Cosmology and the Big Bang Theory

• General Science Test #4 Review covers stars, astronomy, the solar system, cosmology, plate tectonics, and the rock cycle

Why Are Stars Important?

• Stars are important for navigation, culture, providing light, and creating elements
• Stars are responsible for forming nearly all elements, excluding hydrogen, helium, and lithium

What is a Star?

• A star is an immense ball of hydrogen and helium where fusion takes place

Fission vs. Fusion

• Fission involves splitting a larger atom into two or more smaller ones
• Fusion involves joining two or more lighter atoms into a larger one

Astronomy

• Astronomy studies celestial objects and phenomena using math, physics, and chemistry
• Celestial objects include planets, moons, stars, nebulae, galaxies, and comets

Tools of the Trade

• Electromagnetic radiation serves as the main source of information in astronomy
• Optical and radio telescopes are types of telescopes
• Astronomers measure wavelength, intensity, direction/position, and variations over time

Galileo Galilei

• Galileo recorded telescope observations in 1609
• He coined the term "telescope" from the Greek words "tele" (far) and "skopos" (seeing)
• Galileo used a refracting telescope

Refracting vs. Reflecting Telescopes

• Refracting telescopes use lenses to bend light
• Light is focused by the objective lens causing parallel lines to converge
• At the focal point, the lines cross each other such that the image actually becomes upside down
• The eyepiece lens then re-bends the light and makes it parallel for the viewer
• Some incoming light is reflected off of the lens, making them inefficient
• Reflecting telescopes use mirrors to reflect light making them more efficient
• Mirrors can be made larger than lenses
• The largest refracting telescope had a 40" diameter lens
• The largest single mirror reflecting telescope has a 200" mirror
• Some telescopes use segmented mirrors
• The segmented mirrors of the Keck Observatory telescopes are 10 m across

Orbiting Telescopes

• Earth's atmosphere absorbs space waves
• Satellites provide an unobstructed view

Future Telescopes

• They use segmented mirrors for adjustments
• Most are being in the Atacama Desert, Chile

Telescopes Over Time

• Eye: 1x magnification
• Galileo's telescope: 27x magnification
• Largest refractor: 1,600x magnification
• 100-inch mirror telescope: 50,000x magnification
• 200-inch mirror telescope: 975,000x magnification
• Keck telescope: 3,800,000x magnification
• Magellan telescope: 19,000,000x magnification
• Extremely Large Telescope: 100,000,000x magnification

The Sun

• Studying the Sun helps in understanding other stars
• Only the thin outer photosphere (~150 km deep) of the Sun can be seen
• The Sun has no sharp boundary and is composed of gas and energy
• During a total eclipse, the chromosphere and corona become visible
• A halo of plasma is hidden by the Sun's light
• The Sun constantly emits solar wind, consisting of ions of helium and hydrogen from fusion
• Aurora Borealis is created charged particles interacting with Earth's atmosphere creating dancing colors

Northern Lights

• The Sun emits charged particles (plasma)
• Earth's magnetic field protects Earth from plasma
• Large solar emissions can overpower the magnetic field
• When particles enter the atmosphere, chemical reactions release creating photons, creating the lights

How Much Energy Does the Sun Have?

• 19th-century scholars estimated 10,000 years if the Sun burned coal
• The Sun is powered by nuclear fusion, not coal
• Hydrogen fusion creates helium and releases elements
• Hydrogen is the most common element in the universe

Nuclear Fusion in the Sun

• Two protons come together to form deuterium
• One proton turns into a neutron
• Byproducts include energy, a neutrino, and a positron
• Another proton collides with the deuterium, producing a hydrogen isotope
• By products include energy, and a photon
• Two helium-3 isotopes collide to form the final helium-4
• By products include energy, protons, and a photon

How Much Energy Does the Sun Have?

• The Sun has a total lifetime of ~11 billion years
• The Sun is currently ~5 billion years old
• When hydrogen runs out, the Sun will become a red giant, not disappear

Hertzsprung-Russell Diagram

• In the early 1900's, 2 astronomers independently discovered a way to organize and name stars
• Energy is calculated based on distance and brightness
• Temperature is determined by the colour spectrum of light
• All stars vary slightly
• Most stars aligned with a sloping line called the main sequence
• The sun is on the main sequence, and these stars burn hydrogen
• Some stars emit lots of energy but seem cool, meaning they are enormous in size and they are red giants
• Some stars are hot but produce little energy so they are small, hot objects called white dwarfs
• H-R diagrams plot a star's temperature versus its energy output
• Stars in the hydrogen-burning stage lie on the main sequence
• Red giants and white dwarfs represent subsequent stages of stellar life

Star Formation

• The Nebular Hypothesis is the most widely accepted model for star formation
• A nebula, a large cloud of dust and gas, forms and is common in the galaxy
• Gravity pulls particles together, causing the nebula to collapse and spin faster

What Keeps a Star Together?

• Heat and pressure push outward, while gravity pulls inward
• A star's size depends on its mass (gravity) and heat/pressure

Life Cycle of Stars

• All stars begin as an immense ball of hydrogen and helium
• Most stars burn hydrogen through nuclear fusion to create pressure and balance against gravity
• Depletion of hydrogen reduces fusion, causing the star to contract, heat up, and burn helium
• Helium burning causes the star to expand greatly, potentially consuming nearby planets
• Once helium is depleted, the star collapses under gravity, generating heat and energy
• Most stars cool to become white dwarfs
• Low-mass stars, or brown dwarfs, have weak gravity and slow fusion, glowing dimly for a hundred billion years

Life Cycle of Massive Stars

• Massive stars (over 10% of the Sun's mass) end in either a supernova or black hole
• Most stars fuse hydrogen rather than helium and stop there
• Large stars fuse elements up to iron, forming an iron core that can't fuse further
• Without fuel gravity causes rapid collapse
• Supernova explosions cause shockwaves that radiate light for months before fading
• Black holes form from stars with immense mass, being so dense they have gravitational pull so strong light cannot escape; they grow over time

Chapter 15: Cosmology

• Cosmology studies the origin and evolution of the universe

Edwin Hubble

• In 1917, the 100-inch Hooker Telescope was built near L.A., California
• In 1919, Hubble began working at Mount Wilson Observatory
• Hubble studied pulsating stars in nebulae
• Hubble discovered that Andromeda was a galaxy ~2 million light-years away, not part of the Milky Way
• This discovery led to a new branch of astronomy

Key Terms

• Astronomy studies celestial bodies and the universe
• Cosmology studies the origin and evolution of the universe
• A galaxy is a system of stars, dust, gas, and dark matter bound by gravity
• Andromeda is a galaxy
• A nebula is a dust and gas cloud
• Our Sun & planets makeup the Solar System, but there are 3,000+ other stars with planets in the Milky Way

Galaxies

• Hubble demonstrated that the universe is much larger than the Milky Way
• There are billions of galaxies, each with millions to hundreds of billions of stars
• The Milky Way is a spiral galaxy

Detecting Galaxies

• Long-exposure photos of empty sky regions reveal galaxies
• There is 1 universe and over 100 billion galaxies
• Billions of trillions of stars exist

Red Shift

• Hubble observed that galaxies appear redder than expected, indicating movement away from Earth
• In the Doppler Effect, things moving away experience red shift

Hubble's Law

• Celestial objects showed greater red shift the further they were, indicating that distant objects move away faster than nearby objects
• Galaxies are moving away at speeds proportional to their distance

Big Bang Theory

• The universe began at a specific time and has been expanding since
• It describes expansion from a high-density, high-temperature point
• It does not explain how energy, time, or space were created
• A theory has to be tested and repeatedly supported

Evidence for the Big Bang Theory

• The discovery of the universe's expansion was the first strong evidence, suggesting that everything was once together
• Radio astronomers detected a constant microwave hiss (Cosmic Microwave Background, or CMB) from all directions
• Steady-state theory cannot predict CMB but Big Bang theory does

Abundance of Light Elements

• Big Bang models predict early formation of hydrogen, helium, and lithium
• Heavier elements formed later in stars via nuclear fusion
• Observed element ratios match Big Bang predictions

Quick Review

• The Great Debate was about whether nebulae were nearby dust clouds or faraway galaxies
• Hubble discovered universal expansion and founded cosmology
• Since the universe is expanding, it must have once been compact

Key Takeaways

• The universe was once extremely small, then rapidly expanded (inflation)
• All forces were once united, with gravity separating first
• Gravity shapes the universe, stars, and beyond

The Future of Our Universe

• Is the universe going to expand forever?
• 3 models depend on gravity's ability to slow or stop expansion
• Is there enough mass for gravity to stop expansion?

3 Models of the Universe

• Closed Universe (Sphere-shaped)
  • Acts like a rubber band pulling back together.
  • Gravity will stop & reverse expansion, leading to a Big Crunch
• Open Universe (Saddle/Pringles chip shape)
  • Acts like a rubber band that snaps.
  • Gravity can't stop expansion, so it will expand forever
• Flat Universe (Sheet of paper shape)
  • Acts like a rubber band that stretches but stops expanding.
  • Gravity slows the expansion but never reverses it

Dark Energy vs. Dark Matter

• Requires more energy to stay in motion
• Distant objects seem to orbit at the right speed
• There must be a force (dark energy) accelerating expansion

Dark Matter

• Mysterious matter that has mass but doesn't interact with normal objects
• It is invisible but exerts a gravitational pull
• 5x more abundant than normal energy
• Theorized to weakly interact with normal matter

Dark Matter vs. Dark Energy

• Dark matter doesn't emit light but has gravity while dark energy is unknown energy accelerating expansion
• Dark matter might be tiny while dark energy can make up 70% of the universe
• Dark matter explains galaxy rotation while dark energy was discovered through supernova observation

Chapter 16: The Solar System

• The Solar System has eight planet of two types with the asteroid belt and the kuiper belt

What is a Planet?

• Per the International Astronomical Union (IAU), a planet must orbit the Sun, have enough mass for gravity to form a spherical shape, orbit objects of similarly sized objects

Why Isn't Pluto a Planet?

• Pluto is too small to clear its orbit
• Charon (Pluto's largest moon) is nearly the same size and affects Pluto's motion
• Pluto is classified as a Dwarf Planet
• Ceres was an asteroid classified as a planet in 1801 but became an asteroid in the 1860s

Measuring Distance in Space: Astronomical Units (AU)

• 1 AU Earth-Sun distance -150 million km);
• Mercury is 0.4 AU
• Venus Is 0.7 AU
• Earth is 1 AU
• Mars is 1.5 AU
• Jupiter is 5 AU
• Saturn is 10 AU
• Uranus is 20 AU
• Neptune is 30 AU
• Pluto is 40 AU

Formation of the Solar System: Nebular Hypothesis

• Interstellar gas & dust collapsed under gravity
• Most material became the Sun, heating until nuclear fusion began
• Leftover spinning material formed planets & other objects

Why Are the Planets Far From the Sun Much Larger?

• Less-dense planets are mostly lightweight and expand, unlike terrestrial planets, tightly held together

Terrestrial Planets Formation

• Protoplanetary disc of dense mineral grains and solids orbiting the Sun
• Over time, grains collided and stuck, forming planetesimals (boulders to small mountains)
• These collied and became protoplanets

Giant Game of Cosmic

• 20-30 protoplanets orbited the Su
• Some were sucked into the Sun, and some escaped the Sun's pull
• Many collided with each other
• Debris scattered and slammed into protoplanets

The Moon

• Big Splash Theory: a planet named Theia collided with Earth ~4.5 billion years ago
• Debris formed the Moon

Why is the Moon Less Dense than Earth?

• Earth had already undergone differentiation
• Heavy materials sunk to Earth's cores lighter material formed lighter mantle material
• Moon rocks confirm it's made of lighter material compared to Earth's core

The 4 Terrestrial Planets

• Mercury, Venus, Earth, Mars

Mercury (Closest to the Sun)

• Visible as a fast-moving star at 0.4 AU
• 1/3 the size of Earth
• Massive iron-nickel core collision ripped off its mantle during differentiation
• Has no atmosphere and a heavily cratered surface
• The Bepi-Colombo mission (European and Japanese) launches in 2018 and will reach 2025

Venus (2nd Closest to the Sun)

• 85% of Earth's mass at a similar diameter
• The atmosphere is mostly CO2 leading to a runaway greenhouse effect
• With no plants or life, planets heated to around 462°C

Earth (3rd Closest to the Sun)

• Has perfect conditions for life, ideal atmosphere, water, and temperature

Mars (4th Closest to the Sun)

• 1/10th the mass of Earth
• Very thin CO2 atmosphere, equivalent to being 40 km above sea level
• Explored and studied planet (other than Earth)
• Found liquid water once exited in 1971; Viking 1 and 2 found potential for microbial life
• 6 rovers have landed including Curiosity (2012, active) and perserverance (2021, with drone)
• Mars has ice, and possible liquid water underground
• Jezero Crater targeted by Perserverance used drill to search for life

Asteroid Belt

• Located between the terrestrial and Jovian planets and very sparse
• Material never formed a planet due to gravitational influence of Jupiter

Jovian Planets

• Jovian planets, also known as gas giants, are composed mostly of hydrogen, helium, and ices
• Larger and thicker atmospheres
• Include Jupiter, Saturn, Uranus, and Neptune

Jupiter

• The largest planet in the solar system with mass 317x that of Earth
• Most of Jupiter is solid or liquid metal
• Rings are made of dust, and 30-12,000 km thick

Europa (Jupiter's Moon)

• 61 moons; Europa is the size of Earth
• Galileo spacecraft detected more likely water than on Earth with saltwater oceans
• Possible hypothesis suggests Europa could harbor the building blocks of microbial life
• Human colonization possible in distant future
• Galileo spacecraft was deliberately crashed to avoid contamination

Saturn

• Less dense than Jupiter with rings viewed only from above
• Average thickness of 10 meters and made of countless meters of rocks and ice; may have derived from broken moon moon

Titan (Saturn's Moon)

• Largest moon in the solar system with an atmosphere
• The Cassini spacecraft orbited Titan from 2004-2017 with water and water ice oceans

Enceladus (Saturn's Moon)

• The Cassini spacecraft found subsurface geysers
• Cassini crashed into Saturn to avoid contamination

Uranus

• Ice giant and the 2nd least dense planet with 21 moons
• Appears bluish due to methane absorbing red wavelengths
• Sparse and dark
• Only rotations as it "laying down" likely from early collision

Uranus Summarized

• Cold, gassy, and not so dense due to early collision
• Cold, gassy and not so dense due to an early collision, and rings and moons

Neptune

• An ice giant with an atmosphere and 4x wider than Earth with a 6-hour day and year of 162 Earth years
• Rings confirmed by Voyager 2 in 1989 and moons confirmed by various other instruments Rings are composed of dust and ice

Chapter 17: Plate Tectonics

• Earthquakes result from the Earth shaking due to underground movements that produce seismic waves release energy in lithosphere

Predicting Earthquakes

• Animal behavior dates to 373 BC in Greece
• US Geological Survey Reports and 100% of Earthquakes happening somewhere today
• Predictions describe time, location, and magnitude, while no prediction is reliable in this case
• Studying plate tectonics from biologists understanding life distribution on Earth

Biogeography

• How our species are distributed geography and geological time has evolved for understanding them now

Key Figures in Biogeography

• Carolus Linnaeus (1707-1778) sparked the theory of evolution after reconciling Noah's Ark and species distribution
• Georges Buffon (1707-1788) helped suggest "northern origin" and nature
• Charles Darwin helped propel the theory of species evolution after variation in inherited offspring and 1831 HMS Beagle's Voyage
• Alfred Wallace' research influenced Darwin's

Wegner's Theory on Continents

• Suggested that continents connected and moved over time
• His geological theory would be validated posthumously

Terms of of Plate Tectonics

• Hypothesis is data with scientific tests and educated experts
• Theories are explanations with data points accepted to be real

Theory of Plate Tectonics

• Plates tectonics explains how the Earth's crust (and upper mantle) is broken into a fluid-like thermal convection moving plates
• Plates are dragged and the mantle rises

Plate Tectonics Support

• Advances in sonar revealed geological features on ocean floors during World War II
• The true structure of ocean floors revealed mountains, ridges, and canyons
• The striped pattern of rocks support what the seafloor holds
• New molten rock emerges and the polarity alternates creating a new, alternating pattern

Plate Tectonics: A Unifying View of Earth

• The Atlantic 7km wide spreads 5 cm / year, taking a 140 million years
• After 200 million years the ocean began breaking apart and unifying the Americas, Europe, Africa

Mantle Movement Causes

• Has three plate boundaries including divergence, convergence, and transformation

Divergence Plate

• Plates moving away magma and the formation of new rocks, leading to ocean rifts and splitting
• The is an example of what that boundary is and stretches in our world

Convergence Plate

• Oceanic is about 10km while continental is 35km and of lighter granite
• The ocean is less dense than the earth leading it to subducting and creating volcanic mountains
• Both converging plates subduct creating ocean trenches
• These often form island arcs in the ocean

Volcanoes

• Divergence plates form in three ways diverging, colliding, and forming hotspots

Hotspot Formation

• Thins spots in area allow volcanos to form chains from magma

Transform Plate Boundaries

• Horizontal plates more than the San Andreas Fault can cause friction and cause earthquakes on large scales

Rock Cycle Phases

• The phases includes the metamorphic stage, sedimentary stage, and igneous state

The Igneous State

• Sedimentary occurs from weathered and compacted/lighified sediments
• Igneous occurs from all cooling lava which creates stone (and or granite)
• Metamorphic results from heat

Sedimentary and Cementation

• Sedimentary accumulates when and and earth's surface bind together
• Minerals can come from organic materials too
• The sedimentary layers are compacted from bottom to top

Lithification

• New structures in rocks results in high heat and pressure including crystallization forming new textures and structures

Processes

• Foliation can create shiest and slate with layer with rock to magma
• Non-foliated does not show rocks with with more uniform patterns

The process with Magma

• Metamorphic creates magma in which a subduction zone occurs and new solids form