Luis Hernan was always curious about how wireless technologies like radio are transmitted through the air. So after finishing up his studies in architecture, computer science, and design, Hernan decided to research these invisible signals through a PhD at Newcastle University. Hernan set up a system that turned the wireless signals around him into colourful, ghostlike images using long-exposure photography, allowing people to see the strength of the signals around them. (Photo by Luis Hernan)

A Russian ground staff member signals to the pilot of a Sukhoi Su-25 fighter jet at the Hmeymim air base near Latakia, Syria, in this handout photograph released by Russia's Defence Ministry October 22, 2015. (Photo by Reuters/Ministry of Defence of the Russian Federation)

A Tibetan man stirs butter tea made for the arriving guest during the function organised to mark Losar or the Tibetan New Year at a Tibetan Refugee Camp in Lalitpur February 19, 2015. Tibetans across the world marked the arrival of the New Year with prayers and festivities. (Photo by Niranjan Shrestha/AP Photo)

Women perform square dancing at a park square in Beijing, China, April 9, 2015. Chinese-style square dancing is running circles around other hobbies for the elderly, with millions taking to parks and plazas across China, swivelling their hips and rolling their arms – but it's not to everyone's liking. (Photo by Kim Kyung-Hoon/Reuters)

People celebrate Nowruz, considered as the harbinger of spring, awakening of nature and brotherhood, with traditional costumes and at Gobustan National Park in Baku, Azerbaijan on March 21, 2022. People from different regions of Azerbaijan attended celebration with colorful dresses and various music groups performed. (Photo by Resul Rehimov/Anadolu Agency via Getty Images)

A girl cools off in a public fountain in Vilnius, Lithuania, Wednesday, August 16, 2023. The heat wave continues in Lithuania as temperatures rise to as high as 32 degrees Celsius (89.6 degrees Fahrenheit). (Photo by Mindaugas Kulbis/AP Photo)

Canadian fashion model Winnie Harlow and American rapper Doja Cat attend Darren Dzienciol & Richie Akiva's Oscar Party 2021 on April 25, 2021 in Bel Air, California. (Photo by Rochelle Brodin/Getty Images for Darren Dzienciol)

Birds are seen at Kizilirmak Bird Paradise in Turkey's Samsun on April 22, 2021. Kizilirmak Delta Bird Sanctuary, which is on the UNESCO World Heritage Tentative List and hosts 359 to 487 species of birds in Turkey, became more active with the arrival of spring. (Photo by Mehmet Kumcagiz/Anadolu Agency via Getty Images)