Thor, Virginia Tech College of Engineering, Robotics and Mechanisms Laboratory, tries to connect the hose to a firehose connection during the hose task at the Homestead-Miami Speedway, Friday, December 20, 2013, in Homestead, Fla. (Photo by Alan Diaz/AP 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.

Models blow kisses backstage at the Red Beard show during MBFWI presented by American Express Fall/Winter 2014 on March 13, 2014 in Istanbul, Turkey. (Photo by S. Alemdar/Getty Images for IMG)

These two young siblings appear to cling on to a tree for dear life and even hold hands as they learn the ropes of climbing, on June 25, 2013. (Photo by Tim Fitzharris/Minden/Solent)

This photo released Saturday March 22, 2014 by Stichting Ambulance Wens or Ambulance Wish Foundation shows a giraffe at Blijdorp Zoo in Rotterdam giving a lick to terminally ill Mario Eijs on Wednesday March 19, 2014. The Stichting Ambulancewens “Ambulance Wish Foundation” offers transport for terminally ill patients who cannot walk to help fulfill a last wish, in Eijs' case to be taken to the Blijdorp Zoo in Rotterdam where he worked doing odd jobs for 25 years. Eijs, who has a mental handicap, is dying of a brain tumor and has difficulty walking or speaking. (Photo by AP Photo/Stichting Ambulance Wens)

“The Mikoyan MiG-31 (NATO reporting name: Foxhound) is a supersonic interceptor aircraft developed to replace the MiG-25 “Foxbat”. The MiG-31 was designed by the Mikoyan design bureau based on the MiG-25”. – Wikipedia

Photos: The Mikoyan MiG-31 “Foxhound”. Russia, April 2012. (Photo by Alexandr Pak; Source: LiveJournal)

“The giant clam, Tridacna gigas (known as pā’ua in Cook Islands Māori), is the largest living bivalve mollusc. T. gigas is one of the most endangered clam species. It was mentioned as early as 1825 in scientific reports. One of a number of large clam species native to the shallow coral reefs of the South Pacific and Indian oceans, they can weigh more than 200 kilograms (440 lb) measure as much as 120 cm (47 in) across, and have an average lifespan in the wild of 100 years or more”. – Wikipedia

Photo: Tridacna Gigas, or Giant Clams spew water as a traditional fisherman passes by a small sanctuary on January 23, 2004 near Bolinao in the Northern Philippines. The clams, prime builders for coral reefs and providing shelter for spawning fish and other marine life, are exposed by low tides in the sanctuary. Overfishing and pollution throughout the country are not only threatening food security, but are also starting to choke one of the few working clam sanctuaries in the world. (Photo by David Greedy/Getty Images)

A street performer jumps in the air inside Central Park as the colors of autumn become more prevalent in New York, October 29, 2015. (Photo by Lucas Jackson/Reuters)