Universe Formation, Structure, and Evolution
Origin of the Universe
Universe: Set of all matter and energy existing in space. The observable part is the observable universe.
Cosmology: Science that studies the universe.
Age
13.7 billion years. Events: Discovery of America; Birth of Jesus Christ; Beginning Egyptian empire; Appearance of Homo sapiens.
Dimensions
The universe is measured using a unit called a light-year, which corresponds to the distance light travels in one year.
Composition
- 73% dark energy (counteracts gravity)
- 23% dark matter (does not emit or reflect electromagnetic radiation)
- 4% atoms (observable matter, mostly helium and hydrogen)
Structure
Composed of nebulae and galaxies.
Nebulae: Clusters of cosmic dust with a diffuse aspect.
Galaxy: Clusters of stars and cosmic dust moving together in space.
White Dwarf: A stellar remnant generated when a star exhausts its nuclear fuel.
Red Giant: A star with a mass similar to the Sun, close to becoming a white dwarf.
Theories of the Universe
Theory of Relativity
Einstein proposed this theory to explain the universe’s balance. Without experimentation, he concluded (and observations confirmed):
- The universe cannot distinguish whether a body is at rest or moving at a constant velocity.
- Absolute time does not exist.
- Space and time are a single reality called space-time.
- Mass and energy are two aspects of the same reality (E=mc2).
- Light is made up of photons.
Big Bang Theory
The Universe originated from a large explosion that dispersed all existing energy and matter. Galaxies originated from the explosion of a cosmic egg (initial core of neutrons). Natural forces involved: gravity, strong nuclear interaction, electromagnetic force, and weak nuclear interaction.
Steady State Theory
The universe is uniform, does not vary in time, and its density remains constant due to the continuous creation of new matter.
Pulsating Universe Theory
Successive explosions (Big Bang) and contractions (Big Crunch), called beats, repeat forever. In a closed universe, gravity would slow expansion, cause contraction into a cosmic egg, and then another expansion.
Future and Shape of the Universe
Future Evolution
- Open: The universe continues expanding indefinitely.
- Closed: Expansion slows, leading to contraction and the formation of a cosmic egg.
Shape
Three models: spherical, hyperbolic, and plane.
Formation of the Earth
From a rotating nebula:
- The nebula contracted.
- Matter condensed at the center, forming a protosun.
- Smaller masses condensed around the protosun, forming planets.
Earth’s Layers: Atmosphere, hydrosphere, crust, mantle (upper and lower), and core (inner and outer).
Global Tectonics
The lithosphere is broken into plates (plate tectonics). Magma flow generates and moves lithospheric plates on the asthenosphere. Plate displacement causes collisions.
Margins: Constructive, destructive, passive.
Effects of Plate Movement: Mountain ranges, earthquakes, tsunamis, volcanoes.
Life and its Origin
Living Beings
A living being has a life and performs vital functions.
Features:
- Act with intent. Nutrition: Capturing matter and energy for growth and development. Value: Essential for nourishment and reproduction. Reproduction: Originating new individuals.
- Complex beings made of organic matter (carbon and hydrogen atoms) or inorganic matter (minerals, rocks, water).
- Composed of one (unicellular) or more (multicellular) cells.
- Maintain a relatively constant internal environment (homeostasis).
- Anatomy and physiology are determined by nucleic acids.
Origin of Life Theories
Theory of Spontaneous Generation
Life arises from inert materials (e.g., sweat, mud). Aristotle supported this. Redi’s experiments disproved it.
Coacervates Theory
Oparin argued life emerged after chemical evolution. Early Earth’s atmosphere (hydrogen, water, ammonia) cooled, forming organic molecules in a primeval soup.
Coacervates: Microscopic structures with a polymer membrane and internal environment (possibly with enzymes).
Protobiant: Common ancestor to all living beings.
Updated Oparin Hypothesis
The primitive atmosphere was not entirely reductive; it had some oxygen. The current atmosphere contains neon. Heavy gases were released from Earth’s interior due to meteorite impacts. Protobiant components: membranes formed first, then coacervates, enzymatic proteins, and finally genes.
Cell Types
Prokaryote: Cells without a nucleus (DNA dispersed in cytoplasm).
Eukaryotic cell: Cells with a nucleus. The evolution from prokaryotes to unicellular eukaryotes took approximately 2.3 billion years, starting 1.4 billion years ago.