Two F-15E Strike Eagles wait to receive fuel from a KC-135R Stratotanker during exercise Red Flag 15-1 on their way to Nellis Air Force Base, Nev., Jauary 23, 2015. The F-15s are assigned to the 4th Fighter Wing. U.S. (Photo by Airman 1st Class Aaron J. Jenne/Reuters)

This photo provided by Steamboat Ski Resort shows hot air balloons that visitors can tour in above the town and mountains in Steamboat Springs, Colo. Wild West Adventures offer continental breakfast, champagne ceremony with flight certificates and courtesy pick-up are included. (Photo by Larry Pierce/AP Photo/Steamboat Ski Resort)

People stroll alongside one of the hills of the Tio Pio park in Madrid, Monday, January 25, 2016. The park is a high viewpoint frequented mostly by locals due to its view of the Spanish capital skyline. (Photo by Francisco Seco/AP Photo)

Long shadows are cast by players as Mitch Wallis of the Bulldogs passes the ball during the 2016 AFL Round 08 match between the Melbourne Demons and the Western Bulldogs at the Melbourne Cricket Ground, Melbourne on May 15, 2016. (Photo by Scott Barbour/AFL Media/Getty Images)

A hogweed bonking beetle and yellow dung fly in a stalk standoff (the fly gave in), in Burley-in-Wharfedale, Yorkshire, England. (Photo by Rebecca Cole/Alamy Stock Photo)

These goats threw caution to the wind and scaled this Argan tree right to the very top, even balancing on the most unsturdy of branches. It looks like a bit of a baa-lancing act, but the goats hooves are perfectly adapted to climbing the trees, where they graze on the Argan fruit. Amateur photographer Burak Senbak, 51, took these photos whilst travelling through Morocco in July 2016. Burak is originally from Turkey and works as a mechanical engineer, but has pursued his passion for photography for 10 years. Intrigued by the sight of goats in a tree, Burak couldnt resist the opportunity to take some photos, and said the goats proved a perfect subject. (Photo by Burak Senbak/Caters News)

This image made available by the Johns Hopkins University Applied Physics Laboratory on Wednesday, May 31, 2017 depicts NASA's Solar Probe Plus spacecraft approaching the sun. On Wednesday, NASA announced it will launch the probe in summer 2018 to explore the solar atmosphere. It will be subjected to brutal heat and radiation like no other man-made structure before. (Photo by Johns Hopkins University Applied Physics Laboratory via AP Photo)

The Aurora Borealis (Northern Lights) is seen over the sky near the village of Pallas (Muonio region) of Lapland, Finland September 8, 2017. (Photo by Alexander Kuznetsov/Reuters)