Siolar Systems Quiz 2

What is the solar nebula

A cloud of gas and dust that collapsed to form the Sun and solar system.

What force caused the solar nebula to collapse

Gravity.

What formed at the center of the solar nebula?

The proto-Sun.

Where did most of the mass of the solar system go

Into the Sun (~99.99%).

Why did the solar system form a flat disk

Rotation + centrifugal force flattened the collapsing cloud.

In what direction do planets orbit the Sun

Counterclockwise (viewed from above the Sun’s north pole).

What is a planetesimal

A small body formed from dust and rock that can combine to form planets.

How do planetesimals initially form

Cold chemical bonding (particles sticking together).

What causes planetesimals to form planets

Gravity pulling them together.

What determines if an object is spherical

Gravity (large objects become round).

Why are asteroids irregularly shaped

They are too small for gravity to shape them.

What are the three sources of heat in early Earth

impact- compression-radioactive decay

What effect did this heat have on Earth

It melted the entire planet.

What is differentiation

Separation of materials by density in a molten planet.

What sank to Earth’s core

Iron and nickel (dense metals).

What formed the crust

Lighter materials floating upward.

What is the epoch of heavy bombardment

A period (~4.5–4.0 billion years ago) when planets were heavily hit by planetesimals.

What caused the heavy bombardment

Leftover debris from planet formation.

Why was Earth also bombarded

Larger mass → stronger gravity → attracts more impacts.

What are lunar highlands

Old

What are lunar maria

Smooth basalt plains formed from lava (~3.5–3.8 billion years old).

Why are maria smoother than highlands

Lava filled in craters after impacts.

Why does the Moon have more craters than Earth

No atmosphere

What is anorthosite

Light-colored rock forming the Moon’s highlands.

What is basalt

Dark volcanic rock forming lunar maria and Earth’s ocean crust.

Why is there no granite on the Moon

Granite requires water

What is regolith

Fine lunar dust created by micrometeorite impacts.

What is radioactive dating

Using decay of isotopes to determine rock age.

What is half-life

Time for half of a radioactive substance to decay.

What does radioactive dating measurs

Solidification age of rocks.

Age of the solar system

~4.5 billion years.

Age of oldest moon rocks

~4.3–4.4 billion years.

Age of lunar maria

~3.5–3.8 billion years.

Age of oldest Earth rocks

~3.8–3.9 billion years.

Age of oldest meteorites

~4.55 billion years.

Why does Earth have fewer craters than the Moon

Erosion

What type of rock dominates Earth’s continents

Granite.

What type of rock dominates ocean floors and lunar maria

Basalt.

What did Apollo missions provide

Moon rocks and direct evidence (ground truth).

What are lunar laser reflectors used for

Measuring Earth–Moon distance.

What do telescopes observe in star-forming regions

Protoplanetary disks forming planets.

What is the interstellar medium

Gas and dust between stars.

What happens when parts of it collapse

Forms new stars and solar systems.

Why did the Moon cool faster than Earth

It is smaller.

Why can we study early solar system history on the Moon

It is geologically inactive and preserves ancient surfaces.

Why is early Earth history harder to study

Geological activity erased old evidence.

What was the main idea of the Copernican Revolution?

The shift from an Earth-centered (geocentric) model to a Sun-centered (heliocentric) model.Who proposed the heliocentric model?

Who proposed the heliocentric model?

Copernicus.

Who provided observational support for heliocentrism?

Galileo.

Who collected precise planetary data?

Tycho Brahe.

Who developed the laws of planetary motion?

Kepler.

Who explained planetary motion using gravity?

Newton

What is Kepler’s First Law?

Planets orbit the Sun in ellipses.

What is Kepler’s Second Law?

Planets move faster when closer to the Sun.

What is Kepler’s Third Law?

The farther a planet is from the Sun, the longer its orbital period.

What did Newton contribute to astronomy?

He explained planetary motion using gravity and laws of motion.

What is Newton’s First Law?

An object stays at rest or in constant motion unless acted upon.

What is Newton’s Second Law?

Force causes acceleration.

What is inertia?

Resistance to changes in motion.

What is uniform motion?

Motion at constant speed in a straight line.

What is acceleration?

A change in speed or direction.

Why is circular motion considered acceleration?

Because direction is constantly changing.

What determines gravitational force?

Mass and distance.

What happens to gravity if distance doubles?

It becomes 1/4 as strong.

Why does Earth orbit the Sun?

Because it is constantly accelerating due to gravity.

What is mass?

The amount of matter in an object.

What is weight?

The force of gravity acting on an object

Does mass change with location?

No

Does weight change with location?

Yes

What are common units for velocity?

m/s or km/h.

What are units for acceleration?

m/s².

How fast do objects accelerate due to gravity on Earth?

About 10 m/s each second.

What causes a solar eclipse?

The moon blocks the sun

Why are solar eclipses rare in one location?

They are only visible in a narrow path.

How often do solar eclipses occur globally?

1.5 years

What causes a lunar eclipse?

The Moon passes through Earth’s shadow.

Why are lunar eclipses more widely visible?

They can be seen from half of Earth.

How often do lunar eclipses occur?

once a year

Why does the Moon appear red during a lunar eclipse?

Earth’s atmosphere bends red light onto the Moon.

How are Moon phases and Earth phases related?

They are opposite.

What does Earth look like from the Moon during a full Moon?

a New Earth

What does Earth look like from the Moon during a new Moon?

a full earth

Do Kepler’s laws explain why planets move?

No, they describe motion but don’t explain it.

What explains why planets move the way they do?

Newton’s laws of motion and gravity.