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14 | NewScientist | 16 July 2011 ONLY cat burglars can match the stealth of dark energy, credited with speeding up the universe’s expansion over time, but now its fingerprints have been glimpsed in the universe’s oldest radiation. The strongest evidence for dark energy comes from supernovae, which suggest the universe is expanding faster now than in the past. But the force should also change the extent to which the cosmic microwave background, relic radiation from the big bang, is warped by the gravity from galaxies and dark matter. Such “gravitational lensing” is tough to pick out because the CMB contains random fluctuations. Using a mathematical function that analyses the CMB, a team based at the Atacama Cosmology Telescope in Chile has identified distinctive distortions from Cold-blooded problem solving CLEVER lizards have worked out how to unplug holes to reach food, suggesting that problem- solving is not the sole preserve of warm-blooded birds and mammals. Anolis evermanni lives in trees in Puerto Rico. Manuel Leal and Brian Powell of Duke University in Durham, North Carolina, captured six and presented them with a platform containing two holes, one sealed with a plain disc and hiding a food reward, the other sealed with a patterned disc and empty. The lizards quickly learned to lever or pull the plain disc out of the way to reach the food (Biology Letters, DOI: 10.1098/rsbl.2011.0480). However, the lizards were slow to adapt when the food was placed beneath the patterned disc instead, points out Alex Kacelnik of the University of Oxford. That suggests they are not as flexible as crows or primates. Second world war bombers changed the weather ALLIED bombing raids during the second world war inadvertently experimented on the weather by producing huge contrails over south-east England. A study of one 1944 raid offers a rare opportunity to check our models of how contrails change temperatures. Contrails have two opposing effects on climate. On the one hand, they act as a blanket, trapping heat that would otherwise escape into space. On the other, during the day they reflect sunlight, cooling the Earth below. Overall, however, climatologists agree they warm the planet. There was hardly any civilian air traffic during the war, KEYSTONE-FRANCE/GETTY IN BRIEF Dark-energy fingerprints in ancient light gravitational lensing and used this to deduce the presence of dark energy. Without dark energy, the warping would be stronger than observed, they say, because the accelerating expansion of the universe prevents the growth of particularly massive structures (Physical Review Letters, vol 107, pp 021301 and 021302). The measurement, while not breaking any records for accuracy, bolsters the case for dark energy’s existence. so historical records offer an opportunity to test the daytime effects. Using records from the US Army Air Forces and the British Royal Air Force, and archived weather data, Roger Timmis of Lancaster Environment Centre in the UK and colleagues compared temperatures beneath one particular flight path with those several kilometres upwind, where there were no contrails. Conditions were ideal for contrails as the raid took off on the morning of 11 May 1944. Where the aircraft were circling, it was significantly cloudier and 0.8 °C cooler than the area upwind (International Journal of Climatology, DOI: 10.1002/joc.2392). Field studies of contrails are rare, so studies like this are essential to check model-based conclusions, says David Travis of the University of Wisconsin-Whitewater. A PROTEIN that causes the agony of sunburn has been identified. Steve McMahon at Kings College London took skin biopsies from rats and 10 healthy humans after reproducing sunburn by exposing them to ultraviolet-B radiation. In all, a protein called CXCL5 was overproduced. Sunburn is an inflammatory response to UV damage; CXCL5 and other molecules are recruited to the damaged area and activate nerve fibres, causing lasting pain. Inflammatory pain also causes arthritis. Finding ways to neutralise pain mediators like CXCL5 could lead to new treatments for such conditions, says McMahon (Science Translational Medicine, DOI: 10.1126/scitranslmed.3002193). Protein puts the sting in sunburn
