The Northern Lights glow green in a spectacular light show above a field of trees frozen solid with snow. (Photo by Jaak Sarv/Solent News & Photo Agency)

A man photographs the main engines of the space shuttle orbiter Discovery on display at the Udvar-Hazy Smithsonian National Air and Space Annex Museum in Chantilly, Virginia August 28, 2015. Shuttle Discovery had 27 years of service and flew 39 times before being retired in 2011. (Photo by Gary Cameron/Reuters)

Luling, Louisiana, US. New evidence contradicts previous claims of the relative safety of glyphosate, the world’s most widely used herbicide, which is manufactured here. It is often used in conjunction with seeds that have been genetically modified to tolerate its application, meaning that anyone consuming these crops is eating a genetically modified plant, and whatever residue of the pesticide that remains. (Photo by J. Henry Fair/Industrial Scars/Papadakis Publisher)

A vehicle leaves light trails in a long exposure photograph as it drives beneath the 500-metre Aperture Spherical Radio Telescope in Pingtang county, China. Construction on the device began in 2011 and is nearing completion. (Photo by Liu Xu/AP Photo)

Spacewalker Mark Vande Hei took his own photograph during the first spacewalk of 2018, on January 23, 2018. These sky-high pictures are better known as “space-selfies”. (Photo by Mark Vande Hei/NASA)

North Korean cheerleaders arrive at a rest stop, or service station, as their bus convoy carrying a 280- member delegation on its way to the 2018 Pyeongchang winter Olympic games, makes its way past Gapyeong on February 7, 2018 More than 200 young North Korean women arrived in South Korea to root for athletes from both sides of the peninsula at the Winter Olympics. (Photo by Ed Jones/AFP Photo)

A Hawaiian cleaner wrasse provides its cleaning services to a yellowfin goatfish in a reef community off the Big Island in Hawaii. Cleaner species help rid their hosts of ectoparasites, dead tissue, bacteria and fungi. Studies have shown cleaning to play a vital role in keeping many reef ecosystems healthy. (Photo by Marty Snyderman/Caters News Agency)

A man wearing a water-filled helmet in which a goldfish swims performs an act titled “Aquaman” during the Night Festival 2016 in Singapore, 20 August 2016. The ninth edition of the festival will run from 19 to 27 August and features installations and performances by a range of international and local artists. (Photo by Wallace Woon/EPA)