![]() But that's only the tip of the iceberg, as Einstein discovered when he finally succeeded in adding gravity into the mix, in his theory of general relativity. Black holes and wormholesĮinstein's theory of special relativity showed that space-time can do some pretty weird things even in the absence of gravitational fields. Related: The world's biggest laser: Function, fusion power and solving a supernova 4. But the world got there in the end, and people are still finding new applications for lasers today, from anti-drone weapons to super-fast computers. As a theoretician, Einstein didn't take the idea any further, while other scientists were slow to recognize the enormous practical potential of stimulated emission. This results in a cascade effect as more and more virtually identical photons are produced. ![]() In 1917, Einstein wrote a paper on the quantum theory of radiation that described, among other things, how a photon of light passing through a substance could stimulate the emission of further photons.Įinstein realized that the new photons travel in the same direction, and with the same frequency and phase, as the original photon. The word laser, coined in 1959, stands for "light amplification by stimulated emission of radiation" - and stimulated emission is a concept Einstein developed more than 40 years earlier, according to the American Physical Society. Although lasers are not commonly associated with Einstein, it was ultimately his work that made them possible. Lasers are an essential component of modern technology and are used in everything from barcode readers and laser pointers to holograms and fiber-optic communication. ![]() (Image credit: Encyclopaedia Britannica/UIG via Getty Images) The stages of stimulated emission in a laser cavity. According to the European Council for Nuclear Research ( CERN), if sufficiently energetic particles are smashed together, the energy of the collision can create new matter in the form of additional particles. ![]() Besides being a mind-blowing idea, the concept has practical applications in the world of high-energy particle physics. It also means that even an inert, stationary object has a huge amount of energy locked up inside it. This means that an object gains mass as it moves faster, simply because it's gaining energy. However, Einstein's equation says that mass and energy are essentially the same thing, as long as you multiply the mass by c^2 - the square of the speed of light, which is a very big number - to ensure it ends up in the same units as energy. Additionally, energy can exist in the complete absence of matter, for example in light or radio waves. In traditional physics, mass measures the amount of matter contained in an object, whereas energy is a property the object has by virtue of its motion and the forces acting on it. The equation expresses the equivalence of mass (m) and energy (E), two physical parameters previously believed to be completely separate. (Image credit: VICTOR HABBICK VISIONS/SCIENCE PHOTO LIBRARY via Getty Images)Īn unexpected offshoot of special relativity was Einstein's celebrated equation E = mc^2, which is likely the only mathematical formula to have reached the status of a cultural icon. ![]()
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