### theory | relativity:

General relativity
* Some general relativity predicts energy.
* addresses the problem of accelerated motion and gravity.
* assumes a continuous, curved space time.
* describes gravity as a manifestation of the curvature of space-time
  - how spacetime is curved and bent by mass and energy
* explains gravity as the curvature of space- time by mass
  - that light is bent by mass
* forms the basis of our understanding of gravitational processes.
* great theory of gravity, but it ignores quantum mechanics.
* has a number of physical consequences.
* is constructed in terms of light signal
  - tested by astronomy and astrophysics
* is the foundation for modern cosmology - the study of the universe as a whole
  - modern theory of gravity, due originally to Einstein
  - premier theory of how gravity works
* predicts how gravity and space-time operate.
* says that gravity is nothing more than an inertial force.
* scientific theory
+ Gravity, General relativity: Force :: Basic physics ideas

### theory | relativity:

Special relativity
* Some special relativity explains light.
* appears only at the end, if at all, and after electromagnetism and optics.
* holds in all the universe in local space and time.
* is also limited to non-accelerating reference frames
  - demonstrated with high speed trains
  - one of the best-confirmed theories in history
* local approximation to a far more complex global geometry for space-time.
* says that every person has their own time.
* scientific theory
* shows that time behaves surprisingly like the three spatial dimensions.
* special case of a more general physics.
* subset of general relativity.
+ Theory of relativity, Special relativity: Relativity :: Albert Einstein
  * Special relativity says that every person has their own time. One person's clock says something different from another person's clock. The reason a person's time can be different from another's is because of time dilation, which can be thought of more easily by the twin paradox.
+ Universe, Basic data on the Universe: Reality
  * Special relativity holds in all the universe in local space and time. Otherwise, general relativity holds. There is no explanation for the particular values that physical constants appear to have throughout our Universe, such as Planck's constant 'h' or the gravitational constant 'G'. Several conservation laws have been identified, such as the conservation of charge, conservation of momentum, conservation of angular momentum and conservation of energy.

Representation theory
* continues of fundamental importance in mathematics and other sciences.
* is the study of how symmetry is expressed, especially through matrices.
* powerful way of studying groups using linear algebra.
* studies the ways in which a group acts on vector spaces.

### theory:

Scientific theory
* Most scientific theories make predictions.
* Scientific theories are a more reliable source of knowledge than religious ones
  - also an enemy of religion
  - historical entities
  - mental constructs that have objective reality as their content
  - ones which are open to disproof
  - part of science
  - validated by empirical testing against physical observations
  - attempt to understand the world of observation and sense experience
  - can never provide a complete and definite description of reality
* Scientific theories explain how or why something is happening
  - the unstable, irregular, yet structured features of everyday experience
  - gain acceptance
  - require empirical confirmation through observation and experiment
* Some scientific theories are used by biologists.