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book reviews
Light non-fiction booksreviewed by T. Nelson |
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book reviews
Light non-fiction booksreviewed by T. Nelson |
Reviewed by T. Nelson
If you want to understand anything in modern physics, you have to know about Lagrangians. But what is a Lagrangian, and what does it do?
A Lagrangian is nothing more than the difference between kinetic energy and potential energy (L = T − V). From that simple description of how something changes, you can predict the behavior of almost anything that changes in some way. This book spells it out in detail. There are no skipped steps here and no “it is obvious that”s, but it's not a For Dummies text either. Just a matter-of-fact explanation of what they do and how to use them.
The Lagrangian is usually printed as an upper-case
in Brush or mathcal script.
The main advantage of Lagrangians over Newtonian mechanics is that you no longer need the concept of forces. Instead, as Hirvonen explains, everything is described by energy. This means no more worries about curved coordinate systems or non-inertial accelerating frames. There are no more “fictitious” forces to define and no problems with non-conservative forces like friction. And unlike Newtonian mechanics, Lagrangians can be used to derive conservation laws.
The math is quite easy to follow if you've had calculus and partial differential equations. Hirvonen even explains variational calculus and functionals. Although the formulas sometimes give you a simple numerical answer, often they can only be solved numerically. The real goal in physics, he says, is not to solve the equations, but to find them and gain understanding. After reading this book, you'll be so good at this you'll be creating Euler-Lagrange equations in your sleep.
The main drawback is that the examples showing exactly how to do that are too simple. For example, the see-saw problem of where to place weights on a beam to balance it against gravity is something you can calculate in your head. People would feel embarrassed if they had to define a Lagrangian and derive partial differential equations to solve it, but the author shows it definitely can be done.
This book is from the Profound Physics website, which has many free instructional articles about physics topics as well as some inexpensive courses.
jan 30 2025
Reviewed by T. Nelson
According to E.J. Lowe, metaphysics is the branch of philosophy that decides the boundaries of other fields, including other branches of philosophy. It decides whether human behavior is based on free will or by the laws of physics. It decides whether reality consists of things that exist in space and time, whether motion is an intrinsic property of a moving object, and whether motion is even possible at all. In short, it decides questions about the fundamental structure of reality as a whole.
Deciding things is one thing; deciding them correctly is another. Lowe says people all do metaphysics all the time, but not all people are doing it equally well, otherwise there would be no need for this book to exist.
So, is there a need for this book to exist or not? I'd say yes, but I'd also slap a label on the cover saying “Caution: may contain sophistry and/or metaphysics, inasmuch as the two are ontologically distinct.”
Most of this pleasantly written undergraduate-level textbook covers very basic stuff: presentism vs actualism, causation, modal logic, necessary vs contingent, identity, and possible worlds. A typical problem in metaphysics is: If a straight wire is bent, is it still the same wire? Another one, under what philosophers would call mereological essentialism, is: If the parts that get replaced in the ship of Theseus are used to build a new ship, do we now have two ships that can claim to be the original ship? [p.27] It leaves the impression that much of metaphysics deals with paradoxes.
Probably the most interesting section is Chapter 15, where Lowe talks about the nature of space. Physicists now mostly agree that empty space is not just “nothing.” But at one time, people were divided into substantivalists, who said space is a real thing, and relationalists, who said without objects space would not exist because it's derived solely from whatever is in it. One argument that came up was that a solitary hand must be either left or right, so handedness had to be an intrinsic property of a hand. This means you need space to exist independently of your hand so you can define the left and right parts of the hand. But then the question arose about what to do if spacetime turned out to be like a Möbius strip, so that moving your left hand a certain distance changed it into a right hand, and the arguments kind of went downhill after that. Lowe defends them by saying:
[W]e do not know for sure to which ontological category we belong—whether, for instance, we are immaterial souls, living organisms, or bundles of psychological states. In which case, we can hardly complain that it is impossible that we should be in such a predicament regarding space. [p. 285]
The idea that space could be like a Möbius strip might sound bizarre, but Roger Penrose's theory that space is composed of twistors may actually give it some support.*
Serious students would not need this book, as you can pick up these arguments from original sources. For a beginner, this book is logically written, non-technical and easy to follow, The downside is that we read philosophy not just to learn the general themes, but also to learn who said what, what the technical terms are, and why they've decided that previous writers on the topic were wrong. There's not much of that, so the question is: with all the jargon removed, all we have are stories about faulty arguments made with no reference to who made them. With no slagging off, no inscrutable hyphenated words, no shes and hers jammed into every sentence, is this still philosophy?
A good topic for the next 400-page metaphysics book.
* In Spinors and Space-Time , Penrose and Rindler talk about how a Möbius band could create a topologically distinctive vector space differing from normal space. An article that might be interesting to readers of this book is Quantum time travel revisited: noncommutative Möbius transformations and time loops" by J.E. Gough.
apr 14 2025. updated apr 16 2025
In this nicely written book, Ross Douthat says that scientific discoveries actually make Christianity more plausible. Douthat takes to task those people, including Richard Dawkins and Some Guy On The Internet (SGOTI), who he says pretend to know all the answers and then says religion is a better answer.
But while Douthat tries hard to be inoffensive, his argument doesn't work because he's somehow picked up a lot of strange ideas that don't represent what science actually says. For instance, he thinks that science has shown that a conscious observer collapses quantum possibility into physical reality. He also seems to believe science's only explanation of “fine-tuning” is the multiverse theory:
[I]t seems better to skeptics to posit an infinity of invisible universes, all inaccessible to one another, rather than make a concession to the seeming evidence for intelligence and order and design. [p. 102]
He takes the absence of an explanation of consciousness as evidence that the mind is incorporeal and not “reducible to physical substances and their interactions”:
In the end, the idea that we have available some clearly more rational or more scientific alternative to a “naively” supernatural understanding of the mind is itself fundamentally naive. [p.58]
Needless to say, that approach is not going to convince too many people, and it's probably not intended to. The book is really just a pep talk to explain why a religious person would believe and help them keep the faith.
In Chapter 1 he invokes the fine-tuning argument. Physicists say “fine tuning” is not real but one of many unsolved problems in the current theory: a good theory, which we don't yet have, would have no free physical constants, called free parameters, because it would explain why things are the way we observe them, so no fine-tuning would be necessary or possible. Douthat says fine-tuning means that God set the constants so humans could exist. If we believe the universe has orderly rules, he says, we must believe God must have created it.
In Chapter 2 he argues that human consciousness is non-corporeal because science can't explain it. In Chapter 3 he argues that too many people have had near-death experiences, so they must be real. Those are the three main reasons Douthat says should motivate people to “believe.”
I haven't read the New York Times, where Douthat works, in years. Maybe its science pages are full of jackasses who claim that the multiverse theory—if one can call it that—obtains wide currency in science and that neuroscientists have proved that consciousness is but an illusion. It doesn't and they haven't. The ‘multiverse’ and ‘quantum consciousness’ ideas weren't really theories; they were just physicists thinking out loud, testing outlandish ideas as they're supposed to do.
Out here in the real world, away from the Internet and the media bubble, most atheists don't fit his stereotype of the sneering arrogant prick that he portrays them as. Even so, it's not sneering to point out that our standard of proof differs from that in antiquity. The standard of proof now is to explain how you know. If you can't explain that, nobody will believe what you say.
Science doesn't have answers to everything, but religion doesn't have answers to any of the questions Douthat criticizes science for not knowing: in religion's creation story, the answer is just ‘a miracle occurred.’ There's nothing at all about the mystery of consciousness. There's a boatload of priceless wisdom, which is the province of religion; the history stories may be true or they may be morality tales, but to criticize science for not knowing answers to questions religion doesn't even ask is disingenuous.
For instance, Leviticus 11:16 and 11:17 say we're not supposed to eat owls. Why? What does God have against owls? Are they toxic? My guess it's because owls eat mice and rats, which reportedly makes them taste awful, but the Bible doesn't say.
Would it have killed God to add, “ . . . because they tasteth like shit”?
How did the universe get started? No scientifically literate person would write off the possibility of a deity. If some evidence came along we'd accept it. But unlike Pascal, my wager is that many of these questions will turn out like the other questions people used to agonize over, like whether we have free will or what is life: either the question is meaningless, or the answer is unimaginably complicated, or both.
Maybe it will turn out that none of us exists at all: we're just pixels somehow, and after the Great BSOD we get mercilessly shredded and converted to photons in somebody's electric heater. Or maybe the laws of physics will turn out to be sentient and the laws of civilized behavior don't really come from God but are principles that must be obeyed lest your civilization court a grisly death of internecine civil war.
I agree with Douthat on one point: there are mysteries in the universe. Religion is a valuable cultural tradition. If you want to be comforted or if you need a reason to behave morally, religion is a good place to turn. But if it's answers to the mysteries of the universe you want, no religion, not even my favorite, Cthulhucism, comes close to science.
mar 28 2025. updated mar 29 2025
Moved to here