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)

The world's biggest copy of the Mona Lisa is unveiled on October 28, 2009 in Wrexham, Wales The giant version of Leonardo da Vinci's masterpiece measures 17.5 metres across and is 50 times bigger than the original painting and was created by community groups in Wrexham and artist Katy Webster. (Photo by Christopher Furlong/Getty Images)

Bob Woodward looks at the reconstruction he built of the Orpheus Pavement at Prinknash Abbey on March 31, 2010 in Gloucester, England. The replica mosiac, made of more than one-and-a-half million pieces of stone is described as one of the most significant archaeological projects of recent times. (Photo by Matt Cardy/Getty Images)

A Dalek, a Cyberman and a Silence invade the Melbourne Cricket Ground on February 2, 2012 in Melbourne, Australia. The Doctor Who Daleks this weekend are performing for the first time outside of the UK with the Melbourne Syphony Orchestra at Plenary Hall. (Photo by Scott Barbour/Getty Images for BBC Worldwide)

A woman leaves sauna during the sauna marathon in Otepaa, Estonia on February 2, 2019. Participants have to track down, locate and visit designated saunas in the Otepaa area as fast as possible during the event. The team that completed all of the saunas in the shortest time wins. (Photo by Ints Kalnins/Reuters)

Encyclopedia Britannica editions are seen at the New York Public Library on March 14, 2012 in New York City. Encyclopedia Britannica announced it will be ceasing its print edition of reference books for the first time in its 244-year history to focus solely on digital versions. (Photo by Mario Tama/Getty Images)