S8U2L1 - Historical Models of the Solar System

S8U2L1 - Historical Models of the Solar System

Introduction

Vocabulary

Moving Backwards

Open Ended

What have you noticed when you've observed the night sky?

What does the phrase "a star's location relative to other stars" mean?

• It means the distance and placement of a star compared to the stars around it.

The solar system

Extend and Reflect:

Before Galileo, astronomers did not have the use of telescopes. How do you think they made their observations?

• They used the background stars and the motions of objects in the sky.

• They were very careful observers, drawing and measuring sky changes from night to night.

What is an "astronomer?"

An astronomer is a scientist--physicist--who studies celestial bodies such as planets, stars, and galaxies.

What is "celestial?"

• Of or relating to the sky.

Evolution of solar system models

CORE CONCEPT

What was the difference between Copernicus's model of the solar system and Kepler's model of the solar system?

• Copernicus's model of the solar system suggested that the planets moved in circular orbits.

• Kepler correctly determined that the planets move in elliptical orbits.

What was the difference between Galileo's model of heliocentrism and Copernicus's model of heliocentrism?

• Galileo had data from telescope observations to back up his model.

• 
  

Why couldn't Aristarchus get people to support his heliocentric model even though, as we know now, it was closer to the truth than the geocentric theory?

• He had no data to back it up.

How did Copernicus explain the apparent, occasional backward motion of planets?

• Copernicus realized an inner planet revolving more quickly around the Sun on a smaller orbit than an outer planet revolving more slowly on a larger one could explain the apparently irregular, backward, motion of the planets. 

VOCABULARY

What is "parallax?"

• Parallax is an apparent change in the position of an object, such as a star, caused by a change in the observer's position that provides a new line of sight.

What does it mean to "remain stationary?"

• It means to stay in one place.

Model misconceptions

Parallax

CORE CONCEPTS

Why couldn't early astronomers see star parallax, as they would have expected to if the Earth was rotating around the Sun?

• The stars were too far away to observe the parallax without a telescope.

• They didn't know this, so they reasoned there was no parallax, and therefore Earth must be standing still.

End of Part 1

to be continued