Reality Is Not What It Seems: The Journey to Quantum Gravity

I read Carlo Rovelli’s book about quantum gravity (for the first time, it will take me a few goes, at least, to get all that is in it.) He is quite a good writer and this book, like his seven lessons in physics, is clear and extremely literate (I imagine he wrote it in Italian, but the English is smooth and demotic and lucid. It is a pleasure to read, which is not the norm in books that try to explain physics to non-specialists; God help the guy who tries to read the specialist literature.After a review from Democritus to Einstein et al, he gives us three big conclusions. At the smallest level, the universe is granular, relational, and indeterminate. He makes some other amazing statements like that ‘time’ disappears at this level and that things only exist when they collide into each other (or as ‘events’ as he puts it.) I have a notion about these other statements, but I have to determine if I understand the big three first.Everything (like Democritus and Feynman told us) is made of “atoms” or actually irreducible ‘quanta.’ Each of which is a unit of stuff that cannot be further divided; matter is not infinitely divisible (NB; big point.) Eventually, you get to a tight-pack of Plank scale bits of somethingness that all fit together. They in their constellation are gravity, space, and at bottom, everything else.There is no overarching, organizing anything outside these quanta. Time is absolutely a characteristic of the situation of the observer and the variable being measured “in” or as “time;” it measures differently at different altitudes and in different circumstances of proximity to matter and because of other factors. There are times all over the place and they do not generalize. At the level of the granular quanta, it disappears as a factor entirely.The stuff of the universe is not strictly determined in terms of how things interact and the results of any given intervention in it. We can pretty much depend on certain things happening as if by cause and effect on the macro level, but on the basic level, you get all kinds of stuff going on that is not absolutely predictable based on the setting conditions. This is the quantum probability/uncertainty thing, but it has to be understood in one of two ways; either it means our tools or our theory is inadequate and we don’t understand what is going on entirely, or the way the universe works is not determined by rules associated with forces, etc., and compatible with mathematics but instead things do their own thing, which usually results in rule governed outcomes, but doesn’t always.I am here confronted with the issue of the void that keeps on giving me a problem; there is no such thing as nothing and stuff cannot move around in it. Nothing cannot function either as a nominative, nor accusative, nor prepositional object in a sentence relating to stuff that exists except insofar as it is used to designate and absence that serves no purpose (e.g. “nothing happened,” or “you know nothing,” or “it is surrounded by nothing,” none of which are statements to be taken literally.) Therefore, matter cannot be conceptualized as floating around or moving in nothing or a ‘void’ (which is either nothing something and cannot function as both.) Democritus knew this right at the start; “space” he explained both is and isn’t nothing. He was just being gnomic and communicating that his atomic theory needed more work.If that is so, and how can you say anything else and be sane? Then certain conclusions follow. The quanta, for example, that make up everything are the whole show. There is nothing else in the cosmos but them, configured as they be. They are not in nothing (the statement doesn’t mean anything.) Nor are they in ‘space’ since they are space. They are not held together by gravity because they are gravity.More to the point, they are not held together by gravity because they are not “held together” at all. Since there is only these quanta irreducible and adhesive upon each other, they relate to no other cohesive force, they just are together with nowhere else to go.That means the quanta do not move; they cannot. There would have to be some medium of environment into which they could go and there isn’t anything but they themselves. They are irreducible so they cannot split into smaller chunks to let others slither through them. Since there is nothing but them, they have no interstices; there isn’t anything else in the cosmos that could come between them. Thus, you have inseparable grains and nothing else and these grains are where they are in relation to each other, but there is no force or principle or anything else that affects them all, like time or gravity or space or motion.They are not determined by any law or cause or force because no such thing exists outside of them (I am deliberately repetitious because the notion blows my mind.) For that reason, the prediction of occurrences among them is hit or miss. This is the part the author doesn’t exactly state, but if I am following him, the cosmos works something like this: There is no Aristotelian/Newtonian ‘time’ at the level of the quanta, but they configure according to the warped, curved, four-dimensional morphology of space-time. That is to say the that way the quanta fit together is not only according to the three axes of a prism, but also in relationships of sequence within the prism’s extension. That means that the entirety of the universe, including what we call past and present and future exists with all the quanta co-existent in all parts of space-time.Should this be the state of play of the cosmos, and I believe it is both in general relativity and in Rovelli’s construction (he calls it “loop” theory to distinguish it from the feckless “string” theory he deprecates) then, there is no determinacy or any causes or effects or any changes at all; just all the bits configured exactly how they are and the positions they have relative to each other and the observer are not caused by anything but just are.So, the discoveries of things are like looking at a map of twelve inches by six inches but only being able to see it a centimeter at a time from the left-hand margin. You guess what is coming in the next centimeter(s) based on what you already have seen of the terrain on the map, but a sink-hole or an inexplicable mountain peak can turn up on the map that relates to nothing else on the landscape, it is just there. The cosmos is like that; things don’t pop in and out of existence; the quanta that are there are just the quanta that are there, the observer has inferred the quark or electron out of stuff that he saw in one part of the map, but it isn’t to be inferred as in the next slice because the (existing) configuration of space-time just isn’t like that.The notion that only events exist is basically pretty anthropomorphic if you ask me, almost solipsistic. You only measure something by looking at it, which is a kind of collision. Since you cannot talk about things you cannot measure, only measured things exist according to this view. I think we can stretch and hazard that stuff exists even when not being measured, but I think the point is precious and not all that interesting.Change is something the observer infers when he looks over the cosmos along a sequence of space-time and mistakes the irreducible quanta, each of which is a grain that extends the Plank scale in ALL FOUR dimensions, as continuous, surviving unities across time. Parmenides knew this.Goedel understood this too, which is why he said that time travel is not a silly idea. As Einstein said, all parts of the cosmos are always available to the observer. They are all co-existent, which means they are all made of different stuff. Continuity is mental construction of the imaginative observer. (You can ask Descartes how the observer arises from these quanta and you will get an answer no more satisfactory than one I can give you, but consciousness is no more extraordinary than any of the rest of this stuff.)If I am right, and this is what the professor is saying, then what a great book since it made something quite clear to me that I had not understood hitherto.If I misunderstood it all (like I usually do) then I cannot blame him, and I still really enjoyed the book.

One of the very few books to provide an understandable discussion of quantum phenomena and cosmic structure that isn't overly simplistic, but doesn't require deep understanding of the mathematics that underlie and support the theory either. Readable, with engaging historical allusions. One star off for dismissing religion in a seemingly personal way when scientific dismissal would have been sufficient.

Carlo Rovelli is an Italian theoretical physicist who is the head of the Quantum Gravity group at Aix-Marseille University in France. He is one of the early proponents of the loop quantum gravity theory and the author of “Seven Brief Lessons on Physics.”As impressive as all of that is, however, don’t let it put you off if you are a lay person like me. While Rovelli admits early on in the book that he wants to make the book satisfying to his colleagues, he wrote it for us.It is a thoroughly accessible book that is brimming with enthusiasm for the topic, a quality that I have always found pleasing in its own right but essential to giving the reader the strength of curiosity necessary to get through a book about, say, quantum theory.The story, albeit one of revelation, not fiction, begins in 450BCE, on a boat from Miletus to Abdera. The author introduces us to Anaximander, and takes us all the way up to Stephen Hawking, the current crop of the top theoretical physicists in the world, and beyond, leaving us with a concise but thorough list of that which we still do not know or understand about the reality we live in.And that, in the end, is one of the defining qualities of this book. The author goes to great lengths to differentiate between established knowledge (i.e. That which has withstood the test of time and observation.), theory, and conjecture.There are only a handful of equations in the entire book and those can easily be ignored. Rovelli includes them only so that we non-colleagues know they exist and because he, in the most literal sense, finds them to be things of great beauty. (That enthusiasm I talked about.)He also goes out of his way to avoid the kind of scientific jargon that is hard to digest if you aren’t immersed in it everyday. The language is relatively plain and simple although the concepts may cause you to sit back and think for a minute before you are ready to fully absorb them.My favorite line in the whole book is, “Our culture is foolish to keep science and poetry separated…” As a writer and armchair philosopher, I have always felt the same way about science and philosophy, which, during the age of Newton, were considered two words to describe the same thing. This is actually a very quantum concept, since the three primary elements of quantum mechanics, or quantum theory, are granularity, indeterminism, and relationality. The world is finite (although very small in many respects), the future can only be defined by probabilities, and everything is definable only in relational context.I find relationality to be the most critical and relevant in this era of social media and political and cultural division. Individual words, or even sentences, are essentially meaningless without context. We will never understand each other, or agree on anything, if we don’t make the effort to understand the context of who we are and how we got there.The two pillars of twentieth-century physics are general relativity and quantum mechanics. And while the two “could not be more different from each other”, Rovelli shows that they are complementary, not contradictory, as many of us have been taught. General relativity deals with gravity, space, and time. Quantum theory, on the other hand, deals with some of the challenges to general relativity, such as the concept of infinity, and teaches us to think in terms of processes, not things. (“The theory [quantum theory] does not describe things as they ‘are’; it describes how things ‘occur,’…) In a way, I suppose, it brings general relativity to life.And what are some of the conclusions? Reality is relational, as noted. The water droplet at the tip of a wave has not been carried from some distant shore. Only the wave has made that journey. “Now doesn’t exist” and nothing is truly infinite. Time, as we have come to think of it, does not exist either. And even the most hardened stone is not motionless. (“The world is not made up of tiny pebbles. It is a world of vibrations, a continuous fluctuation…”) Only heat distinguishes the past from the future, which, of course, we can’t possibly know with certainty. Reality, including us, the homo sapiens, are not atoms. Everything is defined by "the order in which atoms are arranged." (Relationality, in the same way that the alphabet is just symbols until the letters are combined in a certain way to create an epic poem or story.) “Space is no longer different from matter.” And “the gravitational field [which is not fixed, but moves and undulates] is space.”This is a fascinating book (I read it in one day.) and I highly recommend it to anyone who wants to better understand the world around us. It is, in the end, a very optimistic take on the world and its future. And that is certainly something we can all use in the midst of the chaos we currently find ourselves in.