Astronomy190 - Topics in Astronomy

Astronomy and Astrobiology

Lecture 2 : History of Science & Astrobiology

Ty Robinson

Questions of the Day

• How has our understanding of the Universe changed over the last 2,500 years?

• What role did Copernicus, Tycho, Kepler, Galileo and Newton have in changing our understanding of the Universe?

• Why was the Copernican Revolution so important?

There are infinite worlds both like and unlike this world of ours…

We must believe that in all worlds there are living creatures and plants and other things we see in this world.

- Epicurius 300BC

Contributions from Ancient Greece

scientific inquiry and debate

geometry

reasoning from observations

Question: What aspects of Ancient Greece may haveallowed for these developments?

Motions of the Heavens I

the heavens move in circles… so the heavens are a rotatingsphere centered on Earth

Question: What objects in the sky do not rotate with the stars?

Motions of the Heavens II

the Sun, Moon and planets donot move with the stars…

so these objects rotate aboutEarth on their own concentric

rings

Question: What aspect of planetary motion must still be explained by this model?

Motions of the Heavens III

some planets exhibit retrograde motion…

so the planets move on smallcircles turning on larger circles

Question: Can you think of a different model that explainsthese observations?

Earth

Motions of the Heavens IV

Aristarchus (c. 310-230 B.C.E)

Dark Ages I

Library of Alexandria~250 BCE - ?

Question: What ‘Wonder of the Ancient World’ was built inAlexandria?

Dark Ages II

The Burning of the Library of Alexandria

The knowledge center for Europe and the Middle East moves to Baghdad

The Dark Ages

Renaissance

The Siege of Constantinople (1453 CE)

Question: What ‘age’ begins in Europe around this time?

Copernican Revolution

Nicolaus Copernicus (1473-1543)

Question: Why are there only 6 planets in this illustration?

Questions?

Which of the following is the most important aspect of the Copernican Revolution?

It proved Earth was not at the center of the Universe.

It demonstrated that science can solve any problem.

It removed humans from their pedestal at the center of the Cosmos.

It fully explained all observations regarding planetary motion.

Tycho and Kepler

Tycho Brahe (1546-1601) Johannes Kepler (1571-1630)

Question: What is the fundamental problem with Copernicus’ system?

Kepler’s Laws

Kepler’s Three Laws1 - Orbits are elliptical2 - The closer you are to your parent body, the faster you move3 - period2 = (mean separation)3

Questions?

Earth’s orbit is non-circular, placing Earth closest to the Sun during summer in the Southern Hemisphere. This implies

N. Winter shorter than S. Winter, N. Summer shorter than S. Summer

N. Winter shorter than S. Winter, N. Summer longer than S. Summer

N. Winter longer than S. Winter, N. Summer shorter than S. Summer

N. Winter longer than S. Winter, N. Summer longer than S. Summer

Questions?

A planet orbiting 4 times further away from the Sun than Earth would take how many years to orbit the Sun?

0.5

1.0

2.0

8.0

Still a problem…

Aristarchus (c. 310-230 B.C.E)

Galileo I

Galileo Galilei (1554-1642)

Galileo II

Galileo Galilei (1554-1642)

“Dialogue Concerning the Two Chief World Systems”

Newton

Isaac Newton (1643-1727)

Questions of the Day

• How has our understanding of the Universe changed over the last 2,500 years?

• What role did Copernicus, Tycho, Kepler, Galileo and Newton have in changing our understanding of the Universe?

• Why was the Copernican Revolution so important?

Quiz

1 - What is the purpose of the Astrobiology Roadmap?

2 - Why was the Copernican Revolution so important?

3 - What is one thing you did not understand from today’s lecture?