Earth and Space Science: Key Concepts and Phenomena

Posted on Jan 30, 2025 in Geology

Key Concepts in Earth and Space Science

Atmospheric Science

Fronts: Boundary surfaces that separate air masses of different densities.

Fujita Scale: A scale used to measure tornado intensity based on the damage produced by the storm.

Saffir-Simpson Scale: A scale used to measure the intensity of hurricanes.

Composition of Dry Air:

  • Nitrogen (N): 78.084%
  • Oxygen (O): 21%
  • Argon (Ar): 0.934%
  • Neon (Ne): 18.2 ppm
  • Helium (He): 5.24 ppm
  • Methane (CH4): 1.5 ppm
  • Krypton (Kr): 1.14 ppm
  • Hydrogen (H): 0.5 ppm
  • Carbon Dioxide (CO2): 0.0387%

Layers of the Atmosphere (by temperature, pressure, and moisture):

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Thermosphere

Atmospheric Circulation: Occurs on multiple scales of distance and time, including global, regional, and severe weather patterns.

Energy Transfer in the Atmosphere:

  • Radiation
  • Conduction
  • Convection (mass transport carries heat energy as mass moves; wind and other atmospheric circulation)

Reasons for Seasons:

  1. Tilt of the Earth (less energy from the Sun per unit area hitting the Earth’s surface in winter and more in summer)
  2. Tilt also causes different lengths of day during seasons
  3. Tilt causes more absorption and reflection of solar energy by the atmosphere in the polar regions because of low-angle Sun rays

Climate

(a) Classification:

  • Tropical
  • Desert
  • Alpine

Based on average temperature and precipitation.

(b) Methods of Climate Study (Climate Change):

  • Average weather statistics
  • Paleo records
  • Numerical modeling of atmospheric circulation

(c) Recent Climate Change:

  • Last glaciation
  • Climate optimum
  • Little Ice Age

(d) Causes of Climate Change:

  1. Astronomical effects
  2. Plate tectonics
  3. Changes in solar constant: The total amount of solar energy may change over long periods
  4. Intense volcanism
  5. Greenhouse gases

Weather vs. Climate

Weather: Refers to the state of the atmosphere at a given time or place; it is constantly changing.

Climate: Generalizations of the variations in weather over a long period.

Aerosols: Tiny solid particles suspended in the atmosphere.

Earth’s Motion

Rotation: The spinning of a body, such as Earth, around its axis.

Revolution: The motion of one body about another, such as Earth around the Sun.

Circle of Illumination: The great circle that separates daylight from darkness on Earth.

Tropic of Cancer: The parallel latitude marking the northern limit of the Sun’s vertical rays; the band of Earth that receives the most direct sunlight.

Tropic of Capricorn: The parallel 23.5 degrees south of the equator.

Astronomy

Significance of Astronomy:

  1. Earth’s position in the solar system
  2. Origin of the universe
  3. Natural interest in observing the night sky

Problems in Astronomy:

  • Scale
  • Frame of reference
  • Vast distances and time

Galileo’s Observation: His observation of Jupiter’s moons demonstrated that moons revolved about a planet, providing support for the Copernican theory that the Sun was the center of the solar system.

Solar System Bodies

Asteroids: Small bodies that remain from the formation of the solar system, which means they are about 4.6 billion years old.

Comets: Leftover material from the formation of the solar system.

Meteoroids: Small solid particles in space.

Dwarf Planets: Essentially spherical due to their own gravity but are not large enough to sweep their orbits clear of other debris.

Stars and Galaxies

Stellar Parallax: Distance determined from the parallax angle; the smaller the parallax angle, the greater the distance to the star. A parallax angle of 1 second of arc (1/3600 degrees angle) corresponds to a distance of 3.09E13 km and is called 1 Parsec.

Sun’s Composition:

  • Hydrogen: 73.46%
  • Helium: 24.85%
  • Oxygen: 0.77%
  • Carbon: 0.29%
  • Iron: 0.16%

Hertzsprung-Russell Diagram: A graph created by plotting the absolute magnitudes and temperatures of stars, showing the relationship between luminosity, surface temperature, and absolute magnitude.

Stellar Evolution:

  • Medium and small stars: Expansion causes a red shift, leading to a white dwarf.
  • Large stars: Red shift, leading to a supernova or black hole.

Galaxies:

  • Elliptical
  • Spiral
  • Irregular
  • Dwarf

Doppler Effect: An observer senses different wavelengths (hears different sounds) from approaching and receding objects. Note that an object moving away results in longer wavelengths. The faster the object is moving away, the lower the wavelength. The Doppler effect can be used to determine distances to very distant stars and galaxies by measuring the shift of hydrogen spectral peaks to longer wavelengths (a “red shift”).

Big Bang Theory: The theory that all of the matter in the universe existed in an incomprehensibly hot and dense state, causing an explosion which then expanded, cooled, and evolved into the solar system.

Variable Stars: Huge stars that pulsate (are brighter then dim). Found in globular clusters, their rate of pulsation can identify how far away the globular cluster is.

Hubble’s Law: A law that states that galaxies are retreating from the Milky Way at a speed that is proportional to their distance.