Comprehensive Study Guide to Astronomy and Geographical Science and Astronomical Systems

Theories on the Origin and Evolution of the Universe

The birth of the universe is largely explained by the Big Bang theory, proposed by George Gamow. This theory posits that the universe originated from a primordial state known as YLEM, characterized by extremely high pressure and high density. Following the initial explosion or expansion, the universe remains in a state of constant expansion, a principle associated with the Hubble constant. In contrast, the Steady State theory (Teoría del Estado Estable), championed by Thomas Gold, suggests a stable universe that does not change over time. Another model is the Oscillating or Pulsating theory (Teoría Oscilante o Pulsante), which suggests that the universe will eventually stop expanding and undergo a collapse known as the Big Crunch.

Measurements and Astronomical Distances

To describe the vastness of the universe, several units of measurement are employed. A Parsec is equivalent to $3.26$ light-years ($años luz$). A Light-Year is defined as the distance light travels in one year. The Astronomical Unit ($Unidad Astronómica$ or $UA$) is the average distance between the Earth and the Sun, approximately $150 \times 10^6\,km$. Additionally, Parallax (Paralaje) is a method used to determine distances to stars by observing their apparent displacement from different points in Earth's orbit.

Galactic Structures and Stellar Phenonmena

The Milky Way (Vía Láctea) is categorized as a barred spiral galaxy (espiral barrada). It consists of visible matter, accounting for less than $10\%$ of its composition, and dark matter (materia oscura), which accounts for less than $95\%$. Within this galaxy lies Sagittarius A, which serves as a notable example of a black hole (agujero negro), a concept further explored by scientists like Roger Penrose. Stars are born from nebulae (nebulosas) composed largely of hydrogen. Specific types of stars include Pulsars, which are highly magnetized neutron stars. A Galactic Year (año galáctico) represents the time it takes for the Sun to complete one full orbit around the center of the galaxy.

The Solar System: Formation and Planetary Characteristics

The most widely accepted explanation for the formation of the Solar System is the Nebular Theory, proposed by Pierre-Simon de la Place and Emanuel Kant, which suggests a rotating nebula flattened into a disk. An alternative, the Tidal or Collision Theory (Teoría de la Colisión o Mareal) by Rose and Chamberlin, suggested a collision with another star led to the formation of the planets, but this theory has been largely discarded.

Planets are divided into two main categories: Inner (Interiores/Terrestres) and Outer (Exteriores/Jovianos). The Inner planets are Mercury, Venus, Earth, and Mars; they are smaller, rocky, have high density, fewer satellites, and shorter orbital periods. The Outer planets are Jupiter, Saturn, Uranus, and Neptune; they are larger, gaseous, have lower density, many satellites, and longer orbital periods. Notable satellites include Ganymede (Jupiter), Titan (Saturn), Titania (Uranus), and Triton (Neptune). Most planets rotate West-to-East, but Venus and Uranus exhibit retrograde rotation (giro retrógrado), moving East-to-West. There is also an Asteroid Belt (Cinturón de asteroides) located between the inner and outer regions.

Earth Dynamics: Translation, Seasons, and Distance

Earth's movement around the sun is known as translation (movimiento de traslación) and takes exactly $365\text{ days}$, $5\text{ hours}$, $48\text{ minutes}$, and $46\text{ seconds}$. The path of the Earth lies on the ecliptic plane (plano de la eclíptica). Throughout the year, the distance from the sun varies: Perihelion (Periehlio) occurs when Earth is closest to the sun at $148 \times 10^6\,km$, while Aphelion (Afelio) occurs at its furthest point of $152 \times 10^6\,km$. The solstices (Summer and Winter) and equinoxes (Spring and Autumn) mark changes in seasons as light is reflected differently across the equator.

Foundations and Principles of Geography

The term Geography was coined by Eratosthenes in the $III\,BC$, and the field was advanced by figures like Hecataeus and Aristotle. Geography is defined as the study of the interaction between humans (homo) and the geographical space (espacio geográfico) they inhabit. It distinguishes between a Geographical Phenomenon (Fenómeno geográfico), which is a rapid or abrupt change, and a Geographical Fact (Hecho geográfico), which is stable or long-lasting. Historically, the field shifted from the Geocentric model (Earth at the center, supported by Ptolemy) to the Heliocentric model (Sun at the center, supported by Copernicus).

The methodology of geography relies on several core principles: Localization (Localización) by Friedrich Ratzel, Comparison (Comparación) by Karl Ritter, Description (Descripción) by Paul Vidal de la Blache, Causality/Explanation (Causalidad/Explicación) by Alexander von Humboldt, and Activity/Evolution (Actividad/Evolución) by Jean Brunhes, who noted that everything in the geographic space is in constant change (todo transforma).

Branches of Geographic Study and Earth Sciences

Geography is supported by various specialized sciences. Demography (Demografía) studies populations, while Edaphology (Edafología) focuses on soil composition. Geology (Geología) examines the internal structure of the Earth. Speleology (Espeleología) is dedicated to the study of caves and caverns. Ecology (Ecología) studies ecosystems, and Geomorphology (Geomorfología) focuses on the forms and relief of the Earth's surface.