One of humanity's earliest mathematical inquiries might have involved the geometric patterns in plants. The arrangement of leaves on a branch, seeds in a sunflower, and spines on a cactus appear with an intriguing regularity, providing a simple demonstration of mathematically complex patterns.

In a recent study, researchers have experimentally demonstrated for the first time a celebrated model of "phyllotaxis," the study of mathematical regularities in plants. In 1991, S.L. Levitov proposed a model of phyllotaxis suggesting that the appearance of the Fibonacci sequence and golden mean in the pattern of spines on a cactus can be replicated for cylindrically constrained, repulsive objects. Now, researchers have constructed a "magnetic cactus" with 50 outward-pointing magnets acting as spines, which are mounted on bearings and free to rotate on a vertical axis acting as the plant stem. With this setup, the researchers, from Los Alamos National Laboratory in New Mexico; Cornell University in Ithaca, New York; and The Pennsylvania State University (PSU), have verified Levitov's model, and their study has been published in a recent issue of Physical Review Letters.

In their experiment, the researchers put the system in a low-energy state by mechanical agitation. Then the scientists observed as the magnets (spines) arranged to form phyllotactic spirals, generating a so-called Farey tree of unfavorable angles. The unfavorable angles are fractional multiples of 2π (i.e. 2πi/j, such as 2π/3, 4π/3, etc.). The spines on the magnetic cactus, like those on a plant, form a helix around the cylindrical stem by growing around these particular angles.

Some people claim to never forget a face. And the ability can prove to be socially awkward.

A new study finds some people can remember faces of people they met years ago and only in passing. Others of us, of course, aren't blessed with that ability. In fact about 2 percent of the population have prosopagnosia, a condition characterized by great difficulty in recognizing faces.

The "super-recognizers," as they're being called, excel at recalling faces and suggest that there is - as with many things - a broad spectrum of ability in this realm. The research involved administering standardized face recognition tests. The super-recognizers scored far above average on these tests - higher than any of the normal control subjects.

"There has been a default assumption that there is either normal face recognition, or there is disordered face recognition," said Richard Russell, a postdoctoral researcher in the Department of Psychology at Harvard. "This suggests that's not the case, that there is actually a very wide range of ability."

Super-recognizers recognize other people far more often than they are recognized. So they often compensate by pretending not to recognize someone they met in passing, so as to avoid appearing to attribute undue importance to a fleeting encounter, Russell said.

The US Government has warned that the worldwide network of satellites that makes up the Global Positioning System could fail by next year, affecting millions of people around the globe.

Many depend on the satellite navigation network to beam precise directions from A to B into users' cars or on their mobile phones.

But mismanagement and a lack of investment means the 20-year-old system could lead consumers into nothing but trouble.

The first replacement satellite was supposed to be launched into space in 2007, but won't be ready until November - nearly three years too late.

The twin STEREO probes that image the sun's activity have caught sight of a burp of ionised gas that blasted into space from our star's surface without warning.

The find confirms suspicions that some solar ejections can occur even though the surface of the sun looks tranquil.

The eruption was a coronal mass ejection (CME) - a bubble of plasma that, if energetic enough and pointed at Earth, could zap satellites, endanger astronauts, and knock out power grids (see Space story alert: 90 seconds from catastrophe).

For centuries the ancients believed the Earth was flat. Evidence to the contrary was either ignored or effortlessly integrated into the dominant world view. Today we dismiss flat-Earthers as ignorant, yet we may be making an almost identical mistake - not about our planet, but about the entire universe.

When it comes to the universe, "flatness" refers to the fate of light beams travelling large distances parallel to each other. If the universe is "flat", the beams will always remain parallel. Matter, energy and dark energy all produce curvature in space-time, however. If the universe's space-time is positively curved, like the surface of a sphere, parallel beams would come together. In a negatively curved, saddle-shaped universe, parallel beams would diverge.

Thanks in part to the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, which revealed the density of matter and dark energy in the early universe, most astronomers are confident that the universe is flat. But that view is now being questioned by Joseph Silk at the University of Oxford and colleagues, who say it's possible that the WMAP observations have been misinterpreted.

The glittering "grills" of some hip-hop stars aren't exactly unprecedented. Sophisticated dentistry allowed Native Americans to add bling to their teeth as far back as 2,500 years ago, a new study says.

Ancient peoples of southern North America went to "dentists" - among the earliest known - to beautify their chompers with notches, grooves, and semiprecious gems, according to a recent analysis of thousands of teeth examined from collections in Mexico's National Institute of Anthropology and History (such as the skull above, found in Chiapas, Mexico).

The study of ancient lake sediment from high altitude lakes in the Andes has revealed for the first time that mercury pollution occurred long before the start of the Industrial Revolution.

University of Alberta Earth and Atmospheric Sciences PhD student Colin Cooke's results from two seasons of field work in Peru have now provided the first unambiguous records of pre-industrial mercury pollution from anywhere in the world and will be published in the May 18th Early Edition of the Proceedings of the National Academy of Sciences (PNAS).

Chicago - "Angels and Demons," the recently released film version of the Dan Brown thriller, focuses on a plot to destroy the Vatican using a small amount antimatter pilfered from the European particle physics laboratory CERN, the world's largest particle accelerator.

Some of the world's top particle physicists attempted to sort through facts and fiction about antimatter on Tuesday, and comment on their real quest behind CERN -- to unlock secrets about the origins of the universe.

"Antimatter atoms exist, but it is very difficult to make them," Rolf-Dieter Heuer, director-general of CERN, or the European Organization for Nuclear Research, said on Tuesday in a telephone briefing.

Houston - Rejuvenated by hours of repairs in space, the Hubble Space Telescope floated out of shuttle Atlantis' cargo bay on Tuesday to reclaim its place as the world's flagship observatory for astronomical research.

Atlantis astronauts spent more than 36 hours over five marathon spacewalks to make upgrades and outfit Hubble with new instruments. These included a panchromatic wide-field camera that should be able to see objects formed just 500 million years after the universe's birth in the big bang explosion some 13.7 billion years ago.

Using the shuttle's robot arm, astronaut Megan McArthur gently lifted the 13-tonne observatory from a work platform in Atlantis' payload bay where it had been positioned since Wednesday.

Holding the telescope high overhead, she released Hubble at 8:57 a.m. EDT as the spacecraft soared 350 miles over the planet.

"There are folks who thought we couldn't do this. They told us, 'You're too aggressive,'" said lead flight director Tony Ceccacci. "I don't want to say, 'We told you so,' but, 'We told you so.'"

New York - Scientists on Tuesday unveiled the well preserved fossilized remains found in Germany of a primate from 47 million years ago that may have been a close relative of the common ancestor of monkeys, apes and people.

It is the most complete fossil primate ever found, only missing part of one leg below the knee, and could shed light on an early stage of primate evolution, the scientists said.

Norwegian paleontologist Jorn Hurum, who led a team of scientists who analyzed the fossil in the past two years, said it may resemble one of the earliest ancestors of humans but was not likely to have been a direct ancestor.