Albert Einstein first suggested the theory of relativity in 1905, which states every observer has their own unique measure of time, though the laws of science and the speed of light are the same for all observers. The later proposed special theory of relativity neglects gravitational effects. Einstein proposed the general theory of relativity in 1915, which is widely used today. It incorporates gravity, not as a force, but as a consequence of the fact space-time is not flat. Instead, it is curved by mass and energy, and objects take as straight a line as they can as they move through this warped space-time.
Theories of Relativity Term Timeline in A Brief History of Time
The timeline below shows where the term Theories of Relativity appears in A Brief History of Time. The colored dots and icons indicate which themes are associated with that appearance.
...applying Newton’s law of gravity. Albert Einstein’s slightly different prediction, via his general theory of relativity, matched with what was seen, a critical confirmation of his new theory. Newton’s theory is... (full context)
...searching for the ultimate theory becomes hard to justify. Then again, people argued this about relativity and quantum mechanics, which eventually gave us nuclear power and microelectronics. Thus, the search for... (full context)
...straight paths through three-dimensional space. Light should also be bent by gravity, according to general relativity. Light cones near the sun ought to bend slightly inward, because of the sun's mass.... (full context)
...what took place within them. People thought they both went on forever. But with general relativity that thinking has changed considerably. Space and time are affected by objects' movement and forces,... (full context)
...believing in a static universe. Even Einstein overlooked this idea in his general theory of relativity. Instead he thought up a kind of anti-gravitational force he called the cosmological constant. (full context)
...space is curved, like the surface of the earth. When combining the general theory of relativity with quantum mechanics (as discussed later), space and time can be finite without a boundary.... (full context)
...our understanding has changed significantly. Penrose and Hawking’s work showed that Einstein’s general theory of relativity is only a partial theory. It breaks down at the beginning of the universe. When... (full context)
...Dirac was the first to propose a theory consistent with both the general theory of relativity and quantum mechanics. He showed mathematically how spin ½ works and predicted that electrons should... (full context)
...radiation rubbed people up the wrong way, and was the first significant example of general relativity and quantum theory combining. John G. Taylor opposed Hawking when he announced these discoveries. But... (full context)
To know how the universe started, we need laws that hold at the beginning. General relativity relies on singularities, which involve the break down of scientific law. Really, what singularity theories... (full context)
...predict these values, which is a serious drawback. When incorporating the uncertainty principle and general relativity one can either adjust the strength of gravity or the cosmological constant. But this still... (full context)
...gravity, but only if the tension were significantly higher. This would leave most of general relativity’s predictions unchanged, except on the miniscule level. Their work didn’t gain much attention at first.... (full context)
...to date on all subjects. Eddington suggested only two people understood the theory of general relativity in his day. Today many thousands do. If we were to find the unifying theory... (full context)