New Scientist: For the first 2 billion years after Earth’s formation, the Sun was 25% less bright than it is now, so Earth’s surface temperature would have been about −10 °C. However, the geologic record shows that Earth was covered in liquid water, not ice. Robin Wordsworth and Raymond Pierrehumbert of the University of Chicago believe that Saturn’s moon Titan, which has liquid on its surface, can help explain liquid water on early Earth. Titan has a liquid surface because of the high concentration of hydrogen and nitrogen in its atmosphere. Because of the pressure they are under, they act as greenhouse gases, trapping heat and warming the surface. Wordsworth and Pierrehumbert suggest that if early on Earth’s atmosphere was made up of 10% hydrogen and nitrogen that was at a level two to three times its current concentration, then the surface temperature would have been 10–15 degrees higher, allowing for liquid water. They admit that the geologic evidence doesn’t show those concentrations, but they point to several factors that could have allowed it. They include the lack of oxygen, increased volcanism, and the potential lack of hydrogen-consuming microbes. However, there is much that the model still has to explain and a lack of hard evidence to support it.
Nature: Absolute zero corresponds to the theoretical state in which the average energy of a system of particles is zero. During the normal state of a gas, the majority of the particles are at energies near the average, with just a few at higher energy levels. Theorists predicted in the 1950s that if a gas could be created in which the situation was reversed—the majority of the particles had higher energy levels—then the temperature could drop to below absolute zero. Ulrich Schneider, with Ludwig-Maximilians University in Munich, and his colleagues appear to have done just that. Using lasers and magnetic fields, the researchers arranged a stable lattice structure out of a quantum gas of potassium atoms. Quickly adjusting the magnetic field caused the atoms to attract rather than repel each other, and they shifted from their lowest-energy state to a high-energy state. Normally, that would cause the lattice to collapse, but the researchers used the lasers to make it too difficult for the atoms to leave their positions. The result is a gas that has a temperature just a few billionths of a degree below absolute zero. The experiment opens the way to potential stable states of exotic materials, and the theoretical behavior of other systems at sub-absolute-zero temperatures may provide some answers about cosmological phenomena such as dark energy.
Los Angeles Times: Just more than half of the 27 dwarf galaxies orbiting the Andromeda galaxy have been found to share the same orbital plane. And 13 of those 15 are orbiting in the same direction, much as the planets in our solar system all orbit in the same direction around the Sun. The arrangement was detected by a team led by Rodrigo Ibata of the Strasbourg Astronomical Observatory in France using data from the Pan-Andromeda Archaeological Survey. No currently accepted models for galaxy formation predict such dwarf galaxy behavior. Dwarf galaxies are believed to be the remnants of the material that coalesced into giant galaxies such as the Milky Way and Andromeda, so they are expected to be scattered randomly around their parent galaxies. Of further interest in the arrangement, the 15 plane-sharing dwarf galaxies are also on the plane shared by both the Milky Way and Andromeda. Although that may be coincidental, it may also provide more understanding of the structure of galaxy arrangements.
BBC: A meteorite—called Northwest Africa (NWA) 7034 and nicknamed “Black Beauty”—discovered in the Moroccan desert in 2011 resembles others from Mars but is distinctly different in its elemental composition, according to Carl Agee from the University of New Mexico. Unlike any of the three current classes of Martian meteorites, the specimen is a basaltic breccia composed of fragments fused together in a volcanic eruption, is made up primarily of alkali elements such as potassium and sodium, and has about 10 times more water. It is also much older—NWA 7034 is about 2 billion years old, whereas most of the other Martian meteorites are 200 million to 400 million years old. Because of its greater age, the specimen could provide clues to the early geologic history of Mars, which may have been a lot warmer and wetter than it is now.
Ars Technica: One test of the wave–particle duality of quantum objects is a class of experiments, in which a measurement made on one photon determines the wave-like or particle-like behavior of its entangled partner. However, this type of experiment has only been conducted in single laboratories, which leaves open the possibility that the photon detectors might have interacted, leading to spurious results. Xiao-Song Ma of the University of Vienna and colleagues have now conducted the experiment by separating the entangled photons over 144 km, between two labs in the Canary Islands. After entangling two photons in one lab, they sent one of them through the open air to the other facility and into a device that determines the photon’s polarization, a state correlated with that of its entangled partner. The device was randomly switched between two modes to measure either circular polarization or linear polarization. If the distant device detected a photon that was circularly polarized, then the photon that passed through a polarizing beam-splitter in the original location would behave like a wave; if the distant device detected linear polarization, then the photon in the original lab would behave like a particle.