Einstein is only credited with inventing a single item: the Einstein Refrigerator. Einstein and Leo Szilard developed the idea for the fridge and patented it in 1930. The model lacks moving parts and, unlike modern-day fridges, needs only a heat source to function, eliminating the need for electricity. Modern fridges contain freon, which is more environmentally damaging than carbon dioxide, and use a great deal of electricity, but they are selling in huge numbers worldwide, as demand is increasing in developing countries. As environmental activism grows, though, Einstein's only invention has found a new audience. Researchers in both Britain and the United States are revisiting the idea of an eco-friendly refrigerator.
Before Einstein burst onto the scene, scientists understood, to a degree, that certain concepts such as motion were relative to the observer. Einstein changed the game by suggesting that concepts like space, time and distance may also be relative. He claimed that acts that appear to one observer to happen simultaneously might not appear that way to a different observer in another state. Einstein's special theory of relativity also posited that the speed of light, regardless of the state or position of the observer, is always the same.
Einstein's general theory of relativity turned the classic view of the physical world on its head. Among other things, the theory states that gravitational fields affect all things, even light. This claim has been confirmed. At its core, the theory looked on space-time, classically viewed as a two-dimensional plane, as a curved surface. The world that Einstein envisioned was totally new and led to a number of new concepts, including Big Bang models (theories for the creation of the universe) and black holes.
Einstein also proposed the concept of the photoelectric effect, which said light was transmitted in particles, rather than waves. Although his theory was widely panned at the time, future experimentation proved it correct, and in 1922, Einstein received the Nobel Prize in physics, largely for this accomplishment. In addition to his well-known theories of relativity, Einstein made countless other scientific contributions, including the first theoretical treatment of Brownian motion, the seemingly random movement of particles suspended in a fluid.