World Geography: Our Universe and Solar System

Comprehensive vocabulary flashcards covering the basic definitions and facts regarding the Universe, Solar System, planets, and celestial bodies based on the lecture notes.

Universe

The totality of everything that can exist or that we know exists, including all matter, energy, planets, stars, galaxies, and intergalactic space.

Cosmology

The scientific study of the Universe.

Big Bang Theory

The theory explaining the origin of the Universe, propounded by the Belgian cosmologist Georges Lemaitre in 1927 and Alexander Friedmann in 1922.

Heavenly bodies

Also known as "Celestial bodies," these include the Sun, Moon, and all glittering bodies in the sky like stars and planets.

Stars

Heavenly bodies made of gases that are extremely hot and large, possessing their own heat and light which they radiate in huge amounts.

Proxima Centauri

The nearest star to the Earth after the Sun, located about $4.22$ light years away.

Planets

Heavenly bodies that do not have their own heat and light; the word means "To be rover."

Solar System

The collective system consisting of the Sun, eight planets, satellites, asteroids, meteoroids, comets, interplanetary dust, and plasma.

Elliptical orbit

The path in which planets revolve around the Sun.

Sun

The largest member and center of the solar system, with a surface temperature of about $6000\text{ }^{\circ}\text{C}$, situated $150 \times 10^{6}\,km$ from Earth.

Mercury

The smallest planet and nearest to the Sun; it is the fastest revolving planet, completing an orbit in $88$ days.

Dwarf planet

A celestial body, such as Pluto, that orbits the Sun but is smaller than traditional planets and does not dominate its neighborhood.

Nebular hypothesis

The most acceptable theory regarding the evolution of planets.

Inner planets

Also called Terrestrial planets, these include Mercury, Venus, Earth, and Mars; they are relatively small and composed mostly of rock.

Outer planets

Also known as Gaseous or Jovian planets, including Jupiter, Saturn, Uranus, and Neptune; they are huge, ringed, and have many natural satellites.

Velocity of light

$3 \times 10^{8}\,m/s$; light from the Sun reaches Earth in about $8$ minutes.

Sunspots

"Cool" regions on the Sun caused by magnetic field disturbances, appearing about $2700\text{ }^{\circ}\text{F}$ ($1500\text{ }^{\circ}\text{C}$) cooler than the surrounding area.

Asteroids

Groups of small bodies located between Mars and Jupiter that revolve around the Sun.

Satellite

Meaning "companion," these bodies reflect Sun's light and revolve around planets; Saturn has the largest number of them in our solar system.

Moon

The Earth's only natural satellite, with a diameter one-fourth of Earth's and gravity equal to $1/6\text{th}$ of Earth's gravity.

Venus

The "twin planet" of Earth, the hottest and brightest planet, known as the "morning and evening star," and rotating from East to West.

Blue Planet

A name for Earth due to the existence of water as seen by astronauts from space.

Milky Way

The galaxy in which our solar system is situated.

Light year

The distance traveled by light in one year, used to measure distances in the Universe.

Andromeda

The nearest galaxy to our own, located $22,00,000$ light years away.

Mars

Known as the "red planet," it has nearly the same angle of inclination and length of day as Earth.

Jupiter

The biggest planet in the solar system and also the fastest rotating planet.

Geoid

Also called an oblate spheroid, this describes the Earth's shape: spherical with compression at the poles and a bulge at the equator.

Hydra

The largest constellation.

International Date Line

A person crossing this line from East to West loses $1$ day.