A life size animatronic Tyrannosaurus Rex dinosaur arrives at Bristol Zoo Gardens on May 14, 2012 in Bristol, England. Twelve animatronic dinosaurs arrived at Bristol Zoo Gardens this morning after being transported in crates from Texas, USA. They will form part of the zoo's summer exhibition “DinoZoo” which opens later this month. (Photo by Matt Cardy)

Mary McHugh mourns her slain fiance Sgt. James Regan at “Section 60” of the Arlington National Cemetery May 27, 2007. Regan, a US Army Ranger, was killed by an IED explosion in Iraq. (Photo by John Moore/Getty Images)

People walk past a downed tree in Central Park on October 31, 2011 in New York City. Central Park may lose 1,000 trees following a freak October snowstorm while the park only lost 125 trees due to Hurricane Irene. (Photo by Mario Tama/Getty Images)

Visitors attend a press preview of the 2012 Whitney Biennial at the Whitney Museum of American Art on February 27, 2012 in New York City. The contemporary art exhibition includes sculpture, photography, painting, installations, dance, theater, film and music and runs from March 1 through May 27. (Photo by Mario Tama/Getty Images)

Female Chimpanzee “Fifi” eats carrots as she sits in her enclosure at Taronga Zoo on her 60th birthday May 21, 2007 in Sydney, Australia. Fifi is the oldest of the Zoo's chimp population, which consists of 19 individuals. (Photo by Ian Waldie/Getty Images)

“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)

Darren Julien poses with two of Princess Diana's dresses which will be auctioned through WE tv & Wedding Central at Julien's Auctions in Beverly Hills on May 7th in celebration of the Royal Wedding, with a portion of the proceeds going to charity are shown at Times Square on April 20, 2011 in New York City. (Photo by Slaven Vlasic/Getty Images)

Adult gentoo penguins keep an eye on their newly born chick at Edinburgh Zoo on June 10, 2011 in Edinburgh, Scotland. The gentoo chicks which started hatching in early May are looked after by both parents who regurgitate part digested food. When the chicks are hungry they peck the beaks of their parents to signal feeding time. (Photo by Jeff J Mitchell/Getty Images)