Earth science

• Earth is the only planet in the solar system known to have life
• Earth is the third planet from the Sun and the fifth largest in the Solar System
• Earth has a radius of 3,959 miles and is an oblate spheroid in shape
• Earth's rotation and revolution

  1. Rotates on its axis in 24 hours

  2. Orbits the sun once every 365 days

  3. Creates seasons due to axial tilt
• Earth's seasons


  • winter
  • spring
  • summer
  • autumn
• Places near the equator like the Philippines only have 2 seasons: the rainy season and the dry season
• Winter Solstice


  December 21-22
• Autumnal Equinox


  September 22-23
• Vernal Equinox


  March 20-21
• Summer Solstice


  June 20-22
• It actually takes 23 hours, 56 minutes and 4 seconds for the Earth to rotate once completely on its axis, this is called Sidereal day
• Solar Day is the total of the Earth's rotation and its orbit around the Sun
• Earth's characteristics that make it habitable

  • Surface
  • Atmosphere
  • Water
  • Magnetic field
• Earth's surface is made up of 30% land and is the only planet in the Solar System with plate tectonics
• The Earth's atmosphere is made up of five main layers
• Earth's atmosphere layers


  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
• Ozone


  An inorganic molecule with the chemical formula O3 that blocks ultraviolet light
• Earth is covered with 70% water and has acquired the nickname "Blue Planet"
• Water makes up nearly 60% of our bodies
• Without water, life on Earth would have never begun
• Greenhouse effect


  The process by which radiation from a planet's atmosphere warms the planet's surface
• Carbon cycle


  The biogeochemical cycle by which carbon is exchanged among the biosphere, geosphere, hydrosphere, and atmosphere of the Earth
• Earth's subsystems


  • Atmosphere
  • Lithosphere
  • Hydrosphere
  • Biosphere
• The sun is Earth's major source of energy
• Atmosphere


  The gaseous layer that envelopes the Earth, composed of Nitrogen (78%), Oxygen (21%), and other traces of gases
• Lithosphere


  The rocks and layers of the Earth
• Hydrosphere


  The part of Earth that is covered with liquid water
• Biosphere


  The set of all forms of life on Earth, including humans and all ecosystems
• Earth's subsystems are interdependent
• Events can occur naturally or be caused by humans
• An event can cause changes to occur in one or more of the spheres
• The cycling of matter and energy in the Earth system through interactions makes life on Earth possible
• Earth is within the habitable zone in the solar system
• Habitable zone


  The orbital region around a star where a planet can possess liquid water on its surface and possibly support life
• Liquid water is essential to all life
• Earth is the only planet in our solar system that permits life
• Terrestrial planets


  • Mercury
  • Venus
  • Earth
• Jovian planets are made up of gases mainly hydrogen without land surfaces
• Jovian planets


  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• SAQ-1: What makes a planet in a habitable zone able to sustain life?