A woman carries a piglet as she runs on ice during a running challenge in Changsha, Hunan province February 8, 2015. A total of 20 people participated in the challenge requiring them to choose a pig ranging between 15 kg and 115 kg in weight, and carrying it while running on a 20.15-metre-long ice track. The participants that complete the challenge will be rewarded with the pig they carried, local media reported. (Photo by Darwin Zhou/Reuters)

In this Monday, July 20, 2015 photo, Bill Lattin, the Southern California Timing Association president and Speed Week race director, stands in the Bonneville Salt Flats in Utah. A small city of tents, trailers and thousands of visitors appears almost every August in the Utah desert to watch cars, motorcycles and anything with wheels rocket across gleaming white sheets of salt at speeds of 400 mph. But wet weather has forced the cancellation of Speed Week for the second straight year and revived a debate about whether nearby mining is depleting the Bonneville Salt Flats of their precious resource. (Photo by Rick Bowmer/AP Photo)

An Afghan National Army (ANA) soldier assigned to the Mobile Strike Force Kandak fires a RPG-7 rocket-propelled grenade launcher during a live-fire exercise supervised by the Marines with the Mobile Strike Force Advisor Team on Camp Shorabak, Helmand province, Afghanistan, May 20, 2013. The Marines with the Mobile Strike Force Advisor Team instructed and mentored their ANA counterparts on how to properly utilize their weapons systems. (Photo by SSgt Ezekiel R. Kitandwe/RCT 7)

The Ivanpah Solar Electric Generating System is seen in an aerial view on February 20, 2014 in the Mojave Desert in California near Primm, Nevada. The largest solar thermal power-tower system in the world, owned by NRG Energy, Google and BrightSource Energy, opened last week in the Ivanpah Dry Lake and uses 347,000 computer-controlled mirrors to focus sunlight onto boilers on top of three 459-foot towers, where water is heated to produce steam to power turbines providing power to more than 140,000 California homes. (Photo by Ethan Miller/Getty Images)

A woman lays dead outside the Redemption Hospital on Saturday September 20, 2014 in Monrovia, Liberia. Ebola patients come to the hospital, which has become a transfer and holding center to intake Ebola patients, but there is no space and some die while waiting outside. Redemption is located in one of the poorest neighborhoods of Monrovia that locals call "New Kru Town”. Health workers are overwhelmed with a constant stream of new patients since the Ebola outbreak. (Photo by Michel du Cille/The Washington Post)

Students from St Andrew's University indulge in a tradition of covering themselves with foam to honour the “academic family” on October 20, 2014, in St Andrews, Scotland. Every November the “raisin weekend” which is held in the university's Lower College Lawn, is celebrated and a gift of raisins (now foam) is traditionally given by first year students to their elders as a thank you for their guidance and in exchange they receive a receipt in Latin. (Photo by Jeff J. Mitchell/Getty Images)

Katjinga, a Rhodesian ridgeback dog who lives on a 20-acre farm in Germany, adopted an abandoned pot-bellied piglet in August 2009. The tiny black piglet, named Paulinchen, had been so small at birth that her mother likely overlooked it. Katjinga's owner, Roland Adam, found the piglet alone and cold and brought it to his 8-year-old dog. (Photo by Fame Pictures)

“A Double Eagle is a gold coin of the United States with a denomination of $20. (Its gold content of 0.9675 troy oz was worth $20 at the then official price of $20.67/oz). The coins are made from a 90% gold (0.900 fine = 21.6 kt) and 10% copper alloy”. – Wikipedia

Photo: A “Double Eagle” gold twenty dollar coin is displayed above a catalogue picture showing the reverse side of the coin at Goldsmith's Hall on March 2, 2012 in London, England. Nearly half a million of these coins were originally minted in the midst of the Great Depression in the US. Only 13 are known today after the rest were melted down before they ever left the US Mint, sacrificed as part of a strategy to stabalise the American economy. In 2002 a Double Eagle sold at auction for $7.6 million. (Photo by Peter Macdiarmid/Getty Images)