On the western side of Mount Hood lies the longest glacier cave system in the contiguous United States. In 2012, these caves were mapped to a combined length of 7,166.8 feet by cave explorers Brent McGregor and Eddy Cartaya. Currently, the total passage length is hundreds of feet less. Glaciers are frozen rivers; they are always moving and changing... (Photo and caption by Josh Hydeman)

Revellers from Russia parade during the Aoussou Carnival in Sousse, Tunisia July 26, 2015. (Photo by Anis Mili/Reuters)

Astronaut Donald R. Pettit would often rig an array of as many as six cameras in the cupola windows and set them all to fire continuously for events such as sunsets, which only last around seven seconds on the ISS. (Photo by Donald R. Pettit)

Madame Tussauds's wax figure of Audrey Hepburn sits at an empty table to comply with coronavirus disease (COVID-19) social distancing requirements in a dining room at Peter Luger Steak House in Brooklyn, New York U.S., February 26, 2021. (Photo by Brendan McDermid/Reuters)

A racegoer reacts to picking a winner in the first race on the third day of the Royal Ascot horserace meeting, which is traditionally known as Ladies Day, at Ascot, England Thursday, June 17, 2021. (Photo by Alastair Grant/AP Photo)

A woman walks with her daughter through an empty street on April 27, 2020 in Malaga, Spain. Since April 27 children under 12 are allowed to come and go from their homes more freely. Spain has had more than 209,000 confirmed cases of COVID-19 and over 23,000 reported deaths, although the rate has declined after weeks of lockdown measures. (Photo by Daniel Perez Garcia-Santos/Getty Images)

Musicians play as bathers run into the chilly waters of English Bay while celebrating New Year's Day with the Polar Bear Swim in Vancouver, British Columbia, Canada on January 1, 2024. (Photo by Chris Helgren/Reuters)

A man takes a photo of a radio antenna that's part of the Atacama Large Milimeter Array Observatory on March 12, 2013 at Llano de Chajnantor, about 43 miles (70 kilometers) from San Pedro de Atacama, Chile. The $1.5 billion ALMA facility, which had its official inauguration on March 13, is considered the world's most expensive ground-based observatory. (Photo by Felipe Trueba/EPA)