GPS works only because engineers account for Einstein’s relativity.
Satellite clocks tick about 38 microseconds faster per day than clocks on Earth, because of the combined effects of their speed and weaker gravity. Without correcting for that tiny difference, GPS location errors would grow by roughly 10 kilometers each day.
Your phone gets you to the right café partly by accounting for how gravity changes time.
Peeling ordinary adhesive tape can produce X-rays—if you do it in a vacuum.
As the tape separates, electrical charges build up on the newly exposed surfaces. When those charges discharge, electrons accelerate and strike the material, producing X-rays. Researchers demonstrated this in 2008, even using the radiation to image a finger.
Your desk tape dispenser isn’t a radiation hazard: ordinary air prevents the charges from building up in the same way.
Earth had nuclear reactors long before humans built any.
About two billion years ago, uranium deposits at Oklo, in what’s now Gabon, naturally sustained nuclear fission. Groundwater slowed the neutrons enough to keep the reaction going; as the water heated and boiled away, the reaction paused. When water returned, it could restart.
Nature had built a water-regulated nuclear reactor.