1.2.2 Astronomy Becomes a Science

Astronomy Becomes a Science
1.2.2

Objectives

- discuss the Copernican model of the solar system

- explain Kepler's laws of planetary motion

- list Galileo's observations of the solar system

- describe Newton's law of gravity 

The Medieval Era

Astronomers were respected in many royal courts because of their connection with astrology and mysticism.

Each celestial object carried a different meaning and tracking the movements and positions was very important.

The names of the days of the week originally came from the important of celestial objects.

Influences of Astronomy

Celestial Objects and Music - there was a belief that the movement of the planets made music and this persisted for centuries.

Fear of Comets - the ancients didn't know comets had orbital periods and their sudden appearance sparked fear and dread. It was said comets brought fire and floods.

Fear of Solar Eclipses - the movement of the moon in front of the sun scared many uneducated people. 

Questioning the Geocentric Model

View Across the Globe

European Astronomers - Sometimes the planets moved backwards. They had to keep adding new circles into the model.

Muslim Astronomers - Proposed rotation; the Earth is not stationary, but moves like a top! Later, proposed that while the Earth rotates, it also revolves around the Sun.

Drag and Drop

Ancient astronomers thought comets were​

Placeholder

Drag these tiles and drop them in the correct blank above

evil omens.

heavenly messengers.

wandering spirits.

cosmic blessings.

Renaissance Astronomy

Nicolaus Copernicus - introduced a new model of the solar system that accounted for the motion of the planets. This explained the changing brightness of the planets and the retrograde motion.

Heliocentric model - the sun is the center of the solar system and all the planets, including the Earth, revolve around it in circular orbits

Labelling

Label the two models.

Drag labels to their correct position on the image

Geocentric Model

Heliocentric Model

Tycho Brahe

Developed a new model after studying the motion of the planets and hundreds of stars.

The model was a combo of the geocentric and heliocentric models - the Earth is the center, the Moon orbits it, the planets orbit the Sun, the Sun orbits earth, and there are fixed stars revolving around the Earth.

Kepler's Laws of Planetary Motion

Kepler was Brahe's assistant, and after his death, he spent 15 years developing these laws.

First Law - The planets' orbits are ellipses (not circles) and the Sun is not at the center, but on one side of the ellipse.

Second Law - the planets don't move at a constant speed, they move faster closer to the sun and slower farther away.

Third Law - planets closer to the sun orbit faster than more distant planets.

Multiple Choice

Compared to a nearby planet, which of the following best describes how a more distant planet orbits the Sun?

• at the same speed

• slower

• faster

Galileo

Galileo was the first known person to point a telescope at celestial objects. He revolutionized astronomy!

He observed: Venus has phases like the moon, four of Jupiter's moons (today these are called the Galilean moons), the Milky Way is made of stars, the Moon's surface is rough, with mountains.

Isaac Newton

He discovered gravity, which is what keeps celestial objects in their orbits!

Proposed ALL objects have gravity, but the more mass an object has, the more gravity it has.

Match

Match the following astronomers with their contributions to astronomy.

• Galileo Galilei

• Isaac Newton

• Johannes Kepler

• Nicolaus Copernicus

four moons of Jupiter

gravity

elliptical motion of the planets

heliocentric model

• four moons of Jupiter

• gravity

• elliptical motion of the planets

• heliocentric model

Draw

You Choose! Either draw the heliocentric model OR the geocentric model. Be sure to label your model.

Good Job!

Today, you learned:

- the struggle of Copernicus to propose a heliocentric model of the solar system

- Kepler's three laws of planetary motion

- how the invention of the telescope helped Galileo to support Copernicus's heliocentric solar system

- Newton's law of gravity