The First U.S. Spacewalk – Gemini 4 Ed White made the United States' first spacewalk on June 3, 1965 during the Gemini 4 mission. The extra-vehicular activity (EVA) started at 19:45 UT (3:45 p.m. EDT) on the third orbit when White opened his hatch and used the hand-held manuevering oxygen-jet gun to push himself out of the capsule. (Photo by NASA)

The Villarrica Volcano is seen at night from Pucon town, Chile, July 12, 2015. Villarrica, located near the popular tourist resort of Pucon, is among the most active volcanoes in South America. (Photo by Cristobal Saavedra/Reuters)

Soldiers stand guard in Maua square where a cotton candy vendor passes by in Rio de Janeiro, Brazil, Saturday, July 9, 2016, as security is deployed to get to know the areas they'll be patrolling during the Olympics. Roughly twice the security contingent at the London Olympics will be deployed during the August games in Rio, which are expected to draw thousands of foreigners to a city where armed muggings, stray bullets and turf wars between heavily armed drug gangs are routine. (Photo by Leo Correa/AP Photo)

In this Monday, January 23, 2017 photo, chicken feet snacks shop owner Leung Kin-kung testes a chicken feet in Hong Kong. Saturday marks the start of the lunar Year of the Rooster and families in China will reunite for festivities, fireworks and food. While tradition calls for feasting on “auspicious” foods, many will also munch on staple snacks like “phoenix claws”, the Chinese name for chicken feet. (Photo by Vincent Yu/AP Photo)

Take me away, deer, Russia. The Nenet people of Arctic Russia use reindeer and sledges as a prime mode of transport. The animals’ navigational ability means that in severe conditions they are sometimes the only hope of survival. (Photo by Kamil Nureev/Smithsonian Photo Contest)

The fourth annual BigPicture Natural World Photography Competition aims to celebrate the diversity of life on Earth, and encourages people to protect and conserve it. Here: “The Salmon Catchers”. Terrestrial Wildlife. To capture this view of a mother grizzly bear and her cub, photographer Peter Mather set up a camera trap on a log that he knew the bears tended to traverse while fishing for salmon, in the Yukon River watershed in Canada. (Photo by Peter Mather/BigPicture Natural World Photography Competition 2017)

Women walk past a mannequin with a covered face as they shop ahead of the Muslim festival of Eid-al-Adha in Aleppo, Syria September 23, 2015. (Photo by Hamid Khatib/Reuters)

1: Dubai's Burj Khalifa is the tallest building in the world, but perhaps not for long. Saudi Arabia has announced plans to build a 1 kilometer (3,280 foot) tower into the sky, to be named the Jeddah Tower, scheduled for completion in 2020. The Burj Khallifa currently stands at 2,716 ft. (Photo by Matthias Seifert/Reuters)