Cosmological Koans: A Journey to the Heart of Physical Reality, by Anthony Aguirre

Category: Non-Fiction.  Rating: 4 out of 5.  Tags:  Cosmology, Physics, Quantum Physics, Relativity

Cosmological Koans is a book about the nature of physical reality, explored through a series of chapters modelled after Zen koans.  Not to be confused with the elementary particles called kaons, a koan is a riddle meant to provoke enlightenment.  The chapters also follow an unnamed character – “You” – on a journey across southern Eurasia.  The author, Anthony Aguirre, has a knack for finding concrete analogies to help explain abstract concepts, and the experiences of the book’s traveller provide a starting point for introducing various topics in physics.

An arrow flies toward the traveller, opening a discussion of Zeno’s paradox and the nature of time.  Is time infinitely divisible into smaller and smaller segments?  If so, how does anything move?  If not, what determines the smallest division?

A sailing boat moves, and balls of light are tossed back and forth between gondolas in Venice.  The laws of motion as discovered by Galileo and Newton are thus introduced, as well as the paradoxical differences in the behaviour of light compared to everyday objects.

General relativity, the curvature of space-time by massive objects, and quantum physics are similarly illustrated with analogies to everyday experiences.  One of my favourites is about the weird results seen in the double slit experiment:  some imagined monks enter a monastery through two gates, their spinning prayer wheels showing the effect of phase differences in creating interference patterns.

Other topics include entropy, the arrow of time, the nature of information, the origin of consciousness, and the many worlds theory.  To prove or disprove the many worlds theory, there’s a fun thought-experiment involving a strange form of Russian roulette.  It’s like you’re the cat in the Shrödinger’s cat experiment, only you’re the observer, too.

The wide-ranging discussion eventually boils down to some suggestions about the nature of reality.  There is no clear separation between the probabilistic world of quantum mechanics and the deterministic world of everyday life.  We think there must be a true state of the universe at any point in time, but fundamentally, not only is there uncertainty about that state, there is no instant we can call “now” that applies throughout the universe.  Matter isn’t solid.  An electron is “an excitation of the electron field, which pervades space-time.”  If you want to know what an electron field is, it’s “an entity able to create and destroy electrons!”  As Aguirre admits, “This is a rather displeasingly circular response.”  Another way of looking at it is that an electron is something that gives a specific set of answers when observed in experiments.  When we get those answers, we say we’ve observed an electron.  In quantum theory, there’s nothing more to it; it’s just information.

As with koans, the book provides lots of food for thought, but doesn’t always have the answers.  It does, however, provide comprehensive coverage of many of the big questions.

Visit my blog at Books I’ve Read, where you can search and filter by category, rating, tag and date.

A Brief History of Time: From the Big Bang to Black Holes, by Stephen W. Hawking

Category: Non-fiction; Rating: 3 out of 5; Tags: Cosmology, Physics

Published in 1988, Stephen Hawking’s “A Brief History of Time” has a reputation as a book frequently bought, but seldom read. I certainly contributed to that reputation – I received the book as a gift shortly after it was published, and after a single unsuccessful attempt to read it, left it to languish on my shelves for over thirty years. That has now changed, and I can proudly join the ranks of the few who have actually read the book from cover to cover.

The book covers the history of cosmological thinking from Galilean and Newtonian physics (in which objects move in space and time in response to forces), through the theories of relativity and quantum mechanics (in which time is not absolute, gravity is a distortion of spacetime, and there are unavoidable uncertainties in certain pairs of measurements). Two chapters explain the origin of black holes and their characteristics, and the final chapters address the fate of the universe, explain why we experience time as moving in one direction and not the other, and discuss the potential to unify the theories of electromagnetism and the weak and strong nuclear forces with a relativistic theory of gravity, perhaps using string theory. After the conclusion, there are brief biographies of Einstein, Galileo, and Newton, which are somewhat odd. The note about Einstein focusses on his role in politics, anti-nuclear campaigning, and Zionism; the one about Newton begins by saying, “Isaac Newton was not a pleasant man,” and highlights his disputes with other scientists.

The subtitle is quite explanatory – time, according to cosmological theory, begins with the big bang and ends in a black hole, at least for large enough collapsing stars and anything else that falls into one. These two singularities mark, in a sense, the boundaries of time.

Hawking doesn’t hide the messy nature of science, with its false starts and blind alleys. Having worked hard to convince the scientific community that there really was a singularity at the time of the big bang, he then changed his mind and worked to convince people that quantum effects meant there didn’t have to be a singularity.

Thirty years after the first attempt at reading it, it’s good to find the book humorous, clearly written and not too intimidating after all.

Visit my blog at Books I’ve Read, where you can search and filter by category, rating, tag and date.

In Search of the Multiverse, by John Gribbin

Category: Non-Fiction;  Rating: 3 out of 5;  Tags: Cosmology, Physics, Science

The Multiverse is a weird idea. There could be regions of spacetime, out of our reach, in which different physical parameters cause different rules to apply, and in which complex life as we know it could not develop.  These regions of spacetime could be separated from us by time, distance, or other dimensions.  We cannot communicate with them, yet there are interactions that suggest they must exist.

First, some definitions.  If the universe includes “all that there is,” then any other “universes” must really be just part of the larger universe, so we need to define some terms.  Following modern usage, Gribbin chooses “Universe” with a capital ‘U’ to indicate “everything…of which we could ever, in principle, have direct knowledge – our component of the Multiverse.”  A mathematical or computer model of spacetime is a “universe” with a small ‘u’, and may describe parts of the Multiverse that we cannot access.  So it’s really the “Multiverse” that includes “all that there is.”

There are different kinds of Multiverse.  Coming to grips with them means first delving into quantum physics and cosmology.  The weirdest might be the many worlds interpretation of quantum events, in which the universe splits every time a quantum event occurs – one universe with one outcome, another with the opposite.  Or one can think of an infinity of parallel universes, with some evolving very much like ours, but in ours the event turns out one way, and in the other it turns out the other way.  This interpretation explains the strange results of the double slit experiment, in which a single photon is interfered with in some mysterious way to deflect it depending on which slit is open.  David Deutsch, in “The Fabric of Reality”, says these mysterious interfering entities act just like invisible photons, and actually are photons in adjacent, parallel universes, interacting with ours only under these special circumstances.  It makes me wonder whether some clever coding scheme could be devised to communicate with, or at least prove the existence of at least one parallel universe.

Other parts of the Multiverse might just be too far away for us ever to observe them.  Still others might have been born from a bubble of quantum foam, conjured from the nothing of a vacuum fluctuation, and developed differently from ours, with different physical constants and ratios which could never lead to the evolution of life.  These could appear within our own Universe, or outside it.  Or perhaps our Universe was created by the collision in some higher dimension of two other universes – there are models and math to support all these theories.

As I read the book, I confess that the mind-expanding challenge of grasping the concept of yet another infinity of universes, or series of infinities of universes, with some infinities bigger than others, left me nodding in my chair.  Perhaps my powers of abstraction are not up to the task, or maybe I just had too much turkey over the Christmas break.

The Order of Time, by Carlo Rovelli

The Order of Time follows Carlo Rovelli’s earlier books, Seven Brief Lessons on Physics and Reality is Not What it Seems.  In The Order of Time, Rovelli explains how relativity, quantum mechanics, and the still-developing theory of quantum gravity affect our view of time.

We’re used to thinking of 3-dimensional space as a stage or framework, within which things change with time.  However, one by one, the things we thought were true about time have been disproved.

Time is not constant; it slows down near massive bodies, so on earth, it passes more slowly at sea level than it does in the mountains.

Time has no fundamental direction.  It has direction for us, but not in the fundamental equations of physics, except for things that involve the flow of heat and an increase in entropy.  We remember the past, but not the future, because we cannot distinguish between the many, many states that average out to our perception of the world.

There is no instant we may call “now” that applies to the whole universe. Because of relativity and the speed limit imposed by the speed of light, there is no special moment on some distant star that matches what we think of as the present here on earth.  Instead of thinking of an instant in time that applies to the whole universe, we must instead imagine an extended present that broadens with increasing distance from ourselves.  “There is our past: all the events that happened before what we can witness now.  There is our future: the events that will happen after the moment from which we can see the here and now.  Between this past and this future there is an interval that is neither past nor future and still has duration: fifteen minutes on Mars, eight years on Proxima b; millions of years in the Andromeda galaxy.”

Time is not a special, independent thing forming the structure of the universe, but an aspect of a dynamic field.  Physical variables change with respect to one another, but do not have to change with respect to time.

If time is quantized, as Rovelli thinks it is, time is not continuous, but makes jumps and materializes only in interactions with physical systems, and there is a minimum scale below which time cannot be divided.

Entropy, not energy, drives the world, and it only from our unique perspective that our conventional idea of time emerges.

Reality is Not What it Seems: The Journey to Quantum Gravity, by Carlo Rovelli

Carlo Rovelli is the author of the best-selling book “Seven Brief Lessons on Physics,” published in 2015.  “Reality is Not What it Seems” was actually written first, but not translated from Italian into English until now.  It provides more detail, more depth, and more historical context than “Lessons”.

Rovelli lays it out very clearly, with little tables showing what the universe was thought to have consisted of through history.  Let’s start with the Newtonian view of the world: there are particles, changing position in space as time passes.  This is the world most of us think we live in, with 3-dimensional space providing a stage or framework in which thing move around with time.  Faraday and Maxwell added the concept of fields, such as electromagnetic fields; these are modifications of the properties of space that change the way particles move.  With his theory of Special Relativity, Einstein showed that space and time are not separate, but a unified “spacetime”, so now particles were understood to move through spacetime under the influence of fields.

Then it starts to get weird.  General Relativity says that the gravitational field IS space.  And it’s not a fixed frame, it gets warped by mass.  So we’ve gone from thinking of the universe as being made of space, time, and particles (Newton); to space, time, particles, and fields (Faraday and Maxwell); to spacetime, particles and fields (Einstein); to (since space is a field), just fields and particles (Einstein again).

And then it gets weirder still.  Quantum Mechanics says that fields are granular; they are quantized; and particles are really the quanta of a field.  Dirac wrote the equations for those fields for electrons and other elementary particles.  Now all we have are quantum fields.  No space, no time, no particles.

This is the historical foundation that provides the jumping off point for more speculative theories about quantum gravity.  Given the historical development as provided by Rovelli, it seems almost inevitable that space must be quantized.  If fields are quantized, and gravity is a field, and gravity is space, then space is quantized!  Now we’re really through the looking glass, dealing with loop theory, quantum spin foams, black holes, and the eradication of time.  Rovelli has a knack for explaining things clearly, even poetically, to the point where you almost think you understand it.

The Universe Within: From Quantum to Cosmos, by Neil Turok

Niel Turok is the director of the Perimeter Institute for Theoretical Physics based in Waterloo, Ontario, and delivered the Massey Lectures in 2012.  This is a publication in book form of those lectures.  It’s a masterful summary of our understanding of physics to date, tracing the history of science from the time of the ancient Greeks to the modern day.

The history of discoveries in mechanics, electricity and magnetism, and light are all presented, along with the personalities involved in those discoveries.  Weird results from relativity and quantum physics are described, and there’s an excellent explanation of the importance of the double slit experiment.  The big bang is explained, and even the question, “What banged?” is considered, as well as the influence of big bang processes on the structure of the universe.  Dark matter, dark energy, and quantum computing make an appearance, too.  Turok does not neglect the human side of the equation either, examining the potential for harm or benefit to mankind depending on how scientific understanding is pursued and how the results are used.

This is a thoroughly engaging and readable account of the current state of understanding in physics, delivered by a world-class expert in the field.

Schrodinger’s Kittens and the Search for Reality, by John Gribbin

More quantum weirdness.  Gribbin updates ideas about the deeper meaning of quantum physics, starting with detailed descriptions of double slit experiments, which show conclusively the dual wave-particle nature of light, electrons, and even atoms.  Then he dives into a good historical summary of scientific ideas about light, from the ancient Greeks through Newton, Faraday, and Maxwell to Einstein.

Einstein showed that light has some very strange properties.  You may have heard of time dilation, where moving clocks run more slowly, or of Lorentz contraction, which describes the shortened length scales of moving bodies.  In the extreme, for something moving at light speed, time stands still, and there is no distance between objects.  An electromagnetic wave touches everything at once, or exists everywhere along its path at the same time.  For an entity like this, interfering with itself in a double slit experiment is easy!

A photon can spontaneously become an electron and a positron, and when an electron meets its anti-matter counterpart, they annihilate to produce a photon.  But we can equally view this process as involving an electron that meets a photon, sending the electron back in time (looking like a positron to us), until it meets another photon, which sends it forward in time again as an electron.

The vacuum of space is not empty at all, but consists of a superposition of many states of the electromagnetic field.  (Indeed, Einstein said it’s meaningless to talk of space in the absence of the fields that fill it).  When an atom emits a photon, it affects the surrounding  vacuum state.

These are strange phenomena, and Gribbin describes many more before exploring the underlying implications for the nature of reality.  He shows why the Copenhagen Interpretation cannot be the last word, and presents other interpretations (like the many worlds interpretation), labelling some of them “desperate remedies.”  The most reassuring analysis is in the section about what we mean when we say we know something.  There is only so far the reductionist approach to science can take us.  Are atoms the fundamental particles of reality?  Protons and neutrons?  Quarks?  Strings?  Photons?  In the end, the descriptions we use for quantum phenomena are all based on analogies to help us visualize, understand, and predict what’s going on.  None of them really say what a photon, electron, or quark really “is”, and each explanation is helpful in the specific circumstances to which it applies.

Relativity: The Special and the General Theory, by Albert Einstein

Having first read about Einstein in Walter Isaacson’s biography, I thought it would be interesting to read something by Einstein himself.  This book was written by Einstein for a general audience, for those “who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics.”  First written in 1916, my copy includes an appendix added to the fifteenth edition in 1952, and was published in 1961 by Einstein’s estate.

After reading Einstein, I can say that Isaacson did a good job summarizing Einstein’s reasoning in developing the special and general theories of relativity.  For the special theory, what stands out is how careful reasoning from two simple postulates, followed by a little basic algebra, gives rise to revolutionary physics.  For the general theory, I can’t say my level of understanding is any greater after reading Einstein’s book.  There are two problems.

First, these are tricky concepts, and discussing them stretches the capacity of language.  Reading a translation from the German, with its inevitably awkward sentence structures, only makes it harder.  Second, developing the general theory of relativity requires some advanced mathematics.  For special relativity, the math is at the high school algebra level, so it’s fairly straight-forward to follow it through from premise to conclusion and acquire a certain confidence, a belief, in the results, however strange they are.  For general relativity, the conclusions seem more like assertions, and we need to trust that someone with the requisite math skills has worked it out correctly.

However, what is again remarkable is that the general theory also starts with some simple postulates and easily visualized thought experiments.  Again, these are followed up by consistent reasoning and math to reach some extraordinary conclusions.  For example,  there’s no such thing as empty space – it doesn’t exist without something (whether matter or a field) to fill it.  To paraphrase Einstein, there is no space-time existing independently of the objects of physical reality.

Once again, weird but true.

In Search of Schrodinger’s Cat, by John Gribbin

Talk about things that don’t make sense.  Nothing about quantum physics makes sense.  It seems impossibly weird, and yet it’s true.

The book was recommended by an acquaintance after learning I had enjoyed reading Walter Isaacson’s biography of Einstein.  He also suggested I read a more recent book by Gribbin, Schrödinger’s Kittens, which I plan to do.

In his acknowledgements, Gribbin mentions a disappointing aspect of his university physics education:  “…the simplicity and beauty of the underlying ideas was smothered in a wealth of detail and mathematical recipes for solving specific problems with the aid of the equations of quantum mechanics.”  They were probably unrealistically simplified problems, too.  Using mathematical recipes in what Gribbin later calls “quantum cookery” successfully solves many problems, but can interfere with contemplating the utterly bizarre nature of quantum reality.  Gribbin wrote this book in part to compensate for that deficiency in his university physics education.

Consider the properties of light.  In some situations light behaves like a wave, and in others like a particle.  “Particles” like electrons also have wave-like properties in some situations.  But how can they be both?  Gribbin says they’re not, they never exhibit both wave-like and particle-like behaviour at the same time, and really they’re neither waves nor particles, but something…different.

If that seems strange, quantum physics also undermines the classical notion of causality.  Atomic nuclei can decay spontaneously, without anything to trigger the event and the associated emission of particles and energy.  Except that to a photon, time stands still, so instead of thinking of the atom as having emitted a photon, we can equally well view the photon as having travelled backwards in time to trigger the event.  It is equivalent.  That’s so strange, I have to repeat it: the two ways of viewing the event are equivalent.

The uncertainty principle tells us we cannot measure with absolute accuracy, and at the same time, both elements of certain pairs of complementary properties, such as position and momentum, or energy and time; there will always be an inherent uncertainty.  But it’s worse than that – until we measure it, the object does not have a definite position or momentum.  Our observations crystallize reality at the quantum level, and some say our observations have crystallized the reality of the entire universe.

The uncertainty principle allows particles to appear out of nothing.  Mass is energy, and there is uncertainty in the amount of energy available to a particle  for a short enough time, so there is uncertainty about whether a particle exists or not for that time.  A group of particles can appear out of vacuum, then recombine with one another and disappear.

And it just keeps getting weirder.  The cat in Schrödinger’s famous thought experiment really is alive and dead at the same time, or, equally consistent with quantum mechanics, the universe has split into two; one in which the cat is alive, and one in which it is dead.  We don’t know which one we’re in until we lift the lid and check on the cat.

We live in a very weird universe.

The 4 Percent Universe, by Richard Panek

If you liked Robert Kirshner’s 2002 book, The Extravagant Universe, then I think you might like Richard Panek’s 2011 book even more.  The subject is cosmology and the search for two key numbers describing the universe:  how fast is the universe expanding, and how quickly is that expansion slowing down?  Kirshner’s sub-title was “exploding stars, dark energy and the accelerating cosmos,” while Panek’s is “Dark Matter, Dark Energy, and The Race to Discover the Rest of Reality.”  Both sum things up very well.

The surprise is that the rate of expansion is not slowing down, it is increasing, thus requiring mysterious Dark Energy to explain the acceleration.  This, and the need for invisible mass to explain galactic rotation, represents a major change in our understanding of the cosmos.

Panek writes in a very accessible style, making the complex concepts of cosmology easy to understand.  He provides a balanced, outsider’s perspective when describing the race to use supernovas to calculate the two key numbers, where Kirshner was associated with one of the teams and writes from that team’s perspective.  Panek also provides an update on the efforts to understand dark matter and dark energy, and how strange it is that most of the universe – 72.8% dark energy, 22.7% dark matter – is unknown to us, leaving only 4.5% composed of familiar baryonic matter.