The cruise ship Viking Sky as it drifts after sending a Mayday signal because of engine failure in windy conditions near Hustadvika, off the west coast of Norway, Saturday March 23, 2019. The Viking Sky is forced to evacuate its estimated 1,300 passengers. (Photo by Odd Roar Lange/NTB Scanpix via AP Photo)

Julian Ryerson of Borussia Dortmund during the Bundesliga match between Borussia Dortmund and 1. FC Union Berlin at Signal Iduna Park on April 8, 2023 in Dortmund, Germany. (Photo by Alexandre Simoes/Borussia Dortmund via Getty Images)

Filipinos wade through floodwaters along a road in Manila, Philippines, 22 August 2025. The National Disaster Risk Reduction and Management Council (NDRRMC) on 22 August raised its alert level and warned residents of flooding in low-lying areas and landslides in mountainous communities brought by a storm. The government weather bureau said a Tropical Cyclone Wind Signal Number 01 is raised over 17 areas due to Tropical Depression “Isang”, which made landfall over the Aurora province. (Photo by Francis R. Malasig/EPA)

A member of the German wireless police picks up signals on the radio equipment he carries on his back, while his colleague takes notes. (Photo by General Photographic Agency/Getty Images). Circa 1925

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)

People wear masks to help guard against the Coronavirus in downtown Tehran, Iran, Sunday, February 23, 2020. On Sunday Iran's health ministry raised the death toll from the new virus to 8 people in the country, amid concerns that clusters there, as well as in Italy and South Korea, could signal a serious new stage in its global spread. (Photo by Ebrahim Noroozi/AP Photo)

The Haʻikū Stairs, also known as the Stairway to Heaven or Haʻikū Ladder, is a steep hiking trail on the island of Oʻahu. The trail began as a wooden ladder spiked to the cliff on the south side of the Haʻikū Valley. It was installed in 1942 to enable antenna cables to be strung from one side of the cliffs above Haʻikū Valley to the other. A building to provide a continuous communication link between Wahiawā and Haʻikū Valley Naval Radio Station was constructed at the peak of Puʻukeahiakahoe, elevation about 2,800 feet (850 m). The antennae transmitted very low frequency radio signals from a 200,000-watt Alexanderson alternator in the center of Haʻikū valley. The signals could reach US Navy submarines as far away as Tokyo Bay while the submarines were submerged.

A man wearing the traditional Carnival Neapolitan mask of Pulcinella performs on Via Caracciolo avenue in Naples, Italy, Saturday, November 14, 2020. The regions of Campania and Tuscany were designated red zone on Friday, signaling the dire condition of a hospitals struggling with a surge of new admissions. (Photo by Gregorio Borgia/AP Photo)