In this July 10, 2014 photo, Chris Minore, of Orange, Conn., performs the under chop technique at the Adirondack Woodsmen's School at Paul Smith's College in Paul Smiths, N.Y. Eighteen young students in matching gray sports shirts took part recently in a weeklong crash course on old-school lumberjack skills such as sawing, chopping, ax throwing, log boom running and pole climbing. (Photo by Mike Groll/AP Photo)

Dhofar Region, Oman. Much of Oman is desert, but the Arabian Sea coast in the Dhofar region represents a startling difference in climate. This coastal region catches the monsoon rains, or khareef, during the summer months. Drenching rains fall primarily on the mountainous ridge that separates the lush, fertile areas along the coast from the arid interior, recharging streams, waterfalls and springs that provide plentiful water supplies in the fertile lowlands for the remainder of the year. Image taken by Landsat 5 on April 2, 2005. (Photo by USGS/NASA)

These frozen caves seem almost otherworldly as they daylight illuminates them. Matej Kriz’s shots reveal the beauty of the brilliant caves, but he’s also very aware of how deadly they can be. The photographer captured the amazing shots in the Vatnajokull National Park on the Breidamerkurjokull glacier tongue. Here: The ice caves, taken in the Vatnajokull National Park in Iceland, on November 11, 2017. (Photo by Matej Kriz/Caters News Agency)

Pedestrians cover their face as they walk along the dusty road in Kathmandu, Nepal February 27, 2017. Nepal has forced 2,500 old vehicles off roads in its capital city of Kathmandu, part of a fight against alarming air pollution levels that have hit nine times World Health Organisation (WHO) limits. Air pollution has been a chronic problem in rapidly growing Kathmandu, which sits in a Himalayan valley and is home to more than 3mn people. (Photo by Navesh Chitrakar/Reuters)

European Space Agency astronaut Tim Peake will return home after a six-month long mission on the International Space Station,on June 18, 2016. Peake was the first British ESA astronaut to visit the ISS and captured hundreds of photographs of the Earth during his mission. Here: “Lots of sun-glint right now during our whole orbit – we haven't seen a sunset for over 3 days”, he wrote. (Photo by Tim Peake/ESA/NASA)

Some of the best entries so far in the 2016 Insight Astronomy Photographer of the Year competition. There are two weeks left to enter, and the winners will be announced in September. Here: Aurora over Laksvatn Fjord, Laksvatn, Norway. The aurora borealis dances in the skies over the town of Laksvatn, with the Milky Way to the left. The image is a single shot with no compositing, only post-processing to bring out the aurora, and some colour corrections. The photographer Matt Walford said: “I love the way the northern lights look like they are just wistfully dancing over the fjord, framed by the mountains on either side”. (Photo by Matt Walford/National Maritime Museum)

Brush your teeth and get cleaned up for the week ahead! These animals answered the call of good dental hygiene. Here: Hamster holds toothbrush. (Photo by Neo Vision/Getty Images/Amana Images RM)

Photographer holding digital camera during photoshoot of fashion model. (Photo by grinvalds/Getty Images)