Einsteins' two most known and talked about theories: his theory of relativity and the mass-energy equivalence. These theories are one of the best discoveries of physics in the past 200 years. But while many think of these theories in the scale of the large, these theories also effect the physics of the small, the physics of particles. In this section, we'll talk about special relativity and how it affects physics in terms of particles.
Relativity consists of two kinds: Special and General Relativity. Special Relativity deals with the relationship between space and time and how it changes as we travel through it. This theory of special relativity was born out of two postulates:
Postulate I: The principle of relativity: The laws of physics are the same in all inertial reference frames.
Postulate II: The speed of light in vacuum is always constant, the speed c (~300,000 km/s), independent of the motion of the source.
This may not sound much, but these two postulates changed how we viewed physics from time immemorial. One example of the fact of the matter [More information and links about how this affected physics] But the most profound of them is how this caused space and time to be joined into a four-dimensional combination called space and time. Space and Time are inextricably linked, and causing change in one will lead to a change in the other.
While relativistic kinematics, might sound like a complicated term, it's just a way of observing and calculating motion, during very fast speed. But what constitutes a fast speed? Well, in this term, we are talking about speeds that are close to the speed of light. Light is the fastest speed that is possible in space and time[ Doesn't mean space can't travel faster than the speed of light, the current expansion of the universe is going faster than the speed of light!]. Also the fact that time and space are connected and the fact that universal limit of speed in space and time is the speed of lights leads to interesting events like length contraction and time dilation. These files in the face of classical study in the fact of the matter