GENIUS: EINSTEIN

To most of us who aren’t physicists, Albert Einstein’s theoretical exploration of space-time and the relationship between energy and matter might seem so intellectually lofty and abstract that they would have little bearing on our everyday existence. But nothing could be further from the truth. In the century since Einstein did his most important work, application of his ideas and the technological innovations that they’ve inspired have shaped modern life in myriad ways. “His fingerprints are all over today’s technologies,” Einstein biographer Walter Isaacson has written. “Photoelectric cells and lasers, nuclear power and fiber optics, space travel, and even semiconductors all trace back to his theories.”

Here are a few of the modern technologies that are linked in some way to Einstein’s work.

GPS Navigation

If it weren’t for the application of Einstein’s theories of special and general relativity, the GPS unit on your dashboard would give you increasingly wacky wrong directions . That’s because GPS units get a fix on your location by relying upon an array of satellites, which are orbiting the Earth at close to 8,700 miles per hour. Einstein’s theory tells us that relative to a person on the ground, the satellites are moving faster, that means that their clocks should run more slowly than, say, your wristwatch, an effect called time dilation. But at the same time, because the satellites are high above the Earth, they’re further from the curvature of space-time caused by the Earth’s mass than you are, which has the effect of speeding up their clocks. When those two effects are combined, it results in the satellites’ clocks being about 38 microseconds—that is, billionths millionths of a second—faster than clocks on Earth. That may not seem like much, but it’s enough to throw off your GPS unit’s measurement of distance by 6.2 miles each day. But fortunately, because Einstein’s work predicts this sort of effect, the GPS system is designed to compensate for it.

Weather Forecasting and Stock Market Investing

One of Einstein’s lesser-known achievements was his explanation of a phenomenon that had long puzzled scientists—the crazy zig-zag movements of particles suspended in a liquid, which is also known as Brownian Motion. They didn’t know why the particles moved, and weren’t even able to measure the movement. Einstein made the assumption that the particles were being buffeted by molecules in the liquid, and then calculated the average horizontal distance that one of the particles would move in a given time interval. In 1908, a French scientist named Jean Perrin did experiments with a microscope and a stopwatch, and his results matched Einstein’s predictions—providing the first proof of the existence of molecules, a feat that won Perrin the Nobel Prize. But it also was the first time that the role of probability in physics was established. As physicist Carmac O’Raifeartaigh has written, Einstein’s work is the underpinning of our modern understanding of complex systems, which has influenced everything from weather forecasting to investing in stocks.

Automatic Doors, Burglar Alarms, Solar Panels, and Digital Cameras

Though Einstein is most famous for relativity, it wasn’t what won him the Nobel Prize in physics. Instead, he was recognized primarily for his explanation of the photoelectric effect. Even before Einstein’s time, scientists had known that exposing certain materials to light could generate an electrical current. But as science writer Sarah Laskow explained in 2014 Atlantic article, they didn’t know why. They thought of light as waves, and didn’t see how light could put enough energy into a metal such as selenium for it to give off electrons. In a 1905 paper, Einstein, building on work by Max Planck, came up with a different explanation.

What if light behaved like a particle instead of a wave? Each of the particles, or photons, contained some energy, and if the frequency of the particles was high enough, they could transfer enough energy to electrons that they would be ejected away from the selenium atoms. The most obvious application of the photoelectric effect is in solar panels, but it also led to the development of devices that could be triggered by light exposure, or by the interruption of a beam of light—such as those doors that swing open when you walk up to the supermarket. The photoelectric effect also enables today’s digital cameras to turn images into code that can be read by a computer.

DVD Players, Supermarket Scanners, and Laser Eye Surgery

In a 1917 paper, Einstein raised the theoretical possibility of a process called stimulated emission, in which atoms could be prodded to emit a concentrated stream of photons. Decades later, physicists developed devices to achieve what Einstein had described. They called them lasers, an acronym for Light Amplification by Stimulated Emission of Radiation, and they produced narrow, focused beams of energy that could be used to make more precise cuts than a scalpel—or to play music, or scan the bar code on a box of cereal, or myriad other uses.

Nuclear Weapons and Nuclear Energy

Einstein’s discovery of the link between energy and mass, expressed in his famous equation E = mc2, led others to wonder if the atom could be split by bombarding nuclei with neutrons to release energy. As biographer Walter Isaacson details, Einstein himself was skeptical of the notion, calling it “akin to shooting birds in the dark in a place where there are only a few birds.” But after learning in 1939 that German scientists apparently had managed to achieve nuclear fission on a small scale, Einstein changed his view. Eventually, he wrote to President Franklin Roosevelt, advising him that it might be possible to use the process to create a new source of energy—or a powerful weapon. That message ultimately led to the U.S.’s development of nuclear weapons—and to the nuclear power plants that today provide roughly a tenth of the world’s electricity.