symmetries that are very familiar. One of these is the symmetry between left and right. We all know that in a mirror you reverse left and right and you might think that the laws of physics would be indifferent as to left-handedness or right-handedness but there are particles, fundamental particles, that have a property called spin. They’re spinning and of course, they spin in with a certain handedness. It turns out that the weak nuclear force breaks the symmetry between left-handedness and right-handedness, which came to be a great shock in 1956. That was the case so it’s another example of a symmetry break. On top of that, there is one symmetry that is dear to my heart, which is the symmetry between forward in time and backward in time. We’ve sort of been touching on that topic a bit in our conversation.
What do you mean by time symmetry?
One would think that the laws of physics wouldn’t care time forward time backward, so I’ll give you an everyday example – the earth is going around the sun viewed from a particular perspective you’d say it’s going clockwise around the sun. Could it go anti-clockwise around the sun? Well, absolutely. There’s nothing in the laws of physics to say it’s got to go clockwise and couldn’t go anticlockwise. It could be reversed and this seems to be true for pretty much all of physics – that if there’s any particular process then its reverse process is allowed. You might think, well, in daily life that doesn’t seem true. Rivers don’t flow uphill. But that’s because these are statistical effects. We’re back to causation and all that but at the microscopic level, down the atomic level, time forward time backward are symmetries but once again there’s a very tiny effect that breaks that symmetry. And what is really fascinating, I think, is that the left-right symmetry and the time forward time reverse symmetry connects up with this matter-antimatter symmetry in a very deep way and so these are really important aspects of trying to understand the fundamental nature of matter.
There’s another aspect that I refer to in the book, where symmetry comes in which is that the big bang was almost completely uniform. The universe started out in this very bland state, but now, of course, it’s much more complex. How do we understand this arrow of complexity? Well, one way is through symmetry breaking.