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Physicist, Case Western Reserve University; Author, Atom

What is the Universe Made of and How Will it End?

Like 99% of particle physicists, and 95% of cosmologist (perhaps 98% of theorists and 90% of observers, to be more specific), I was relatively certain that there was precisely enough matter in the universe to make it geometrically flat.  What does geometrically flat mean?  Well, according to general relativity it means there is a precise balance between the positive kinetic energy associated with the expansion of space, and the negative potential energy associated with the gravitational attraction of matter in the universe so that the total energy is precisely zero. This is not only mathematically attractive, but in fact the only theory we have that explains why the universe looks the way it does today tends to predict a flat universe today.

Now, the only problem with this prediction is that visible matter in the universe only accounts for a few percent of the total amount of matter required to make the universe flat.  Happily, however, during the period from 1970 or so to the early 1990's it had become abundantly clear that our galaxy, and indeed all galaxies are dominated by 'dark matter'... material that does not shine, or, as far as we can tell, interact electromagnetically.  This material, which we think is made up of a new type of elementary particle, accounts for at least 10 times as much matter as can be accounted for in stars, hot gas etc.. With the inference that dark matter existed in such profusion, it was natural to suspect that there was enough of it to account for a flat universe.

The only problem was that the more our observations of the universe improved, the less evidence there appeared to be that there was enough dark matter to result in a flat universe. Moreover, all other other indicators of cosmology, from the age of the universe, to the data on large scale structure, all began to suggest a flat universe dominated by dark matter was inconsistent with observation.  In 1995, this led my colleague Mike Turner and I to suggest that the only way a flat universe could be consistent with observation was if most of the energy, indeed almost 75% of the total energy, was contributed not by matter, but by empty space!

As heretical as our suggestion was, to be fair, I think we were being more provocative than anything, because the one thing that everyone knew was that the energy of empty space had to be precisely zero.  The alternative, which would have resulted in something very much like the 'Cosmological Constant' first proposed by Einstein when he incorrectly thought the universe was static and needed some exotic new adjustment to his equations of general relativity so that the attractive force of gravity was balanced by a repulsive force associated with empty space, was just too ugly to imagine.

And then, in 1998 two teams measuring the recession velocity of distant galaxies using observations of exploding stars within them to probe their distance from us at the same time discovered something amazing.  The expansion of the universe seemed to be speed up with time, not slowing down, as any sensible universe should be doing!  Moreover, if one assumed this acceleration was caused by a new repulsive force throughout empty space that would be caused if the energy of empty space was not precisely zero, then the amount of extra energy needed to produce the observed acceleration was precisely the amount needed to account for a flat universe!

Now here is the really weird thing.  Within a year after the observation of an accelerating universe, even though the data was not yet definitive, I and pretty well everyone else in the community who had previously thought there was enough dark matter to result in a flat universe, and who had previously thought the energy of empty space must be precisely zero had completely changed our minds... All of the signals were just too overwhelming to continue to hold on to our previous rosy picture... even if the alternative was so crazy that none of our fundamental theories could yet account for it.

So we are now pretty sure that the dominant energy-stuff in our universe isn't normal matter, and isn't dark matter, but rather is associated with empty space!  And what is worse (or better, depending upon your viewpoint) is that our whole picture of the possible future of the universe has changed..  An accelerating universe will carry away almost everything we now see, so that in the far future our galaxy will exist alone in a dark, and seemingly endless void....

And that is what I find so satisfying about science.  Not just that I could change my own mind because the evidence of reality forced me to... but that the whole community could throw out a cherished notion, and so quickly!  That is what makes science different than religion, and that is what makes it worth continuing to ask questions about the universe ... because it never fails to surprise us.

Psychologist, Harvard University; Author, Wet Mind

The World in the Brain

I used to believe that we could understand psychology at different levels of analysis, and events at any one of the levels could be studied independently of events at the other levels. For example, one could study events at the level of the brain (and seek answers in terms of biological mechanisms), the level of the person (and seek answers in terms of the contents of thoughts, beliefs, knowledge, and so forth), or the level of the group (and seek answers in terms of social interactions). This approach seemed reasonable; the strategy of "divide and conquer" is a cornerstone in all of science, isn't it? In fact, virtually all introductory psychology textbooks are written as if events at the different levels are largely independent, with separate chapters (that only rarely include cross-references to each other) on the brain, perception, memory, personality, social psychology, and so on.

I've changed my mind. I don't think it's possible to understand events at any one level of analysis without taking into account what occurs at other levels. In particular, I'm now convinced that at least some aspects of the structure and function of the brain can only be understood by situating the brain in a specific cultural context. I'm not simply saying that the brain has evolved to function in a specific type of environment (an idea that forms a mainstay of evolutionary psychology and some areas of computer vision, where statistics of the natural environment are used to guide processing). Rather, I'm saying that to understand how any specific brain functions, we need to understand how that person was raised, and currently functions, in the surrounding culture.

Here's my line of reasoning. Let's begin with a fundamental fact: The genes, of which we have perhaps only some 30,000, cannot program us to function equally effectively in every possible environment. Hence, evolution has licensed the environment to set up and configure each individual's brain, so that it can work well in that context. For example, consider stereovision. We all know about stereo in audition; the sound from each of two loudspeakers has slightly different phases, so the listener's brain glues them together to provide the sense of an auditory panorama. Something similar is at work in vision. In stereovision, the slight disparity in the images that reach the two eyes are a cue for how far away objects are. If you're focused on an object directly in front of you, your eyes will converge slightly. Aside from the exact point of focus, the rest of the image will strike slightly different places on the two retinas (at the back of the eye, which converts light into neural impulses), and the brain uses the slight disparities to figure out how far away something is.
There are two important points here. First, this stereo process — of computing depth on the basis of the disparities in where images strike the two retinas — depends on the distance between the eyes. And second, and this is absolutely critical, there's no way to know at the moment of conception how far apart a person's eyes are going to be, because that depends on bone growth — and bone growth depends partly on the mother's diet and partly on the infant's diet.
So, given that bone growth depends partly on the environment, how could the genes set up stereovision circuits in the brain? What the genes did is really clever: Young children (peaking at about age 18 months) have more connections among neurons than do adults; in fact, until about eight years old, children have about twice as many neural connections as they do as adults. But only some of these connections provide useful information. For example, when the infant reaches, only the connections from some neurons will correctly guide reaching. The brain uses a process called pruning to get rid of the useless connections. The connections that turn out to work, with the distance between the eyes the infant happens to have, would not be the ones that would work if the mother did not have enough calcium, or the infant hadn't had enough of various dietary supplements.
This is a really elegant solution to the problem that the genes can't know in advance how far apart the eyes will be. To cope with this problem, the genes overpopulate the brain, giving us options for different environments (where the distance between eyes and length of the arms are part of the brain's "environment," in this sense), and then the environment selects which connections are appropriate. In other words, the genes take advantage of the environment to configure the brain.

This overpopulate-and-select mechanism is not limited to stereovision. In general, the environment sets up the brain (above and beyond any role it may have had in the evolution of the species), configuring it to work well in the world a person inhabits. And by environment I'm including everything outside the brain — including the social environment. For example, it's well known that children can learn multiple languages without an accent and with good grammar, if they are exposed to the language before puberty. But after puberty, it's very difficult to learn a second language so well. Similarly, when I first went to Japan, I was told not even to bother trying to bow, that there were something like a dozen different bows and I was always going to "bow with an accent" — and in my case the accent was so thick that it was impenetrable. 
The notion is that a variety of factors in our environment, including in our social environment, configure our brains. It's true for language, and I bet it's true for politeness as well as a raft of other kinds of phenomena. The genes result in a profusion of connections among neurons, which provide a playing field for the world to select and configure so that we fit the environment in which we inhabit. The world comes into our head, configuring us. The brain and its surrounding environment are not as separate as they might appear. 

This perspective leads me to wonder whether we can assume that the brains of people living in different cultures process information in precisely the same ways. Yes, people the world over have much in common (we are members of the same species, after all), but even small changes in the wiring may lead us to use the common machinery in different ways. If so, then people from different cultures may have unique perspectives on common problems, and be poised to make unique contributions toward solving such problems.

Changing my mind about the relationship between events at different levels of analysis has led me to change fundamental beliefs. In particular, I now believe that understanding how the surrounding culture affects the brain may be of more than merely "academic interest."

Research Psychologist; Founder, Klein Associates; Author, The Power of Intuition

Exchanging Your Mind

It's generally a bad idea to change your mind and an even worse idea to do it publicly. Politicians who get caught changing their minds are labeled "flip-floppers." When managers change their minds about what they want they risk losing credibility and they create frustration in subordinates who find that much of their work has now been wasted. Researchers who change their minds may be regarded as sloppy, shooting from the hip rather than delaying publication until they nail down all the loose ends in their data.

Clearly the Edge Annual Question for 2008 carries with it some dangers in disclosure:  "What have you changed your mind about? Why?" Nevertheless, I'll take the bait and describe a case where I changed my mind about the nature of the phenomenon I was studying.

My colleagues Roberta Calderwood, Anne Clinton-Cirocco, and I were investigating how people make decisions under time pressure. Obviously, under time pressure people can't canvass all the relevant possibilities and compare them along a common set of dimensions. So what are they doing instead?

I thought I knew what happened. Peer Soelberg had investigated the job-choice strategy of students. In most cases they quickly identified a favorite job option and evaluated it by comparing it to another option, a choice comparison, trying to show that their favorite option was as good as or better than this comparison case on every relevant dimension. This strategy seemed like a very useful way to handle time pressure. Instead of systematically assessing a large number of options, you only have to compare two options until you're satisfied that your favorite dominates the other.

To demonstrate that people used this strategy to handle time pressure I studied fireground commanders. Unhappily, the firefighters had not read the script. We conducted interviews with them about tough cases, probing them about the options they considered. And in the great majority of cases (about 81%), they insisted that they only considered one option.

The evidence obviously didn't support my hypothesis. Still, I wasn't convinced that my hypothesis was wrong. Perhaps we hadn't phrased the questions appropriately. Perhaps the firefighters' memories were inaccurate. At this point I hadn't changed my mind. I had just conducted a study that didn't work out.

People are very good at deflecting inconvenient evidence. There are very few facts that can't be explained away. Facts rarely force us to change our minds.

Eventually my frustration about not getting the results I wanted was replaced by a different emotion: curiosity. If the firefighters weren't comparing options just what were they doing?

They described how they usually knew what to do once they sized up the situation. This claim generated two mysteries:  How could the first option they considered have such a high likelihood of succeeding?  And how could they evaluate an option except by comparing it to another?

Going back over the data we resolved each of these mysteries. They were using their years of experience to rapidly size up situations. The patterns they had acquired suggested typical ways of reacting. But they still needed to evaluate the options they identified. They did so by imagining what might happen if they carried out the action in the context of their situation. If it worked, they proceeded. If it almost worked then they looked for ways to repair any weaknesses or else looked at other typical reactions until they found one that satisfied them.

Together, this forms a recognition-primed decision strategy that is based on pattern recognition but tests the results using deliberate mental simulation. This strategy is very different from the original hypothesis about comparing the favorite versus a choice comparison.

I had an advantage in that I had never received any formal training in decision research. One of my specialty areas was the nature of expertise. Therefore, the conceptual shift I made was about  peripheral constructs, rather than core constructs about how decisions are made. The notions of Peer Soelberg that I was testing weren't central to my understanding of skilled performance.

Changing one's mind isn't merely revising the numerical value of a fact in a mental data base or changing the beliefs we hold. Changing my mind also means changing the way I will then use my mind to search for and interpret facts. When I changed my understanding of how the fireground commanders were making decisions I altered the way I viewed experts and decision makers. I altered the ways I collected and analyzed data in later studies. As a result, I began looking at events with a different mind, one that I had exchanged for the mind I previously had been using.

Bendheim Professor of Economics and Public Affairs at Princeton University; Author, What Makes a Terrorist: Economics and the Roots of Terrorism

I used to think the labor market was very competitive, but now I think it is better characterized by monopsony, at least in the short run.

Quantum Mechanical Engineer, MIT, Author, Programming the Universe

I have changed my mind about technology.

I used to take a dim view of technology. One should live one's life in a simple, low-tech fashion, I thought. No cell phone, keep off the computer, don't drive. No nukes, no remote control, no DVD, no TV. Walk, read, think — that was the proper path to follow.

What a fool I was! A dozen years ago or so, by some bizarre accident, I became a professor of Mechanical Engineering at MIT. I had never had any training, experience, or education in engineering. My sole claim to engineering expertise was some work on complex systems and a few designs for quantum computers. Quantum-mechanical engineering was in its early days then, however, and MIT needed a quantum mechanic. I was ready to answer the call.

It was not my fellow professors who converted me to technology, uber-techno-nerds though they were. Indeed, my colleagues in Mech. E. were by and large somewhat suspicious of me, justifiably so. I was wary of them in turn, as one often is of co-workers who are hugely more knowledgeable than one is oneself. (Outside of the Mechanical Engineering department, by contrast, I found large numbers of kindred souls: MIT was full of people whose quanta needed fixing, and as a certified quantum mechanic, I was glad to oblige.) No, it was not the brilliant technologists who filled the faculty lunchroom who changed my mind. Rather, it was the students who had come to have me teach them about engineering who taught me to value technology.

Your average MIT undergraduate is pretty technologically adept. In the old days, freshmen used to arrive MIT having disassembled and reassembled tractors and cars; slightly later on, they arrived having built ham radios and guitar amplifiers; more recently, freshmen and fresh women were showing up with a scary facility with computers. Nowadays, few of them have used a screwdriver (except maybe to install some more memory in their laptop), but they are eager to learn how robots work, and raring to build one themselves.

When I stepped into my first undergraduate classroom, a controls laboratory, I knew just about as little about how to build a robot as the nineteen and twenty year olds who were expectantly sitting, waiting for me to teach them how. I was terrified. Within a half an hour, the basis for my terror was confirmed. Not only did I know as little as the students, in many cases I knew significantly less: about of the quarter of the students knew demonstrably more about robotics than I, and were happy to display their knowledge. I emerged from the first lab session a sweaty mess, having managed to demonstrate my ignorance and incompetence in a startling variety of ways.

I emerged  from the second lab session a little cooler. There is no better way to learn, and learn fast, than to teach. Humility actually turns out to have its virtues, too. It turns out to be rather fun to admit one's ignorance, if that admission takes the form of an appeal to the knowledge of all assembled. In fact, it turned out that, either through my training in math and physics, or through a previous incarnation, I possessed more intuitive knowledge of control theory than I had any right to, given my lack of formal education on the subject. Finally, no student is more empowered than the one who has just correctly told her professor that he is wrong, and showed him why her solution is the right one.

In the end, the experience of teaching the technology that I did not know was one of the most intellectually powerful of my life. In my mental ferment of trying to learn the material faster and deeper than my students, I began to grasp concepts and ways of looking at the world, of whose existence I had no previous notion. One of the primary features of the lab was a set of analog computers, boxy things festooned with dials and plugs, and full of amplifiers, capacitors, and resistors, that were used to simulate, or construct an analog, of the motors and loads that we were trying to control. In my feverish attempt to understand analog computers, I constructed model for a quantum-mechanical analog computer that would operate at the level of individual atoms. This model resulted in one of my best scientific papers. In the end, scarily enough, my student evaluations gave me the highest possible marks for knowledge of the material taught.

And technology? Hey, it's not so bad. When it comes to walking in the rain, Goretex and fleece beat oilskin and wool hollow. If we're not going to swamp our world in greenhouse gases, we damn well better design dramatically more efficient cars and power plants. And if I could contribute to technology by designing and helping to build quantum computers and quantum communication systems, so much the better. Properly conceived and constructed technology does not hinder the simple life, but helps it.

OK. So I was wrong about technology. What's my next misconception? Religion? God forbid.

Computer Scientist; 1st Generation Artificial Intelligence Pioneer, Stanford University

Attitudes Trump Facts

I have a collection of web pages on the sustainability of material progress that treats many problems that have been proposed as possible stoppers. I get email about the pages, both unfavorable and favorable, mostly the latter.

I had believed that the email would concern specific problems or would raise new ones, e.g. "What about erosion of agricultural land?"

There's some of that, but overwhelmingly the email, both pro and con, concerns my attitude,  not my (alleged) facts. "How can you be so blithely cornucopian when everybody knows ..." or "I'm glad someone has the courage to take on all those doomsters."

It seems, to my surprise, that people's attitude that the future stems at least as much from personality as from opinions about facts. People look for facts to support their attitudes — which have earlier antecedents.

Neuroscientist, Chairman, Board of Directors, Human Science Center and Department of Medical Psychology, Munich University, Germany; Author, Mindworks

Being Caught In The Language Trap — Or Wittgenstein's Straitjacket

When I look at something, when I talk to somebody, when I write a few sentences about "what I have changed my mind about and why", the neuronal network in my brain changes all the time and there are even structural changes in the brain. Why is it that these changes don't come to mind all the time but remain subthreshold?  Certainly, if everything would come to mind what goes on in the brain, and if there would not be an efficient mechanism of informational garbage disposal, we would end up in mental chaos (which sometimes happens in unfortunate cases with neuronal dysfunctioning). It is only sometimes that certain events produce so much neuronal energy and catch so much attention that a conscious representation is made possible.

As most neuronal information processing remains in mental darkness, i.e. happens on an implicit level, it is in my view impossible to make a clear statement why somebody changed his or her mind about something. If somebody gives an explicit reason for having changed the mind about something, I am very suspicious. As "it thinks" all the time in my brain, and as these processes are beyond voluntary control, I am much less transparent to myself as I might want, and this is true for everybody. Thus, I cannot give a good reason why I changed my mind about a strong hypothesis or even belief or perhaps a prejudice in my scientific work which I had until several years ago.

A sentence of Ludwig Wittgenstein from his Tractatus Logico-Philosophicus (5.6) was like a dogma for me: "Die Grenzen meiner Sprache bedeuten die Grenzen meiner Welt. — The limits of my language signify the limits of my world " (my translation). Now I react to this sentence with an emphatic "No!".

As a neuroscientist I have to stay away from the language trap. In our research we are easily misguided by words. Without too much thinking we are referring to "consciousness", to "free will", to "thoughts", to "attention", to the "self", etc, and we give an ontological status to these terms. Some people even start to look at the potential site of consciousness or of free will in the brain, or some people ask the "what is ..." question that never can find an answer. The prototypical "what is ..." question was formulated 1600 years ago by Augustinus who said in the 11th book of his Confessions: "Quid est ergo tempus? Si nemo ex me quaerat scio, si quaerenti explicare velim nescio. — What is time? If nobody asks me, I know it, but if I have to explain it to somebody, I don't know it" (my translation).

Interestingly, Augustinus made a nice categorical mistake by referring to "knowing" at first on an implicit, and second on an explicit level. This categorical mistake is still with us when we ask questions like: "What is consciousness, free will,..."; one knows, but one does not. As neuroscientists we have to focus on processes in the brain which rarely or perhaps never map directly onto such terms as we use them. Complexity reduction in brains is necessary and it happens all the time, but the goal of this reductive process is not such terms, that might be useful for our communication, but efficient action. This is what I think today, but why I came to this conclusion I don't know; it was probably several reasons that finally resulted in a shift of mind. i.e. overcoming Wittgenstein's straitjacket.

Chief Curator, Utah Museum of Natural History; Associate Professor, University of Utah; Host, Dinosaur Planet TV series

The Death of the Dinosaurs

An asteroid did it . . . .

Ok, so this may not seem like news to you. The father-son team of Luis and Walter Alvarez first put forth the asteroid hypothesis in 1980 to account for the extinction of dinosaurs and many other lifeforms at the end of the Mesozoic (about 65.5 million years ago). According to this now familiar scenario, an asteroid about 10 km in diameter slammed into the planet at about 100,000 km/hour. Upon impact, the bolide disintegrated, vaporizing a chunk of the earth's crust and propelling a gargantuan cloud of gas and dust high into the atmosphere. This airborne matter circulated around the globe, blocking out the sun and halting photosynthesis for a period of weeks or months. If turning the lights out wasn't bad enough, massive wild fires and copious amounts of acid rain apparently ensued. 

Put simply, it was hell on Earth. Species succumbed in great numbers and food webs collapsed the world over, ultimately wiping out about half of the planet's biodiversity. Key geologic evidence includes remnants of the murder weapon itself; iridium, an element that occurs in small amounts in the Earth's crust but is abundant in asteroids, was found by the Alvarez team to be anomalously abundant in a thin layer within Cretaceous-Tertiary (K-T) boundary sediments at various sites around the world. In 1990, announcement came of discovery of the actual impact crater in the Gulf of Mexico. It seemed as if arguably the most enduring mystery in prehistory had finally been solved. Unsurprisingly, this hypothesis was also a media darling, providing a tidy yet incredibly violent explanation to one of paleontology's most perplexing problems, with the added bonus of a possible repeat performance, this time with humans on the roster of victims.

To some paleontologists, however, the whole idea seemed just a bit too tidy.

Ever since the Alvarezes proposed the asteroid, or "impact winter," hypothesis, many (at times the bulk of) dinosaur paleontologists have argued for an alternative scenario to account for the K-T extinction. I have long counted myself amongst the ranks of doubters. It is not so much that I and my colleagues have questioned the occurrence of an asteroid impact; supporting evidence for this catastrophic event has been firmly established for some time. At issue has been the timing of the event. Whereas the impact hypothesis invokes a rapid extinction—on the order of weeks to years—others argue for a more gradual dying that spanned from one million to several million years. Evidence cited in support of the latter view includes an end-Cretaceous drop in global sea levels and a multi-million year bout of volcanism that makes Mount St. Helens look like brushfire. 

Thus, at present the debate has effectively been reduced to two alternatives. First is the Alvarez scenario, which proposes that the K-T extinction was a sudden event triggered by a single extraterrestrial bullet. Second is the gradualist view, which proposes that the asteroid impact was accompanied by two other global-scale perturbations (volcanism and decreasing sea-level), and that it was only this combination of factors acting in concert that decimated the end-Mesozoic biosphere.

Paleontologists of the gradualist ilk have argued that dinosaurs (and certain other groups) were already on their way out well before the K-T "big bang" occurred. Unfortunately, the fossil record of dinosaurs is relatively poor for the last stage of the Mesozoic and only one place on Earth — a small swath of badlands in the Western Interior of North America — has been investigated in detail. Several authors have argued that the latest Cretaceous Hell Creek fauna, as it's called (best known from eastern Montana), was depauperate relative to earlier dinosaur faunas. In particular, comparisons are often been made with the ca. 75 million year old Late Cretaceous Dinosaur Park Formation of southern Alberta, which has yielded a bewildering array of herbivorous and carnivorous dinosaurs.

For a long time, I regarded myself a card-carrying member of the gradualist camp. However, at least two lines of evidence have persuaded me to change my mind and join the ranks of the sudden-extinction-precipitated-by-an-asteroid group. 

First is a growing database indicating that the terminal Cretaceous world was not stressed to the breaking point, awaiting arrival of the coup de grâce from outer space. With regard to dinosaurs in particular, recent work has demonstrated that the Hell Creek fauna was much more diverse than previously realized. Second, new and improved stratigraphic age controls for dinosaurs and other Late Cretaceous vertebrates in the Western Interior indicate that ecosystems like those preserved the Dinosaur Park Formation were not nearly as diverse as previously supposed. 

Instead, many dinosaur species appear to have existed for relatively short durations (< 1 million years), with some geologic units preserving a succession of relatively short-lived faunas. So, even within the well sampled Western Interior of North America (let alone the rest of the world, for which we currently have little hard data), I see no grounds for arguing that dinosaurs were undergoing a slow, attritional demise. Other groups, like plants, also seem to have been doing fine in the interval leading up to that fateful day 65.5 million years ago. Finally, extraordinary events demand extraordinary explanations, and it does not seem parsimonious to make an argument for a lethal cascade of agents when compelling evidence exists for a single agent capable of doing the job on its own.

So yes, as far as I'm concerned (at least for now), the asteroid did it.

Futurist, Business Strategist; Cofounder. Global Business Network, a Monitor Company; Author, The Long Boom

In the last few years I have changed my mind about nuclear power. I used to believe that expanding nuclear power was too risky. Now I believe that the risks of climate change are much greater than the risks of nuclear power. As a result we need to move urgently toward a new generation of nuclear reactors.  

What led to the change of view? First I came to believe that the likelihood of major climate related catastrophes was increasing rapidly and that they were likely to occur much sooner than the simple  linear models of the IPCC indicated. My analysis developed as a result of work we did for the defense and intelligence community on the national security implications of climate change. Many regions of the Earth are likely to experience an increasing frequency of extreme weather events. These catastrophic events include megastorms, super tornados, torrential rains and floods, extended droughts, ecosystem disruptions all added to steadily rising sea levels. It also became clear that human induced climate change is ever more at the causal center of the story.

Research by climatologists like William Ruddiman indicate that the climate is more sensitive to changes in human societies ranging from agricultural practices like forest clearing and  irrigated rice growing to major plagues to the use of fossil fuels. Human societies have often gone to war as a result of the ecological exhaustion of their local environments. So it becomes an issue of war and peace. Will Vietnam simply roll over and die when the Chinese dam what remains of the trickle of the Mekong as an extended drought develops at is source in the Tibetan highlands?

 Even allowing for much greater efficiency and a huge expansion of renewable energy, the real fuel of the future is coal, especially in the US, China and India. if all three go ahead with their current plans on building coal fired electric generating plants then that alone will over the next two decades double all the CO2 that human kind has put into the atmosphere since the industrial revolution began more than two hundred years ago. And the only meaningful alternative to coal is nuclear power. It is true that we can hope that our ability to capture the CO2 from coal burning and sequester it in various ways will grow, but it will take a decade or more before that technology reaches commercial maturity.

At the same time I also came to believe that risks of  nuclear power are less than we feared. That shift began with a trip to visit the proposed nuclear waste depository at Yucca Mountain in Nevada. A number of Edge folk went including Stewart Brand, Kevin Kelly, Danny Hillis, and Pierre Omidyar. When it became clear that very long term storage of waste (e.g. 10,000 to 250,000 years) is a silly idea and not meaningfully realistic we began to question many of the assumptions about the future of nuclear power. The right answer to nuclear waste is temporary storage for perhaps decades and then recycling the fuel as much of the world already does, not sticking it underground for millennia. We will likely need the fuel we can extract from the waste.

There are emerging technologies for both nuclear power and waste reprocessing that will reduce safety risk, the amount of waste and most especially the risk of nuclear weapons proliferation as the new fuel cycle produces no plutonium, the offending substance of concern. And the economics are increasingly favorable as the French have demonstrated for decades. The average French citizen produces 70% less CO2 than the average American as a result. We have also learned that the long term consequences of the worst nuclear accident in history, Chernobyl were much less than feared.

So the conclusion is that the risks of climate change are far greater than the risks of nuclear power. Furthermore, human skill and knowledge in managing a nuclear system are only likely to grow with time. While the risks of climate change will grow as billions more people get rich and change the face of the planet with their demands for more stuff. Nuclear power is the only source of electricity that we can now see that is likely to enable the next three or four billion who want what we all have to get what they want without radically changing the climate of the Earth.

Neurologist & Cognitive Neuroscientist, The New School; Coauthor, Children's Learning and Attention Problems

The Impressionable Brain

When the phenomenon of "mirror neurons" that fire both when a specific action is perceived and when it is intended was first reported, I was impressed by the research but skeptical about its significance. Specifically, I doubted, and continue to doubt, that these circuits are specific adaptations for purposes of various higher mental functions. I saw mirror neurons as simple units in circuits that represent specific actions, oblivious as to whether they had been viewed when performed by someone else, or represented as the goal of one's own intended action (so-called reafference copy). Why have two separate representations of the same thing when one will do? Activity elsewhere in the brain represents who the agent is, self or another. I still think that this is the most economical interpretation. But from a broader perspective I have come to realize that mirror neurons are not only less than meets the eye but also more. Instead of being a specific specialization, they play their role as part of a fundamental design characteristic of the brain; that is, when percepts are activated, relevant intentions, memories and feelings automatically fall into place.

External event are "represented" by the patterns of neuronal activity that they engender in sensory cortex. These representations also incorporate the actions that the percepts potentially afford. This "enactive coding" or "common coding" of input implies a propensity in the observer's brain to imitate the actions of others (consciously or unconsciously). This propensity need not result in overt imitation. Prefrontal cortex is thought to hold these impulses to imitate in check. Nonetheless, the fact that these action circuits have been activated, lowers their threshold by subtle increments as the experience in question is repeated over and over again, and the relative loading of synaptic weights in brain circuitry become correspondingly adjusted. Mirror neurons exemplify this type of functioning, which extends far beyond individual circuits to all cell assemblies that can form representations,

That an individual is likely to act in the same ways that others act is seen in the documented benefit for sports training of watching experts perform. "Emotional contagion" occurs when someone witnesses the emotional expressions of another person and therefore experiences that mood state oneself. People's viewpoints can subtly and unconsciously converge when their patterns of neural activation match, in the total absence of argument or attempts at persuasion. When people entrain with each other in gatherings, crowds, assemblies and mobs, diverse individual views reduce into a unified group viewpoint. An extreme example of gradual convergence might be the "Stockholm Syndrome"; captives gradually adopt the worldview of their captors. In general, interacting with others makes one converge to their point of view (and vice versa). Much ink has been spilled on the topic of the lamentable limitations of human rationality. Here is one reason why.

People's views are surreptitiously shaped by their experiences, and rationality comes limping after, downgraded to rationalization. Once opinions are established, they engender corresponding anticipations. People actively seek those experiences that corroborate their own self-serving expectations. This may be why as we grow older, we become ever more like ourselves. Insights become consolidated and biases reinforced when one only pays attention to confirming evidence. Diverse mutually contradictory "firm convictions" are the result. Science does take account of the negative instance as well as the positive instance. It therefore has the potential to help us understand ourselves, and each other.

If I am correct in my changed views as to what mirror neurons stand for and how representation routinely merges perception, action, memory and affect into dynamic reciprocal interaction, these views would have a bearing on currently disputed issues. Whether an effect is due to the brain or the environment would be moot if environmental causes indeed become brain causes, as the impressionable brain resonates with changing circumstances. What we experience contributes mightily to what we are and what we become. An act of kindness has consequences for the beneficiary far beyond the immediate benefit. Acts of violence inculcate violence and contaminate the minds of those who stand by and watch. Not only our private experiences, but also the experiences that are imposed on us by the media, transform our predispositions, whether we want them to or not. The implications for child rearing are obvious, but the same implications apply beyond childhood to the end of personal time.

What people experience indeed changes their brain, for better and for worse. In turn, the changed brain changes what is experienced. Regardless of its apparent stability over time, the brain is in constant flux, and constantly remodels. Heraclitus was right: "You shall not go down twice to the same river". The river will not be the same, but for that matter, neither will you. We are never the same person twice. The past is etched into the neural network, biasing what the brain is and does in the present. William Faulkner recognized this: "The past is never dead. In fact, it's not even past".

Editor-At-Large, Wired; Author, New Rules for the New Economy

Much of what I believed about human nature, and the nature of knowledge, has been upended by the Wikipedia. I knew that the human propensity for mischief among the young and bored — of which there were many online — would make an encyclopedia editable by anyone an impossibility. I also knew that even among the responsible contributors, the temptation to exaggerate and misremember what we think we know was inescapable, adding to the impossibility of a reliable text. I knew from my own 20-year experience online that you could not rely on what you read in a random posting, and believed that an aggregation of random contributions would be a total mess. Even unedited web pages created by experts failed to impress me, so an entire encyclopedia written by unedited amateurs, not to mention ignoramuses, seemed destined to be junk.

Everything I knew about the structure of information convinced me that knowledge would not spontaneously emerge from data, without a lot of energy and intelligence deliberately directed to transforming it. All the attempts at headless collective writing I had been involved with in the past only generated forgettable trash. Why would anything online be any different?

So when the first incarnation of the Wikipedia launched in 2000 (then called Nupedia) I gave it a look, and was not surprised that it never took off. There was a laborious process of top-down editing and re-writing that discouraged a would-be random contributor. When the back-office wiki created to facilitate the administration of the Nupedia text became the main event and anyone could edit as well as post an article, I expected even less from the effort, now re-named Wikipedia.

How wrong I was. The success of the Wikipedia keeps surpassing my expectations. Despite the flaws of human nature, it keeps getting better. Both the weakness and virtues of individuals are transformed into common wealth, with a minimum of rules and elites. It turns out that with the right tools it is easier to restore damage text (the revert function on Wikipedia) than to create damage text (vandalism) in the first place, and so the good enough article prospers and continues. With the right tools, it turns out the collaborative community can outpace the same number of ambitious individuals competing.

It has always been clear that collectives amplify power — that is what cities and civilizations are — but what's been the big surprise for me is how minimal the tools and oversight are needed. The bureaucracy of Wikipedia is relatively so small as to be invisible. It's the Wiki's embedded code-based governance, versus manager-based governance that is the real news. Yet the greatest surprise brought by the Wikipedia is that we still don't know how far this power can go. We haven't seen the limits of wiki-ized intelligence. Can it make textbooks, music and movies? What about law and political governance?

Before we say, "Impossible!" I say, let's see. I know all the reasons why law can never be written by know-nothing amateurs. But having already changed my mind once on this, I am slow to jump to conclusions again. The Wikipedia is impossible, but here it is. It is one of those things impossible in theory, but possible in practice. Once you confront the fact that it works, you have to shift your expectation of what else that is impossible in theory might work in practice.

I am not the only one who has had his mind changed about this. The reality of a working Wikipedia has made a type of communitarian socialism not only thinkable, but desirable. Along with other tools such as open-source software and open-source everything, this communtarian bias runs deep in the online world.

In other words it runs deep in this young next generation. It may take several decades for this shifting world perspective to show its full colors.  When you grow up knowing rather than admitting that such a thing as the Wikipedia works; when it is obvious to you that open source software is better; when you are certain that sharing your photos and other data yields more than safeguarding them — then these assumptions will become a platform for a yet more radical embrace of the commonwealth. I hate to say it but there is a new type of communism or socialism loose in the world, although neither of these outdated and tinged terms can accurately capture what is new about it.

The Wikipedia has changed my mind, a fairly steady individualist, and lead me toward this new social sphere. I am now much more interested in both the new power of the collective, and the new obligations stemming from individuals toward the collective. In addition to expanding civil rights, I want to expand civil duties. I am convinced that the full impact of the Wikipedia is still subterranean, and that its mind-changing power is working subconsciously on the global millennial generation, providing them with an existence proof of a beneficial hive mind, and an appreciation for believing in the impossible.

That's what it's done for me.

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John Brockman, Editor and Publisher
Russell Weinberger, Associate Publisher

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