Special relativity is known for it's publication in 1906; it is used for microscopic physics, such as atoms and small objects. The other type of relativity, the general, is known for its publication in 1916, well after the birth of it's counterpart. The general half of the theory is intended for astrophysics and cosmology, such as solar systems, planets, and large objects. A British Astronomer named Sir Arthur Eddington, was one of the first to fully understand the Theory of Relativity. A little humor about his intelligence can be seen to when he was asked about there being three people who understood the Theory of Relativity, his response was "who is the third?" The discovery of Quasars, the 3 kelvin microwave background radiation, pulsars, and possibly blackholes were studied with to see the accuracy of the Theory of Relativity with gravity. This led the development of the space program, telescopes, computers, etc to make better calculations of the accuracy of the theory. The Theory of Relativity has two main parts, the special and the general. The internal part of the special theory is in reference to any region, such as a free falling laboratory, in which objects move in straight lines and have uniform velocities. In the lab, nothing would appear to be moving if everything in the lab was falling, the movement of the lab is relevant to the person that is in the lab. The principle of relativity theorizes that experiments in an internal frame, is independent from uniform velocity of the frame. An example of this is the speed of light. The speed of light within the internal frame is the same for all, regardless of the speed of the observer. Two events that are simultaneos in one frame, may not be simultaneos when viewed from a frame moving relative to the first one. Movement looks different depending on where the observer is located, how fast it is moving, and in what direction. An interesting fact about the special relativity, is that the mechanical foundations of special relativity were researched in 1908 by a german mathmetician named, Hermann Minkowski.
