Origin of the Universe and the Big Bang Theory

• This lecture introduces fundamental concepts related to the chemistry and composition of our universe
• The lecture's focus is on the origin of the universe and the dynamics that have shaped its current state

Origin of Matter

• The subject of the origin of matter has been debated for years
• The most recent scientific explanation relies on the Big Bang theory

Big Bang Theory

• The Big Bang theory describes the universe's emergence from an initial state of ultra-high energy, density, temperature, and pressure with homogeneous and isotropic properties
• This led to a rapid expansion and cooling, forming the large-scale structure of the universe
• After inflation stopped, reheating occurred to produce a plasma and elementary particles
• High temperatures caused relativistic speeds in particles, leading to continuous creation and destruction of particle-antiparticle pairs during collisions
• At some point, baryogenesis led to the creation of quarks and leptons
• Quarks and leptons are unstable at ordinary temperatures and pressures, leading them to combine and form atoms
• The generated atoms coalesced to form light elements like Hydrogen (H), Helium (He), Lithium (Li), Boron (B), and Beryllium (Be)
• After that point, the universe began expanding and has been expanding ever since
• Concentrations of gas and dust became galaxies with millions of stars
• Within larger stars, nuclear fusion created heavier elements like Carbon (C), Silicon (Si), Calcium (Ca), Magnesium (Mg), Potassium (K), and Iron (Fe)
• Eventually, stars collapse and explode in a supernova
• During a supernova, heavier elements are formed, ranging from Iron (Fe) to Uranium (U)
• Throughout galaxies, gas clusters start rotating and accreting into stars and solar systems due to gravity
• The solar system is 4.6 billion years old
• The ball at the center of the solar system grows dense and hot, eventually starting nuclear fusion reactions and a star is born (the sun)

Origin of Earth

• Rings of gas and dust orbiting the sun condensed into small particles
• Particles attracted each other to form bigger bodies, accumulating into a larger mass, creating an irregularly shaped proto-Earth
• The Earth's interior heated up becoming soft, and gravity shaped the Earth into sphere
• Differentiation occurred, resulting in a nickel-iron core and a stony (silicate) mantle
• A small planetoid collided with Earth, forming debris around the Earth
• The debris coalesced, creating the Moon
• The atmosphere then developed from volcanic gases
• When Earth cooled, moisture condensed and accumulated, forming the oceans

Composition of the Earth

• The Earth is made of compositional layers and mechanical layers
• Compositional layers include the crust, mantle, and core
• Each layer has unique chemical, mineral, and rock compositions

Crust Composition

• The oceanic crust consists of dark-colored, mafic rocks enriched in MgO, FeO, and CaO, averaging around 50% SiO2
• The continental crust is complex, with lighter-colored felsic rocks enriched in K2O, Na2O, and SiO2 averaging around 60% SiO2
• Oceanic crust is denser and less buoyant with an average density of 2.9-3.1 g/cm³
• Continental crust is less dense and more buoyant, with an average density of 2.6-2.9 g/cm³
• Oceanic crust is thinner, averaging 5-7 km thick, up to 15 km thick under islands with a low surface elevation and is mostly submerged
• Continental crust is thicker, averaging 30 km thick and is up to 80 km thick under mountains with higher surface elevations and is mostly emergent
• Oceanic crust age is up to 180 Ma for in-place crust and is -3.5% of Earth's history
• Continental crust age is up to 4000 Ma and is 85-90% of Earth's history.

Mantle Composition

• At approximately 410 km depth (~14 GPa) in the upper mantle and transition zone, olivine (Mg2SiO4) transforms into (β-spinel)/wadleysite (Mg2SiO4)
• (β-spinel)/wadleysite (Mg2SiO4) transforms into ringwoodite (Mg2SiO4)
• At ~660 km depth (~24 GPa) in the upper mantle and transition zone, ringwoodite (Mg2SiO4) changes to perovskite [(Mg,Fe,Al)SiO3] + oxide phases like periclase (MgO)

Lower Mantle Composition

• The lower mantle (mesosphere) consists of perovskite, periclase [(Mg, Fe)O], magnesio-wustite [(Mg,Fe)O], stishovite (SiO2), ilmenite [(Fe,Mg)TiO2], and ferrite [(Ca,Na,Al)Fe2O4] and ranges from 660 km to 2900 km depth

Core Composition

• The earth's core consists of three parts:

Outer Core

• The outer core primarily contains iron (~85%), small amounts of nickel (~5%), and lighter elements (~8-10%) like oxygen, sulfur, or hydrogen
• The outer core is a highly compressed liquid with a density of ~10-12 g/cm³
• Molten iron produces most of Earth's magnetic field

Inner Core

• The solid inner core has a density of ~13 g/cm³ and largely consists of iron, nickel, and less oxygen, sulfur, and hydrogen than the outer core

Makeup of the World

• The universe is made of space-time and its contents
• From a general point of view, there are three major components of the universe: space-time, radiation and energy, and universal matter

Space-time

• Space-time is where physical events occur, with an event as the basic element
• An event is defined as a unique position at a unique time
• An event in space-time can be identified by four coordinates: x, y, z, and t.

Universal Matter

• Dark energy is the energy of empty space comprising 68.3% of the universe
• Dark matter is a hypothetical matter, invisible to the electromagnetic spectrum, comprising 26.8% of the universe
• Antimatter is a hypothetical matter composed of antiparticles that can annihilate elementary particles
• Ordinary matter (atoms, ions, electrons) comprises 4.9% of the universe

States of Matter

• Solid
• Liquid
• Gas
• Plasma
• Exotic state of matter

Course Goals

• Recognize the origin of events and matter formation
• Appreciating the different states of matter
• Understanding the organization of particles to make atoms

Explore the chemistry and composition of the universe, focusing on its origin. The lecture covers the Big Bang theory, which explains the universe's emergence from a state of ultra-high energy. It describes the rapid expansion and cooling that formed the universe's large-scale structure.