Monday, September 23, 2013
Stephen Hawking + Leonard Mlodinow's "The Grand Design": Book Review
I'm no scientist, but I do enjoy popularizations of cosmology as well as rational vs. theological accounts of the Big Questions. I keep an open mind and I sought out "The Grand Design" to see if I could handle this version--of how progress began and where it's led us--better than the math in "A Brief History of Time," which simplified as it was overwhelmed me. My review sets the main points out and I will convey (if as a layman) how well they are explained.
During chapter two taking you along the history of physics, as to how laws of nature were defined despite the papacy, we learn how those advocating miracles, the suspension of laws, insisted the exceptions to these universal rules. Laplace, removing God from the picture Newton had drawn, formulated "scientific determinism." Cartesian philosophy sought to find out if free will persisted for humans, or whether determinism ruled. The authors side with a neural origin for behavior, not an outside agency such as a divine power. What is less easy to verify is a prediction, given multiples of trillions of variables, however. This combination of confidence and caution again is far from unexpected for a physicist to assert.
Hawking and Mlodinow commence their in-depth advocacy from the concept of determinism, with no miracles or exceptions to the laws of nature. They present how the laws arose and consider if they are the only possible ones. Chapter Three asks "What Is Reality?" "There is no picture- or theory-independent conception of reality." A "model-dependent realism" gives a framework of math-based model and a set of rules to observe. Reality of a model is not the point, but whether a model agrees with observation, our perception of objects. They use the evolution of theories about light to illustrate this.
Chapter Four, "Alternative Histories," enters into quantum mechanics. and the now-familiar co-existence with Newtonian laws. The double-slit experiment works at a sub-atomic level, sure, but it does not have much of an immediate impact on everyday life. Quantum physics by reflecting a "fundamental randomness in nature" allows probabilities "of various futures and pasts" instead of determining them "with certainty." It's shorter than Brian Greene's detailed version in "The Fabric of the Cosmos," but Mlodinow and Hawking feel less convincing than Greene about driving home why this discovery matters so.
Mlodinow's legendary predecessor at Caltech, Richard Feynman, invents a theory of "sum over histories" to show how particles can take all paths at once, if the slits are open. It also shows how Newtonian physics can arise from quantum physics. All possible histories thus construct the probability of an observation. This leads to no single past or history for the universe itself.
Chapter Five applies this concept to everything. Electro-magnetic forces enter. Maxwell's equations that govern the modes of transmission of this message from me to you then open into Einstein's relativity, into gravity and space-time. The challenge a century later comes in how to find field theories: "quantum versions of all the laws of nature." QED's processes via Feynman diagrams assist scientific calculation of how electrons can play off each other with an electromagnetic force. But, "this plague of infinities" can be hard to handle. QCD comes in to help; Grand Unified Theories appear so far not to pan out in tiny details, so a standard ad hoc model's accepted. Supersymmetry and supergravity are posited as scientists try to work around the impasse.
Then, string theory arrives, if in five versions. M-theory may help, but we may be stuck with theories for different versions of reality by "model-dependent realism," and some overlap, as with a Mercator map of regions combined to cover the whole globe in a flat dimension, to use the authors' earlier analogy. M-theory lets us have different (10 to the 500th power) universes with their own laws, "depending on how the internal space is curled."
"Choosing Our Universe" for the sixth chapter looks closer at our origin story, the Big Bang. Creation for cosmologists cognizant of quantum theory cannot match Einstein's general relativity, as the breakdown back into Planck size of the universe just after the Bang must be accepted. Time vanishes then, and only 4-d space existed. (For all the otherwise refreshing lack of formulas, figures of Planck time vs. Planck space would have assisted this necessary distinction of the two states. Oddly, both terms are absent from the glossary.)
Therefore, if time behaves like space, "it removes the age-old objection" to not only a beginning to the universe, but it shows how the laws of science and not a prime mover as God account for the origin. (I am on a long wait list for Lawrence Krauss' 2012 "A Universe from Nothing," which may take a similar rationale, although many religious believers assert that this thinking merely replaces one Mover with a set of Moving Laws, and leaves the question unresolved if the origin remains a "spontaneous" event.) Hawking and Mlodinow take this on with less vigor than I expected, frankly, and remain content to attest that given the lack of a "single definite history" for the universe within Feynman's limitless array of probable multiverses, the replacement of a "bottom-up" model with a "probability amplitude" suffices as a simpler (!) explanation.
They segue 3/4 of the book through into a "top-down" provocative application of the Feynman sum and the denial of independent existences outside of observation as "We create history by our observation, rather than history creating us" without sufficiently elaborating the multiverse approach as better than a single history one for cosmology. I get their point, but it seems to lack emphasis. Teasing out the "probability amplitude," they argue that each universe has different laws and values with allowance for "all possible internal spaces." Fine, if our universal laws "are not uniquely determined," but this seems strangely anticlimactic, if no GUT is to be found after all. Logic may insist we aren't so special after all, and we have no grand gift awaiting us to unwrap.
"The Apparent Miracle" as a seventh chapter places us in a "Goldilocks zone" where temperatures are "just right." Mlodinow and Hawking discuss the weak and strong anthropic principles, therefore, that attempt to elucidate our serendipity. What they call "fine-tuning coincidences" in physical laws may never convince believers who assume a divine plan. But as astrophysicists, the authors remain content to replace "providential design" with a calm if understated (despite the hostility with which many receive its arguments) insistence that if cosmology lifts boundaries and allows multiverses, then this only underlines how many such solar systems exist by the billions out there. We aren't that special after all.
The final chapter asks if we must rely on M-theory for the Grand Design. Why is there something and not nothing, what is the meaning of our existence, and why do we have this set of laws and not another? The laws of nature don't miraculously ring out and satisfy these enduring queries. Hawking and Mlodinow predictably deny the Big Questions at least in the answers preferred by Aquinas. They refuse to invoke divine beings. We're trapped in our mental concepts. They use "The Game of Life" logical set of laws to determine a 2-d universe invented by John Conway in 1970 to demonstrate an analogous situation. "Your reality depends on the model you employ."
They leap from this game, which gains considerable commentary, back into our world (which created that game!) to show how universal laws (in our universe) spring out of "spontaneous creation" when gravity's followed back to its origins as a shaper of space-time, and as a balance of positive and negative energy of matter. M-theory remains as the consistent model of "the most general supersymmetric theory of gravity." It's as close as Einstein sought to get to a unified theory--I am not sure if it's "grand." Abstract logic leads back to the world we see. That's it. This explanation's itself very compressed, however, and raced ahead of me even if it was articulated in basic English.
I wanted more, but it appears this is all I'll get. M-theory is asserted as the best explanation; multiverses exist where laws will explain what our universe cannot for it's our universe, after all. Can profundity can exist alongside simplicity? (Amazon US 7-6-2012)