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1. **WHAT IS COSMOLOGICAL?**

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**Physical cosmology** is a branch of cosmology concerned with the studies of the largest-scale structures and dynamics of the universe and with fundamental questions about its origin, structure, evolution, and ultimate fate. Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed those physical laws to be understood. Physical cosmology, as it is now understood, began with the development in 1915 of Albert Einstein’s general theory of relativity, followed by major observational discoveries in the 1920s: first, Edwin Hubble discovered that the universe contains a huge number of external galaxies beyond the Milky Way; then, work by Vesto Slipher and others showed that the universe is expanding. These advances made it possible to speculate about the origin of the universe, and allowed the establishment of the Big Bang theory, by Georges Lemaître, as the leading cosmological model. A few researchers still advocate a handful of alternative cosmologies;^{} however, most cosmologists agree that the Big Bang theory explains the observations better.

Dramatic advances in observational cosmology since the 1990s, including the cosmic microwave background, distant supernovae and galaxy redshift surveys, have led to the development of a standard model of cosmology. This model requires the universe to contain large amounts of dark matter and dark energy whose nature is currently not well understood, but the model gives detailed predictions that are in excellent agreement with many diverse observations.^{}

Cosmology draws heavily on the work of many disparate areas of research in theoretical and applied physics. Areas relevant to cosmology include particle physics experiments and theory, theoretical and observational astrophysics, general relativity, quantum mechanics, and plasma physics.

Modern cosmology developed along tandem tracks of theory and observation. In 1916, Albert Einstein published his theory of general relativity, which provided a unified description of gravity as a geometric property of space and time.^{} At the time, Einstein believed in a static universe, but found that his original formulation of the theory did not permit it. This is because masses distributed throughout the universe gravitationally attract, and move toward each other over time. However, he realized that his equations permitted the introduction of a constant term which could counteract the attractive force of gravity on the cosmic scale. Einstein published his first paper on relativistic cosmology in 1917, in which he added this *cosmological constant* to his field equations in order to force them to model a static universe. The Einstein model describes a static universe; space is finite and unbounded (analogous to the surface of a sphere, which has a finite area but no edges). However, this so-called Einstein model is unstable to small perturbations—it will eventually start to expand or contract. It was later realized that Einstein’s model was just one of a larger set of possibilities, all of which were consistent with general relativity and the cosmological principle. The cosmological solutions of general relativity were found by Alexander Friedmann in the early 1920s. His equations describe the Friedmann–Lemaître–Robertson–Walker universe, which may expand or contract, and whose geometry may be open, flat, or closed.

2. **WHAT IS THE ESSENTIAL DIALECTIC OF COSMOLOGICAL? **

*The Essential Dialectic of Cosmological is: *

**{Chemistry-Physics ⇆ Physics-Chemistry ⇅ Chemistry-Chemistry} ↻ Physics-Physics**

3. **WHAT IS THE **COMPLETE DIALECTIC **OF COSMOLOGICAL? **

*The Complete Dialectic of Cosmological is: *

**{Physics ⇆ Chemistry ⇅ Biology} ↻ Geology-Astronomy**

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4. **WHAT IS THE EQUIVALENCY **DIALECTIC **OF COSMOLOGICAL?**

*The Equivalency Dialectic of Cosmological is:*

**{Pedagogical ⇆ Cosmological ⇅ Cultural} ↻ Transcendental**

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