lithosphere is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods of many millions of years. Over 70% percent of Earth's surface is covered with wate[ with the remainder consisting of continents and islands which together have many lakes and other sources of water that contribute to the hydrosphere. Earth's poles are mostly covered with ice that is the solid ice of the Antarctic ice sheet and the sea ice that is the polar ice packs. The planet's interior remains active

1. Chapter 1
Cosmology and the Birth of Earth
LECTURE OUTLINE
earth
Portrait of a Planet
Third Edition
©2008 W. W. Norton & Company, Inc.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

2. Prepared by
Ron Parker,
Cosmology and the
Birth of Earth
Earlham College, Department of Geosciences
Richmond, Indiana

3. Our Island in Space
We pass our lives on our one planet Earth.
 Earth may seem endless; it isn’t.
 Viewed from space, Earth is a small, shiny globe.
 It is truly our island oasis in space.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

4. Our Island in Space

The Earth is a very special and unique planet.
 Its temperature, composition and atmosphere favor life.
 It is dynamic and ever-changing.
 It has a long and complex history.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

5. Cosmology

Conscious thought distinguishes humans.
 Developed across thousands of generations.
Earth Flat Disk>>Geocentric Model>>Heliocentric Model
 Lends us curiosity, insight, and the ability to learn.

As a result, we seek to explain our surroundings.
 Where do we come from?
 Where do we fit in the Universe?
 Why are we here?
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

6. Cosmology

Study of the structure and evolution of the Universe.

Cosmology is a complicated science.
 Requires thinking in unfamiliar scales of space and time.
Spatial scales.
Attometers (10-18 meters), to
10s of billions of light years (9.4622 meters +).
Temporal scales.
Attoseconds (10-18 seconds), to
10s of billions of years (3.1517 seconds +).
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

7. Cosmology

Ideas about the Universe have a rich history.
 These ideas are often culturally determined.
The Greeks believed that the mediterranean was at the center
of the universe
 Commonly include supernatural forces.
The Greeks believed that earth was a flat disk, below it was
the underworld governed by the fearsome god Hades

The Western tradition applies scientific discovery.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

8. Science
The systematic analysis of natural phenomenon.
 Has evolved as the most significant human
development for understanding the natural world.
 Rationally explains cosmological evolution.
 Scientific understanding can evolve and change.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

9. Earth’s Changing Place

3,000 years ago, humans knew the heavens well.
 They knew that stars were fixed relative to other stars.
 They knew that stars moved predictably across the sky.
 They saw retrograde motion separating planets from stars.
 They did not think of Earth as a planet, however.

Movement in the heavens was attributed to deities.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

10. An Evolving Image of Earth

The ancients thought the Universe was geocentric.
 Heavenly bodies circle around a motionless central Earth.
 Proven by Ptolemy (100-170 C.E.), the idea was still wrong.
 Yet it held as doctrine for 1,400 years during the dark ages.
 It became religious dogma supporting the importance of
Earth in the scheme of heaven.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

11. The Renaissance

A rebirth of rational thinking in 15th-century Europe.
 Copernicus – Published evidence for heliocentricity.
 Kepler – His elliptical planetary orbits refuted Ptolemy.
 Galileo – Observed moons orbiting Jupiter.

These ideas were considered to be heresy.
 Earth didn’t center the Universe.
 Planetary orbits weren’t circular.
 Not all bodies orbited Earth.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

12. The Enlightenment

Sir Isaac Newton (1642-1727) devised…
 The Law of Universal Gravitation.
 The Three Laws of Motion.
 The mathematics of change (calculus).
He proved that natural law governs natural events.
 Geocentricity faded away.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

13. Earth as a Sphere
A flat Earth was dispelled by ~ 250 B.C.E.
 Abundant evidence suggested a spherical Earth.

 A curved shadow crossed the Moon during eclipses.
 Only the tops of distant sailing ships were visible.

In 1520, Magellan circumnavigated this sphere.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

14. Earth’s Rotation

How do we know that Earth rotates about Polaris?
 Clearly visible in a time-lapse photograph of the night sky.
 Foucault’s pendulum (1851) proved Earth’s rotation.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

15. Earth’s Circumference
Eratosthenes calculated ~25,000 miles in ~ 200 B.C.
 He measured shadows in deep wells 800 km apart.

 Measurement taken at noon on the same day.
 Syene – Shadow absent (directly overhead).
 Alexandria – Shadow at 7.2o.
He calculated that 800 km was
1/50th of Earth’s circumference.
 He was correct!!

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

16. Distances from Earth
The dimensions of the Universe are staggering!
 We must consider huge expanses of space and
time.

 The speed of light (c) is 186,000 miles/s (300,000 km/s).
The Moon is 1.3 light seconds (~237,000 miles) away.
The Sun is 8.3 light minutes (~93 million miles) away.
 A light year measures a distance of 5.87 trillion miles.
 Alpha Centauri, the closest star, is 4.3 light years away.
 The visible Universe is > 13 billion light years away
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

17. Modern View of the Universe

Current concepts differ wildly from 100 years ago.
 Earth is one of nine planets in the solar system.
 The solar system is on an arm of the Milky Way galaxy.
 Our Sun is one of 300 billion stars in this galaxy.
You are HERE!
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

18. Modern View of the Universe

Current concepts differ wildly from 100 years ago.
 The vastness of the Universe is almost incomprehensible.
 Andromeda, the next galaxy, is 2,200,000 light years away.
 The Universe contains more than a billion galaxies.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

19. Questions

Science is the basis for addressing hard questions.
 How did the Universe form?
 Do galaxies move with respect to each other?
 Is the Universe expanding? Contracting?
 How do we know anything about these matters?

The Doppler Effect permits us to detect star motion.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

20. The Doppler Effect
Waves compress or relax with relative motion.
 Applies to waves of both sound and light.

 The stopped train sounds the same to Anna and Bill.
 The moving train sounds different to Anna and Bill.
Anna hears a higher pitch from compressed sound waves.
Bill hears a lower pitch from expanded sound waves.
As the train passed Anna, the pitch would drop (higher to lower).
This is commonly heard as cars whiz by on a road.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

21. The Doppler Effect
Light waves behave like sound waves.
 Visible light is electromagnetic radiation.

 Visible wavelengths range from 400 to 700 nanometers.
400 nm – Blue = Higher frequency
700 nm – Red = Lower frequency
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

22. The Doppler Effect

A moving star displays Doppler-shifted light.
 Light from an approaching star is compressed.
This causes a shift to higher frequencies, so that…
 Stars moving toward Earth are shifted toward blue.
 Light from a receding star is expanded.
This causes a shift to lower frequencies, so that...
Stars moving away from Earth are shifted toward red.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

23. The Expanding Universe
Light from distant galaxies appeared “red shifted.”
 In 1929, Hubble recognized this as a Doppler shift.

 He concluded that galaxies were moving away rapidly.
 No galaxies were found to be moving toward Earth.

This led to the development of the Expanding
Universe Theory, analogous to expanding bread.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

24. Big Bang

When did the expanding Universe begin?
 The best answer so far? The big bang.
 All of the mass and energy in the Universe was packed into
a single small point.
 It exploded 13.7 Ga and has been expanding ever since.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

25. The Modern
Universe
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

26. Big Bang
Rooted in the Laws of Physics.
 Started as a rapid cascade of events.

 Protons and neutrons formed within 1 second.
 Hydrogen atoms formed within 3 minutes.
 Hydrogen fused to form new light elements (He, Be, Li, B)
via big bang nucleosynthesis.
 The Universe continued to…
Expand.
Cool.
Decrease in density.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

27. After the Big Bang

With expansion and cooling, atoms began to bond.
 Hydrogen formed H2 molecules - The fuel of stars.
 Atoms and molecules coalesced into gaseous nebulae.
Gravity caused collapse of gaseous nebulae.
 Collapse resulted in increases in…

 Temperature.
 Density.
 Rate of rotation.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

28. After the Big Bang
Condensed nebulae formed flattened accretion discs.
 Heat and mass from collapse ignited nuclear fusion.
 These 1st-generation stars consumed H2 fuel rapidly.


As the stars became H2 starved, they initiated…
 Collapse and heating.
 Heavy element production.
 Catastrophic explosion
(supernova).
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

29. Nucleosynthesis
Stars are truly “element factories.”
 Big bang nucleosynthesis formed lighter elements.

 Atomic #s 1, 2, 3, 4 and 5 (H, He, Li, Be, and B).

Heavier elements are from stellar nucleosynthesis.
 Atomic #s 6 - 26 (C to Fe).

Elements with atomic #s > 26
form during supernovae.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

30. Nucleosynthesis

The mass of a star governs its element production.
 Smaller-mass stars (like the Sun).
“Burn” slowly.
Live longer (10 Ga).
Create lighter elements up to carbon (C).
 Larger-mass stars (10-100x the mass of the Sun).
“Burn” rapidly.
Are shorter lived (10s of Ma).
Create heavier elements up to iron (Fe).
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

31. Nucleosynthesis
When fuel dwindles, stars heat by inward collapse.
 This leads to a cataclysmic explosion (a supernova).
 The supernova creates heavier elements.

 Uranium (atomic # 92) is the heaviest natural element.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

32. The Solar System

Earth shares the solar system with 7 other planets.
 Planet – A precise definition developed in 2006. A planet…
Is a large solid body orbiting a star (e.g., the Sun).
Has a nearly spherical shape.
Has cleared its neighborhood of other objects.
Thus, Pluto, previously defined as a planet, is excluded.
 Moon – A solid body locked in orbit around a planet.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

33. The Planets: An Overview

Two groups of planets occur in the solar system.
 Terrestrial (Earth-like) - Small, dense, rocky planets.
Mercury, Venus, Earth, and Mars.
 Jovian (Jupiter-like) - Large, low-density, gas-giant planets.
Jupiter, Saturn, Uranus, and Neptune.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

34. The Solar System

Our solar system also includes…
 The Sun – An average star.
 Asteroids – Rocky or metallic fragments.
 Comets – Fragments of ice orbiting the Sun.
 Kuiper Belt and Oort Belt objects.

Planetary systems have been found near other stars.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

35. Solar System Formation
The Nebular Theory
 A 3rd, 4th or nth generation nebula forms 4.56 Ga.
 Hydrogen and helium left over from the big bang.
 Heavier elements produced by stellar fusion and supernovae.

The nebula condenses into an accretion disc.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

36. Solar System Formation
The ball at the center grows dense and hot.
 Fusion reactions begin; the Sun is born.
 Dust in the rings condenses into particles.


Particles coalesce to form planetesimals.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

37. Solar System Formation
 Planetesimals accumulate into a larger mass.
 An irregularly-shaped proto-Earth develops.
 The interior heats and becomes soft.
 Gravity shapes the Earth into a sphere.
 The interior differentiates into…
•
•
a nickel-iron core, and
a stony (silicate) mantle.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

38. Solar System Formation
 Soon, a small planetoid collides with Earth.
 Debris forms a ring around the Earth.
 The debris coalesces and forms the Moon.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

39. Solar System Formation
 The atmosphere develops from volcanic gases.
 When the Earth becomes cool enough,
 moisture condenses and accumulates, and
 the oceans are born.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

40. Solar System Formation
Synopsis
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

41. Solar System Formation
 The Nebular Theory of Solar System Formation is
supported by the configuration of planets.
• The orbital planes of the planets lie within 3° of the Sun's
equator.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth

42. This concludes the
Chapter 1
Cosmology and the Birth of Earth
LECTURE OUTLINE
earth
Portrait of a Planet
Third Edition
©2008 W. W. Norton & Company, Inc.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 1: Cosmology and the Birth of Earth