In November 1915, Albert Einstein gave a series of lectures on his general theory of relativity at the Royal Prussian Academy of Sciences in Berlin. It was the culmination of years of work, beginning with four groundbreaking papers in 1905: on his quantum theory of light (that light is a particle, or photon); on the existence of atoms; on his theory of special relativity (that length and time are not fixed and depend on the observer's frame of reference); and on the equation for which he is most famous, E=MC2 (that energy is equivalent to mass). He published these papers when he was just 26. Science would never be the same.
Ten years later, Einstein shook the physics world even further by theorizing that space and time are dynamic and distorted, affecting the way that objects and light move. This was his general theory of relativity - his unified description of gravity.
(Find a plain-English primer on his main theories here.)
But these theories weren't confined to the lab. In the century since Einstein gave his lectures, what impact have his discoveries had on our everyday lives?
1. Satnavs and Google Maps
It's hard to get lost these days because of GPS - it's what allows our satnavs and smartphone map apps to tell us the quickest route to the restaurant or the beach. But if it weren't for Einstein's general theory of relativity, we wouldn't know to take relativity's effects into account when synchronizing the network of Global Positioning System (GPS) satellites orbiting the Earth. This means their data would be filled with errors, making GPS more or less useless.
2. Your phone's clock
Most ISPs and mobile phone masts use GPS to set the time. And with each GPS satellite containing a number of atomic clocks, the clocks on your computer and mobile phone are ultra-accurate. Without that accuracy, you'd probably be late (or early) for every meeting.
What makes a supermarket's doors open automatically as you approach? Why do home security systems alert you to the presence of an intruder? How do smoke alarms detect fires? Lasers are crucial to all these inventions and more. And it was Einstein's 1916 discovery of the physical principle responsible for the light amplification by stimulated emission of radiation (the long-winded way of saying laser) that made these devices possible.
These are just three examples - there's virtually no corner of science and technology that hasn't experienced the Einstein effect, from supercomputers and supernovas to nuclear weapons and the Big Bang. And in our ever-more-digital world, what happens in the lab is never far from everyday life.