The Copernican Revolution

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Slide 1

The Copernican Revolution

The Birth of Modern Science

Slide 2

What do we see in the sky?

The stars move in the sky but not with respect to each other

The planets (or “wanderers”) move differently from stars

They move with respect to the stars

They exhibit strange retrograde motion

What does all this mean?

How can we explain these movements?

What does the universe look like?

Slide 3

Timeline

Copernicus

1473-1543

Tycho

1546-1601

Kepler

1571-1630

Galileo

1564-1642

Newton

1642-1727

Slide 4

Geocentric (Ptolemaic) System

The accepted model for 1400 years

The earth is at the center

The Sun, stars, and planets on their spheres revolve around the earth: explains daily movement

To account for unusual planetary motion epicycles were introduced

Fit the Greek model of heavenly perfection – spheres are the perfect shape, circular the perfect motion

Slide 5

Heliocentric (Copernican) System

Sun at center (heliocentric)

Uniform, circular motion

No epicycles (almost)

Moon orbited the earth, the earth orbited the sun as another planet

Planets and stars still on fixed spheres, stars don’t move

The daily motion of the stars results from the Earth’s spin

The annual motion of the stars results from the Earth’s orbit

Slide 6

In the heliocentric model, apparent retrograde motion of the planets is a direct consequence of the Earth’s motion

Slide 7

Geocentric vs. Heliocentric

How do we decide between two theories?

Use the Scientific method:

These are both explanations based on the observation of retrograde motion

What predictions do the models make?

How can these predictions be tested?

Slide 8

Phases of Venus

Heliocentric predicts that Venus should show a full phase, geocentric does not

Unfortunately, the phases of Venus cannot be observed with the naked eye

Slide 9

Geocentric vs. Heliocentric

Against heliocentric

It predicted planetary motions and events no better than the Geocentric system

The earth does not move (things do not fly off)