Geo11 - Universe and Earth

• Formation of the Earth

  Offshoot of the formation of the universe
• Big Bang Theory


  • Originated from an incomprehensibly large cosmic “explosion” 13.7 billion years ago
  • First proposed by Belgian priest Georges Lemaître in the 1920s
  • Edward Hubble justified the theory through observations of the universe continuously expanding and moving away from each other
• Evidences supporting the Big Bang Theory

  • Abundance of primordial elements: H and He
  • Hubble’s Law: Galaxies seem to be moving away from us at speeds proportional to their distance (redshift)
  • Cosmic microwave background (CMB) radiation: remnant radiation (2.725 K), snapshot of the oldest light
• Limitations of the Big Bang Theory
• Stars synthesize elements in discrete stages during their lifetime
• Nebular Hypothesis

  Solar system originated from a single rotating cloud of gas and dust (solar nebula) starting 4.6 billion years ago, which contracted due to gravity
• Nebular Hypothesis

  Idea first proposed by Immanuel Kant and Pierre Simon de Laplace in the 18th century
• Nebular Hypothesis

  1. Solar Nebula

  2. Gravitational Collapse

  3. Accretion Disk

  4. Protostar

  5. Planetesimals

  6. Protoplanets

  7. Inner and Outer Planet

  8. Solar Wind
• Components of the Solar System

  • The Sun
  • The planets
  • Satellites and rings
  • Comets and asteroids
  • Meteoroids and dusts
• The Sun

  • Mostly made up of hydrogen, sun's center became compressed enough to initiate nuclear reactions, middle-aged star (yellow dwarf)
• The planets


  • Composition depended on the distance from the sun, planets nearest to the sun contained high-temperature minerals while those far away contained lower-temp materials
• The (terrestrial) planets

  • Rocky composition: largely silicate rocks and metals (Si, Fe, O)
• Mercury

  • Day length: 59 Earth days
  • Year length: 88 Earth days
  • Moon: 0, least explored terrestrial planet
• Earth


  • One of only two places where stable bodies of surface liquid
• Information source

  2024
• Terrestrial planets characteristics

  • Closest to the sun
  • Rocky composition: largely silicate rocks and metals (Si, Fe, O)
• Mercury has a day length of 59 Earth days and a year length of 88 Earth days
• Mercury is the least explored terrestrial planet
• Earth is one of only two places where stable bodies of surface liquid have been observed
• Earth is the only known planet/object with life
• Mars has a day length of 24.6 Earth days and a year length of 687 Earth days
• Mars is known as the red planet (oxidized iron)
• Venus has a day length of 243 Earth days and a year length of 225 Earth days
• Venus is the hottest planet due to the greenhouse effect
• Jovian planets characteristics

  • Giant gas planets farther away from the sun
  • Lack of solid surfaces
  • Composed of light elements (H, He, Ar, C, O, Ni)
• Jupiter has a day length of 10 hours and a year length of 12 Earth days
• Jupiter has 95 moons and features the Great Red Spot (high-pressure region producing anticlyclonic storm)
• Saturn has a day length of 10 hours and a year length of 29.4 Earth days
• Saturn has 146 moons and the most complex ring system in the system (ice, rock, and water)
• Uranus has a day length of 17 hours and a year length of 84 Earth days
• Uranus has 27 moons and experiences the most extreme seasons due to its unique tilt (98° to its orbit)
• Neptune has a day length of 16 hours and a year length of 165 Earth days
• Neptune has 14 moons and is classified as an ice giant (methane, ammonia, water)
• Pluto is neither a terrestrial nor Jovian planet, it is the second-most massive known dwarf planet after Eris and the tenth-most massive body observed directly orbiting the Sun
• In 2006, the IAU redefined the term planet formally excluding dwarf planets such as Pluto
• Some interesting facts about planets: Revolution is counterclockwise, rotation direction is the same as revolution except for Venus, Uranus and Pluto rotate about axes that are tipped nearly on their sides, and Earth's orbital speed is 30 km/s
• Other objects in the solar system

  • Asteroids: bodies of rock and metal ranging from meters to kilometers in diameter
  • Meteoroids: smaller bodies
  • Meteors: enters the atmosphere
  • Meteorites: survives the atmosphere and landed on Earth's surface
  • Comets: orbits the sun like asteroids but made of ice and dust, not rocks