In this Friday, February 27, 2015 photo, an Israeli high-school senior preparing to join the Israeli military later this year participates in a privately run training camp for military combat fitness near Yakum, central Israel. With a mandatory three-year military service looming after graduation, teenage boys, and increasingly girls too, are gearing up for the draft, getting into shape and trying to improve their chances of acceptance into elite combat units. (Photo by Oded Balilty/AP Photo)

A baby rhesus macaque (Macaca mulatta) looks up as it plays with a tiger cub at a zoo in Hefei, Anhui province, August 2, 2012. (Photo by Jianan Yu/Reuters)

Cairo-based artist Chanel Arif's paints for her art project called After Dinner that uses humans and their surroundings as her canvas, in her gallery in the capital of Cairo, Egypt March 2, 2017. (Photo by Sherif Fahmy/Reuters)

Spectators, young and old and of all colors of the rainbow, lined the canals in the Dutch capital to watch the colorful spectacle of the Pride Canal Parade return for the 25th edition after the last two events were canceled due to the COVID-19 pandemic, in Amsterdam, Netherlands, Saturday, August 6, 2022. (Photo by Peter Dejong/AP Photo)

Revellers are sprayed by a water cannon during a street party called “Bloco Das Barbas” in Rio de Janeiro, Brazil on February 18, 2023. Hundreds of street parties traditionally take place every year in the city before and during Rio de Janeiro's carnival. (Photo by Carl de Souza/AFP Photo)

Skeleton involves a person riding a small sled down a frozen track while lying face down. The sport is a more intense form of luge because skeleton competitors leap onto the sled and slide downhill head first. Skeleton athletes can reach up to 80 mph on straightaways, causing forces up to 5g, so the helmet is a critical component for attitude as well as safety.

A volcanic eruption at Mount Etna’s Vorgaine crater in Sicily, Italy on December 3, 2015. (Photo by Marco Restivo/Barcroft Media)

Tourists pose with pigeons in the flooded St. Mark's Square in Venice, on November 7, 2014. The high water, a combination of high tides and a strong Scirocco wind in the Adriatic Sea, stood at 110 centimeters early on November 7. The city has for years been wrestling with the problems posed by the threat of rising sea levels. (Photo by Olivier Morin/AFP Photo)