A tow car for the children's “Grand Prix” races which take place in a parking lot in Livonia, Michigan a suburb of Detroit, circa 1955. (Photo by Three Lions/Getty Images)

Firefighters watch as an air tanker drops retardant while battling the Ferguson fire in the Stanislaus National Forest, near Yosemite National Park, California on July 21, 2018. A fire that claimed the life of one firefighter and injured two others near California's Yosemite national park has almost doubled in size in three days, authorities said Friday. (Photo by Noah Berger/AFP Photo)

Three secondary schoolboys smoking an illicit cigarette in Hyde Park, London. (Photo by Evening Standard/Getty Images). May 1972

Participants dressed as Santa Claus take part in the Great Edinburgh Santa Run on December 11, 2011 in Edinburgh, Scotland. Around a thousand people took part in the annual fundraising event, with all money raised being donated to the charity “When You Wish Upon a Star”. (Photo by Jeff J. Mitchell/Getty Images)

A man walks on the Cobb as storm waves break behind on December 13, 2011 in Lyme Regis, England. (Photo by Matt Cardy/Getty Images)

In this November 28, 1966 file photo, one of the 10 beagles involved in the first test of the Veterans Administration Hospital in East Orange, N.J. smokes a cigarette through a machine linked to its windpipe by a plastic tube to test any link between smoking and emphysema. (Photo by 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.

A visitor passes behind the sculpture “Puma-Dentist” made with plastic, wax and original heads of a puma and a hind by Austrian artist Deborah Sengl during an exhibition at the art gallery Deschler in Berlin April 15, 2008. (Photo by Fabrizio Bensch/Reuters)