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One of Saturn's moons is giving its neighbours a face lift. Astronomers in the US claim that material ejected from Enceladus is "sandblasting" the surfaces of neighbouring satellites, making them appear much more shiny than expected. The observations, which were made using the Hubble Space Telescope, could cast some doubt on how an object's albedo -- or shininess -- is used to determine when a moon or planet was last geologically active (Science 315 815).

The bacterium E. coli has an unusual ability to swim upstream, according to experiments performed in the US and Turkey. By creating tiny microfluidic channels similar to blood vessels, physicists found that the bacterium's ability derives from an innate tendency to swim to the left at surfaces, enabling it to locate flow regimes more favourable to upstream swimming. They now say that the ability could be fundamental to the transport of certain infections (Phys. Rev. Lett. 98 068101).

In recent years physicists have realized that fermions can exhibit superfluid behaviour because of their ability to pair up at very low temperatures. Now a US group has shown that if a mixture of fermions is prepared with the majority in the same spin state, they can appear to pair up without behaving as a superfluid at all. This discovery might eventually enable a greater insight into high-temperature superconductivity, which also involves pairing but is often too complex to study directly (Science 316 867).

In the standard model of cosmology, the early universe underwent a period of fantastic growth. This inflationary phase, after only a trillionth of a second, concluded with a violent conversion of energy into hot matter and radiation. This "reheating" process also resulted in a flood of gravitational waves. (Interestingly, some cosmologists would identify the "big bang" with this moment and not the earlier time=0 moment.)

The strange behaviour of a magnet near absolute zero temperature provides the first direct evidence that some quantum phase transitions proceed very differently than the conventional phase transitions that occur at higher temperatures. Researchers in Germany applied a magnetic field to a metallic compound and watched it transform from a magnet to a non-magnet -- just as expected. The surprise came at higher field strengths, where a puzzling change in the character of the metal was observed. As the temperature was lowered both the magnetic phase transition and the mysterious change converged on the same magnetic field value -- the "quantum critical point" -- defying the conventional method of characterizing phase transitions in terms of a single "universality class" (Science 315 969).

Magnetic heating could be playing a much more prominent role in the evolution of neutron stars than previously expected, claim astrophysicists in Spain and the US. The researchers looked at data describing the surface temperature and magnetic field of about 30 neutron stars and found a mathematical relationship between the two properties that suggests that the stars are being heated by their own magnetic fields. While magnetic heating had been expected in "magnetars" -- neutron stars with very high magnetic fields -- the study provides the first evidence that heating also occurs in stars with much lower fields. This could cause astrophysicists to rethink current theories of how neutron stars cool. (Phys. Rev. Lett. 98 071101).

The Earth generates a magnetic field from the flow of molten metal in its core. Lab experiments have generated fields in a similar way, and in the 26 January Physical Review Letters, researchers report that they can create the self-sustaining magnetic field even when the flow is highly turbulent. The new experiment is a more realistic simulation of Earth's dynamo than previous experiments because the fluid flows freely in a large tank instead of being channeled into prescribed patterns with baffles or tubes. The new design should help researchers better understand the factors that give rise to magnetic fields in planets and stars.

Two pieces of experimental evidence that have been at odds over the existence of the "axion" -- an ultralight particle that could make up dark matter -- may now have been reconciled. Physicists in the US claim to have settled the discrepancy between the PVLAS and CAST experiments by considering the temperatures at which the axions would be produced (Phys. Rev. Lett. 98 050402).

The rise and fall in the popularity of major religions can be described using the same mathematics that is used to model crystallization processes, claim physicists in Belgium. The researchers have modelled the time evolution of the numbers of adherents to religions and claim that their work sheds light on an important social phenomenon -- how a religion such as Christianity can grow rapidly from very small beginnings (Europhysics Letters (EPL) to be published).

For the first time, a group led by Nobel laureate Eric Cornell at the National Institute of Standards and Technology and the University of Colorado in Boulder has confirmed a 1955 prediction, by physicist Evgeny Lifschitz, that temperature affects the Casimir force, the attraction between two objects when they come to within 5 millionths of a meter (approximately 1/5,000 of an inch) of each other or less. These efforts heighten the understanding of the force and enable future experiments to better account for its effects.