EARTH SCIENCE

• The Earth's inner core is a solid sphere made primarily of iron and nickel.
• Age of Universe: 13.8 billion years old
• Age of Solar System: 4.6 billion years old
• From small to big: Solar system < Galaxy < Universe
• Composition of the Universe:

  • Baryonic matter:
  • About 4 - 4.6% of the entire universe
  • Tangible and observable
  • Consists of protons, neutrons, electrons
  • Objects include clouds of cold gas, planets, comets, stars, galaxies
  • Dark matter:
  • About 23 - 27% of the entire universe
  • Cannot be seen or observed
  • Has gravity but does not emit light
  • Evidences include motion of stars, orbits of galaxy, temperature of gas, gravitational lensing
  • Dark energy:
  • About 68 - 73% of the entire universe
  • Source of anti-gravity that causes expansion
  • Non-particulate, has repulsive gravity
• Elements in the Universe:

  • Most abundant elements: Hydrogen, helium, lithium
  • Earth is made of iron
• Stars:

  • Made of hydrogen
  • Building blocks of galaxies
• Protostars:

  • Early stage of star from gravitational collapse of gases
• Thermonuclear reaction:

  • Nuclear fusion reaction in stars for energy production
• Main sequence stars:

  • Fuse hydrogen atoms to form helium atoms in cores
  • Outward pressure from nuclear fusion balanced by gravitational forces
• Stellar evolution:

  • Process of star formation
  • Includes: Planetary Nebula, White Dwarf, Neutron Star, Black Hole, Light Year
• Planetary Nebula:

  • Ring-shaped nebula from expanding shell of gas around aging star
  • Core goes outside
• White Dwarf:

  • Formed after stars exhaust nuclear fuel
  • Hot core remains after expelling outer material
  • Hydrogen is thermonuclear fuel
• Black Hole:

  • Region of space with intense gravitational field
  • Nothing can escape
• Neutron Star:

  • Small radius, high density celestial object
  • Composed predominantly of closely packed neutrons
• Formation of Stars:

  • Nebula made of gases and dust
  • Gases and dust pulled by gravity forces to form compact gas
  • Core formed, nuclear reaction takes place, star is formed
• Nuclear reaction in the core:

  • 4 hydrogen atoms → 1 Helium atom + light energy + heat energy
• Galaxies:

  • Clusters of billions of stars
  • Clusters form super clusters
  • Universe appears clumpy at certain scale, homogeneous and isotropic on larger scale
• Milky Way Galaxy:

  • Our galaxy
  • Stars are building blocks of galaxies
• Light Year:

  • Distance light can travel in a year
  • Equivalent to ≈ 9.5 trillion km or 6 trillion miles
  • Speed of light: 299,792,458 m/s
  • 1 light year: 9.46 x 10^12 km
• Age of the Universe:

  • Estimated at 13.8 billion years
  • Diameter of the universe is infinite
  • Density: 4.5x10^-31 g/cm^3
  • Solar System formation: 4.6 billion years ago
• Expanding Universe:

  • Edwin Hubble:
  • American astronomer who proved the Universe is expanding
  • Hubble's Law: relationship between speed of distant galaxies and their distances
  • Red-shift phenomenon: spectral lines shifted toward red part of spectrum
• Red-shift:

  • Increase in wavelength, decrease in frequency
  • Used to determine distance of distant objects
• Blue-shift:

  • Decrease in wavelength, increase in frequency
  • Indicates objects moving closer
• Cosmic Microwave Background (CMB):

  • Reason why we know the age of the Universe
  • Glow of microwaves emitted by infant universe
  • Remnant heat from Big Bang
  • Discovered in 1964
• Origin of the Universe:

  • Ancient Egyptians believed in many gods and myths
• Ancient Egyptians believed in many gods and myths, narrating that the world arose from an infinite sea at the first rising of the sun
• Kuba people of Central Africa tell the story of a creator god Mbombo (or Bumba) who vomited the stars, sun, and moon after feeling intense stomach pain on a dark and water-covered Earth
• In India, gods sacrificed Purusha, the primal man, whose body parts became the sky, earth, sun, and moon
• Judaism, Christianity, and Islam claim a supreme being created the universe, including man and other living organisms, and that religious belief cannot be tested using the scientific method
• Steady State Model: New matter is created as the universe expands, maintaining its density
• Big Bang Theory: The universe is 13.8 billion years old, started from a tiny dense and hot mass, and rests on General Relativity and the Cosmological Principle
• Theory of General Relativity: Gravity is a distortion of space-time, and mass can "curve" space creating orbits for nearby objects
• Cosmological Principle: On large scales, the Universe is homogenous and isotropic, with no preferred location (Copernican Principle)
• Similarities between Steady State Model and Big Bang Theory: The Universe has been expanding since its beginning
• Differences between Steady State Model and Big Bang Theory: BBT states all matter and energy were compressed into a single space and then exploded, while SSM suggests the Universe has always existed and matter is continuously created
• Mars is known as the "red planet"
• Neptune is the farthest planet from the sun
• Earth is the "Third Rock" from the sun
• Mercury is the closest planet to the sun and was named after the Roman messenger of the Gods