Saturday, August 23, 2008

Black hole star mystery 'solved'

Astronomers have shed light on how stars can form around a massive black hole, defying conventional wisdom.

http://news.bbc.co.uk/2/hi/science/nature/7574255.stm




Scientists have long puzzled over how stars develop in so extreme conditions.

Molecular clouds - the normal birth places of stars - would be ripped apart by the immense gravity, a team explains in Science magazine.

But the researchers say that stars can form from elliptical discs - the relics of giant gas clouds torn apart by encounters with black holes.

They made the discovery after developing computer simulations of giant gas clouds being sucked into black holes like water spiralling down a plughole.

"These simulations show that young stars can form in the neighbourhood of supermassive black holes as long as there is a reasonable supply of massive clouds of gas from further out in the galaxy," said co-author Ian Bonnell from St Andrews University, UK.

Ripped apart

Their findings are in accordance with actual observations in our Milky Way galaxy that indicate the presence of a massive black hole, surrounded by huge stars with eccentric orbits.

The simulations, performed on a supercomputer - and taking over a year of computing time - followed the evolution of two separate giant gas clouds up to 100,000 times the mass of the Sun, as they fell towards the supermassive black hole.

The simulations show how the clouds are pulled apart by the immense gravitational pull of the black hole.

The disrupted clouds form into spiral patterns as they orbit the black hole; the spiral patterns remove motion energy from gas that passes close to the black hole and transfers it to gas that passes further out.

This allows part of the cloud to be captured by the black hole while the rest escapes.

In these conditions, only high mass stars are able to form and these stars inherit the eccentric orbits from the elliptical disc.

These results match the two primary properties of the young stars in the centre of our galaxy: their high mass and their eccentric orbits around the supermassive black hole.

"That the stars currently present around the galaxy's supermassive black hole have relatively short lifetimes of [about] 10 million years, which suggests that this process is likely to be repetitive," Professor Bonnell explained.

"Such a steady supply of stars into the vicinity of the black hole, and a diet of gas directly accreted by the black hole, may help us understand the origin of supermassive black holes in our and other galaxies in the Universe."

Friday, August 22, 2008

Thursday, August 07, 2008

What is collective intelligence and what will we do about it? Thomas W. Malone, Director MIT Center for Collective Intelligence

Edited transcript of remarks at the official launch of the
MIT Center for Collective Intelligence
October 13, 2006

It now falls to me, at this point in the program, to give you an overview of what collective intelligence is, in the first place, and what we’d like to do about it. The working definition of collective intelligence that we’re using is that collective intelligence is groups of individuals doing things collectively that seem intelligent [Q.: mais comment se reconnaissent-ils?].

Now, if you think about it that way, collective intelligence has existed for a very long time. Families, companies, and countries are all groups of individual people doing things that at least sometimes seem intelligent. Beehives and ant colonies are examples of groups of insects doing things like finding food sources that seem intelligent. And we could even view a single human brain as a collection of individual neurons or parts of the brain that collectively act intelligently.

But in the last few years we’ve seen some very interesting examples of new kinds of collective intelligence:

  • Google, for instance, takes the collective knowledge created by millions of people making websites for other purposes and harnesses that collective knowledge--using some very clever algorithms and sophisticated technology--to produce amazingly intelligent answers to the questions we type in.
  • Wikipidia, at another extreme, uses much less sophisticated technology but some very clever organizational principles and motivational techniques to get thousands of people all over the world to volunteer their time to create an amazing on-line collection of knowledge.
  • In just a few minutes, you’ll hear from Alph Bigham the CEO of a company called Innocentive [est-ce vraiement innocent ?] which lets companies with difficult research problems harness the collective intelligence of thousands of scientists in a network all over the world to help solve those problems.
  • A lot of companies today--Hewlett Packard, Eli Lilly, Google and others--are now beginning to use things called prediction markets [mais qui paie quoi à qui et comment ?] where people buy and sell predictions about future events (like sales of their products) in ways that leads to more accurate predictions in many cases than traditional market research or polling or other techniques.

Now, I think these examples are just the beginning. With new information technologies—especially the Internet—it is now possible to harness the intelligence of huge numbers of people, connected in very different ways and on a much larger scale than has ever been possible before. In order to take advantage of these possibilities, however, we need to understand what the possibilities are in a much deeper way than we do so far.

So, I think the time has come make collective intelligence a topic of serious academic study. And that is our goal in the Center for Collective Intelligence.

The key question we’re using to organize our work is: How can people and computers be connected so that collectively they act more intelligently than any individual, group, or computer has ever done before?

In order to answer that question, I think at least three types of research are needed. The first is just collecting examples or case studies [Malone : mais tu ne change jamais de méthode ?]. I think there are going to be a lot of natural experiments going on in the next few years, people trying lots of interesting things--with or without us. But I think that we can help the world learn from its experience with all these natural experiments by systematically describing and collecting examples of interesting cases of collective intelligence.

For instance, Eric von Hippel, in the Sloan School, has done some very interesting case studies of how the collective body of users of a product is often a better source of innovation for a company’s products than the company’s own researchers [Ndr : y-avait-t-il vraiement besoin de faire une étude ???]. This kind of case study research is common in business schools, but it is certainly not the only kind of research we need to do.

Another kind of research we need to do is something that is more typical in an engineering school. That is to create new examples of the phenomena we want to study. If you’re an aeronautical engineer, for instance, you wouldn’t just study birds and flying insects, you’d also want to create some flying machines and study how they work. In our case, that means we want to create some new examples of collective intelligence and study how they work.

For instance, Mark Klein in the Center for Collective Intelligence is leading a group of people in a nascent project that hopes to harness the collective intelligence of thousands of people around the world to help deal with the problems of global climate change [& l'Opus Dei ? Qu'en fait-on ?]. We have some specific technical ideas about how to combine computer simulation techniques with online ways of representing issues and positions and arguments that we think may be helpful in this process.

In the process of creating new examples, we hope to advance the state of the art and to learn new design principles not just for the technologies, by the way [BTW], but also for the human, the organizational, the social, and the motivational systems that are needed for these systems to work effectively.
But case studies and creating new examples are not the only things we need to do. I think we also need to do systematic studies and experiments. For instance, in some cases, we’ll find examples of things that work well but we won’t know why from just a case study. So we need to do systematic experiments to help figure those things out. This is the kind of research that would be more often done in a school of science or a school of social science. For example, Sandy Pentland (in the Media Lab), Drazen Prelec (in the Sloan School), and Josh Tennenbaum (in the Brain and Cognitive Sciences department) are all doing different laboratory experiments about different ways of helping groups make predictions more effectively [c'est joli la diversité !].

But these three things--case studies, new examples, and systematic experiments--are not the only things we need to do. We also need new theories to help tie all these things together [ça devient compliqué ...]. I think that is especially important in the case of collective intelligence because there’s now a lot of hype and prejudice going around about collective intelligence [de qui parle-t-il ?].

On the one hand, there are people who think that collective intelligence is magic, and if you just add it, it’ll make everything wonderful. For instance, there is a book called The Wisdom of Crowds by James Surowiecki who--by the way--does not believe what I just said. But many people who’ve heard about his book do believe it. They think that just doing things “collectively” will make everything great.

On the other hand, there are people who are prejudiced against the very notion of collectiveness and decentralization. Very recently for instance, there have been a number of people who’ve looked at the success of Wikipedia and pointed out ways in which is not perfect. And then, based on that, they have argued that nothing without central control can ever be successful.

Now, I think both of these extremes are equally wrong. Sometimes collective intelligence is good; sometimes it isn’t. Sometimes it works, and sometimes it doesn’t. A very important part of our goal is to help put a more solid scientific foundation under the claims in this area.

Fortunately, we don’t have to start from scratch [scratch] in doing that. There’s already a lot of good work that has been done in many fields, including psychology, organization theory, artificial intelligence, brain science and others. Part of what we want to do is to help organize the work that has already been done.

But even if we had already organized all of the results of all of the previous research, there would still a lot to learn. New technologies are now making it possible to organize groups in very new ways, in ways that have never been possible before in the history of humanity. And no one yet understands how to take advantage of these possibilities.

We certainly don’t have all the answers yet; we’re just beginning to ask the questions [ça c'est prudentiellement bien prudent, bravo!]. We hope we can make a contribution just by helping to frame the questions better [je suis d'accord : le plus important c'est de poser les bonnes questions ... c'est déjà fini la lecture ...]. We’re pretty [pretty] sure we can have a lot of fun trying. And we hope that in the long run the work we do in this center will help contribute to scientific understanding in many different disciplines and help us understand new and better ways to organize businesses, to conduct science, to run governments, and--perhaps most importantly--to help solve the problems we face as society and as a planet.

Sunday, August 03, 2008

L’Albatros


Souvent, pour s’amuser, les hommes d’équipage
Prennent des albatros, vastes oiseaux des mers,
Qui suivent, indolents compagnons de voyage,
Le navire glissant sur les gouffres amers.



À peine les ont-ils déposés sur les planches,
Que ces rois de l’azur, maladroits et honteux,
Laissent piteusement leurs grandes ailes blanches
Comme des avirons traîner à côté d’eux.

Ce voyageur ailé, comme il est gauche et veule !
Lui, naguère si beau, qu’il est comique et laid !
L’un agace son bec avec un brûle-gueule,
L’autre mime, en boitant, l’infirme qui volait !

Le Poète est semblable au prince des nuées
Qui hante la tempête et se rit de l’archer ;
Exilé sur le sol au milieu des huées,
Ses ailes de géant l’empêchent de marcher.

Charles Baudelaire
Les fleurs du mal