Special Relativity and General Relativity
Einstein's theory of special relativity describes the motion of particles moving at close to the speed of light. Newton's laws are still valid as an accurate approximation of objects moving at everyday speeds, and while Newton's laws are involved in the movement of seen objects common on the earth, the modern laws of physics that Einstein proposed do not necessarily affect our everyday lives. "E equals mc-squared" is the most well-known example of Einstein's theory of special relativity, first proposed in 1905. The University of California, Riverside, Department of Mathematics describes Einstein's theory of general relativity (1916) as explaining "gravity as the curvature of spacetime." Einstein's theories are still essentially valid today and they merge into the field of quantum physics to form a unified theory of quantum gravitation.
Quantum Entanglement
A photon is an elementary particle or basic unit of light. When an original photon splits into two photons, the resulting photon is considered to be "entangled" with the first photon. The first photon affects the activity of the second photon. Elementary particles are considered to be entangled even if they are not in physical contact. If one particles causes another particle to take on a complementary value, as an example, and an original particle causes a secondary particle to spin in the opposite direction it is spinning, the pair is said to be entangled.
Dark Energy
In theory, dark energy describes the energy that permeates all of space. Dark energy is believed to increase the acceleration of the expansion of the universe, that is, the universe is expanding at an ever-increasing pace. The continuous expansion of the universe was first hypothesized in 1927 and was an outgrowth from the general relativity theory. Scientists believe that dark energy accounts for 74 percent of the energy in the universe. The National Radio Astronomy Observatory, a facility of the National Science Foundation, states that "Measuring the equation of state of dark energy is one of the biggest efforts in observational cosmology today."
Black Hole Thermodynamics
Black holes are not empty space; rather, they are areas where a great amount of matter is packed into a small area. If you were to take the sun and condense it into an area the size of New Jersey, you'd get a good idea of the scales of mass involved with black holes. In black hole thermodynamics, the laws of thermodynamics are harmonized with black hole event horizons. A black hole event horizon is the outer boundary of the black hole, where matter and light cannot escape the gravitational force of the black hole, and plunge inward.