Movement in Space

Movement in Space

Middle School

​

Learning Objectives

• Describe the geocentric and heliocentric models of the solar system.

• Explain how Earth's rotation and revolution affect observations of constellations.

• Describe the cyclic patterns of lunar phases and the causes of eclipses.

• Explain how Earth's tilted axis and its revolution around the sun cause seasons.

Key Vocabulary

​

Satellite

A satellite is a celestial body or artificial object that orbits a larger astronomical body in space.

​

Rotation

Rotation is the action of a celestial body, such as a planet, spinning on its axis.

​

Revolution

Revolution refers to the movement of one celestial body in a complete orbit around another body.

​

Geocentric Model

The geocentric model is an early astronomical theory that proposed Earth as the center of the universe.

​

Heliocentric Model

The heliocentric model is the astronomical model in which the Earth and planets revolve around the Sun.

​

Ellipse

An ellipse is a regular oval shape that describes the actual path of a planet's orbit.

Key Vocabulary

​

Earth's Axis

The tilted imaginary line that the Earth spins on, causing our planet's seasons to change.

​

Lunar Phases

The different ways the Moon appears from Earth, depending on how much sunlight illuminates its surface.

​

Solar Eclipse

An event where the Moon passes between the Sun and Earth, blocking the Sun's light.

​

Lunar Eclipse

An event where Earth's shadow falls on the Moon, blocking the sunlight that usually illuminates it.

​

Waxing

The phase when the visible illuminated portion of the Moon's surface appears to be growing larger.

​

Waning

The phase when the visible illuminated portion of the Moon's surface appears to be shrinking.

​

​

Objects in the Night Sky

Meteors

• Meteors are streaks of light from space rock or ice burning in our atmosphere.

• They are commonly known as 'shooting stars' because of their fast-moving, bright trails.

• These streaks appear for only a few seconds before the object completely burns up.

Comets

• Comets are cold mixtures of dust, rock, and ice that orbit the sun.

• As a comet gets closer to the sun, it heats up and releases gas and dust.

• This forms a glowing head and a long tail that can stretch for millions of kilometers.

Multiple Choice

What is a meteor?

• A streak of light from space rock burning in the atmosphere.

• A mixture of dust, rock, and ice that orbits the sun.

• A glowing head with a long tail that stretches for millions of kilometers.

• A large object in space that has its own gravitational pull.

Multiple Choice

What causes a comet to form a glowing head and a long tail?

• It heats up as it gets closer to the sun, releasing gas and dust.

• It enters Earth's atmosphere and begins to burn up.

• It is made of cold mixtures of rock and ice.

• It moves so fast that it creates a bright trail.

Multiple Choice

An astronomer observes a bright streak of light in the night sky that vanishes after only two seconds. What is the most likely explanation for this event?

• A meteor burning up quickly in the atmosphere.

• A comet developing its tail as it nears the sun.

• A comet orbiting the sun far from Earth.

• A meteor moving slowly across the sky.

​

​

Constellations and Apparent Motion

Constellations

• A constellation is a group of stars that forms a pattern representing a figure, animal, or an object.

• Scientists have divided the sky into 88 official constellations, which were named by many different cultures over time.

• For example, the constellation Pegasus is a group of stars that people imagine as a winged horse.

Apparent Motion

• Objects in the sky, such as stars, appear to move across the sky from east to west.

• This visible movement is called apparent motion because the stars are not actually moving across our sky.

• This illusion is caused by Earth's rotation on its axis, which spins from the west towards the east.

Multiple Choice

What is a constellation?

• A group of stars that forms a pattern in the sky.

• A single star that is brighter than all the others.

• A collection of planets and moons in our solar system.

• A type of galaxy that is visible from Earth.

Multiple Choice

What is the primary reason that stars appear to move across the sky?

• The rotation of the Earth on its axis.

• The stars are revolving around the Earth.

• The movement of clouds in the atmosphere.

• The Earth is moving closer to the stars.

Multiple Choice

An observer sees a constellation in the eastern sky at 9:00 PM. If the observer looks for the same constellation at 1:00 AM, where is it most likely to be found?

• Higher in the sky, towards the west.

• In the exact same position in the eastern sky.

• Lower in the sky, back towards the east.

• It would have disappeared completely from view.

The Cause of Seasons

• Earth's axis is tilted at an angle of about 23.5 degrees.

• This tilt causes one hemisphere to receive more direct sunlight than the other.

• This difference in sunlight intensity is the primary cause of the seasons.

Multiple Choice

What is the primary reason Earth experiences different seasons?

• The tilt of Earth's axis relative to its orbit

• The distance between the Earth and the sun

• The speed at which the Earth rotates

• The time it takes for the Earth to orbit the sun

Multiple Choice

How does the 23.5-degree tilt of Earth's axis cause a difference in conditions between hemispheres?

• It changes the overall temperature of the sun.

• It results in one hemisphere getting more direct sunlight.

• It makes the Earth's orbit more circular.

• It causes the planet to spin more quickly.

Multiple Choice

Based on the relationship between Earth's tilt and sunlight, what would most likely happen if Earth's axis were not tilted?

• The seasons would become much more extreme.

• There would be no significant seasonal changes.

• The Northern Hemisphere would be permanently cold.

• The Southern Hemisphere would be permanently warm.

​

​

Why the Moon Has Phases

• The Moon reflects sunlight; phases are not caused by Earth's shadow.

• Phases result from our changing view of the Moon's sunlit side.

• The cycle begins with a New Moon and waxes, showing more light.

• After a Full Moon, it wanes, showing less light until the cycle repeats.

Multiple Choice

What is the primary reason we see the phases of the Moon?

• The Moon passing through the Earth's shadow.

• The changing amount of the Moon's sunlit side that we can see.

• The Moon creating and changing the amount of its own light.

• Clouds on Earth blocking the view of the Moon.

Multiple Choice

How does the Moon's orbit around Earth lead to the cycle of phases?

• The orbit changes which side of the Moon is lit by the Sun.

• The orbit causes our viewing angle of the Moon's sunlit side to change.

• The orbit makes the Moon appear to grow and shrink in size.

• The orbit moves the Moon in and out of the Earth's shadow.

Multiple Choice

If the Moon stopped orbiting the Earth but remained visible, what would be the most likely consequence for its phases as seen from Earth?

• The Moon would always appear as a Full Moon.

• The Moon would appear to be stuck in a single phase.

• The Moon would stop reflecting any sunlight.

• The Moon would cycle through its phases much more quickly.

​

​

Solar and Lunar Eclipses

Solar Eclipse

• The moon passes directly between the sun and Earth, casting a shadow on a small part of Earth.

• This alignment blocks the sun's light from reaching a specific area on our planet for a short time.

• From Earth, it looks like the moon is covering the sun, either partially or completely.

Lunar Eclipse

• Earth passes directly between the sun and the moon, casting a large shadow over the moon’s surface.

• This alignment causes Earth’s shadow to darken the moon, making it less bright in the night sky.

• The moon can sometimes appear dark or take on a reddish color during a total lunar eclipse.

Multiple Choice

What is the fundamental difference in the alignment of celestial bodies during a solar eclipse versus a lunar eclipse?

• In a solar eclipse, the Moon is between the Sun and Earth, while in a lunar eclipse, Earth is between the Sun and Moon.

• In a solar eclipse, Earth is between the Sun and Moon, while in a lunar eclipse, the Moon is between the Sun and Earth.

• In a solar eclipse, the Sun is between Earth and the Moon, while in a lunar eclipse, Earth is between the Sun and the Moon.

• In both eclipses, the Moon is between the Sun and Earth, but its distance from Earth changes.

Multiple Choice

How does the alignment during a lunar eclipse affect the Moon's appearance from Earth?

• The Moon's shadow is cast upon Earth, blocking the Sun's light.

• Earth's shadow is cast upon the Moon, causing the Moon to appear darker.

• The Sun's light is reflected off Earth, making the Moon appear brighter.

• The Moon moves closer to Earth, making it seem larger in the sky.

Multiple Choice

Given that a solar eclipse is visible from a 'small part of Earth' while a lunar eclipse involves a 'large shadow over the moon's surface,' what can be concluded about their visibility?

• Earth casts a larger shadow on the Moon than the Moon casts on Earth.

• The Moon moves much more slowly during a lunar eclipse.

• A lunar eclipse only happens at night when more people are looking up.

• The reddish color of a lunar eclipse makes it easier to see from far away.

The Geocentric Model

• The Earth is at the center of this model.

• The sun, moon, and planets orbit the stationary Earth.

• Planets also move in small circles called epicycles.

Multiple Choice

Which statement best describes the main principle of the geocentric model?

• The Sun is stationary and at the center.

• The Earth is stationary and at the center.

• The planets orbit the Sun in epicycles.

• The Earth and Sun orbit each other.

Multiple Choice

How does the geocentric model explain the movement of the sun, moon, and planets?

• They orbit the Sun in large circles called epicycles.

• They remain stationary in the sky.

• They orbit the Earth while the Earth remains stationary.

• They travel in straight lines past the Earth.

Multiple Choice

Within the geocentric model, what would be the most likely reason a planet appears to change its direction of movement in the night sky?

• The Earth has moved to a different position.

• The planet has stopped moving altogether.

• The planet is moving in a small circle as it also orbits the Earth.

• The Sun's gravity is pushing the planet backward.

​

​

Models of the Solar System: The Heliocentric View

• The Heliocentric Model places the sun at the center of the solar system.

• Ancient scientist Aristarchus developed an early version of this sun-centered model.

• Nicolaus Copernicus later proposed Earth’s rotation explains celestial movements.

• Johannes Kepler used Tycho Brahe's observations to find the planets' true orbits.

Multiple Choice

What is the main principle of the Heliocentric Model?

• The sun is at the center of the solar system.

• The Earth is at the center of the solar system.

• The planets do not move in the sky.

• The moon is the largest object in the solar system.

Multiple Choice

What was Nicolaus Copernicus's primary contribution to the Heliocentric Model?

• He proposed that Earth's rotation could explain the movement of objects in the sky.

• He was the first scientist to suggest a sun-centered model.

• He used observations to discover the true orbital paths of planets.

• He proved that the Earth was the center of the universe.

Multiple Choice

What do the combined efforts of Aristarchus, Copernicus, and Kepler suggest about the development of the Heliocentric model?

• The model was gradually improved over time by different scientists.

• The model was developed completely by a single scientist.

• The model was accepted immediately without any changes.

• The model was based only on ideas, not on observations.

Evidence for the Heliocentric Model

• Galileo discovered moons orbiting the planet Jupiter.

• He observed that Venus has a full set of phases, like our moon.

• Kepler found that planets travel in elliptical orbits, not perfect circles.

Multiple Choice

The observations that moons orbit Jupiter and that Venus has a full set of phases are key pieces of evidence that support which scientific model?

• The Heliocentric Model, which states that planets revolve around the Sun.

• The Geocentric Model, which states that the Sun and planets revolve around Earth.

• The theory that planets travel in perfect circular paths.

• The idea that only planets with moons can orbit the Sun.

Multiple Choice

How did Galileo's discovery of moons orbiting Jupiter challenge the older, geocentric view of the solar system?

• It demonstrated that some celestial bodies orbit objects other than Earth.

• It proved that Jupiter was the largest planet in the solar system.

• It showed that planets' orbits are elliptical, not circular.

• It confirmed that Earth has only one moon.

Multiple Choice

What did Kepler discover about the paths of planets around the Sun?

• Planets travel in elliptical orbits

• Planets travel in perfect circles.

• Planets travel in straight lines.

• Planets move randomly.

​

Common Misconceptions

Misconception	Correction
Seasons are caused by Earth’s closeness to the sun.	Seasons result from Earth's 23.5-degree axial tilt and the directness of sunlight.
Lunar phases are caused by Earth's shadow on the moon.	Phases are our changing view of the moon’s sunlit side.
The 'dark side' of the moon never gets sunlight.	All parts of the moon get sunlight because it rotates.
The planets orbit the sun in perfect circles.	Planets travel in oval-shaped orbits called ellipses.

​

Summary

• Scientific understanding shifted from an Earth-centered to a sun-centered solar system.

• The rotation of the Earth on its axis causes the apparent daily motion of stars.

• Seasons are caused by the tilt of Earth’s axis, not its distance from the sun.

• The phases of the moon result from our changing view of its illuminated surface.

• Eclipses are rare events that occur when the Sun, Earth, and Moon align perfectly.

• Planets travel in elliptical orbits, not perfect circles, around the sun.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4