Milky Way’s Giant Black Hole Awoke from Slumber 300 Years Ago

Robert Naeye / Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
301-286-4453 / 4044

Release No. 08-32

This Chandra image shows our Galaxy’s center. The location of the black hole, known as Sagittarius A*, or Sgr A* for short, is arrowed. Credit: NASA/CXC/MIT/Frederick K. Baganoff et al.
> Larger image GREENBELT, Md. - Using NASA, Japanese, and European X-ray satellites, a team of Japanese astronomers has discovered that our galaxy’s central black hole let loose a powerful flare three centuries ago.

The finding helps resolve a long-standing mystery: why is the Milky Way’s black hole so quiescent? The black hole, known as Sagittarius A* (pronounced "A-star"), is a certified monster, containing about 4 million times the mass of our Sun. Yet the energy radiated from its surroundings is billions of times weaker than the radiation emitted from central black holes in other galaxies.

"We have wondered why the Milky Way’s black hole appears to be a slumbering giant," says team leader Tatsuya Inui of Kyoto University in Japan. "But now we realize that the black hole was far more active in the past. Perhaps it’s just resting after a major outburst."

The new study, which will appear in the Publications of the Astronomical Society of Japan, combines results from Japan’s Suzaku and ASCA X-ray satellites, NASA’s Chandra X-ray Observatory, and the European Space Agency’s XMM-Newton X-ray Observatory.

The observations, collected between 1994 and 2005, revealed that clouds of gas near the central black hole brightened and faded quickly in X-ray light as they responded to X-ray pulses emanating from just outside the black hole. When gas spirals inward toward the black hole, it heats up to millions of degrees and emits X-rays. As more and more matter piles up near the black hole, the greater the X-ray output.

Four X-ray satellites imaged a small region in the gas cloud Sagittarius B2, and saw pockets brighten and fade over the course of nearly 12 years. These light echoes are caused by varying X-ray output from our galaxy’s central black hole. Credits: ASCA and Suzaku: JAXA; Chandra: NASA/CXC; XMM-Newton: ESA.
> Larger ASCA image
> Larger Chandra image
> Larger XMM-Newton image
> Larger Suzaku image
These X-ray pulses take 300 years to traverse the distance between the central black hole and a large cloud known as Sagittarius B2, so the cloud responds to events that occurred 300 years earlier. When the X-rays reach the cloud, they collide with iron atoms, kicking out electrons that are close to the atomic nucleus. When electrons from farther out fill in these gaps, the iron atoms emit X-rays. But after the X-ray pulse passes through, the cloud fades to its normal brightness.

Amazingly, a region in Sagittarius B2 only 10 light-years across varied considerably in brightness in just 5 years. These brightenings are known as light echoes. By resolving the X-ray spectral line from iron, Suzaku’s observations were crucial for eliminating the possibility that subatomic particles caused the light echoes.

"By observing how this cloud lit up and faded over 10 years, we could trace back the black hole’s activity 300 years ago," says team member Katsuji Koyama of Kyoto University. "The black hole was a million times brighter three centuries ago. It must have unleashed an incredibly powerful flare."

This new study builds upon research by several groups who pioneered the light-echo technique. Last year, a team led by Michael Muno, who now works at the California Institute of Technology in Pasadena, Calif., used Chandra observations of X-ray light echoes to show that Sagittarius A* generated a powerful burst of X-rays about 50 years ago -- about a dozen years before astronomers had satellites that could detect X-rays from outer space. "The outburst three centuries ago was 10 times brighter than the one we detected," says Muno.

The galactic center is about 26,000 light-years from Earth, meaning we see events as they occurred 26,000 years ago. Astronomers still lack a detailed understanding of why Sagittarius A* varies so much in its activity. One possibility, says Koyama, is that a supernova a few centuries ago plowed up gas and swept it into the black hole, leading to a temporary feeding frenzy that awoke the black hole from its slumber and produced the giant flare.

Launched in 2005, Suzaku is the fifth in a series of Japanese satellites devoted to studying celestial X-ray sources and is managed by the Japan Aerospace Exploration Agency (JAXA). This mission is a collaborative effort between Japanese universities and institutions and NASA Goddard.

Robert Naeye
Goddard Space Flight Center

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Volunteers sought for Mars test

The Aurora programme envisages Europeans on Mars

The European Space Agency (Esa) is seeking volunteers for a simulated human trip to Mars, in which six crew spend 17 months in an isolation tank.

They will live and work in a series of interlocked modules at a research institute in Moscow.

Once the hatches are closed, the crew's only contact with the outside world is a radio link to "Earth" with a realistic delay of many minutes.

It sounds like Big Brother, but there are no plans to televise the test.

The modular "spacecraft" measures some 550 cubic metres (19,250 cubic feet), the equivalent of nine truck containers. It is based at the Russian Institute for Biomedical Problems in the Russian capital.

The goal is to gain insight into human behaviour and group dynamics under the kinds of conditions astronauts would experience on a journey to Mars.

Big commitment

With the exception of weightlessness and radiation, the crew will experience most other aspects of long-haul space travel, such as cramped conditions, a high workload, lack of privacy, and limited supplies.

The volunteers will be put through a number of scenarios, such as a simulated launch, outward journey of up to 250 days, an excursion on the Martian surface, followed by the return home.

The 500-day duration is close to the minimum estimated timescale needed for a human trip to the Red Planet.

The Earthbound astronauts will have to deal with simulated emergencies and perhaps even real ones.

But, while Esa says it will do nothing that puts the lives of the simulation crew at unnecessary risk, officials running the experiment have made it clear they would need a convincing reason to let someone out of the modules once the experiment had begun.

"The idea behind this experiment is simply to put six people in a very close environment and see how they behave," Bruno Gardini, project manager for Esa's Aurora space exploration programme, told BBC News.

Team ethic

In all, 12 European volunteers will be needed. They must be aged 25-50, be in good health, have "high motivation" and stand up to 185cm tall. Smokers, or those with other addictions, to alcohol or illicit drugs, for example, will be rejected.

Esa is also looking for a working knowledge of both English and Russian.

"We will do pre-selection, medical tests, psychological tests, etc. But at the end, you really have to see how they react in as close to a real situation as possible on Earth," explained Mr Gardini.

He added that the results would help define the selection criteria for a future Mars mission.

"This is the beginning; it will be a long time before we go to Mars," the Esa official said.

"But this is a field which is difficult to quantify. It's human behaviour, so there's no method. The Russians have done lots of study in the past and we will be sharing some data.

"We have to look at the mix of people; at the end of the day, we want a team."

Robots first

Marc Heppener, of Esa's Science and Application Division, said the crewmembers would get paid 120 euros (158 dollars) a day.

Viktor Baranov, of Russia's Institute of Biomedical Problems, said his organisation had received about 150 applications, only 19 of which had come from women.

A precursor 105-day study is scheduled to start by mid-2008, possibly followed by another 105-day study, before the full 520-day project begins in late 2008 or early 2009.

European scientists have been asked to submit proposals for experiments in the areas of psychology, medicine, physiology and mission operations.

Mounting a mission to Mars would face many other hurdles, not least of which would be shielding the crew against the potentially deadly dose of radiation they would receive on the journey.

Esa's Aurora programme has already begun preparations to land a rover - called ExoMars - on the Red Planet. It has the stated aim, however, of trying to get European astronauts to Mars at some time in the future.

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John A. Wheeler, Physicist Who Coined the Term ‘Black Hole,’ Is Dead at 96

John A. Wheeler, a visionary physicist and teacher who helped invent the theory of nuclear fission, gave black holes their name and argued about the nature of reality with Albert Einstein and Niels Bohr, died Sunday morning at his home in Hightstown, N.J. He was 96.

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The cause was pneumonia, said his daughter Alison Wheeler Lahnston.

Dr. Wheeler was a young, impressionable professor in 1939 when Bohr, the Danish physicist and his mentor, arrived in the United States aboard a ship from Denmark and confided to him that German scientists had succeeded in splitting uranium atoms. Within a few weeks, he and Bohr had sketched out a theory of how nuclear fission worked. Bohr had intended to spend the time arguing with Einstein about quantum theory, but “he spent more time talking to me than to Einstein,” Dr. Wheeler later recalled.

As a professor at Princeton and then at the University of Texas in Austin, Dr. Wheeler set the agenda for generations of theoretical physicists, using metaphor as effectively as calculus to capture the imaginations of his students and colleagues and to pose questions that would send them, minds blazing, to the barricades to confront nature.

Max Tegmark, a cosmologist at the Massachusetts Institute of Technology, said of Dr. Wheeler, “For me, he was the last Titan, the only physics superhero still standing.”

Under his leadership, Princeton became the leading American center of research into Einsteinian gravity, known as the general theory of relativity — a field that had been moribund because of its remoteness from laboratory experiment.

“He rejuvenated general relativity; he made it an experimental subject and took it away from the mathematicians,” said Freeman Dyson, a theorist at the Institute for Advanced Study across town in Princeton.

Among Dr. Wheeler’s students was Richard Feynman of the California Institute of Technology, who parlayed a crazy-sounding suggestion by Dr. Wheeler into work that led to a Nobel Prize. Another was Hugh Everett, whose Ph.D. thesis under Dr. Wheeler on quantum mechanics envisioned parallel alternate universes endlessly branching and splitting apart — a notion that Dr. Wheeler called “Many Worlds” and which has become a favorite of many cosmologists as well as science fiction writers.

Recalling his student days, Dr. Feynman once said, “Some people think Wheeler’s gotten crazy in his later years, but he’s always been crazy.”

John Archibald Wheeler — he was Johnny Wheeler to friends and fellow scientists — was born on July 9, 1911, in Jacksonville, Fla. The oldest child in a family of librarians, he earned his Ph.D. in physics from Johns Hopkins University at 21. A year later, after becoming engaged to an old acquaintance, Janette Hegner, after only three dates, he sailed to Copenhagen to work with Bohr, the godfather of the quantum revolution, which had shaken modern science with paradoxical statements about the nature of reality.

“You can talk about people like Buddha, Jesus, Moses, Confucius, but the thing that convinced me that such people existed were the conversations with Bohr,” Dr. Wheeler said.

Their relationship was renewed when Bohr arrived in 1939 with the ominous news of nuclear fission. In the model he and Dr. Wheeler developed to explain it, the atomic nucleus, containing protons and neutrons, is like a drop of liquid. When a neutron emitted from another disintegrating nucleus hits it, this “liquid drop” starts vibrating and elongates into a peanut shape that eventually snaps in two.

Two years later, Dr. Wheeler was swept up in the Manhattan Project to build an atomic bomb. To his lasting regret, the bomb was not ready in time to change the course of the war in Europe and possibly save his brother Joe, who died in combat in Italy in 1944.

Dr. Wheeler continued to do government work after the war, interrupting his research to help develop the hydrogen bomb, promote the building of fallout shelters and support the Vietnam War and missile defense, even as his views ran counter to those of his more liberal colleagues.

Dr. Wheeler was once officially reprimanded by President Dwight D. Eisenhower for losing a classified document on a train, but he also received the Atomic Energy Commission’s Enrico Fermi Award from President Lyndon B. Johnson in 1968.

When Dr. Wheeler received permission in 1952 to teach a course on Einsteinian gravity, it was not considered an acceptable field to study. But in promoting general relativity, he helped transform the subject in the 1960s, at a time when Dennis Sciama, at Cambridge University in England, and Yakov Borisovich Zeldovich, at Moscow State University, founded groups that spawned a new generation of gravitational theorists and cosmologists.

One particular aspect of Einstein’s theory got Dr. Wheeler’s attention. In 1939, J. Robert Oppenheimer, who would later be a leader in the Manhattan Project, and a student, Hartland Snyder, suggested that Einstein’s equations had made an apocalyptic prediction. A dead star of sufficient mass could collapse into a heap so dense that light could not even escape from it. The star would collapse forever while spacetime wrapped around it like a dark cloak. At the center, space would be infinitely curved and matter infinitely dense, an apparent absurdity known as a singularity.

Dr. Wheeler at first resisted this conclusion, leading to a confrontation with Dr. Oppenheimer at a conference in Belgium in 1958, in which Dr. Wheeler said that the collapse theory “does not give an acceptable answer” to the fate of matter in such a star. “He was trying to fight against the idea that the laws of physics could lead to a singularity,” Dr. Charles Misner, a professor at the University of Maryland and a former student, said. In short, how could physics lead to a violation itself — to no physics?

Dr. Wheeler and others were finally brought around when David Finkelstein, now an emeritus professor at Georgia Tech, developed mathematical techniques that could treat both the inside and the outside of the collapsing star.

At a conference in New York in 1967, Dr. Wheeler, seizing on a suggestion shouted from the audience, hit on the name “black hole” to dramatize this dire possibility for a star and for physics.

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The black hole “teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as ‘sacred,’ as immutable, are anything but,” he wrote in his 1999 autobiography, “Geons, Black Holes & Quantum Foam: A Life in Physics.” (Its co-author is Kenneth Ford, a former student and a retired director of the American Institute of Physics.)

In 1973, Dr. Wheeler and two former students, Dr. Misner and Kip Thorne, of the California Institute of Technology, published “Gravitation,” a 1,279-page book whose witty style and accessibility — it is chockablock with sidebars and personality sketches of physicists — belies its heft and weighty subject. It has never been out of print.

In the summers, Dr. Wheeler would retire with his extended family to a compound on High Island, Me., to indulge his taste for fireworks by shooting beer cans out of an old cannon.

He and Janette were married in 1935. She died in October 2007 at 99. Dr. Wheeler is survived by their three children, Ms. Lahnston and Letitia Wheeler Ufford, both of Princeton; James English Wheeler of Ardmore, Pa.; 8 grandchildren, 16 great-grandchildren, 6 step-grandchildren and 11 step-great-grandchildren.

In 1976, faced with mandatory retirement at Princeton, Dr. Wheeler moved to the University of Texas.

At the same time, he returned to the questions that had animated Einstein and Bohr, about the nature of reality as revealed by the strange laws of quantum mechanics. The cornerstone of that revolution was the uncertainty principle, propounded by Werner Heisenberg in 1927, which seemed to put fundamental limits on what could be known about nature, declaring, for example, that it was impossible, even in theory, to know both the velocity and the position of a subatomic particle. Knowing one destroyed the ability to measure the other. As a result, until observed, subatomic particles and events existed in a sort of cloud of possibility that Dr. Wheeler sometimes referred to as “a smoky dragon.”

This kind of thinking frustrated Einstein, who once asked Dr. Wheeler if the Moon was still there when nobody looked at it.

But Dr. Wheeler wondered if this quantum uncertainty somehow applied to the universe and its whole history, whether it was the key to understanding why anything exists at all.

“We are no longer satisfied with insights only into particles, or fields of force, or geometry, or even space and time,” Dr. Wheeler wrote in 1981. “Today we demand of physics some understanding of existence itself.”

At a 90th birthday celebration in 2003, Dr. Dyson said that Dr. Wheeler was part prosaic calculator, a “master craftsman,” who decoded nuclear fission, and part poet. “The poetic Wheeler is a prophet,” he said, “standing like Moses on the top of Mount Pisgah, looking out over the promised land that his people will one day inherit.” Wojciech Zurek, a quantum theorist at Los Alamos National Laboratory, said that Dr. Wheeler’s most durable influence might be the students he had “brought up.” He wrote in an e-mail message, “I know I was transformed as a scientist by him — not just by listening to him in the classroom, or by his physics idea: I think even more important was his confidence in me.”

Dr. Wheeler described his own view of his role to an interviewer 25 years ago.

“If there’s one thing in physics I feel more responsible for than any other, it’s this perception of how everything fits together,” he said. “I like to think of myself as having a sense of judgment. I’m willing to go anywhere, talk to anybody, ask any question that will make headway.

“I confess to being an optimist about things, especially about someday being able to understand how things are put together. So many young people are forced to specialize in one line or another that a young person can’t afford to try and cover this waterfront — only an old fogy who can afford to make a fool of himself.

“If I don’t, who will?”

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Russia tests monkeys for Mars trip

Monkeys previously orbited Earth in the Bion capsule

They won't utter Yuri Gagarin's famous phrase "Let's go!" But the monkeys of Sochi have already proven their worth as trailblazers in space - and now they are being groomed for a trip to Mars.

The macaques will be the first to experience the radiation that poses a big risk to astronauts - or Russian cosmonauts - on any flight to the Red Planet.

The Sochi Institute of Medical Primatology, at Vesyoloye near the Black Sea, has a proud history of involvement in the Russian - formerly Soviet - space programme.

"People and monkeys have approximately identical sensitivity to small and large radiation doses," explains the institute's director, Boris Lapin. "So it is better to experiment on the macaques, but not on dogs or other animals."

The institute will select macaques that may eventually fly to Mars before humans do. After two years of experiments the most suitable 40 monkeys will be sent to the Institute of Biomedical Problems in Moscow, where scientists study aerospace biomedicine.

Experiments on the monkeys will be carried out at the same time as the Mars-500 project. That project - due to start early next year - is aimed at simulating the conditions of interplanetary flight. Volunteers will have to spend 17 months in a mock-up "spaceship" in Moscow.

Monkeys may touch down on boulder-strewn Mars before humans

But a real expedition to Mars is not likely to happen for another 10 years at the very least.

Gruelling mission

In addition to the effects of radiation, space scientists want to see how the monkeys react to prolonged weightless conditions, isolation and a special diet of juices and pureed food.

Mars-500 director Viktor Baranov says 520 days "are enough for the flight to Mars - 250 days to fly there, 250 days to come back and a month for the landing on Mars".

Today Russia is one of the few countries where experiments on primates are carried out.

"Humanity sacrifices more than 100 million animals a year in the name of health and beauty. It's time to think of an alternative to experiments with animals," says Andrei Zbarsky of the international nature conservation group WWF.

The son of space veteran Krosh may one day fly to Mars

"I'm sure scientists will repeat the story of Laika, the first dog in space. Today it's no secret that the dog died from the nervous stress immediately after the rocket launch and its dead body revolved in orbit for two weeks."

Mr Lapin admits that his institute has received some objections from European colleagues concerned about the animal experiments.

A researcher at the institute, Anaida Shaginyan, says "certainly, I feel sorry for the monkeys, they might die, but the experiments are necessary to preserve the lives of the cosmonauts who will fly to Mars in future".

Veteran cosmonauts

The institute has a breeding programme for the macaques, so it is not necessary to catch them in the wild.

Twelve macaques have flown in Russian and Soviet spaceships on previous missions.

Krosh flew in space in 1992 and is still in rude health

Abrek and Bion were the first into space, in December 1983. After a five-day flight they landed in Kazakhstan and after rehabilitation returned to the pack.

Two years later the monkeys Verny and Gordy spent seven days in space.

In 1987 Dryoma and Yerosha spent two weeks in orbit. After returning from space Dryoma was presented to Cuban leader Fidel Castro.

After that there were three two-week flights: in 1989, 1992 and 1996. Then the project stopped - Russia did not have enough money for the programme. Now experiments are conducted on Earth under conditions which simulate weightlessness.

Sixteen-year-old space veteran Krosh is a star of the institute.

"Old man Krosh is about 60 years old, if we translate his monkey age to a human life span. He is very active. He responds well to food and is aggressive with his female partners," says Ms Shaginyan.

"After rehabilitation he produced offspring. And that's proof that spaceflight did not harm his health," she added.

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2008 April 15

Sky Delights Over Sweden
Credit and Copyright: P-M Hedén (Clear Skies, TWAN)

Explanation: This night was a sky enthusiast's delight. While relaxing in Sweden last week, many a cosmic wonder was captured with a single snapshot. They are described here from near to far. In the foreground are nearby trees and more distant snow covered mountains. In silhouette, Clouds can be seen just above the horizon, and a careful eye can even discern the more distant green and red auroras which occur in Earth's upper atmosphere. Red emission nebulas dot the sky, including the Heart and Soul Nebulas, IC 1396 and the North America Nebula. Running diagonally from the upper left to the lower right is the majestic glowing band of our Milky Way Galaxy's central plane.. More distant than everything else, appearing as it did over two million years ago, is the Andromeda galaxy, visible above the horizon toward on the lower left.

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Scientists develop 'CyberWalk'

Advertisement

German researchers have developed a treadmill which allows people to have the sensation of walking while staying in the same place.

Footage courtesy of the Max Planck Institute for Biological Cybernetics.

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Elephant ancestors were semi-aquatic

A primitive ancestor of today's elephants grazed in swamps 40 million years ago, according to a study of fossil teeth.
Moeritherium, a 37 million-year-old amphibious relative of elephants

The evidence that the ancient relative of today's elephants lived in fresh water is published today by an international team led by an Oxford University scientist.

The scientists were investigating the lifestyle of the two early elephants - called proboscideans - Moeritherium ('the beast from Lake Moeris') and Barytherium, which looked like a slender version of today's Asian elephant - that lived over 37 million years ago in what today is Egypt's Fayum Desert.

By analysing isotopes in tooth enamel from Moeritherium - a creature a little larger than a pygmy hippo with a prehensile upper lip, like that of a tapir, rather than a full blown trunk - they were able to deduce that it was very likely a semi-aquatic mammal, spending its days in water eating freshwater plants when the region was much wetter and lusher than today.

'We know from molecular data that modern elephants share a common ancestry with the sirenians - aquatic sea cows and dugongs', said Alexander Liu of Oxford's Department of Earth Sciences, lead author of a report published in the Proceedings of the National Academy of Sciences.

The genetic evidence strongly suggested that elephants may have an ancestor which was amphibious in its mode of life and "we wanted to know if Moeritherium or Barytherium was this semi-aquatic ancient relative.

Unfortunately only few remains of the skeletons of these early elephants survive, so instead of looking at their bones we looked at the chemical composition of their teeth to determine what they ate and how they lived'.

Mr Liu, with colleagues Erik Seiffert from Stony Brook University and Elwyn Simons from the Duke Lemur Centre, both in America, analysed the oxygen and carbon isotope ratios contained within tooth enamel.

While carbon isotopes can give clues as to an animal's diet, oxygen isotopes found in teeth come from local water sources, and their variability in mammal populations can give an indication of the type of environment the animals lived in, in this case showing that Moeritherium was semi-aquatic. The results for Barytherium were ambiguous but do not rule out it being another swamp lover.

Mr Liu adds: 'We now have substantial evidence to suggest that modern elephants do have ancient relatives which lived primarily in water. The next steps are to conduct similar analyses on other elephant ancestors to determine when the switch from water to land occurred'.

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Physicists model how we form opinions

The model updates the state of a node (individual) depending on the fraction of the states of its neighbors. In this case, that fraction (“laggard parameter”) is 80%. In (a), the central node keeps its original state. In (b), the central node is updated since 80% of its neighbors are in the opposite state. Credit: P. Klimek, et al.

In large part, a society’s image stems from its overall opinions – its political, religious, and ethical beliefs – and how much diversity it tolerates. For example, how do some areas develop images of being either liberal or conservative, and, in others, liberals and conservatives live side by side?

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As a team of researchers explains, our individual opinions both influence and are influenced by our surroundings. By following a set of rules, the researchers have modeled the opinion formation process in societies where individuals’ opinions are strongly influenced by others they interact with. The scientists found that, depending on two criteria – how strongly individuals are influenced by each other and how many connections individuals have – a society’s overall state can exhibit either large segregated patches of consensus, or areas with closely intermingled opinions.
Peter Klimek from the Medical University of Vienna, Renaud Lambiotte from the University of Liege and the Catholic University of Louvain in Belgium, and Stefan Thurner of the Medical University of Vienna and the Santa Fe Institute in the US have published their study in a recent issue of Europhysics Letters.

In their model, individuals are represented as nodes in a network. The nodes are binary, and they display an individual’s opinion on some subject, such as yes/no, liberal/conservative, Clinton/Obama, or any other choice.

Then, the society’s overall stance on a subject can be determined for the future by evolving the system. First, an algorithm checks the state of all nodes connected to the node in question. If the fraction of the state of neighboring nodes exceeds a certain threshold (which the researchers call the “laggard parameter” and must be above 50%), then the central node adopts that state. If not, the node remains in its original state. This process is iterated several times, until it can no longer be updated, and the society freezes.

“The original opinions of the individuals are 'a priori' inclinations toward some subject,” Thurner told PhysOrg.com. “To stay within the Clinton/Obama example, although most of my peers may be democrats, some of them may consider political experience to be more important, while others think that a fresh start is needed. Given such individual initial dispositions, our work shows under which circumstances individuals will stick to them or change their mind.”

Depending on the laggard parameter and the system’s average connectivity, the model produces societies with different features. For example, as the laggard parameter increases (when individuals require a greater fraction of neighbors holding the opposite opinion in order to change their opinions), the regions of consensus shrink, and the society’s diverse views intermingle. In other words, individuals stubbornly hold on to their opinions, even if many of their neighbors have the opposite view. But the more that people are influenced by others, the less likely it is that the society will ever reach such an intermixed state.

Secondly, changing the connectivity parameter affects how quickly the system transitions from the segregated state to the intermixed state. For the same laggard parameter, a system with higher connectivity (10 or more connections in the model) creates a sharper transition from a segregated society to a mixed society. Systems with lower connectivity take longer to intermingle, and may never completely mix, as the system could stop evolving after fewer iterations.

Because social ties fluctuate, the researchers also modified their model by randomly rewiring the connections after the system reached its final update. This rewiring represents how individuals lose and make new friends and acquaintances, resulting in a more realistic model.

Overall, the researchers explain that a society’s public opinion can form one of two scenarios: segregated or coexistence of differences. But, as the team explains, even segregated societies can be versatile, with clusters of different groups – just as long as they aren’t forced to interact too much.

“Our model predicts that the formation of consensus depends on how actively an issue is under debate, especially if the original sets of opinions are balanced, i.e. there is roughly the same amount of people sharing each of the two opinions,” Thurner explained. “This is, of course, the most interesting case. In societies where debate is encouraged, a group of people is more likely to find consensus on a topic than, say, in a society where active discussions are not appreciated, suppressed or even forbidden.”

As the researchers explain, the model could be used as a tool to make statistical predictions in real-life scenarios.

“In principle, all our model parameters can be determined in real life,” Thurner said. “Presently, large efforts are made by dozens of groups to map social networks. The outcome of these efforts can be straight forwardly taken as an input to our model. The nature of social influence that individuals exert on each other (in the model this is the laggard parameter), can be assessed through polls, behavioral surveys, etc.

“However, predictions of our model are of statistical nature, and results predict most likely outcomes,” he added. “Predicting the outcome of a specific election can be compared to playing poker. Just from knowing that I hold an above average hand there is no guarantee that I will actually win this round.”

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Would you steal a buck? How about a can of soda?

Unexpected and surprising connections are at the heart of the fascinating research conducted by Dan Ariely, who holds joint appointments in MIT's Media Lab and Sloan School of Management. His studies of behavioral economics have demonstrated in a variety of creative ways that people often make decisions that seem to defy logic--but they do so in very predictable, consistent ways.
Hence the title of Ariely's new book, "Predictably Irrational" (HarperCollins), which catapulted onto The New York Times' bestseller list upon its Feb. 19 debut and has stayed there ever since.

Take those dollar bills as an example. Ariely has been fascinated with the way people rationalize their decisions about what is ethical or not. The small-scale tests he has carried out, though they involve only a few dollars, reveal patterns of thought that may be relevant to understanding how the leaders of a company such as Enron would engage in criminal activity involving hundreds of millions of dollars.

Here's how the test worked: Ariely and his students went around and left six-packs of Coke in randomly selected dorm refrigerators all over campus. When he checked back in a few days, all of the Cokes were gone.

But when he later placed plates of six loose dollar bills in those same refrigerators, not a single bill was missing when he checked back. Even though the value was comparable--and thus the situations were supposed to be equivalent--people responded in opposite ways. Why is that?

Ariely says that when he started reading about the Enron case, he was struck by what he calls some bizarre contradictions. "They didn't seem like career criminals," he says of the Enron officials. "They gave money to charity. This is not the image of people who are purely evil." And there were 10,000 people working for the company; obviously those were not all bad people. "Could it be that there was something in the structure of the company that allowed normal people to act this way?"

So Ariely, now the Alfred P. Sloan Professor of Behavioral Economics at the MIT Sloan School of Management and director of the eRationality Group at the Media Lab, started his small, simple tests of people's ethical decisions in everyday situations. The results, as with Cokes and dollars, were often quite striking.

For example, he gave people a test consisting of very easy math questions--but without giving them nearly enough time to finish. On average, people got four right out of 20. Then he had people take the test, score it themselves, shred the answer sheet and tell him how they did. Suddenly the average jumped to seven.

He repeated the experiment, paying people according to how many right answers they got. Same result. "Everybody cheated, but just a little." Even when there was no chance of getting caught--the evidence was shredded and participants paid themselves from a jar of money with over $100--nobody claimed 20 right answers. They just padded their results by a bit.

But then he tried another variation: Before doing the test, he asked one group of subjects to name 10 books they had read in high school. He asked another group to name as many of the Ten Commandments as they could remember. The group that listed the books followed the same pattern as the earlier test--they all cheated a little. But the group that named the commandments was different: Nobody cheated at all!

"Just the act of contemplating morality eliminated cheating," Ariely explains.

Though Ariely's book is often compared to the bestseller "Freakonomics"--both certainly share a quirky, hands-on approach to questions of everyday behavior--he says that in fact his research is almost the opposite of that book's. Those researchers found cases where people's behavior, even in seemingly irrational contexts, was perfectly rational and followed established economic principles. Ariely's work, by contrast, shows the consistently irrational ways people behave in situations where traditional economics predicts they would follow a course of rational self-interest.

Ariely's fascination with why people behave as they do and how they justify their own actions initially grew out of his own personal experience of suffering. He grew up in Israel, and at the age of 18 was in a bomb blast that burned 70 percent of his body. He spent three years in a hospital going through an excruciating recuperation that involved a daily hour-long ordeal of removing bandages from his burned flesh.

He was convinced that there was a better way of doing this process--starting with the most painful ones first, and taking frequent breaks to rest up. But the nurses insisted on the opposite--no breaks, and building up to the worst areas. After his discharge, Ariely decided to do some research on the question. The study, in which volunteers were subjected to controlled pain in different ways, confirmed that his approach was better.

"The nurses were wrong," he says. "But why were they wrong, when they had lots of experience and good intentions?" The question caused him to begin a lifelong exploration of situations "where good intentions and experience are not enough," and things somehow end up going wrong.

And so he began doing empirical testing of how people make choices. "MIT as a whole has a very applied perspective to the world," he says. Working here, "I fell in love with the experimental method."

Ariely explains that the ultimate goal of all of his research is a simple and earnest one.

"Behavioral economics can give kind of a depressing view" of how people make decisions, he says, but it can also be used to improve the way people make choices. Using these principles wisely, he says, "we might be able to design a better world."

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Retired NYC Subway Cars Creating a Reef off the Coast of Delaware

Image Credit: Tim Shaffer for The New York Times

If you think subway cars are only useful so long as they are efficiently carrying urban travelers from point A to point B, well, you're wrong! It turns out that hundreds of retired New York City subway cars have been finding a second home--80 feet underwater, and 16 nautical miles off the coast of Delaware. There they are helping to transform "a barren stretch of ocean floor into a bountiful oasis, carpeted in sea grasses, walled thick with blue mussels and sponges, and teeming with black sea bass and tautog." So far, 666 subway cars have already made their way to the ocean floor, and the results have been impressive: "a 400-fold increase in the amount of marine food per square foot in the last seven years," and "In the last several years, the reefs have drawn swift open-ocean fish, like tuna and mackerel, that use the reefs as hunting grounds for smaller prey. Sea bass like to live inside the cars, while large flounder lie in the silt that settles on top of the cars." This is great news, as ocean acidification from climate change and other human disruptions are harming reefs around the world.

So what about the environmental impacts from the subway cars themselves?

Some environmental groups, such as the American Littoral Society, "opposed the use of the Redbird cars because they have small levels of asbestos in the glue used to secure the floor panels and in the insulation material in the walls." However, "State and federal environmental officials approved the use of the Redbirds and other cars for artificial reefs in Delaware and elsewhere because they said the asbestos was not a risk for marine life and has to be airborne to pose a threat to humans."

The only significant problem, it seems, is that other states are catching on to the trend, but unfortunately there is only a limited number of retired subway cars available. As a result, "States have experimented with other types of artificial reef materials, including abandoned automobiles, tanks, refrigerators, shopping carts and washing machines." But none have worked very well; the fish seem to like the roominess of the subway cars, and their weight ensures that the structure stays stably anchored to the sea bed. Besides, while the environmental impacts of dumping subway cars are, at worst, minimal, it doesn't seem like a great idea to begin throwing all our abandoned appliances in the sea in the hopes of restoring aquatic ecosystems...

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We Drive, They Starve.

A demonstrator eats grass in front of a U.N. peacekeeping soldier during a protest against the high cost of living in Port-au-Prince

We drive, they starve. The mass diversion of the North American grain harvest into ethanol plants for fuel is reaching its political and moral limits.

"The reality is that people are dying already," said Jacques Diouf, of the UN's Food and Agriculture Organization (FAO). "Naturally people won't be sitting dying of starvation, they will react," he said.

The UN says it takes 232kg of corn to fill a 50-litre car tank with ethanol. That is enough to feed a child for a year. Last week, the UN predicted "massacres" unless the biofuel policy is halted.

We are all part of this drama whether we fill up with petrol or ethanol. The substitution effect across global markets makes the two morally identical.
Mr Diouf says world grain stocks have fallen to a quarter-century low of 5m tonnes, rations for eight to 12 weeks. America - the world's food superpower - will divert 18pc of its grain output for ethanol this year, chiefly to break dependency on oil imports. It has a 45pc biofuel target for corn by 2015.

Argentina, Canada, and Eastern Europe are joining the race.

The EU has targeted a 5.75pc biofuel share by 2010, though that may change. Europe's farm ministers are to debate a measure this week ensuring "absolute priority" for food output.

"The world food situation is very serious: we have seen riots in Egypt, Cameroon, Haiti and Burkina Faso," said Mr Diouf. "There is a risk that this unrest will spread in countries where 50pc to 60pc of income goes to food," he said.

Haiti's government fell over the weekend following rice and bean riots. Five died.

The global food bill has risen 57pc in the last year. Soaring freight rates make it worse. The cost of food "on the table" has jumped by 74pc in poor countries that rely on imports, according to the FAO.

Roughly 100m people are tipping over the survival line. The import ratio for grains is: Eritrea (88pc), Sierra Leone (85pc), Niger (81pc), Liberia (75pc), Botswana (72pc), Haiti (67pc), and Bangladesh (65pc).

This Malthusian crunch has been building for a long time. We are adding 73m mouths a year. The global population will grow from 6.5bn to 9.5bn before peaking near mid-century.

Asia's bourgeoisie is switching to an animal-based diet. If they follow the Japanese, protein-intake will rise by nine times. It takes 8.3 grams of corn feed to produce a 1g of beef, or 3.1g for pork.

China's meat demand has risen to 50kg per capita from 20kg in 1980, but this has been gradual. The FAO insists that this dietary shift is "not the cause of the sudden food price spike that began in 2005".

Hedge funds played their part in the violent rise in spot prices early this year. To that extent they can be held responsible for the death of African and Asian children. Tougher margin rules on the commodity exchanges might have stopped the racket. Capitalism must police itself, or be policed.

Even so, the funds closed their killer "long" trades in early March, causing a brief 20pc mini-crash in grains. The speculators are now neutral on the COMEX casino in New York.

What about the California state retirement fund (Calpers), the Norwegian Petroleum fund, the Dutch pension giants, et al, pushing a wall of money into the $200bn commodity index funds?

They have undoubtedly bid up the futures contracts, but the FAO says this has no durable effect on food prices. These index funds never take delivery of grains. All they do is distort the shape of the maturities curve years ahead, allowing farmers to lock in eye-watering prices. That should cause more planting.

Is there any more land? Yes, in Russia, Ukraine, and Kazakhstan, where acreage planted has fallen 12pc since Soviet days. Existing grain yields are 2.4 tonnes per hectare in Ukraine, 1.8 in Russia, and 1.11 in Kazakhstan, com-pared with 6.39 in the US. Investment would do wonders here. But the structure is chaotic.

Brazil has the world's biggest reserves of "potential arable land" with 483m hectares (it currently cultivates 67m), and Colombia has 62m - both offering biannual harvests.

The catch is obvious. "The idea that you cut down rainforest to actually grow biofuels seems profoundly stupid," said Professor John Beddington, Britain's chief scientific adviser.

Goldman Sachs says the cost of ethanol from corn is $81 a barrel (oil equivalent), with wheat at $145 and soybeans $232. It is built on subsidy.

New technology may open the way for the use of non-edible grain stalks to make ethanol, but for now the only biofuel crop that genuinely pays its way is sugar cane ($35). Sugar is carbohydrate: ideal for fuel. Grains contain proteins made of nitrogen: useless for fuel, but vital for people.

Whatever the arguments, politics is intruding. Food export controls have been imposed by Russia, China, India, Vietnam, Argentina, and Serbia. We are disturbingly close to a chain reaction that could shatter our assumptions about food security.

The Philippines - a country with ample foreign reserves of $36bn (Britain has $27bn) - last week had to enlist its embassies to hunt for grain supplies after China withheld shipments. Washington stepped in, pledging "absolutely" to cover Philippine grain needs. A new Cold War is taking shape, around energy and food.

The world intelligentsia has been asleep at the wheel. While we rage over global warming, global hunger has swept in under the radar screen.

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Biofuel Rule Will Do More Harm Than Good, Oxfam Says (Update1)

April 15 (Bloomberg) -- U.K. fuels for cars and trucks must contain biofuels starting today, a move that may do more harm than good to the environment and drive food prices higher, charities including Oxfam and Greenpeace said.

Under the Renewable Transport Fuel Obligation, suppliers must ensure that 2.5 percent of fuel sold at U.K. pumps consists of biofuels, which are made from crops and grasses. The requirement will rise to 5 percent by 2010. The Department for Transport says the plan will cut carbon-dioxide emissions by 2.5 million metric tons a year.

Scientists in the U.K. and U.S. have found that the cultivation of biofuels can increase the output of CO2 and other gases blamed for global warming because of changes in land use. U.K. Prime Minister Gordon Brown last week wrote to leaders of the Group of Eight nations to say the government is concerned that biofuels are pushing up food costs around the world.

``The sorts of problems that biofuels are causing are irreversible,'' Robert Bailey, policy adviser to the development charity Oxfam, said in a telephone interview. ``If rainforest gets chopped down, it's gone forever. If somebody loses access to food, they become malnourished, their physical and mental development is impaired and they may die.''

Tailpipe emissions from burning biofuels are about the same as those from fossil fuels, the transport department said. The carbon savings are made because the crops for biofuels are replanted, taking the same amount of CO2 out of the atmosphere as burning them puts in. Depleted oil fields don't absorb CO2, as do plants such as corn and wheat used for biofuel stock.

Food Prices

The policy ``helps send a message to industry that it is worth their while to significantly invest in improving existing biofuels and accelerate the development of new ones,'' Jeremy Woods, a scientist with Royal Society biofuels working group, said in a statement. The society is the U.K.'s national science academy.

Food prices have increased 83 percent in three years, according to the World Bank. The rising costs of both food and fuel have caused tensions and riots in developing nations including Haiti, Burkina Faso, Egypt, Indonesia and Ivory Coast.

According to Oxford-based Oxfam, the U.K. policy will cost taxpayers 500 million pounds ($1 billion) a year, and may lead to 60 million people being forced from their land to make way for biofuel plantations. About 30 percent of recent food price inflation can be attributed to biofuel production, the group said, citing the International Food Policy Research Institute.

Sustainable Plantations

Both Oxfam and the environmental campaign group Greenpeace called the policy ``reckless,'' because fuel providers are not yet obliged to source biofuels from sustainable plantations.

``Right now, rainforests are being destroyed to make way for biofuel crops in places like Indonesia,'' Belinda Fletcher, forests campaigner at Greenpeace, said in an e-mailed statement. ``This destruction leads to massive greenhouse-gas emissions and completely undermines the point of these so-called green fuels.''

Deforestation accounts for about a fifth of the world's greenhouse-gas emissions, according to Greenpeace. Destruction of peatland forests in Indonesia, driven by the expansion of plantations of the biofuel palm oil, now contributes about 4 percent of global emissions, the group said.

Converting new land to cultivate fuel crops can cause emissions of carbon dioxide 420 times greater than the annual savings, U.S. scientists said in the journal Nature in February. A U.K. parliamentary committee said Jan. 21 that the European Union and U.K. should scrap targets to expand the use of biofuels because of the potential harm to the environment.

New Agency

Transport Secretary Ruth Kelly on Nov. 5 said the government was setting up the Renewable Fuels Agency to ensure that biofuels used in the U.K. come from sustainable sources. Under Department for Transport rules, companies will have to report on the source of their biofuels, starting today. There will be no mandatory requirements to meet sustainability standards until 2011.

``If we're going to have mandatory standards, we need to be sure they can work, and this reporting system will give us the evidence we need,'' a ministry official said yesterday in a telephone interview. ``We will be naming and shaming those that don't perform well in this area.''

The government should drop the obligation until they can guarantee the crops used are sustainable, Oxfam's Bailey said.

``People aren't going to look at these reports to try and work out who the most sustainable supplier of biofuels is,'' Bailey said.

Consumer Survey

Almost 90 percent of consumers don't even know that biofuels will be added to their petrol and diesel, said the environmental charity Friends of the Earth, citing a YouGov survey it commissioned. The group said that European governments should scrap biofuels targets and instead focus on improving public transport and vehicle fuel efficiency.

``People want to see real green transport solutions that will make a difference to their lives, like better public transport and smarter cars that burn less fuel,'' Kenneth Richter, biofuels campaigner for the group, said yesterday in a statement. ``Most people will be horrified to know the government is putting biofuels in our petrol when the damage they do to forests could make climate change worse.''

To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net.

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China 'now top carbon polluter'

The new research suggests China's emissions were underestimated

China has already overtaken the US as the world's "biggest polluter", a report to be published next month says.

The research suggests the country's greenhouse gas emissions have been underestimated, and probably passed those of the US in 2006-2007.

The University of California team will report their work in the Journal of Environment Economics and Management.

They warn that unchecked future growth will dwarf any emissions cuts made by rich nations under the Kyoto Protocol.

The team admit there is some uncertainty over the date when China may have become the biggest emitter of CO2, as their analysis is based on 2004 data.

Until now it has been generally believed that the US remains "Polluter Number One".

Next month's University of California report warns that unless China radically changes its energy policies, its increases in greenhouse gases will be several times larger than the cuts in emissions being made by rich nations under the Kyoto Protocol.

The researchers say their figures are based on provincial-level data from the Chinese Environmental Protection Agency.

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Video showing the extent of China's smog problem

They say analysis of the 30 data points is more informative about likely future emissions than national figures in wider use because it allows errors to be tracked more closely.

They believe current computer models substantially underestimate future emissions growth in China.

We are awaiting a formal comment from the UK Chinese Embassy, but Dr Max Auffhammer, the lead researcher, said his projections had been presented widely and no-one had raised a serious complaint.

All those concerned about climate change agree that China's emissions are a problem - including China itself.

CARBON EMISSIONS Global carbon emissions statistics were last published in 2004. They show Chinese emissions began rising rapidly in 2002. University of California research suggests China overtook the US as the worst producer of carbon emissions in 2006

But China and many other developing countries struggling to tackle poverty are adamant that any negotiated emissions reductions should not be absolute, but relative to a "business-as-usual" scenario of projected growth.

That is why this study is of more than academic interest.

If it becomes widely accepted that China's future emissions are likely to be much higher than previously estimated, that will have to factored into any future global climate agreement if the Chinese are to be persuaded to take part.

In brief, although this study looks bad for China's reputation, it may be good for China's negotiating position.

The Chinese - and the UN - insist that rich countries with high per capita levels of pollution must cut emissions first, and help poorer countries to invest in clean technology.

America's per capita emissions are five to six times higher than China's, even though China has become the top manufacturing economy.

US emissions are still growing too, though much more slowly.

Dr Auffhammer told BBC News that his projections had made an assumption that the Chinese government's recent aggressive energy efficiency programme would fail, as the previous one had failed badly.

"Our figures for emissions growth are truly shocking," he said.

"But there is no sense pointing a finger at the Chinese. They are trying to pull people out of poverty and they clearly need help.

"The only solution is for a massive transfer of technology and wealth from the West."

He acknowledged that this eventuality was unlikely.

Those scientists aspiring to stabilise global emissions growth before 2020 to prevent what they believe may be irreversible damage to the climate may be wondering how this can possibly be achieved.

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Amazon tribe enlists Google in battle with illegal loggers

You may know it as Google, but in bamboo-and-thatch roundhouses deep in the Amazon rainforest the iconic brand goes by another name. The Surui people, one of the most remote on Earth, call it ragogmakan – "messenger" – and they're banking on the search engine to save them and their ancestral lands from extinction.

The tribe – whose first contact with the modern world was less than 40 years ago – are replacing their bows and arrows with hi-tech gadgets in their battle for survival. They have already begun using satnav on their traditional trails through the trees. And Google Earth has just agreed to provide high-resolution satellite images of their forest home.

The initiative is the brainchild of their chief, Almir Narayamoga Surui, who is leading their struggle against illegal loggers besieging their territory, an isolated 600,000-acre green oasis in Rondonia, in the wild Brazilian west. Last year the 34-year-old Almir visited Google near San Francisco to ask it to help monitor the loggers' incursions. He said he also hoped to be able to use the internet firm to "alert the world". He added: "We call Google ragogmakan because we hope it will help us get our message out."

For countless centuries the nomadic people – who call themselves Paiter, meaning simply "we ourselves" – lived far from the outside world, until the official "first contact" with Brazilian authorities on 7 September 1969, national Independence Day. "The date that Brazil became independent was the day our independence ended," Almir says. "Our people were very, very scared when they first saw white men." A warrior people (Surui, the name bestowed on them by outsiders, means "enemy"), they decided to fight.

"We thought we could beat them with bows and arrows," says Almir. "But it didn't work." The Surui were reduced from 5,000 to just 250 people by massacres and diseases such as chicken pox, measles, tuberculosis and flu, to which they had no immunity. "The survivors were so weak from disease that they did not have the strength to bury their dead. So we went to Plan B, a peace plan." Did that work? "In terms of absolute survival, yes. Other tribes in Rondonia completely disappeared."

They got medical help, but lost half their land, and only got the remainder protected after a prominent Surui drew an arrow on a leading Brazilian senator in his office and demanded official demarcation. The land is still under constant attack. Almir says that 300 sawmills, employing 4,000 people, surround it and other Indian reserves in the area. Eleven local chiefs have been killed trying to protect their land, and he himself has a £50,000 price on his head.

He cottoned on to cyberspace when first trying out Google Earth and – like almost everyone – immediately searched for where he lived. He saw clear signs of logging, and realised he could enlist an eye in the sky.

With the help of the US-based Amazon Conservation Team he has been training his people in IT. They use satnav not to find their way around the jungle they know so well, but to enable them to record the co-ordinates of any logging they find so that they can report it. And Almir envisages the Surui with solar-powered laptops using Google to download information and to tell the world how their forest is much more valuable if left standing.

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Suspending Life

If almost every species on Earth was killed some 250 million years ago, how did our ancient ancestors survive and evolve into us?

In the deep history of our planet, there have been at least five short intervals in which the majority of living species suddenly went extinct. Biologists are used to thinking about how environmental pressures slowly select the organisms most fit for survival through natural selection, shaping life on Earth like an artist sculpting clay. However, mass extinctions are drastic examples of natural selection at its most ruthless, killing off vast numbers of species at one time in a way that is hardly typical of evolution.

In the 1980s, Nobel Prize-winning physicist Luis Alvarez and his son first hypothesized that the impact of comets or asteroids caused the mass extinctions of the past. Most scientists slowly came to accept this theory of extinction, and since then a great scar in the Earth--an impact crater--has been discovered off the coast of Mexico that dates to around the time the dinosaurs went extinct. An asteroid probably did kill off the dinosaurs, but the causes of the other four mass extinctions are still obscured beneath the accumulated weight of hundreds of millions of years, and no one has found any other credible evidence of impact craters.

But now, together with Mark Roth of the Fred Hutchinson Cancer Research Center in Seattle, I believe we have found a possible biochemical scar, present within living animals, that links Earth's greatest mass extinction to a single substance: hydrogen sulfide (H₂S). Hydrogen sulfide is a relatively simple molecule that gives rotten eggs their distinctive foul odor and is quite toxic--in high concentrations a single breath can kill. And it looks like that is what happened: Hundreds of millions of years ago, hydrogen sulfide probably saturated our oceans and atmosphere, poisoning nearly every creature on Earth.

Yet some creatures, like our very distant ancestors, must have somehow survived this toxic environment. What Roth has discovered is that H₂S, incredibly, also has the ability to preserve and save lives. In small doses the chemical puts many animals into a state of "suspended animation," a useful adaptation that would have allowed creatures to, in essence, hibernate through the catastrophe of mass extinction. If this idea is correct, our understanding of the deep past could lead to a dramatic medical revolution very soon.

Reptiles are pretty tough. It's much harder to kill a snake than a rat, and lizards can exist in extremes of temperature and oxygen that would kill most mammals. The key is their metabolism. We endothermic, or warm-blooded, mammals maintain our inner body temperatures while the ectothermic (cold-blooded) reptiles adapt to external temperatures. Paleontology still can't pinpoint when the first warm-blooded animals appeared, but a best guess is that some 260 million years ago, in the Permian Period, a branch of reptiles called the therapsids, or "mammal-like reptiles," evolved. Their metabolism must have given them an immediate Darwinian advantage because the group soon underwent a dramatic expansion in numbers, diversity, and disparity (diversity not of species, but of
separate morphologies). But why this great evolutionary change?

Probably because the world was so cold. At that time, the Earth had been in the grip of its longest-ever ice age, a global icebox that by the time of the therapsids' appearance was already tens of millions of years old. For the reptiles, until then the most complex creatures on the planet, the cold was a real problem. Getting started in the morning meant lying in the sun until internal temperatures rose to the point of allowing motion. Like a car on a subzero morning, the panting, white-breathed reptiles would have needed substantial amounts of time to warm up enough to commence hunting for food. The appearance of warm-blooded predators would have wreaked havoc on the ectothermic reptiles, and even warm-blooded prey had the advantage of being capable of rapid activity anytime, day or night. The endotherms soon dominated Earth's landscape, and did so for 10 million years.

There was a trade-off, of course, to being warm-blooded--all of this internal heat needed to be fueled. The new warm-bloods had to eat more, and more frequently. They also needed more oxygen than their cold-blooded ancestors to keep the internal fires burning. But the endotherms had no problem out-competing the reptiles while it was cold. Then the Earth started to warm. Far off in what would someday be Siberia, a very large volcanic area spilled enormous volumes of lava onto the Earth's surface, eventually covering an area larger than present-day Texas. It was not the lava that caused the temperature to rise, however; it was the large volumes of carbon dioxide and methane emitted into the atmosphere. Carbon dioxide levels shot up from their Permian lows (the reason for the long ice age in the first place) of perhaps 100 ppm, to 3000 ppm or more.

By about 251 million years ago, the planet had lost all of its ice, and with the final glaciers melting away, there was no longer a sufficient heat difference between the tropics and poles to maintain the various ocean currents that had kept the waters both cold and oxygenated. Stagnation ensued as the currents slowed; the ocean bottoms lost their oxygen and sea animals died. With this shift in ocean chemistry and temperature, new microbes that thrive without oxygen bloomed into dominance and rapidly reproduced to ocean-filling numbers. Some of these microbes were relatively benign to the life on Earth that does depend on oxygen, but some produced toxins such as those found now in red tides. A few others produced something even worse--hydrogen sulfide.

The oceans became much like the modern Black Sea, with warm, deep, oxygen-less water masses covering the bottom and oxygenated regions at the surface. Slowly yet inexorably, the warming oceans began to bring oxygen-less bottom waters toward the surface. By the time this process was complete, the microbes producing hydrogen sulfide were able to live at every depth. Vast new suites of other microbes appeared, belonging to the purple and green sulfur bacteria groups that require both hydrogen sulfide in the water around them and sunlight to run their photosynthetic pathways. These microbes took over in the oxygen-free water, rich in poisonous H₂S and shallow enough to provide sufficient light for energy.

What I believe happened next still reverberates through life's history. The H₂S-producing microbes eventually grew to such numbers that the toxic byproduct of their metabolism could no longer be contained in seawater solution. Large oily bubbles of hydrogen sulfide came out of the purple-stained sea and entered the atmosphere, where the gas increased in concentration to levels that surely had destructive effects. Where the H₂S was concentrated at more than 200 ppm, it was toxic to both plants and animals. But more globally, H₂S began to break down the Earth's protective ozone layer, allowing harmful ultraviolet light to enter.

The fossil record shows us that at this point, the most catastrophic mass extinction in Earth's history occurred. Claims that this "great dying" was caused by the effects of an asteroid from space, just like what killed the dinosaurs, simply don't hold up. Almost everywhere we find biomarkers indicating that there existed an oxygen-free, toxic ocean--and that on land, almost all plants and animals quickly died out.

Hydrogen sulfide, directly or indirectly, probably killed almost every creature on Earth. Both groups of major land vertebrates, the endotherms and the ectotherms, were almost wiped out. But the reptiles, with their cold blood, would have enjoyed a slight advantage over the ectotherms because they could adapt to the changing temperatures faster. Recent experiments from the lab of Mark Roth have also shown that warm-blooded creatures had another disadvantage: They fare worse than reptiles in H₂S-rich environments. This finding certainly bolsters research, including my own paleontological work in South Africa, showing that more than 90 percent of the mammal-like reptiles disappeared in the great dying, leaving the world primarily to the reptiles. But there's more.

When the warmth and H₂S levels gradually receded after the volcanic episode, the biological life left behind was vastly different. The era would have been rough for the mammals that survived. And over the next 100 million years, this cycle leading to the anoxic ocean and H₂S venting into the sky that caused the "greenhouse" mass extinction, was repeated. Dinosaurs evolved slowly into dominance until a 10 km asteroid killed them off. Yet through it all, some proto-mammals did survive, and after the age of the dinosaurs, conditions once again began to favor these mammals and their warm-bloodedness.

We mammals, who evolved from the creatures that survived this inhospitable time, were marked by what happened. All animals bear the physiological scars left by the past greenhouse extinctions and hydrogen sulfide events, and we mammals are no exception. The difficulty is knowing where to look for the scars.

I believe the work of Mark Roth and his group may have finally uncovered the survival mechanism of our ancestors. While high levels of H₂S kill mammals, Roth's team has found that very low levels of the toxin can prolong their lives. H₂S reduces oxygen levels in the body, and though too much causes death by oxygen starvation, a bit less slows a creature's metabolism. This alone is an amazing finding. But Roth has gone further, inducing suspended animation in mammals. By exposing lab mice to small doses of H₂S, Roth and his team can put them into the deepest of sleeps--with very slow, or even no heartbeats--for several hours. In that time, the mice can be cooled to temperatures that would have killed them prior to the H₂S exposure.

Roth has already begun testing his work on other mammals. If he is correct, hydrogen sulfide may provide a way of saving lives so revolutionary that it will change trauma medicine forever. He is redefining what we thought we knew about death and dying. Death may not be as final as we think.

When we humans are cut or injured, our bodies naturally produce small quantities of hydrogen sulfide. In essence, the body may be trying to put itself into suspended animation to survive the injury, an instinct held over millions of years in our genes. Yet whenever one of us is dying, say from a heart attack, our first instinct is to give that person oxygen. The problem with this "life-saving" first response may be that the oxygenated red blood cells rush to the damaged cells and act like gasoline on a fire. Oxygen is one of the most chemically active substances on Earth, and though we need it to survive, it can ravage our bodies. The oxygen increases the reactions causing the heart attack in the first place; it tears up more cells and overwhelms the virtual suspended animation that the body-produced hydrogen sulfide created. Then it kills you.

Perhaps our first instinct in instances of a heart attack should be to cool the body and let hydrogen sulfide do its natural work. To save life, in other words, you may first have to effectively suspend it with hydrogen sulfide. This tactic may just be what got us so far in the first place.

There is no clear understanding yet of why our injured bodies are able to produce hydrogen sulfide or why H₂S puts some mammals into suspended animation. But I believe that Roth has found our body's own memory of the ancient events that nearly killed our distant ancestors. Some proto-mammals may have been exposed to H₂S, and instead of dying, they were placed into a state of suspended animation that allowed them to survive until the initial hydrogen sulfide levels subsided and they were reanimated. Some lucky evolutionary accident ensured the mammals' safety through a deep sleep, and that accident may still be dormant within us. That which allowed our ancestors to survive millions of years ago might also be a means of our survival now.

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