Ars Technica: Quantum entanglement has been shown to exist and, so far, has not been affected by the distance between the entangled particles. How entanglement works without violating relativity’s limit on the speed of information transfer is still not understood. One explanation is the idea of nonlocality, which suggests that entangled particles are still considered part of the same quantum system regardless of the distance between them. But the concept of nonlocality is uncomfortable to some theorists. An alternative theory suggests that there are hidden, nonmeasurable, variables in quantum systems, but a new analysis has shown that hidden variables would still allow faster-than-light communication. In a paper in Nature Physics, researchers describe how they examined a theoretical entangled system in which hidden variables were allowed to communicate faster than light. They determined that because of the symmetry inherent in quantum systems, the measurable variables would also transfer information faster than light. But faster-than-light communication violates the theory of relativity. Although that fact doesn’t necessarily disprove hidden-variable explanations for quantum entanglement, it might mean that relativity would need to be adjusted.
Chemistry World: Researchers in Korea have created a high-power LED lens modeled on the bioluminescent structures of fireflies. The insects’ lantern comprises three layers: a luminous layer sandwiched between a cuticle layer and a dorsal layer. Using a scanning electron microscope, Jae-Jun Kim and colleagues at the Korea Advanced Institute of Science and Technology studied the intricate nanostructure of the cuticle layer. They found that it acts much like an LED’s dome lens. By combining the latest nanoscale processing techniques with what they learned about fireflies’ cuticle layer, the researchers created a nanostructured reflecting surface for LEDs that enhances light emission and increases overall efficiency.
Technology Review: In 1990, NASA scientists detected an anomaly in the telemetry of the Galileo spacecraft while it was using Earth as a gravitational slingshot to help it on its way toward Jupiter. During the flyby, the craft’s speed suddenly increased 4 mm/s. A similar effect has been seen in three other flybys since. The anomaly only occurs when the observed trajectory of the spacecraft can’t be fit to a single hyperbolic arc. When the scientists have to use separate equations for the incoming and outgoing paths, there is a discrepancy that neither equation accounts for. But what causes the anomalous speed change is still uncertain. The European Space Agency is planning to launch a satellite in 2022 or 2024 that will have a highly eccentric orbit around Earth and may provide the opportunity to collect data that will help explain the slingshot anomaly.
Talking Points Memo: Using NASA’s Fermi Gamma-Ray Space Telescope (Fermi), astronomers have measured the total extragalactic background light (EBL), the “cosmic fog” created by all the visible and UV photons emitted by all the stars that have ever existed. Launched in 2008, Fermi uses its primary instrument, the Large Area Telescope, to scan the entire sky for high-energy gamma rays emitted by blazars—distant galaxies with supermassive black holes. Because some of the gamma rays will collide with photons in the EBL and become electrons and positrons, the number of gamma rays emitted by a given source decreases over distance; hence, the more distant the blazar, the fewer high-energy gamma rays are detected by Fermi. By calculating the average gamma-ray attenuation across several distance ranges, astronomers were able to estimate the EBL’s thickness. They found the average stellar density to be about 1.4 stars per 100 billion cubic light-years, which means the average distance between stars is about 4150 light-years. Their paper was published online yesterday in Science Express.