Storm clouds blanket the sky over Great American Ball Park as Starlin Castro #13 of the Chicago Cubs fields a ground ball in the fifth inning against the Cincinnati Reds as on July 7, 2014 in Cincinnati, Ohio. (Photo by Jamie Sabau/Getty Images)

This undated image provided by World View shows World View capsule and balloon spacecraft that will rise to 100,000 feet above Earth for passengers to see the curvature of the planet and the blackness of space. Space tourism companies are employing designs including winged vehicles, vertical rockets with capsules and high-altitude balloons. While developers envision ultimately taking people to orbiting habitats, the moon or beyond, the immediate future involves short flights into or near the lowest reaches of space without going into orbit. (Photo by World View via AP Photo)

U.S. Army helicopters providing support for U.S. ground troops fly into a staging area fifty miles northeast of Saigon, Vietnam, August 28, 1966. Helicopter fuel is stored in the large rubber tanks, foreground. (Photo by Henri Huet/AP Photo)

A young woman cools herself in a fountain in Budapest, Hungary July 6, 2015. Over the weekend, a heat wave has reached Hungary with temperatures topping 38 degrees Celsius (100.4 degrees Fahrenheit). (Photo by Laszlo Balogh/Reuters)

A humanoid robot named “Robi” sits during a promotional event for the launch of a weekly Robi Magazine in Tokyo, Japan, 20 January 2015. Created by roboticist Tomotaka Takahashi, the 34-centimeter tall humanoid robot can recognize and respond to more than 200 words and phrases, walk and dance. Parts of the robot will be put on sale in a weekly magazine to be fully assembled with 70 issues. (Photo by Franck Robichon/EPA)

This picture taken on January 25, 2015 shows a participant taking part in an ice water challenge in Zhangjiajie, central China's Hunan province. Participants were required to stay in an ice pond, holding an ice block while eating ice-cream with an electric fan blowing at them. (Photo by AFP Photo/Stringer)

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)

A working team appointed by the Archaeological Superintendence of Pompeii performs a Cat scan (Computerized axial tomography) one out of thirty casts of victims of the eruption of Vesuvius in 79 AD in Pompeii, in Napoli, Italy, 29 September 2015. The project which aims to trace the habits of life, employment and social class of the victims, involves a working team of archeologists, anthropologists, radiologists, dentists and engineers to obtain results from the scan. (Photo by Cesare Abbate/EPA)