16 - The Sun-Earth-Moon System

Question 1

Define:

Earth’s rotation

Answer 1

The spinning of Earth on its axis.

Earth’s rotation takes approximately 24 hours and is responsible for the cycle of day and night.

Question 2

Define:

Earth’s revolution

Answer 2

The movement of Earth around the Sun.

Earth takes about 365.25 days to complete one revolution, which defines the length of a year.

Question 3

Identify:

What is the imaginary line around which Earth rotates?

Answer 3

Earth’s axis

The axis is tilted at an angle of about 23.5 degrees, influencing seasonal changes.

Question 4

Describe:

What happens during Earth’s rotation?

Answer 4

Earth spins counterclockwise, causing the cycle of day and night.

As Earth rotates, different parts face the Sun, experiencing daylight, while others move into darkness, experiencing night.

Question 5

Identify:

What imaginary line receives the most direct sunlight year-round?

Answer 5

The Equator

The Equator consistently gets nearly direct sunlight, leading to warm temperatures throughout the year.

Question 6

Explain:

Why does Earth’s axial tilt affect the seasons?

Answer 6

It changes the intensity and angle of sunlight in different regions.

When a hemisphere is tilted toward the Sun, it experiences summer; when tilted away, it experiences winter.

Question 7

Explain:

What are the four main astronomical seasons?

Answer 7

1. Spring
2. Summer
3. Autumn (Fall)
4. Winter

These events occur because Earth’s axis is tilted at 23.5° relative to its orbit.

Spring – Begins at the vernal equinox, with nearly equal day and night.

Summer – Starts at the summer solstice, the longest daylight period.

Autumn (Fall) – Begins at the autumnal equinox, balancing day and night.

Winter – Starts at the winter solstice, the shortest daylight period.

Question 8

True or False:

Earth is closest to the Sun during summer in the Northern Hemisphere.

Answer 8

False

Earth is actually closest to the Sun in early January, but seasons are determined by axial tilt, not proximity.

Question 9

Identify:

When do day and night become nearly equal twice a year?

Answer 9

During the equinoxes.

The vernal equinox (March 20-21) and autumnal equinox (September 22-23) occur when the Sun is directly over the Equator, resulting in nearly equal day and night lengths.

Question 10

Fill in the blank:

The longest and shortest days of the year are called the _______.

Answer 10

solstices

The summer solstice (June 20-21) has the longest daylight hours, while the winter solstice (December 21-22) has the shortest.

Question 11

Explain:

Why do time zones exist?

Answer 11

Because Earth rotates, creating different local times across the globe.

The world is divided into 24 time zones, each roughly 15 degrees of longitude apart.

Question 12

Define:

What is the Coriolis effect?

Answer 12

The deflection of moving air and water due to Earth’s rotation.

The Coriolis effect causes winds and ocean currents to curve right in the Northern Hemisphere and left in the Southern Hemisphere.

Question 13

Identify:

What is the reference point for global timekeeping?

Answer 13

The Prime Meridian (Greenwich Mean Time).

The Prime Meridian (0° longitude) is the standard reference for determining time zones worldwide.

Question 14

Define:

leap year

Answer 14

• Leap years add an extra day (February 29th) to synchronize the calendar with Earth’s slightly longer than 365-day orbit.
• The Gregorian calendar dictates leap years as those divisible by 4, except for century years not divisible by 400.

Question 15

Explain:

How does Earth’s motion affect day length?

Answer 15

It varies near the poles but stays constant at the Equator.

Near the poles, daylight can last 24 hours in summer or nearly disappear in winter due to Earth’s axial tilt.

Question 16

True or False:

All parts of Earth experience the same duration of daylight year-round.

Answer 16

False

The duration of daylight varies by latitude, with polar regions having extreme variations due to the axial tilt.

Question 17

Define:

Sun-Earth-Moon system

Answer 17

The gravitationally bound relationship between the Sun, Earth, and Moon.

This system governs motions like Earth’s orbit, the Moon’s phases, tides, and eclipses.

Question 18

Identify:

What force keeps the Sun-Earth-Moon system together?

Answer 18

Gravity

Gravity controls the orbits of Earth around the Sun and the Moon around Earth.

Question 19

Identify:

What is the point in Earth’s orbit closest to the Sun?

Answer 19

Perihelion

Perihelion occurs in early January when Earth is closest to the Sun, though its tilt, not distance, primarily determines seasonal temperatures.

Question 20

Identify:

What is the point in Earth’s orbit farthest from the Sun?

Answer 20

Aphelion

Aphelion occurs in early July when Earth is farthest from the Sun, but summer still happens in the Northern Hemisphere due to Earth’s tilt.

Question 21

Describe:

How does the Moon orbit Earth?

Answer 21

In an elliptical path.

The Moon’s orbit is slightly oval-shaped, causing variations in its distance from Earth.

Question 22

Explain:

Why do we always see the same side of the Moon from Earth?

Answer 22

Because of synchronous rotation.

The Moon is tidally locked to Earth, meaning its rotation period (27.3 days) matches its orbital period around Earth. As a result, the same hemisphere of the Moon is always facing Earth, while the far side remains unseen from the surface.

Question 23

Define:

lunar phase

Answer 23

The changing appearance of the Moon as seen from Earth.

The phases result from the Moon’s orbit around Earth and the reflection of sunlight.

Question 24

Explain:

What are the eight phases of the Moon?

Answer 24

1. New Moon
2. Waxing Crescent
3. First Quarter
4. Waxing Gibbous
5. Full Moon
6. Waning Gibbous
7. Last Quarter
8. Waning Crescent

New Moon – The Moon is between Earth and the Sun, making it invisible.

Waxing Crescent – A thin sliver of the Moon starts becoming visible.

First Quarter – Half of the Moon is illuminated, appearing as a half-circle.

Waxing Gibbous – More than half of the Moon is visible as it nears fullness.

Full Moon – The entire face of the Moon is fully illuminated.

Waning Gibbous – The Moon starts decreasing in illumination after the Full Moon.

Last Quarter – Half of the Moon is visible again, but now in its waning phase.

Waning Crescent – A thin sliver remains before transitioning back to the New Moon.

Question 25

# Identify: What is the **phase** when the Moon is **completely illuminated**?

Answer 25

Full Moon ## Footnote This occurs when Earth is *between* the Sun and the Moon.

Question 26

# True or False: A **supermoon** happens when the Moon is **closer** to Earth.

Answer 26

True ## Footnote A supermoon happens at **perigee**, when the Moon is closest to Earth, appearing up to 14% larger and 30% brighter than at apogee.

Question 27

# Define: What is a **blue moon**?

Answer 27

A **second full moon** in a **single month**. ## Footnote Blue moons are **rare**, occurring roughly every 2.5 years due to differences between calendar months and the lunar cycle.

Question 28

# Describe: What **happens** during a **solar eclipse**?

Answer 28

The Moon **blocks** sunlight, **casting a shadow** on Earth. ## Footnote This occurs when the Moon is between the Sun and Earth.

Question 29

# Describe: What **happens** during a **lunar eclipse**?

Answer 29

Earth’s shadow **covers** the Moon. ## Footnote A lunar eclipse happens when Earth **blocks** sunlight from reaching the Moon, causing the Moon to pass through Earth’s shadow

Question 30

# Explain: What are the **three types of solar eclipses**?

Answer 30

1. Total Solar Eclipse 2. Partial Solar Eclipse 3. Annular Solar Eclipse ## Footnote **Total Solar Eclipse** – The Moon completely blocks the Sun, casting a full shadow (umbra) on Earth. **Partial Solar Eclipse** – The Moon covers only part of the Sun, creating a partial shadow (penumbra). **Annular Solar Eclipse** – The Moon appears smaller than the Sun, leaving a bright ring (annulus) visible.

Question 31

# Define: What is a **hybrid solar eclipse**?

Answer 31

An **eclipse that** **shifts** between total and annular. ## Footnote This **rare** event happens because Earth’s surface is curved, making different regions see different eclipse types.

Question 32

# Explain: What are the **two types of lunar eclipses**?

Answer 32

1. Total Lunar Eclipse 2. Partial Lunar Eclipse ## Footnote **Total Lunar Eclipse** – The entire Moon is covered by Earth's shadow, turning it a reddish color. **Partial Lunar Eclipse** – Only a portion of the Moon enters Earth's shadow, causing a darkened section.

Question 33

# Explain: Why don’t we see eclipses **every month**?

Answer 33

The Moon’s orbit is **tilted**, preventing perfect alignment. ## Footnote Its **5° tilt** relative to Earth’s orbit explains why eclipses don’t happen every month.

Question 34

# Identify: What is the Sun’s **outer atmosphere** called?

Answer 34

The corona ## Footnote The **corona** is visible during a total solar eclipse and has extremely high temperatures.

Question 35

# Define: tides

Answer 35

The **periodic rise** and **fall** of sea levels. ## Footnote Tides occur due to the gravitational pull of the **Moon** and, to a lesser extent, the **Sun**, causing regular fluctuations in sea levels.

Question 36

# Explain: How does the **Moon** affect **Earth’s tides**?

Answer 36

Its gravity **pulls** on Earth's oceans, creating bulges of water. ## Footnote The Moon’s gravity pulls on Earth’s oceans, creating **tidal bulges**. As Earth rotates, different areas move through these bulges, resulting in **high** and **low tides** twice a day.

Question 37

# Identify: What **type of tides** occur when the Sun, Moon, and Earth align?

Answer 37

Spring ## Footnote This results in **higher** high tides and **lower** low tides than normal.

Question 38

# Identify: What is a region in the ocean with almost **no tidal movement**?

Answer 38

Amphidromic ## Footnote These points form due to *Earth's rotation*, *ocean basin shapes*, and the *Coriolis effect*, causing tides to rotate around them.

Question 39

# Explain: Why are tides **stronger** during a **full moon**?

Answer 39

The Sun and Moon’s gravity **align**, increasing tidal force. ## Footnote This creates *spring tides*, which cause the highest and lowest tides.

Question 40

# Identify: What are tides called that occur when the Sun and Moon are at **right angles**?

Answer 40

neap ## Footnote *Neap tides* occur when the Sun and Moon form a right angle with the Earth, reducing their combined gravitational pull. As a result, neap tides have the **smallest** difference between high and low tide, occurring during the first and third quarter moons.

Question 41

# Explain: Why are there usually **two high tides** and **two low tides** daily?

Answer 41

Earth’s rotation **moves different areas** into the tidal bulges. ## Footnote This cycle repeats approximately every *12 hours*.

Question 42

# Define: precession

Answer 42

The **slow wobble** of **Earth’s axis** over time. ## Footnote This motion gradually shifts *Earth's orientation* in space, impacting the alignment of stars over thousands of years.

Question 43

# True or False: Precession **shifts the poles**, slowly changing Earth's seasons.

Answer 43

True ## Footnote Precession shifts the **timing** of solstices and equinoxes by slowly altering Earth’s orientation in space. Over thousands of years, this affects the calendar dates of seasons but does not significantly change seasonal climate patterns.

Question 44

# Identify: What is the effect of **orbital changes** on **Earth's climate**?

Answer 44

They influence **ice ages** and **warming periods**. ## Footnote Changes in Earth's orbit, axial tilt, and wobble impact how sunlight is *distributed*, driving long-term climate cycles like *glacial* and *interglacial periods*.

Question 45

# Identify: What is the **11-year cycle** of **solar activity** called?

Answer 45

The solar cycle ## Footnote The Sun goes through an 11-year cycle of increasing and decreasing **sunspots**, affecting space weather and sometimes Earth's climate.

Question 46

# Explain: How do **solar flares** affect **Earth**?

Answer 46

They disrupt **satellites** and **power grids**. ## Footnote Solar flares release *bursts of radiation* that can interfere with communications, GPS, and even cause power outages when they interact with Earth’s magnetic field.

Question 47

# Identify: What **natural phenomenon** is caused by **solar particles**?

Answer 47

Auroras ## Footnote When *charged particles* from the Sun hit Earth's atmosphere, they create colorful lights known as the *Northern* and *Southern Lights*, mainly seen near the poles.

Question 48

# True or False: The Sun’s energy output is **always constant**.

Answer 48

False ## Footnote The Sun’s energy output *varies slightly* (~0.1%) over its 11-year solar cycle, affecting space weather and geomagnetic storms. While this can increase solar radiation and impact satellites, it does not drive major climate changes on Earth.