Men wearing costume of traditional firefighters perform acrobatic stunts atop a bamboo ladder following a memorial service for firefighters at Sensoji temple in Tokyo's downtown of Asakusa May 25, 2015. Hundreds of firefighters in traditional costume gathered on Monday for the memorial service for firefighters who were killed performing their duties during the past 300 years. (Photo by Issei Kato/Reuters)

Astronaut Edwin E. Aldrin Jr. walks near the Lunar Module during the Apollo 11 extravehicular activity July 20, 1969 on the Moon. (Photo by NASA/Newsmakers)

Sally Gomez drives to rescue of friend Michele Moore in flooded parking lot at Hyannis, Mass., September 9, 1969, after torrential rains of Hurricane Gerda flooded low areas of Cape Cod. Ann Davis of Osterville stands up in roof opening to lend a hand. Sally and Michele are from Centerville on the Cape. (Photo by Frank C. Curtin/AP Photo)

Leon Samson, 24-year-old showman, grimaces as an automobile is driven across his chest at Perth, Australia on October 9, 1960. Samson said the towel on his chest is to prevent the wheel from tearing his flesh. (Photo by AP Photo)

Samba dancers arrive to perform ahead of the athletics competitions of the 2016 Summer Olympics at the Olympic stadium in Rio de Janeiro, Brazil, Sunday, August 14, 2016. (Photo by Jae C. Hong/AP Photo)

Puerto Rico's Grace Claxton warms up before competing in the Women's 400m Hurdles Round 1 during the athletics event at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 15, 2016. (Photo by Jewel Samad/AFP Photo)

The Mike O'Callaghan–Pat Tillman Memorial Bridge is an arch bridge in the United States that spans the Colorado River between the states of Arizona and Nevada. The bridge is located within the Lake Mead National Recreation Area approximately 30 miles (48 km) southeast of Las Vegas, Nevada, and carries U.S. Route 93 over the Colorado River.

Members of the 3rd U.S. Infantry Regiment place American flags at the graves of U.S. soldiers buried at Arlington National Cemetery in preparation for Memorial Day May 26, 2011 in Arlington, Virginia. “Flags-In” has become an annual event since the 3rd U.S. Infantry Regiment (The Old Guard) was appointed an Army official ceremonial unit in 1948. Every available soldier in the 3rd U.S. Infantry Regiment participates in these annual ceremonies. (Photo by Win McNamee/Getty Images)