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Oolon Colluphid
26 Mar 2009, 10:44 AM
From the book review in today's Nature:

Complexity: A Guided Tour by Melanie Mitchell

Oxford University Press: 2009. 368 pp. £14.99, $29.95

Books and Arts
Nature 458, 411 (26 March 2009) | doi:10.1038/458411a; Published online 25 March 2009


Bringing clarity to complexity
Mark Buchanan

BOOK REVIEWED
-Complexity: A Guided Tour
by Melanie Mitchell

Oxford University Press: 2009. 368 pp. £14.99, $29.95


MEUL/ARCO/NATURE PICTURE LIBRARY

As a colony, ants perform complex tasks that individuals could not achieve alone, such as tending larvae.

For several decades, scientists studying complex systems — rich, collective systems such as ant colonies, economies and cells — have spoken of 'emergence', the mysterious process by which the collective whole acquires resilience, adaptability and other surprising properties, even though its components are simple. The archetypal example is the ant colony, which manages to forage intelligently for food and organize collective defence by exploiting the limited skills of its individual ant citizens.

The ideas of complexity have spread across science, and emergence has become a buzzword. Philosopher Mark Bedau has suggested, however, that it poses a puzzle, as it demands that two seemingly contradictory statements must be true. In complex systems, organized phenomena at higher levels depend on processes at lower levels: everything in a cell, for example, depends on the processes of atomic physics. Yet phenomena emerging at higher levels gain autonomy from lower levels: the body's organs and their interactions can be described and explained without reference to atomic physics.

How can something be dependent and autonomous at the same time? And why do so many systems in nature show this hierarchical organization? No one has answered these questions, but in Complexity, computer scientist Melanie Mitchell of the Santa Fe Institute, New Mexico, offers a valuable snapshot of the growing field of complex-systems science from which the answers may eventually arise. [...]

The book hits its stride in its latter half, with an insightful survey of recent developments in complex-network theory and scaling in biology.
Sounds like one for the brain-y people here, amongst others.

ETA: Amazon's 'Product Description':
As science probes the nature of life, society, and technology ever more closely, what it finds there is complexity. The sophisticated group behavior of social insects, the unexpected intricacies of the genome, the dynamics of population growth, and the self-organized structure of the World Wide Web - these are just a few examples of complex systems that still elude scientific understanding. Comprehending such systems seems to require a wholly new approach, one that goes beyond traditional scientific reductionism and that re-maps long-standing disciplinary boundaries. This remarkably accessible and companionable book, written by a leading complex systems scientist, provides an intimate, detailed tour of the sciences of complexity, a broad set of efforts that seek to explain how large-scale complex, organized, and adaptive behavior can emerge from simple interactions among myriad individuals. In this richly illustrated work, Melanie Mitchell describes in equal parts the history of ideas underlying complex systems science, the current research at the forefront of this field, and the prospects for the field's contribution to solving some of the most important scientific questions of our current century.

lpetrich
26 Mar 2009, 11:29 AM
Emergent properties are not exactly a new philosophical issue, it must be said.

I think that the solution to the seeming contradiction mentioned in the OP is that many emergent properties can be described and derived without reference to what they had emerged from.

To take a simple example, waves have properties that can be worked out independent of what is doing the waving. Properties like wavelengths, frequencies, interference, diffraction, etc.

More importantly, Darwin's principle of natural selection requires only entities that reproduce and transmit alterable hereditary information. It is independent of how those entities reproduce or how that information is represented and transmitted and altered.


Emergent properties also explain why we have been able to do any sort of science, because all of the properties of everything that we know of are the emergent properties of something or other. This extends to the most fundamental physics we know of, the Standard Model, because we expect it to be the emergent properties of some GUT in the low-energy limit.

Emergent properties also explain why we are able to do simulations, because simulations are designed to duplicate various emergent properties despite having different underlying mechanisms than the originals.


I recall someone in some board whom I shall not name, but who is the only person I have ever run into who disbelieves in emergent properties. When I mentioned waves, he claimed that they are composed of energy, and thus that they are not really emergent.

Eudaimonist
26 Mar 2009, 03:15 PM
Yay, emergence! :yay:


eudaimonia,

Mark

Ada
26 Mar 2009, 03:23 PM
Thank you.

It is now on my ever growing "Must Read" list.

:-) Ada

premjan
26 Mar 2009, 03:55 PM
Emergent properties are not really independent of the substrate, the dependence on it is just fairly coarse so some changes in the substrate do not substantially impact the emergent properties. Numbers and mathematics are an emergent property of the universe I would think.

Oolon Colluphid
26 Mar 2009, 04:07 PM
Emergent properties are not really independent of the substrate, the dependence on it is just fairly coarse so some changes in the substrate do not substantially impact the emergent properties.
Not sure I follow you. Except as analogies for each other, you cannot get much different than a sugar-phosphate chain and electronic 1s and 0s, yet an emergent property of them both being copied can be increased complexity and 'fitness' -- DNA making bodies, and evolutionary algorithms for computer programs. The substrates' only relationship is that they're both in chains where the order matters.

David B
26 Mar 2009, 05:29 PM
Thank you.

It is now on my ever growing "Must Read" list.

:-) Ada

Me too:)

David

premjan
26 Mar 2009, 06:55 PM
Not sure I follow you. Except as analogies for each other, you cannot get much different than a sugar-phosphate chain and electronic 1s and 0s, yet an emergent property of them both being copied can be increased complexity and 'fitness' -- DNA making bodies, and evolutionary algorithms for computer programs. The substrates' only relationship is that they're both in chains where the order matters.They depend on substrates that support the storage of information though. Using a substrate that jumbled information would not do. In this sense they aren't independent of the substrate. Calling the emergent property independent of the substrate is not quite right, it is supported by a fairly general kind of substrate.