Geosystems: Solar Energy and the Seasons (Chapter 2)

Vocabulary-style flashcards covering key concepts from the Solar Energy and Seasons chapter.

Planetesimal hypothesis

The idea that planets form from condensed solid bodies (planetesimals) that arise as nebular clouds collapse under gravity.

Nebular cloud

A gas-and-dust cloud from which stars and planetary systems condense under gravity.

Gravity (solar system formation)

Mutual attraction between masses that drives the formation and orbital dynamics of the solar system.

Speed of light

Approximately 299,792 km per second; used to relate cosmic distances (e.g., light-hours across the solar system).

Light-hour

The distance light travels in one hour; used to describe the size scale of the Solar System.

Perihelion

The point in Earth’s orbit closest to the Sun; about 147,255,000 km on January 3.

Aphelion

The point in Earth’s orbit farthest from the Sun; about 152,083,000 km on July 4.

Subsolar point

The location on Earth where the Sun is directly overhead at noon; migrates between the Tropics over the year.

Insolation

Incident solar radiation received at a location; measured in W/m^2; influenced by latitude and season.

Solar constant

Average insolation at the top of Earth's atmosphere, about 1372 W/m^2.

Sunspots

Magnetic storms on the Sun’s surface; associated with solar activity cycles (~11 years).

Solar wind

Streams of electrically charged particles emitted by the Sun that interact with Earth’s magnetosphere.

Magnetosphere

Earth’s magnetic-field region that protects the planet from charged solar wind.

Aurora Borealis

Northern lights; luminous displays caused by solar wind particles exciting Earth's atmosphere.

Electromagnetic spectrum

The full range of electromagnetic radiation from gamma rays to radio waves; includes visible light.

Shortwave radiation

Higher-energy radiation typically emitted by the Sun; part of the solar radiation reaching Earth.

Longwave radiation

Thermal infrared radiation emitted by Earth back into space.

Wavelength

The distance between successive peaks of a wave; determines the type and energy of electromagnetic radiation.

Solar energy budget

Balance between incoming solar radiation to Earth and outgoing infrared energy emitted by Earth.

Declination

Latitude where the Sun is directly overhead at noon; varies seasonally between ±23.5°.

Seasonality

Seasonal variations in Sun’s position, day length, and solar input throughout the year.

Tilt of Earth’s axis

Axial tilt of about 23.5° relative to the plane of the ecliptic.

Axial parallelism

Axis maintains orientation toward the stars during orbit; north pole points toward Polaris.

Sphericity

The Earth is approximately spherical, affecting insolation and seasonal patterns.

Revolution

Earth’s orbit around the Sun (about one year) with average speed ~107,280 km/h.

Rotation

Earth’s spin on its axis every 24 hours; equatorial speed ~1674 km/h.

Tropics

Latitudinal band between 23.5°N and 23.5°S where the Sun can be directly overhead.

Solstice

Points of extreme Sun declination: summer solstice (≈June 20–21) and winter solstice (≈December 21–22).

Equinox

Points when day and night are roughly equal: vernal (spring) and autumnal (fall).