A hiker admires the view as Mt. Etna, Europe's largest active volcano, erupts in the background, in the Bove Valley of Etna Park, on the eastern slope of Mt. Etna, in Sicily, southern Italy, Sunday, July 4, 2021. Since Feb. 16, 2021, Mt. Etna has begun a series of eruptive episodes. (Photo by Salvatore Allegra/AP Photo)

United States Air Force Academy graduates cheer as the United States Air Force Thunderbirds fly over the graduation for the Class of 2021 at Falcon Stadium on May 26, 2021 in Colorado Springs, Colorado. Chairman of the Joint Chiefs of Staff General Mark A. Milley gave the commencement address to the 1,019 graduates from the academy. (Photo by Michael Ciaglo/Getty Images)

The galactic centre of the Milky Way glows brightly in the clear night sky above the lighthouse at Portland Bill on the Dorset Jurassic Coast, United Kingdom on April 13, 2021. (Photo by Graham Hunt/Alamy Live News)

Tourists in traditional costumes visit a rose garden during a rose cultural festival on April 27, 2021 in Huzhou, Zhejiang Province of China. (Photo by VCG/VCG via Getty Images)

A Palestinian youth swings a homemade fireworks sparkler, as people celebrate on the night ahead of the Muslim holy fasting month of Ramadan, in Gaza City on April 11, 2021. (Photo by Majdi Fathi/NurPhoto/Rex Features/Shutterstock)

Spectators cheer after Medina Spirit, ridden by John Velazquez wins 147th Kentucky Derby at. Churchill Downs, in Louisville, Kentucky, U.S. May 1, 2021. (Photo by Bryan Woolston/Reuters)

Nursing students attend a capping ceremony on May 10, 2021 in Jinan, Shandong Province of China. International Nurses Day is observed annually on May 12. (Photo by Zhang Yong/China News Service via Getty Images)

A couple dance by the Golden Horn leading to the Bosphorus Strait separating Europe and Asia, in Istanbul, Friday, May 14, 2021. (Photo by Emrah Gurel/AP Photo)