Origin and Structure of the Earth, Universe, and Solar System

Question-and-Answer flashcards covering cosmology, universe origins, solar-system formation theories, planet categories and characteristics, dwarf planets, and minor solar-system members.

What branch of science studies the origin, evolution, and fate of the universe?

Cosmology

How is the universe defined in terms of its composition?

A large, unimaginable expanse of gas, stars, dust clouds, planets, and galaxies.

Which theory proposes the universe began from a hot, dense singularity and has been expanding ever since?

The Big Bang Theory

Who are the two main proponents of the Big Bang Theory?

Georges Lemaître and George Gamow

What name is given to the super-fast early expansion that increased the universe from atomic size to grapefruit size?

Inflation

Roughly how long after the Big Bang did neutral hydrogen atoms form, allowing light to travel freely?

About 300,000 years

Which cosmological theory claims the universe has no beginning or end and keeps a constant average density?

The Steady State Theory

Name two key scientists associated with the Steady State Theory.

Fred Hoyle and Bondi & Gold

What is the main difference between Big Bang and Steady State cosmologies regarding matter?

Big Bang: matter dilutes as the universe expands; Steady State: matter is continually created as it expands.

Which theory, also called the pulsating universe, says the cosmos alternates between expansion and contraction?

The Oscillating (Pulsating) Universe Theory

Who introduced the "big bounce" concept in the Oscillating Universe Theory?

Richard Tolman

Define the solar system.

The Sun and all objects gravitationally bound to it, orbiting directly or indirectly.

Which early theory suggested the solar system formed after a comet collided with the Sun, ejecting material?

Encounter Theory (Georges Louis Leclerc, Comte de Buffon)

What is the Nebular Hypothesis?

The solar system formed from a rotating cloud of gas and dust called the solar nebula.

List the three major steps in solar-system formation under the Nebular Hypothesis.

(1) Cloud collapse, (2) formation of a protoplanetary disk, (3) growth of planets.

Which planetary group is small, rocky, dense, rotates slowly, and has thin or no atmospheres?

The terrestrial (inner) planets

Name the four terrestrial planets.

Mercury, Venus, Earth, and Mars

Which planetary group consists of large, low-density gas giants with thick atmospheres and fast rotations?

The Jovian (outer) planets

Which four planets are classified as Jovian?

Jupiter, Saturn, Uranus, and Neptune

Why are gas giants’ large masses due more to size than density?

They are composed mainly of light gases like hydrogen and helium.

Name the five officially recognized dwarf planets.

Ceres, Pluto, Haumea, Makemake, and Eris

Which planet has 88-day daylight and night cycles and temperatures from −300 °F to 800 °F?

Mercury

Which planet’s thick CO₂ atmosphere raises surface temperatures to ~900 °F and pressures 90× Earth’s?

Venus

What gives Mars its characteristic reddish color?

Iron-rich rock, sand, and soil.

What is Jupiter’s Great Red Spot?

A giant, long-lived storm with winds up to about 1,000 mph.

Which four large Jovian moons were discovered by Galileo?

Io, Europa, Ganymede, and Callisto

Which planet is famous for its prominent ring system and takes 29.5 Earth years to orbit the Sun?

Saturn

Which planet rotates on its side and appears greenish due to atmospheric methane?

Uranus

What planet is considered Uranus’s twin, also methane-rich and ringed?

Neptune

Why did the IAU reclassify Pluto as a dwarf planet in 2006?

It does not clear other objects from its orbital neighborhood.

Of what are comets primarily composed?

Frozen gases mixed with rocky and metallic materials.

What is the glowing head of a comet called?

The coma

Why does a comet’s tail always point away from the Sun?

Solar radiation pressure and the solar wind push it away.

Where are most asteroids located?

In the asteroid belt between Mars and Jupiter.

What is a meteoroid called once it enters Earth’s atmosphere?

A meteor

What term is given to a meteor that survives to reach Earth’s surface?

A meteorite

What causes a meteor shower?

Earth passes through a stream of meteoroids left along a comet’s orbit.