Geocentric vs. Heliocentric Models, Plate Tectonics, Solar System, and Universe Theories - Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering geocentric vs. heliocentric models, plate tectonics, Earth’s systems, the Solar System, and major universe theories, derived from the provided lecture notes.

Geocentric model

Earth-centered universe where Earth is the center and all celestial bodies revolve around it.

Ptolemy

Ancient astronomer who developed the geocentric model circa 150 CE and explained retrograde motion with epicycles.

Deferent

The large circle around Earth in Ptolemy’s epicycle-deferent system.

Epicycle

A smaller circle whose center moves along the deferent to explain retrograde motion.

Retrograde motion

The apparent backward motion of a planet as seen from Earth, explained by epicycles.

Heliocentric model

Sun-centered model where the Sun is at the center and planets orbit it.

Copernicus

Astronomer who proposed the heliocentric model, initiating a major shift in astronomy.

Galileo Galilei

Astronomer who used the telescope to observe moons of Jupiter, phases of Venus, sunspots, and moon craters, supporting heliocentrism.

Moons of Jupiter

Galileo’s discovery showing that not everything orbits Earth.

Phases of Venus

Venus shows phases consistent with a heliocentric system, observed by Galileo.

Sunspots

Dark spots on the Sun indicating that celestial bodies are not perfectly smooth or ideal.

Moon craters

Impact-created features on the Moon, evidence of imperfect celestial bodies.

Johannes Kepler

Astronomer who used Tycho Brahe’s data to formulate the three laws of planetary motion.

Three laws of planetary motion

1) Planets move in ellipses with the Sun at one focus; 2) Equal areas are swept in equal times; 3) The square of a planet’s orbital period relates to the cube of its semi-major axis.

Tycho Brahe

Astronomer whose precise observations enabled Kepler to derive his laws.

Elliptical orbits

Planetary orbits are ellipses, not perfect circles.

Modern acceptance of heliocentric model

The Sun-centered model is the accepted scientific model today, supported by observation and mathematics.

Lithosphere

Rigid outer shell of Earth, including the crust and upper mantle.

Asthenosphere

Ductile layer of the upper mantle beneath the lithosphere that allows plate movement.

Continental plates

Thick, less dense tectonic plates that form continents.

Oceanic plates

Thin, dense tectonic plates that form ocean floors.

Sea-floor spreading

Formation of new oceanic crust at mid-ocean ridges, pushing older crust outward.

Paleomagnetism

Record of ancient magnetic field orientations on the ocean floor, indicating pole reversals and seafloor spreading.

Convergent boundaries

Where plates collide; produce mountains, volcanic arcs, and earthquakes (e.g., Himalayas).

Divergent boundaries

Where plates move apart; create new crust; mid-ocean ridges and rift valleys.

Transform boundaries

Where plates slide horizontally past one another; frequent earthquakes.

Himalayas

Mountain range formed by the collision of Indian and Eurasian plates at a convergent boundary.

Mid-Ocean Ridge

Undersea mountain range formed by sea-floor spreading at divergent boundaries.

Rift valleys

Valleys formed at divergent boundaries from crustal thinning.

Atmosphere

Layer of gases surrounding Earth; regulates temperature, weather, and climate.

Hydrosphere

All water on Earth (oceans, rivers, glaciers, groundwater); regulates climate and supports life.

Geosphere

Rocks, minerals, soil, mountains; provides resources and nutrients.

Biosphere

All living organisms; drives energy flow and nutrient cycles.

Troposphere

Lowest atmospheric layer (0–12 km) where weather occurs.

Stratosphere

Layer up to about 50 km containing the ozone layer and stable conditions for flight.

Mesosphere

Layer (50–85 km) with very cold temperatures and meteoroid burning.

Thermosphere

High-temperature layer (85–600 km) vital for radio communication and auroras.

Exosphere

Outermost atmospheric layer where air is extremely thin and particles escape to space.

The Sun

The center of the Solar System; a star composed mainly of hydrogen and helium; ~99.8% of the system’s mass; energy from nuclear fusion.

Sun core

Innermost region where nuclear fusion occurs to power the Sun.

Photosphere

Visible surface of the Sun from which light is emitted.

Chromosphere

Layer above the photosphere; emits specific spectral lines and contains the chromosphere.

Corona

The Sun’s outer atmosphere extending far into space.

Inner planets

Mercury, Venus, Earth, Mars; rocky, smaller planets.

Outer planets

Jupiter, Saturn, Uranus, Neptune; gas/ice giants, larger and more distant.

Dwarf planets

Small planetary bodies that orbit the Sun but are not dominant gravitationally in their region.

Asteroids

Rocky bodies, mostly between Mars and Jupiter in the asteroid belt.

Comets

Icy bodies residing in the Kuiper Belt and Oort Cloud; develop tails when near the Sun.

Kuiper Belt

Region beyond Neptune with icy bodies; source of short-period comets.

Oort Cloud

Hypothetical distant spherical shell of icy bodies surrounding the Solar System; source of long-period comets.

Big Bang Theory

Universe began from a singularity and expanded rapidly.

Redshift

Distant galaxies moving away; evidence for cosmic expansion.

CMBR (Cosmic Microwave Background Radiation)

Afterglow of the Big Bang; uniform radiation providing strong evidence for the model.

Abundance of light elements

Predominant presence of hydrogen, helium, and lithium in specific ratios left from the early universe.

Nebular Theory

Solar System formed from a rotating cloud (nebula) of gas and dust.

Planetesimal Theory

Planets formed from the accumulation and accretion of small solid bodies (planetesimals).

Accretion Theory

Planets grew by gradual accumulation of particles through gravity.

Protoplanet Hypothesis

Planets formed from large protoplanets within a solar nebula.

Planetary Collision Theory

Moon formed from Earth colliding with a Mars-sized body.

Gas Cloud Theory

Planets formed as gas condensed into chunks that coalesced under gravity.

Oscillating Universe Theory

Universe alternates between expansion and contraction (Big Bangs and Big Crunches); generally rejected due to observed acceleration.

Steady State Theory

Universe is eternal with continuous creation of matter; rejected due to CMBR evidence.