Objects in Space

Earth and Space: Our Place in Space

pp.306-307

Long ago, astronomers believed Earth was the center of the universe.

Aristotle believed that the planets and the Sun orbited Earth. 

Ptolemy also viewed the universe as Earth-centered, or geocentric.

The Sun and all of the planets orbited the Earth and the other stars formed a backdrop that also orbited Earth.

PTOLEMY'S GEOCENTRIC MODEL

“We revolve around the Sun like any other planet.”

—Nicolaus Copernicus

The idea of a Sun-centered, or heliocentric, view of the Universe had been suggested by ancient Greek astronomers like Aristarchus.

In the 1500s, a Polish astronomer named Nicolaus Copernicus designed a new model, or system, of the universe.

p.306 (HIGHLIGHT)

Nicolaus Copernicus detailed his theory of the universe in which the Earth, along with the other planets, revolved around the Sun.

The astronomical model that Copernicus developed was called heliocentrism (helios means Sun).

Summary of Copernicus’s Theory

• The center of the Earth is not the center of the Universe, only of Earth’s gravity and of the lunar sphere.

• The Sun is fixed and all other spheres revolve around the Sun.

• Earth has more than one motion, turning on its axis and moving in a spherical orbit around the sun.

• The stars are fixed but appear to move because of the Earth’s motion.

Copernicus retained the idea of spheres (celestial objects) and of perfectly circular orbits. 

Copernicus published his ideas in a book in 1543.

"On the Revolutions of Celestial Spheres"

Many believe that the theory and ideas put forward by Copernicus started modern astronomy and were the beginning of a scientific revolution.

Using a telescope he made, Galileo Galilei was the first to see moons orbiting Jupiter.

His observation showed that all objects in space did not orbit Earth.

Galileo Galilei is considered the "Father of Modern Science".

Johannes Kepler correctly described

the shape of the planets’ orbits around the sun.

p.306 (HIGHLIGHT)

He is known for his three laws of planetary motion. 

His calculations showed that the planets revolved around the sun in elliptical [ee▪LIP▪tih▪kuhl] orbits.

Newton explained why the planets moved as they did around the Sun and he gave the force that kept them in check a name: GRAVITY.

All these scientists’ observations changed our idea about Earth’s place in space.​

Multiple Choice

Who was among the first astronomers to design a model in which Earth and the other planets revolved around the sun?

• Aristotle

• Albert Einstein

• Nicolaus Copernicus

• Ptolemy

Multiple Choice

Which astronomer was the first to make observations with a telescope?

• Galileo Galilei

• Isaac Newton

• Wright Brothers

• Abraham Lincoln

Open Ended

Why did some astronomers challenge the model that had the sun and planets revolving around Earth?

Why did some astronomers challenge the model that had the sun and planets revolving around Earth?

They found new evidence that contradicted that model. They used this evidence to make and support a model.

Which evidence did astronomers use to support a sun-centered model of the solar system?

Which evidence did astronomers use to support a sun-centered model of the solar system?

1. Copernicus made a model based on his observations of the motion of the planets.

2. Galileo used a telescope and discovered that all objects in space did not orbit Earth.

3. Kepler did calculations that showed the planets revolve around the sun in elliptical orbits.

What is needed before long-held ideas in science can change?

What is needed before long-held ideas in science can change?

New observations and investigations must present new evidence that supports new ideas.

Open Ended

Describe what you know about the sun-Earth-moon system that astronomers did not know long ago

Summarize

Open Ended

1. Day and night are caused by Earth's revolution around the sun.

1. Day and night are caused by Earth's rotation on its axis.

Open Ended

2. The discovery of moons around Jupiter proved that all objects in space revolve around Jupiter.

2. The discovery of moons around Jupiter proved that all objects in space do not revolve around Earth.

Open Ended

3. Earth's seasons are caused by Earth's revolution and rotation in space.

3. Earth's seasons are caused by Earth's revolution and the tilt on its axis.

Open Ended

4. During winter in the Northern Hemisphere, there are more hours of daylight and its warmer.

4. During winter in the Northern Hemisphere, there are fewer hours of daylight and its cooler.

Open Ended

5. When it is spring in the Northern Hemisphere, the season is summer in the Southern Hemisphere.

5. When it is spring in the Northern Hemisphere, the season is fall in the Southern Hemisphere.

Open Ended

6. Constellations appear to move across the night sky because of Earth's tilt on its axis.

6. Constellations appear to move across the night sky because of Earth's rotation.

Word Play

Open Ended

1. X A S I

[Hint: an imaginary line through Earth]

AXIS

[Hint: an imaginary line through Earth]

Open Ended

​2. T E R A O T

[Hint: Earth’s spinning in space]

ROTATE

[Hint: Earth’s spinning in space]

Open Ended

3. R I B O T

[Hint: Earth’s path in space

ORBIT

[Hint: Earth’s path in space]

Open Ended

4. L E O V R E V

[Hint: Earth does this around the sun once a year.]

REVOLVE

[Hint: Earth does this around the sun once a year.]

Open Ended

5. S T E L C O N A L I O N T

[Hint: a pattern of stars in the night sky]

CONSTELLATION

[Hint: a pattern of stars in the night sky]

HEMISPHERE

[Hint: one half of Earth]

Open Ended

7. D O L E M

[Hint: a representation of the sun-Earth-moon system]​

MODEL

[Hint: a representation of the sun-Earth-moon system]​

Open Ended

8. N A S S E O

[Hint: a time of year with a particular type of weather]

SEASON

[Hint: a time of year with a particular type of weather]

Minimum of 5 sentences

Suppose you are an astronomer who lived at the same time as Galileo.

Write a letter to a friend explaining Galileo’s discoveries, his ideas about

a sun-centered universe, and the conclusions he made about them.​