Rationalbrain comes to you from sunny Budapest today.
The first real sci-fi book I remember reading as a kid was called ‘The Universe Between‘, by Alan E. Nourse, and it blew my mind. It was my first exposure to hidden realities – places you could go by slipping through rips in the fabric of space, or falling through a wormhole, or indeed, even stepping through the back of the wardrobe. The adventures which ensued really tested the imagination, with Nourse describing what it was like in the other universe, invoking disconnected limbs, colours we don’t normally see, and so forth. There have since been countless such stories published, and I’m sure I’ve seen or read most of them.
Interest in, and exposure to such stories has, I think, fed into my ongoing interest in physics and cosmology, which seek to answer the basic questions of how and why we are here, and how and why things are the way they are. Readers of Douglas Adams will recognise this quest as the ‘answer to life, the universe, and everything’.
Since those days as a curious kid, the sci-fi stories have steadily moved from fi to sci, as they tend to do over time. Over the last hundred years or so, physicists and philosophers have sought that ulimate answer to all the questions – the single unifying law which describes our universe. For example, early on we discovered that that electricity and magnetism are the same phenomenon, now commonly (if not imaginatively) known as the electromagnetic force. Subsequent effort has been in unifying all known forces, including gravity. To cut a long, but interesting, story short, to date we have managed to devise pretty good laws to describe most of our physical world, via general relativity (for the macro world of tennis balls and planets) and quantum mechanics (for the micro world of atoms). However, those two areas have stubbornly refused to be united into a single set of laws.
Enter string theory, M-theory and the competing loop quantum gravity theories, on which great minds have been beavering away for the last twenty odd years. I won’t go into any of those now, lest you switch off completely. Suffice to say that it appears for the maths to work, we need to invoke multiple dimensions (beyond our 3 physical dimensions and one of time). And not just additional dimensions of our currently reality – additional whole universes. For a long time this was just that – a mathematical quirk to avoid crazy results when the numbers were crunched. But there is now a broad school of thought that these additional dimensions and universes (also known as the multiverse) may be real, and to understand our universe fully we will need to understand more about them. Put another way, many feel that the additional dimensions described by the maths reflect reality, and that our reality is more than just what we see before our eyes.
I should emphasise that even the most strident supporters of this notion concede that there is no direct evidence for these additional dimensions. However, as time goes by, more and more of what we are able to directly measure is consistent with the concept of additional dimensions. At the same time, we also need to grapple with the philosophical implications of such theories.
And so to the book review. One of my favourite authors in this area has been Brian Greene, a string theorist of some note. His latest effort is entitled ‘The Hidden Reality’, subtitled ‘Parallel universes and the deep laws of the cosmos’, and in it he presents the latest research and understanding in this fascinating area.
Greene distinguishes between 9 different forms of multiverse, and discusses them in detail. For each, there is some rationale based on explaining what we see around us today. The 9 forms are Quilted, Inflationary, Brane, Cyclic, Landscape, Quantum, Holographic, Simulated and Ultimate. Just reeling them off like that makes them sounds like pizzas, but then again, attempting a pithy summary of each make them sound too trivial and the stuff of real sci-fi, so I’ll avoid that, and let you follow up if you feel inclined.
In some of these multiverses, the universes are separated by vast distances, while others are hovering millimeters away. In yet another type, as Green puts it: “the very notion of their location proves parochial, devoid of meaning“.
My personal favourites (see? just like pizza) are the Holographic and Simulated variety. Believe it or not, the Holographic flavour has had some recent strong support by discoveries involving black holes. In short, it appears that the information thought to be lost by matter falling into a black hole, may actually be stored on the surface of its gravitational horizon. The Simulated type is straight out of Hitchhiker’s Guide or the Matrix, but is based on the inability to rule out the situation in which our reality is a sophisticated simulation, and perhaps that one day we will be able to create such simulations. Indeed, if the universe is infinite, this has certainly already happened.
But back to the book.
To reiterate, Greene is not some out-there sci-fi writer, but a serious scientist, and readily acknowledges how speculative this all is. His overall logic is that we are in a sense driven to such speculation by the path we’ve taken. This path has come to something of an impasse, and we are left with the strong feeling that something is missing to complete our understanding of the natural world. A central point is that this is where the maths has led us. In Greene’s own words:
“The subject of parallel universes is highly speculative. No experiment or observation has established that any version of the idea is realised in nature. So my point in writing this book is not to convince you that we’re part of a multiverse. I’m not convinced – and, speaking generally, no one should be convinced- of anything not supported by hard data. That said, I find it both curious and compelling that numerous developments in physics, if followed sufficiently far, bump into some variation on the parallel-universe theme. It’s not that physicists are standing ready, multiverse nets in their hands, seeking to snare any passing theory that might be slotted, however awkwardly into a parallel-universe paradigm. Rather, all of the parallel-universe proposals that we will take seriously emerge unbidden from the mathematics of theories developed to explain conventional data and observations.”
Great reading if you’re interested in this sort of thing, and a basic understanding of quantum mechanics and relativity won’t hurt. I do admit to getting lost in the discussion of fluxlines through tiny manifolds woven into the fabic of space, but in my view, skating over some of the technical detail in no way detracts from the big picture stuff. He has written the book in such a way that you can skip the technical bits, and tells you when safe to do so.
Greens wraps up with a nice discussion of the philosophy of this line of inquiry, and in particular the desire of the science establishment that all conjectures be testable (or at least falsifiable) to qualify as science. To again quote him:
“…this is, after all, how we built the scientific edifice. But I find it parochial to bound our thinking by the arbitrary limits imposed by where we are, when we are and who we are. Reality transcends these limits, so it’s to be expected that sooner or later the search for deep truths will too.”
And now? Back to this universe for a nice dinner, and to see Tosca at the Budpest Opera House.