Earth's Place in the Universe Flashcards

Grade 8 · Science · Flashcards

Key terms and concepts describing Earth's position within the solar system, galaxy, and universe.

Flashcards

Universe: All of space, time, matter, and energy; contains hundreds of billions of galaxies.
Galaxy: A gravitationally bound system of stars, gas, dust, and dark matter; the Milky Way is ours.
Solar system: The Sun and all objects in its gravitational influence, including 8 planets, moons, asteroids, and comets.
Light-year: The distance light travels in one year, about 9.46 trillion km; used for interstellar distances.
Astronomical Unit (AU): The average Earth-Sun distance (~150 million km); standard measure for solar system distances.
Rotation: Earth spinning on its axis once every ~24 hours, producing day and night.
Revolution: Earth orbiting the Sun once every 365.25 days, defining one year.
Axis tilt: Earth's 23.5° tilt relative to its orbit; responsible for the changing seasons.
Big Bang: Scientific theory that the universe began ~13.8 billion years ago from a hot, dense singularity and has been expanding since.
Milky Way: The spiral galaxy containing our solar system, with 200+ billion stars, ~100,000 light-years across.
Lunar phases: The cyclical change in the Moon's appearance caused by varying angles of sunlight as it orbits Earth.
Gravity: The attractive force between masses; responsible for keeping planets in orbit and holding galaxies together.