Women clash with police officers behind riot shields during a protest in support of Victoria Salazar, a Salvadoran woman who died after a Mexican female police officer was seen in a video kneeling on her back, in Mexico City, Mexico on April 2, 2021. (Photo by Raquel Cunha/Reuters)

Fifty years ago, as France exploded in mass protests, words scrawled on the walls of the Sorbonne summed up the revolutionary zeal of the time: “Run free, comrade, we’ve left the old world behind!”. Sexual liberation, artistic creativity and anti-capitalism were the order of the day. For those who were there, it was an unforgettable time. Here: A wounded student is transported by first-aid workers during riots on the Boulevard Saint-Michel, Paris, France on May 6, 1968. (Photo by Gökşin Sipahioğlu/SIPA Press)

An activist shouts amid clashes with Lebanese riot police during a protest to demand the opening of Rafah border crossing between Egypt and the Gaza Strip, outside of the Egyptian embassy in Beirut, Lebanon, 22 February 2024. (Photo by Wael Hamzeh/EPA/EFE)

Texas state troopers in riot gear try to break up a pro-Palestinian protest at the University of Texas, during the ongoing conflict between Israel and the Palestinian Islamist group Hamas, in Austin, Texas, April 24, 2024. (Photo by Jay Janner/USA Today Network via Reuters)

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 refugee sits in front of a Greek riot police cordon during a protest at the Greek-Macedonian border, near the Greek village of Idomeni, March 1, 2016. (Photo by Alexandros Avramidis/Reuters)

A student protester throws a stone against a riot police vehicle during a demonstration to demand changes in the education system in Santiago, Chile, April 21, 2016. (Photo by Ivan Alvarado/Reuters)

Members of p*ssy Riot perform in concert during Day For Night festival on December 16, 2017 in Houston, Texas. (Photo by Gary Miller/Getty Images)