Theories on the Origin of the Universe

Study Notes

Big Bang Theory: Proposed by George Lemaitre; suggests the universe began from a singularity—an infinitely small, dense, and hot entity.
Evidence for Big Bang: Galaxies are moving away, cosmic microwave background radiation exists, and light element abundance supports this theory.
Steady State Theory: Proposed by Herman Bondi, Thomas Gold, and Fred Hoyle; posits that although the universe is expanding, matter density remains constant.
Counter Evidence: Discovery of cosmic microwave background radiation refutes this theory, showing the universe is not compositionally constant.
M-Theory: Proposed by Stephen Hawking and Leonard Mlodinow; suggests the universe’s origin occurs through the interaction of two hyperdimensional branes.
Connection to String Theory: It supports concepts of sheets or branes integral to understanding the universe's structure.
String Theory: Introduced by Gabriele Veneziano; describes the universe as composed of tiny vibrating strings, smaller than subatomic particles.
Evidence: Combines principles of general relativity with quantum mechanics, offering a framework for understanding particle physics.

Descartes’ Vortex Theory: Proposed by Rene Descartes; suggests solar system bodies formed from whirlpool-like motions of pre-solar materials.
Planetary Formation: Primary whirlpool motion creates planets; secondary motion forms satellites.
Buffon’s Collision Theory: Introduced by George-Louis Leclerc, Comte de Buffon; proposes planets formed from debris resulting from a collision between the sun and a giant comet.
Limitations: Fails to account for the unique positions of planets' orbits.
Kant-Laplace Nebular Theory: Proposed by Immanuel Kant and Pierre-Simon Laplace; asserts the solar system formed from a nebula of dust and gas approximately 4.5 billion years ago.
Jeans-Jeffreys Tidal Theory: Suggested by Sir James Hopwood Jeans and Harold Jeffreys; proposes planets form from substances ejected from the sun due to a massive star’s approach.
Solar Nebular Theory: Propounded by Emanuel Swedenborg; considers the solar system's formation from a collapsing interstellar gas and dust cloud.
Protostar Formation: Results from compressing the center, with the sun and planets forming from surrounding materials.

Asteroids: Small rocky bodies located mainly in the asteroid belt between Mars and Jupiter; Ceres is the first known asteroid, now classified as a dwarf planet.
Near-Earth Asteroids: Can be pulled from the main belt and approach Earth.
Comets: Composed mainly of ice and gases; become active near the sun, leading to the formation of vaporous jets.
Origin Sources: Short-period comets like Halley's comet come from the Kuiper belt, while the Oort Cloud, farther away, remains largely unexplored.
Meteoroids: Debris and remnants from comets and asteroids; they glow when entering the atmosphere, creating meteor trails known as shooting stars.
Dwarf Planets: Defined by the International Astronomical Union (IAU) in 2006; these objects orbit the sun, maintain a spherical shape due to gravity but cannot clear their orbital paths.
Examples: Makemake, Haumea, Ceres, Eris, and Pluto.

Earth's Layers: Composed of the inner core (solid), outer core (liquid), mantle (divided into lower and upper), and crust.
Mantle Characteristics: The lower mantle exhibits plasticity, while the upper mantle and the crust form the lithosphere.
Crust Composition: Divided into continental and oceanic crusts, the lithosphere's surface.
Subsystems of Earth: Includes lithosphere, atmosphere, hydrosphere, and biosphere.
Plate Tectonics: Movement of lithospheric plates, integral to understanding geological processes.