Physics

On September 2, 1897, Nikola Tesla filed a patent for a system of electrical transmission without wires. His vision was ambitious: power delivered through the air to homes and factories, eliminating the need for electrical infrastructure entirely. Over a century later, wireless charging exists—but it works nothing like Tesla imagined. The technology that powers modern smartphones operates on principles far more constrained, yet far more practical. Understanding wireless charging requires grasping a fundamental truth: no energy travels “through the air” in the way radio waves or light do. Instead, wireless charging creates a magnetic field that couples two coils together, forming what amounts to a split-apart transformer. The energy still follows paths defined by electromagnetic field lines—it simply crosses a small air gap rather than flowing through a solid iron core. ...

In the winter of 2007, early smartphone adopters discovered an unexpected limitation: their revolutionary device became nearly useless outdoors. The same glass surface that responded to the lightest tap with bare fingers became utterly unresponsive through gloves. This wasn’t a design flaw—it was fundamental physics, and understanding why reveals the invisible electrical dance that happens every time you touch your screen. The Capacitor Hidden in Plain Sight A capacitor, in its simplest form, consists of two conductive plates separated by an insulating material called a dielectric. When voltage is applied, electric charge accumulates on the plates, creating an electric field between them. The amount of charge stored depends on the plate area, the distance between them, and the dielectric constant of the insulating material—expressed mathematically as: ...

A firefighter enters a burning building. Visibility drops to zero as thick smoke fills every corridor. Yet somehow, through the thermal imaging camera mounted on the helmet, the outline of a child becomes visible behind a couch. Minutes later, another firefighter points a thermal camera at a window and sees nothing but a reflection—the glass appears as a solid wall to the infrared sensor. What makes these two scenarios so different? ...

In November 2020, SpaceX requested that the Federal Communications Commission modify its license to operate 348 satellites at an altitude of 560 kilometers with an inclination of 97.6 degrees. These satellites would carry inter-satellite laser links—technology that allows satellites to communicate directly with each other without bouncing signals through ground stations. The physics behind this request reveals something counterintuitive: for long-distance communication, signals traveling through the vacuum of space can arrive faster than signals traveling through fiber optic cables on Earth. ...

The coffee shop has free Wi-Fi. The password is posted on a chalkboard near the counter. You sit in the corner booth, open your laptop, and connect. The signal passes through three walls, a glass window, and a wooden partition before reaching your device. How? This isn’t a minor engineering achievement. Your router is broadcasting radio waves at frequencies measured in billions of cycles per second, encoding gigabytes of data into invisible electromagnetic fields, and somehow that signal arrives intact after bouncing off your refrigerator, penetrating your walls, and competing with your neighbor’s network. Understanding how this works requires peeling back layers of physics that most people never consider—electromagnetic wave behavior, material properties, and the mathematical cleverness of modern encoding schemes. ...

On February 22, 1978, the first Navstar GPS satellite lifted off from Vandenberg Air Force Base. The engineers who built it had solved a problem that seemed impossible: determining a position anywhere on Earth to within meters, using signals from satellites orbiting 20,000 kilometers away. The solution required not just advances in electronics and rocketry, but a practical application of Einstein’s theory of relativity that affects every GPS receiver in existence today. ...