Earth Science – Universe, Solar System & Earth Systems

50 question-and-answer flashcards covering key lecture concepts: universe properties, cosmological theories, solar-system formation models, Earth systems, atmospheric layers, and planetary habitability.

What is the estimated diameter of the observable universe?

About 93 billion light-years.

How old is the universe according to current scientific consensus?

Approximately 13.8 billion years.

How old is the Solar System (and Earth) estimated to be?

Roughly 4.5–4.6 billion years.

Where in the Milky Way is our Solar System located?

On one of the galaxy’s outer spiral arms (the outer limb).

What percentage of the universe is baryonic (ordinary) matter?

About 4.6 %.

What percentage of the universe is cold dark matter?

Roughly 24 %.

What percentage of the universe is dark energy?

Approximately 71.4 %.

Name the three most abundant chemical elements in the universe.

Hydrogen (H), Helium (He), and Lithium (Li).

State the central idea of the Big Bang Theory.

The universe began as an infinitely hot, dense point that expanded and has been expanding for 13.7–13.8 billion years.

What does Inflation Theory add to the Big Bang model?

A brief period of exponential expansion fractions of a second after the Big Bang, explaining the universe’s large-scale uniformity.

Does Inflation Theory oppose the Big Bang Theory?

No; it supports and extends it by describing what happened immediately after the Big Bang.

What is the key premise of the Steady State Theory?

The universe is eternal, always expanding, but maintains constant average density through continuous creation of matter.

What does the Multiverse Theory propose?

That many separate universes may exist, each with its own physical laws and histories.

According to the Mbombo (Bumba) myth, how were the Sun, Moon and stars created?

The creator god Mbombo vomited them into existence.

In the Purusha myth, what did Purusha’s head become?

The sky.

Which Solar System origin model suggests it formed from a rotating nebular cloud?

Kant–Laplace Nebular Theory.

Which model proposes the planets formed from debris pulled from the Sun by a passing comet?

Buffon’s Collision Theory.

Which hypothesis attributes star and galaxy formation to tidal forces acting on gas clouds?

Jeans–Jeffreys Tidal Hypothesis.

List Earth’s four major subsystems.

Geosphere, Hydrosphere, Atmosphere, Biosphere (plus the Cryosphere as the frozen component).

Why is Earth dubbed the “Blue Planet”?

Because ~70 % of its surface is covered by oceans of liquid water.

What is the radius of Earth?

About 3,959 miles (≈ 6,371 km).

Name two protective roles of Earth’s atmosphere.

It blocks harmful solar radiation and retains heat to moderate climate.

Which atmospheric layer contains weather and commercial aircraft?

The Troposphere.

Which atmospheric layer hosts the ozone layer?

The Stratosphere.

Which atmospheric layer burns up most meteors?

The Mesosphere.

In which atmospheric layer do auroras occur?

The Thermosphere (and lower Exosphere).

Define the Hydrosphere.

All water on, under, and above Earth’s surface (~1.386 billion km³).

Define the Geosphere.

Earth’s solid portions: rocks, minerals, and interior layers.

Define the Biosphere.

The regions of Earth where life exists, interacting with air, land and water.

Define the Cryosphere.

Earth’s frozen water components: ice caps, glaciers, sea ice, permafrost.

What temperature range generally allows life and liquid water?

About 15 °C to 115 °C.

Which inner planet has an average surface temperature of 333 °F (167 °C)?

Mercury.

Which planet’s mean temperature is 867 °F (464 °C)?

Venus.

Which two atmospheric gases dominate gas-giant atmospheres?

Hydrogen and Helium.

Why can small planets like Mercury not hold thick atmospheres?

Their low gravity cannot retain lightweight gases.

List the four main factors that make a planet habitable.

Temperature, Atmosphere, Energy source, Nutrients.

Give two examples of planetary energy sources.

Solar radiation and internal (geothermal or nuclear) energy.

According to habitability criteria, why is Earth ideal compared with Mars?

Earth has moderate temperature, thicker O₂–rich atmosphere, abundant liquid water, and active nutrient cycles.

In the crash-landing activity, which listed planet has CO₂-H₂O atmosphere and oceans with many volcanic islands?

Planet 3.

What is the average temperature on Planet 4 in the activity?

2 °C.

Which planet habitability factor provides essential nourishment for life maintenance?

Nutrients.

What classroom game was used to review universe facts?

“Celebrity Bluff” (Fact or Bluff).

What statement about universe age was labeled BLUFF in the game?

That the universe is 4.5–4.6 billion years old.

Translate the Latin root "universus."

"Combined into one."

What fraction of the universe is composed of dark matter and dark energy combined?

Approximately 95.4 % (24 % dark matter + 71.4 % dark energy).

Which mythic creator vomited animals and humans after celestial bodies?

Mbombo (Bumba).

What Earth layer lies beneath the crust?

The Mantle.

Name Earth’s three basic internal layers in order outward from the center.

Core, Mantle, Crust.

What is the primary purpose of reviewing alternative cosmological theories?

To explore different possibilities and deepen scientific understanding of the universe.

Which theory asserts the universe has no beginning or end in time?

The Steady State Theory.

How does the Big Bang Theory explain cosmic expansion today?

Space itself is still stretching, causing galaxies to recede from one another.