People cool off in a fountain outside the Southbank Centre on June 30, 2015 in London, England. The UK is currently experiencing a heatwave, with temperatures of 35 degree celsius forecast tomorrow in some parts of the country. The extreme heat has already seen train cancellations and a health warning has been issued. (Photo by Rob Stothard/Getty Images)

Jimmy Bryan of Phoenix, Ariz., gets the checkered victory flag at the Indiana State Fairgrounds September 17, 1955 as he wins the “Hoosier Hundred” for the second consecutive year. Bryan averaged 83.98 miles an hour for the 100-lap, 100-mile AAA big car race. (Photo by AP Photo)

Dancers from the Philadelphia Ballet perform for Pope Francis (R) as he attends the Festival of Families rally in Philadelphia, Pennsylvania September 26, 2015. (Photo by Brian Snyder/Reuters)

A curious leopard cub toys with a camera at MalaMala Game Reserve in Mpumalanga Province, South Africa. (Photo by Barcroft Media)

In this July 10, 2014 photo, Chris Minore, of Orange, Conn., performs the under chop technique at the Adirondack Woodsmen's School at Paul Smith's College in Paul Smiths, N.Y. Eighteen young students in matching gray sports shirts took part recently in a weeklong crash course on old-school lumberjack skills such as sawing, chopping, ax throwing, log boom running and pole climbing. (Photo by Mike Groll/AP Photo)

One part of “Celestrial Texts – Heavenly Tweets” by Laine Hogarty is seen as part of the “Hidden” annual sculpture exhibition at Rookwood Cemetery on September 15, 2014 in Sydney, Australia. Located in the suburb or Rookwood in Western Sydney Rookwood cemetery is the largest necropolis in the southern hemisphere. The Annual “Hidden” exhibition features works by local artists. (Photo by Mark Kolbe/Getty Images)

An airplane passes the moon as it makes its approach to Philadelphia International Airport, Sunday, September 7, 2014, in Philadelphia. (Photo by Matt Rourke/AP Photo)