Actual and Apparent Motion, Geocentric & Heliocentric Models

• Actual motion refers to how objects truly move, exemplified by Earth's rotation.
• Apparent motion describes how objects seem to move, like the sun's daily rise and set due to Earth's rotation.

Historical Astronomical Models

• The geocentric model, placing Earth at the universe's center, was based on the apparent motion of the sun and stars.
• The heliocentric model later replaced the geocentric model, positioning the sun at the center of the universe.
• The sun is at the center of our solar system, not the entire universe.

Galactic Structure

• A galaxy consists of gas, dust, and stars.
• Earth's solar system is part of the Milky Way galaxy.
• Galaxies cluster into groups; the Milky Way belongs to the Local Group.
• Gravity, an attractive force, holds these systems together.
• Gravitational force depends on the masses of objects and the distance between them, increasing with greater mass and shorter distance.

Solar System Formation

• Our solar system emerged from a gas and dust cloud approximately 4.6 billion years ago.
• It includes the sun, eight planets and their moons, the asteroid belt, and comets.
• The inner planets—Mercury, Venus, Earth, and Mars—feature thin atmospheres, solid surfaces, few or no moons, and no rings.
• The outer planets—Jupiter, Saturn, Uranus, and Neptune—possess thick atmospheres, no solid surfaces, and many rings and moons.
• The asteroid belt, a ring-shaped region with asteroids, separates the inner and outer planets.
• Comets are icy bodies orbiting the sun beyond Neptune, much smaller than planets.

Earth's Seasons

• Earth's tilted axis causes seasons as different parts of Earth point toward or away from the sun during its orbit.
• Summer occurs in the hemisphere pointing toward the sun, receiving more direct sunlight.
• Winter occurs in the hemisphere pointing away from the sun, receiving less direct sunlight.
• The Northern and Southern Hemispheres experience opposite seasons.
• The equator receives the most direct sunlight year-round, resulting in consistently warm temperatures, while the poles receive the least, leading to cold temperatures.

Earth's Moon

• The moon is Earth's sole natural satellite, rotating and revolving around Earth approximately every 27 days.
• Moon phases are the shapes of the moon's sunlit portion visible from Earth, repeating every 29.5 days.
• The new moon appears dark when it is on the same side of Earth as the sun.
• The full moon appears fully lit when it is on the opposite side of Earth from the sun.
• First and third quarter moons appear half-lit on opposite sides when the moon forms a right angle with Earth and the sun.
• A lunar eclipse happens when Earth's shadow covers the moon and can only occur during a full moon.
• A solar eclipse happens when the moon casts a shadow on Earth and can only occur during a new moon.
• Observers within the moon's shadow during a total solar eclipse, when the moon fully covers the sun, experience a temperature drop of approximately 10°F (5.5°C).
• Solar eclipses do not occur every new moon due to the moon's tilted orbit relative to Earth's orbit around the sun.

Water Cycle

• The water cycle is the continuous movement of water between Earth’s surface and atmosphere through physical processes.
• Water enters the atmosphere through evaporation from bodies of water, and through transpiration from plants; both processes are powered by the sun's energy.
• Water forms clouds via condensation, changing from vapor to liquid.
• Precipitation, driven by gravity, returns water to Earth.
• Runoff flows downhill, while some water becomes groundwater.

Weather Patterns and Air Masses

• Weather is the atmospheric condition at a specific time and place, defined by factors such as temperature, rain, and wind.
• Weather changes result from air mass movement from high to low pressure areas.
• Air masses are large air bodies with uniform temperature and humidity.
• Weather fronts form when air masses collide.
• Cold fronts, where cold air moves into warm air, usually bring cool temperatures and heavy rain or thunderstorms.
• Warm fronts, where warm air moves into cold air, generally bring warm temperatures and moderate rain.
• Weather predictions utilize current weather data and computer models but are probabilistic due to weather complexity.

Ocean Currents

• A current is a fluid's steady flow within a larger body of that fluid.
• Prevailing winds are air currents that predominantly blow in one direction, caused by uneven heating of Earth’s surface.
• Prevailing winds drive surface currents in the ocean, both curving due to Earth’s rotation, known as the Coriolis effect.
• Surface currents form large, rotating systems called gyres, which circulate heat by moving warm water from the equator to the poles.
• Deep currents are driven by density differences: denser, colder, and saltier water sinks, while less dense, warmer, and fresher water rises.
• Vertical and horizontal currents form the overturning circulation.

Climactic Factors and Global Resource Distribution

• Climate is the long-term weather pattern of a particular region, influenced by latitude, elevation, and geographic features.
• Higher latitudes receive less direct sunlight, resulting in cooler climates.
• Higher elevations experience cooler climates as air expands and cools.
• Large bodies of water moderate temperatures, resulting in milder climates nearby.
• Mountain ranges can create rain shadows, leading to warmer and drier climates on one side.

Rock Cycle

• The rock cycle describes how rocks form and change over time.
• Magma forms when rocks melt and cool down.
• Igneous rocks form when magma or lava cools and solidifies.
• Weathering breaks rocks into sediment, which erosion transports, and deposition drops in new locations.
• Sedimentary rocks form when sediment is compacted and cemented through lithification.
• Metamorphic rocks form when existing rocks are exposed to intense heat and pressure.

Geological Strata and Dating

• Sedimentary rocks typically occur in horizontal layers called strata.
• In undisturbed strata, younger layers sit on top of older layers, known as the law of superposition.
• Faults are cracks and intrusions are bodies of igneous rock formed within Earth’s crust that cut through strata.
• The law of crosscutting relationships states that when two features intersect, the one that cuts through the other is younger.
• Index fossils are fossils associated with a specific time that can be used to correlate strata.
• By studying strata, geologists have determined the relative order of major events in Earth’s history, which makes the geologic time scale.

Plate Tectonics

• Earth’s lithosphere is broken into tectonic plates that move over the asthenosphere.
• Plates move a few centimeters per year.
• Plate boundaries are where two plates meet, and can be divergent, convergent, or transform.
• Divergent boundaries, where plates move apart, form rift valleys and mid-ocean ridges.
• Convergent boundaries, where plates move together, form mountains and trenches.
• Transform boundaries, where plates move past each other, are sites of earthquakes.
• Complementary coastlines support that continents were once joined together.
• Oceanic plates make up the ocean floor and continental plates make up the continents.
• Oceanic crust is denser than continental crust.
• Trenches form when denser oceanic plates are subducted under less dense plates at convergent boundaries.
• Mid-ocean ridges form at divergent boundaries.
• New oceanic crust is created at mid-ocean ridges, moves away, cools, becomes denser, and is eventually destroyed at trenches.

Shaping Earth's Surface

• Water shapes Earth's surface through weathering, erosion, and deposition.
• Weathering breaks rocks into sediment through mechanical and chemical means; mechanical weathering is physical and chemical weathering is chemical.
• Erosion transports sediment, with faster, higher-volume water having more erosional power.
• Deposition occurs when water drops sediment.

Natural Resources

• Natural resources are materials found in nature that are used by humans.
• Renewable resources can be replaced over human lifetimes, and nonrenewable resources cannot.
• Renewable and nonrenewable resources are unevenly distributed, due to variations in wind and geologic processes.
• Human activity can alter resource distribution through activities like dam construction.

Natural Hazards and Human Impact

• A natural hazard is a natural event that poses a risk to humans such as: tornadoes, hurricanes, earthquakes, and volcanic eruptions.
• Some natural hazards like hurricanes can be predicted, while others like earthquakes are not.
• Increased scientific knowledge improves hazard prediction and preparedness.
• Human activities impact the environment through land and water use, deforestation, and burning fossil fuels.
• Negative human impacts, like habitat loss, increase with population growth and resource consumption.
• Science can provide solutions to reduce our environmental impact.

Explore actual vs. apparent motion with Earth's example. Review the geocentric and heliocentric models, and galactic structures. Understand gravity's role in holding these systems together and its dependency on mass and distance.