Last Week's Top Ten Science Stories

This week we have seen astronomers debating what a planet is, physicists discovering that the electric force that holds the atoms together is a little smaller than they previously thought, neurologists mapping the patterns in the brain that signal us whether we're hungry or not and an archeologist arguing that the American Indians societies have been much more developed than it is usually assumed. Here is the top ten of this week's science stories:

10. Physicist Discovers Exotic Superconductivity

At least on paper. A theoretical physicist from the University of Arizona has imagined a new way of producing superconductivity - the phenomenon of electric current flowing with no resistance. Electrical resistance appears because electrons bump into the crystalline structure of the conductor. But under certain conditions, such as very low temperatures, two electrons can combine together into a single ghostly entity that can pass through things - thus the zero resistance flow.

Andrei Lebed has now imagined another way of such coupling of electrons - forming an "exotic Cooper pair". His proposal involves the breaking of the time symmetry - the idea that at the most fundamental level the laws of physics cannot tell the difference between past and future. "Half of the exotic Cooper pair electrons 'see' time directed from the past to the future, whereas the other half 'see' time directed from the future to the past." Read more.

9. Paleontologist Discovers the Fossils of South American Mammal

Scientists discovered the fossils of a new hoofed mammal that resembles a cross between a dog and a hare and which once roamed the Andes Mountains in southern Bolivia around 13 million years ago. The animal belonged to a group of animals called notoungulates - hoofed mammals native only to South America - which originated in South America soon after the dinosaurs went extinct and evolved to include hundreds of species over a span of more than 50 million years. Nonetheless, all of them are now extinct.

The animals had tall teeth and thus they probably fed on abrasive foods like grasses and other plants close to the ground. They probably lived in open areas but may have burrowed into holes like rabbits.

"As the first member of its family known from this particular time interval, it helps us fill in gaps in the history of this group that existed in South America for 30 million years," said Darin A. Croft who discovered the fossils. Full story.

8. How the Brain Regulates Behavior

Insects are fascinating because they accomplish complex behaviors with relatively few nerve cells. Moths for example go through three distinct body states, each with its own set of behaviors, but all three states are controled by the same brain. Moreover, their brains have easy-to-study nerve cells that are 10 to 20 times as large as those in humans.

"The idea is to look at simpler brains to allow us to generalize broad concepts that are applicable to humans. Much of what we've learned about the human brain at the cellular level has come from the study of invertebrates."

Not only of insects but also of cephalopods - octopuses and squids. While the humans have around one trillion neurons, cephalopods have "only" 100 million nerve cells, while insects manage to function with only 10,000. Read full story.

7. Bison Hunters Were More Advanced Than Previously Thought

An archaeologist from the University of Calgary has proposed a controversial theory suggesting the First Nations of the Canadian Plains developed complex tribal social structures some 1,700 years earlier than many researchers believe.

"There has been a tendency by some to regard them as simple hunter-gatherers with very basic levels of social organization, living hand to mouth in small bands - but that really isn't accurate," he said.

He argues that the American Indians killed so many bisons that they must have had some storage facilities. "There may have been as many as 3,000 people living at some of these sites for as long as eight months at a time, so there would have to have been some more complex level of organization to keep them living there in harmony," he says. Read full story.

6. How Does Your Brain Know When You're Hungry?

The sensation of being hungry is useful - it tells you that you need to eat. And how do you know when to stop? Another sensation is at work - the sensation of being full. These sensations, like all sensations, are the result of the activation of certain patterns of neurons in the brain. But which ones exactly? Until recently, studies of those structures and of the feeding cycle have been only fragmentary - measuring brain regions only at specific times in the feeding cycle.

Now, however, researchers from the Duke University Medical Center have mapped the activity of whole ensembles of neurons in multiple feeding-related brain areas across a full cycle of hunger-satiety-hunger. Their findings open the way to understanding how these ensembles of neurons integrate to form a sort of distributed "code" that governs the motivation that drives organisms to satisfy their hunger. Read full story.

5. What's the Connection Between Global Warming and Hurricane Intensity?

Previous studies have shown that global warming triggers more hurricanes. Now a new study has also shown that the average hurricane is getting wilder and more intense.

"The large increases in powerful hurricanes over the past several decades, together with the results presented here, certainly suggest cause for concern. These results have serious implications for life and property throughout the Caribbean, Mexico, and portions of the United States." Read more.

4. 'Hidden' Milky Way Deuterium Found

Deuterium is heavy hydrogen - a type of hydrogen that has a neutron inside its nucleus alongside its proton. And now astronomers have found that it exists in larger quantities than expected in the Milky Way, a finding that could radically alter theories about star and galaxy formation.

The observations made by NASA's Far Ultraviolet Spectroscopic Explorer, or FUSE, satellite, have solved a 35-year mystery about deuterium but have also raised additional questions. One one hand, scientists have finally understood why deuterium appears to be distributed unevenly in the Milky Way Galaxy: it binds to interstellar dust grains, changing from an easily detectable gaseous form to an unobservable solid form. On the other hand: Why is there so much?

"Our models of the chemical evolution of the Milky Way will have to be revised significantly to explain this important new result," said astrophysicist Jeffrey Linsky. Read full story.

3. The IAU Draft Definition of 'Planet' and 'Plutons'

Should Pluto be considered a planet? What about "Xena" which is even further away from the Sun but which proved to be even larger than Pluto. The International Astronomical Union debated such issues and tried to come up with a definition of "planet". Insofar, their proposal states that anything which is round and orbits the Sun is a planet.

This allows Pluto to remain a planet but also grants the former asteroid Ceres, which is between Mars and Jupiter, the planetary status. Moreover, astronomers noted that Charon, previously considered Pluto's satellite, is in fact so big compared to Pluto that it doesn't really revolve around Pluto - rather, both Pluto and Charon revolve around their center of mass which is somewhere in space outside Pluto itself. Thus, they want to call Charon a planet too - the Pluto-Charon system becomes a "binary planet".

"Xena", still waiting for an official name, is also labeled a planet. And probably there are many more planets to come... At least if this draft definition gets accepted. Read more.

2. Atoms Looser than Expected

A new experiment conducted at Harvard University has yielded a rather stunning result: the electromagnetic force, which holds all the atoms together, is a little bit smaller than expected. This result is amazing because until now the quantum theory of electromagnetism (quantum electrodynamics) has been the only scientific theory with perfect predictions. The new experiments kept getting more and more precise and the theory managed to cope with them, its predictions always fitting the facts.

That is, until now. The new experiment was six times more precise than the previous ones and involved studying an individual electron in isolation from any other particle. Read more.

1. Brain Gene Shows Dramatic Difference from Chimp to Human

The genetic difference between a chimp and a human is only about 1 percent. But that's a pretty important percent! Scientists have long debated why our brain is so much larger than a chimp's brain. Many thought that the genetic difference is too small to account for such a large difference in outcome. Some speculated for example that maybe human diet was responsible for the increase in brain size.

But now scientists have discovered that it's genetic after all. They uncovered that the genetic difference between us and our closest cousins involves some genes that have experienced very fast changes and that these genes are activated during a critical stage in brain development.

"We found 18 differences between chimps and humans, which is an incredible amount of change to have happened in a few million years," lead researcher Katherine Pollard said. Read full story.