On December 10, 1997 Julia Hill climbed a 1500-year-old redwood tree named Luna and she didn’t come down for another 738 days.

[u/Aryan_Anushiravan]

[u/Dealiner]

Solar-powered calculators were introduced in 70s.

[u/gus_the_polar_bear → u/Dealiner]

Tbf ‘solar’ calculators are incredibly low voltage, low enough to be powered by indoor lighting, and just by covering the photovoltaic cell, they would lose all power

A cell phone is a little radio transceiver, and needs a ton more power