How the Laws of Physics Lie [Paperback]

Nancy Cartwright (Author)

Book Description

Publication Date: July 7, 1983 | ISBN-10: 0198247044 | ISBN-13: 978-0198247043 | Edition: First Edition

In this sequence of philosophical essays about natural science, the author argues that fundamental explanatory laws, the deepest and most admired successes of modern physics, do not in fact describe regularities that exist in nature. Cartwright draws from many real-life examples to propound a novel distinction: that theoretical entities, and the complex and localized laws that describe them, can be interpreted realistically, but the simple unifying laws of basic theory cannot.

Editorial Reviews

Review

"An important and challenging book."--International Studies in Philosophy

About the Author

Nancy Cartwright is Professor Philosophy, London School of Economics.

Product Details

• Paperback: 232 pages
• Publisher: Oxford University Press, USA; First Edition edition (July 7, 1983)
• Language: English
• ISBN-10: 0198247044
• ISBN-13: 978-0198247043
• Product Dimensions: 8.3 x 5.9 x 0.6 inches
• Shipping Weight: 11.2 ounces (View shipping rates and policies)
• Average Customer Review: 3.3 out of 5 stars  See all reviews (3 customer reviews)
• Amazon Best Sellers Rank: #1,027,559 in Books (See Top 100 in Books)

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Customer Reviews

Most Helpful Customer Reviews

67 of 74 people found the following review helpful:

4.0 out of 5 stars Reynart's review misstates the issues, September 3, 2004

By 

Kyle Chadwick "Strether" (Alexandria, VA United States) - See all my reviews
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This review is from: How the Laws of Physics Lie (Paperback)

Actually 4+ stars.

The author -- a trained mathematical physicist -- isn't saying physics equations aren't "useful." She argues that they're generally not "true" in the ordinary sense that "grass is green" is true.

Indeed, the "law of gravity" is a great example: No two bodies REALLY interact SOLELY in accordance with the "law of gravity." In the real world, electromagnetic forces, inertia, gravitation from other bodies, and a host of other forces are at play -- and you must "correct" for those other forces, Luc, if you want to land safely on Mars.

So in what sense does "gravity" describe something that really happens? "Gravity," the author would argue, is better understood as a feature of a mental "model" that we build by imagining a world in which gravity is the ONLY force. The same is true of other "fundamental forces" that never exist in isolation.

It's also the case that physicists often use several different, incompatible mathematical models (up to 13 in one famous example!) to describe the same phenomenon, depending on exactly what they want to investigate about that phenomenon. All of the formulas are useful -- but they can't all be literally "true" in the grass-is-green sense.

It gets even more interesting when we enter the world of quantum mechanics and ask whether the "collapse of the wave function" is a "true" event that "truly" occurs out in the world somewhere. (She argues that it's not. You may recognize this as the "Schroedinger's cat" problem.) You might not care about these arguments, as I do, but it's only fair to describe them accurately.

16 of 17 people found the following review helpful:

5.0 out of 5 stars An important argument, but a difficult one, January 19, 2009

By 

Ken (Millbrook, New York, United States) - See all my reviews
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This review is from: How the Laws of Physics Lie (Paperback)

Cartwright's analysis is not easy to follow, but it helps to appreciate that the title is intentionally a pun. She is addressing the question of where the laws of physics stand, epistemologically (how they "lie") as well as how they fail to capture the full complexity of the world they are intended to describe (and thus how they are not true in the sense of giving a complete, God's-eye view of how things work). I think the critical idea is that the laws of physics are concepts that abstract away from a great many messy details that characterize things like interactions among bodies in the real universe. Each law thus comes with a ceteris paribus (all else being equal) clause attached. So, for example, the ideal gas law tells us how pressure, volume, and temperature are related, but it is reliable only for closed systems. When she says that such laws are not very useful she means something quite specific, namely, that such a law is, by itself, almost useless for understanding p-t-v relationships in open systems, like the Earth's atmosphere, where all else is NOT equal. Such laws are extremely useful as foundational concepts in our abstract understanding of how the universe works, but it can take years, or decades, or even centuries after the discovery of a law for engineers and technologists to figure out how to cash out all of the "all else being equal" clauses in the real situations where the laws operate. For example, the central laws governing fusion in plasma are pretty well understood, but turning that understanding into an operating fusion generator is proving extremely difficult. I do agree that there is some slippage in how the word "true" is being used in many of her discussions, with insufficient discussion of some important nuances, but far from rejecting realism, I think she is giving us a very important and powerful new set of conceptual tools for understanding what realism actually requires, epistemologically speaking. In summary, I think this is an extremely important argument in the philosophy of science, one that someone who wants to defend realism and the notion of objectivity has to understand and appreciate. It's tough going, but worth the effort.

23 of 97 people found the following review helpful:

1.0 out of 5 stars A terrible ratatouille, July 19, 2004

By 

Luc REYNAERT (Beernem, Belgium) - See all my reviews
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This review is from: How the Laws of Physics Lie (Paperback)

Nancy Cartwright juggles with all sorts of terms (phenomenological, theoretical, fundamental, realism, anti-realism, appearances, observable, non-observable, ceteris paribus ...).

But ultimately, why does she pretend that the laws of physics lie? She writes: 'Does this law (of universal gravitation) truly describe how bodies behave? Assuredly not.' (p. 57)

Why? Because there are other forces: electromagnetism and the strong and weak radioactive force.

She continues:'For bodies which are both massive and charged, the law of universal gravitation and Coulomb's law ... interact to determine the final force. But neither law by itself truly describes the final force ... These two laws are not true; worse they are not even approximately true.' (p. 57)

So what is true for her? Only the behaviour of bodies: an apple falling from a tree.

More, these crucial sentences are very confusing. The words 'final force' would better be replaced by 'result' (of the interaction). There is no 'new' physical force in play here.

But she goes even further (sic!):' I will allow that this law (of universal gravity) is a true law, or at least one that is held true, within a given theory. But it is not a very useful law.' (p. 58)

So, one of the 4 basic laws of physics is not useful. Also when mankind is bringing a satellite into orbit with a rocket?

And the 3 other forces? I hope the author doesn't have a computer.

Furthermore, the author believes that the wave collapse in the quantum universe doesn't 'truly' occur. Nevertheless, the decoherence theory learns us that it is almost certain that there are no existing particle waves in the whole universe. The quantum experiment with one particle in an empty space isn't realistic (although very important). In the universe, all existing particles are continuously bombarded by other particles.

Don't loose your time with this one.