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Albert Einstein (1879-1955) is one of the most famous scientists of all time, and his name has become almost synonymous with the word “genius”. While his reputation owes something to his eccentric appearance and occasional statements about philosophy, world politics and other non-scientific subjects, his true fame comes from his contributions to modern physics, which changed our entire perception of the universe and helped shape the world we live in today.
Here’s a look at some of the world-changing concepts we owe to Einstein.
Space-time
One of Einstein’s first accomplishments, at the age of 26, was his special theory of relativity – so called because it deals with relative motion in the particular case where gravitational forces are neglected. It may seem trivial, but it was one of the greatest scientific revolutions in history, completely changing the way physicists view space and time. Indeed, Einstein merged them into one space-time continuum. One of the reasons we think space and time are completely separate is that we measure them in different units, such as miles and seconds, respectively. But Einstein showed how they are really interchangeable, linked to each other by the speed of light – approximately 186,000 miles per second (300,000 kilometers per second).
Perhaps the most famous consequence of special relativity is that nothing can travel faster than light. But it also means that things start to behave very strangely as the speed of light approaches. If you could see a spaceship traveling at 80% the speed of light, it would appear 40% shorter than when it appeared at rest. And if you could see inside, everything would appear to be moving in slow motion, with a clock taking 100 seconds to scroll through one minute, according to Georgia State University’s HyperPhysics website. This means that the crew of the spaceship would age more slowly as they traveled rapidly.
E = mc ^ 2
An unexpected offshoot of special relativity was Einstein’s famous equation E = mc ^ 2, which is probably the only mathematical formula to have achieved the status of a cultural icon. The equation expresses the equivalence of mass (m) and energy (E), two physical parameters that were previously believed to be completely separate. In traditional physics, mass measures the amount of matter contained in an object, while energy is a property that the object has due to its movement and the forces acting on it. In addition, energy can exist in the total absence of matter, for example in light or radio waves. However, Einstein’s equation says that mass and energy are essentially the same thing, as long as you multiply mass by c ^ 2 – the square of the speed of light, which is a very large number – for make sure it ends up in the same units as energy.
This means that an object gains mass as it moves faster, simply because it gains energy. It also means that even an inert, stationary object has a tremendous amount of energy locked inside. Besides being a mind-boggling idea, the concept has practical applications in the world of high-energy particle physics. According to the European Council for Nuclear Research (CERN), if sufficiently energetic particles are crushed together, the energy of the collision can create new matter in the form of additional particles.
Lasers
Lasers are an essential component of modern technology and are used in everything from barcode scanners and laser pointers to holograms and fiber optic communication. Although lasers are not commonly associated with Einstein, it was ultimately his work that made them possible. The word laser, coined in 1959, means “amplification of light by stimulated emission of radiation” – and stimulated emission is a concept that Einstein developed more than 40 years earlier, according to the American Physical Society. In 1917, Einstein wrote an article on the quantum theory of radiation which described, among other things, how a photon of light passing through a substance could stimulate the emission of additional photons.
Einstein realized that new photons move in the same direction, and with the same frequency and phase, as the original photon. This results in a cascade effect as more and more nearly identical photons are produced. As a theorist, Einstein took the idea no further, while other scientists were slow to recognize the enormous practical potential of stimulated emission. But the world finally got there, and people are still finding new applications for lasers today, from anti-drone weapons To super fast computers.
Black holes and wormholes
Einstein’s special theory of relativity showed that space-time can do some pretty strange things even in the absence of gravitational fields. But that’s just the tip of the iceberg, as Einstein discovered when he finally managed to add gravity to the mix, in his general relativity theory. He discovered that massive objects like planets and stars actually distort the fabric of spacetime, and it is this distortion that produces the effects we perceive as gravity.
Einstein explained general relativity through a complex set of equations, which have a huge range of applications. Perhaps the most famous solution of Einstein’s equations came from Karl Schwarzschild’s solution in 1916 – a black hole. Even stranger is a solution that Einstein himself developed in 1935 in collaboration with Nathan Rosen, describing the possibility of shortcuts from one point in space-time to another. Originally nicknamed Einstein-Rosen Bridges, these are now known to all sci-fi fans by the more colloquial name of wormholes.
The expanding universe
One of the first things Einstein did with his equations of general relativity, in 1915, was apply them to the universe as a whole. But the answer that came out seemed wrong to him. This implied that the fabric of space itself was in a state of continuous expansion, dragging the galaxies with it, so that the distances between them were constantly increasing. Common sense told Einstein this couldn’t be true, so he added something called the cosmological constant to its equations to produce a high static universe.
But in 1929, Edwin Hubble’s observations other galaxies have shown that the universe is truly expanding, apparently in the same way Einstein’s original equations predicted. It looked like the end of the cosmological constant line, which Einstein later described as his biggest blunder. It wasn’t the end of the story, however. Based on finer measurements of the expansion of the universe, we now know that it is accelerating rather than slowing down as it should in the absence of a cosmological constant. So it seems that Einstein’s “blunder” was not a mistake after all.
Atomic bomb
Einstein is sometimes credited with the “invention” of nuclear weapons through his equation E = mc ^ 2, but according to the Max Planck Institute for Gravitational Physics’s Einstein Online website, the link between the two is tenuous at best. The key ingredient is nuclear physics fission, with which Einstein had no direct involvement. Nevertheless, he played a crucial role in the practical development of the first atomic bombs. In 1939, a number of colleagues alerted him to the possibilities of nuclear fission and the horrors that would follow if Nazi Germany bought such weapons. Finally, according to the Atomic Heritage Foundation, he was persuaded to convey these concerns in a letter to the President of the United States, Franklin D. Roosevelt. The end result of Einstein’s letter was the establishment of the Manhattan Project, which created the atomic bombs used against Japan at the end of World War II.
Although many famous physicists worked on the Manhattan Project, Einstein was not one of them. He was denied the necessary security clearance due to his leftist political views, according to the American Museum of Natural History (AMNH). For Einstein, this was not a great loss – his only concern had been to deny the Nazis the monopoly on technology. In 1947, Einstein told Newsweek magazine: “If I had known that the Germans would not succeed in developing an atomic bomb, I would never have lifted a finger,” according to Time magazine.
Gravitational waves
Einstein died in 1955, but his immense scientific legacy continues to make headlines even in the 21st century. This happened in spectacular fashion in February 2016, with the announcement of the discovery of gravitational waves, another consequence of general relativity. Gravitational waves are tiny ripples that propagate through the fabric of space-time, and it’s often said bluntly that Einstein “predicted” their existence. But the reality is less clear-cut than that.
Einstein never quite decided whether gravitational waves were predicted or excluded by his theory. And it took decades of research for astronomers to settle the question one way or the other.
Eventually they succeeded, using giant facilities such as the Gravitational Wave Laser Interferometer (LIGO) observatories in Hanford, Wash., And Livingston, Louisiana. As well as being another triumph for Einstein’s general theory of relativity (although he wasn’t too sure of himself), the discovery of gravitational waves gave astronomers a new tool for observing the universe. – including rare events like black hole fusion.
Originally posted on Live Science.
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