© 2011, W. W.
Norton
Cosmology and the Birth of Earth Earth: Portrait of a Planet
4th Edition
Stephen Marshak
CHAPTER 1 GLG1A10 – Minerals, Rocks, and Earth Dynamics:
Michael Knoper, Lecturer
Department of Geology, UJ
© 2011, W. W. Norton Chapter 1 Opener
Cosmology is the scientific study of the history and
the structure of the Universe. Many developments
in cosmology have come about in the last 90 years.
© 2011, W. W. Norton
Common human questions: Who am I? Where
do I fit in the grand scheme of nature?
Some answers to questions like these
are approached by cosmology.
© 2011, W. W. Norton Fig. 1.1a
Sun
Earth
The geocentric model of
the Universe held that all
celestial bodies (including
the Sun) revolved around
the Earth. This was
proven to be false during
the Renaissance.
© 2011, W. W. Norton Fig. 1.1b
Earth
Sun
Discoveries during the Renaissance provided evidence for
the heliocentric model, where the Sun is the center of the
Solar System and Earth one of the planets surrounding it.
© 2011, W. W. Norton Fig. 1.2a
This figure shows the planets and the Sun all drawn to
scale. The four terrestrial planets (left) are much smaller
than the four gas-giant planets. All are dwarfed by the
Sun.
© 2011, W. W. Norton Box 1.1a
A time-lapse photo of the stars
reveals that the Earth rotates on
an axis that is pointing directly at
the star Polaris (the North Star).
© 2011, W. W. Norton Box 1.1c
Foucault proved the
rotation of the Earth
in 1851, by creating
a giant pendulum.
The pendulum continued
swinging in the same
plane while the Earth
moved underneath.
© 2011, W. W. Norton Fig. 1.2b
The Solar System consists of the
four inner terrestrial planets and
the four outer gas-giant planets.
The asteroid belt lies
between Mars and Jupiter.
© 2011, W. W. Norton Fig. 1.3
Our Solar System is positioned on a
spiral arm of the Milky Way Galaxy.
Our Sun is one of 300
billion in the Milky Way.
© 2011, W. W. Norton Fig. 1.3
Viewed from Earth,
the Milky Way Galaxy
looks like a
concentration of stars
running in a line
across the sky. This
results from looking
perpendicular to the
axis of rotation.
© 2011, W. W. Norton Fig. 1.4
Eratosthenes correctly calculated the
circumference of the Earth by
measuring the shadow at the bottom of
two wells 800 km apart at the same
time.
© 2011, W. W. Norton Fig. 1.3
The vastness of the Universe is almost beyond human comprehension.
Our galaxy has
~300 billion stars.
There are
hundreds of
billions of galaxies
in the Universe.
© 2011, W. W. Norton Fig. 1.5a,b
The Doppler effect is easily illustrated with
sound waves. As a train approaches, the noise
has a higher pitch than when it is moving away.
© 2011, W. W. Norton Fig. 1.5d
The Doppler Effect works with light waves too. When light
is moving toward an observer it is compressed (blue-
shifted). When moving away, it is expanded (red-shifted).
© 2011, W. W. Norton Fig. 1.5c
A moving star displays Doppler shifted light.
An approaching star will be blue-shifted; a
receding star will be red-shifted.
This observer sees light waves This observer sees light waves
compressed – blue-shifted. “spread out” – red-shifted.
No Doppler shift
All galaxies are observed to have red-shifted light.
© 2011, W. W. Norton Fig. 1.6a
Edwin Hubble recognized that
the red-shifted light from
galaxies was a Doppler effect.
He concluded
that the Universe
is expanding,
like raisin bread.
© 2011, W. W. Norton Fig. 1.6b
The Big Bang theory
proposes that all matter
and energy in the
Universe started out as
a single infinitesimally
small point.
It exploded and has
been expanding since.
© 2011, W. W. Norton Fig. 1.6b
The Big Bang started a big cascade of events.
Hydrogen atoms formed within a
few seconds. After three minutes,
light nuclei (Be, Li, B) were created
by Big Bang nucleosynthesis.
© 2011, W. W. Norton Fig. 1.7
With expansion and cooling, atoms began
to bond. Hydrogen molecules (H2) were
formed.
Gravity collected matter, the
material heated and began
the process of making a star.
© 2011, W. W. Norton Geology at a Glance
Denser parts of nebulae grew mass via gravity. Mass compacted and the material
began to rotate in a flattened disk. The central ball started to glow: a protostar.
© 2011, W. W. Norton Chapter 1 Opener
With continued addition of matter,
the center of the nebular disk
increased greatly in temperature.
Past 10 million degrees, H2 fused
to helium, initiating a star.
© 2011, W. W. Norton Fig. 1.9
First generation stars exhausted H2
quickly. Starving for fuel, they
collapsed and began to generate
heat, driving heavy element
production.
Eventually, supernova!
© 2011, W. W. Norton Fig. 1.8
Big Bang nucleosynthesis formed the lightest elements. Stellar
nucleosynthesis formed elements up to Fe (atomic number 26).
Elements with atomic numbers larger
than 26 formed during supernovae.
© 2011, W. W. Norton
The Sun is a third-, fourth-, or fifth-generation star that has a greater
proportion of heavier elements than previous stars. We are made out of
that material.
We ARE stardust!
© 2011, W. W. Norton Geology at a Glance
A nebular cloud of gas and debris coalesced ~4.6 Ga from
older stars. The nebula condenses into a protoplanetary disk.
© 2011, W. W. Norton Geology at a Glance
The center of the nebular disk glows with heat
and ignites into nuclear fusion. The dust in
the rings coalesces to form planetesimals.
© 2011, W. W. Norton Fig 1.10
Dust particles and stony debris
are the materials that coalesced
to create the planetesimals that
amassed together to form Earth.
© 2011, W. W. Norton Geology at a Glance
Planetesimals accumulate to create a lumpy planetoid. The
interior heats up to the point of melting, the body becomes
spherical and differentiates into core and mantle.
© 2011, W. W. Norton Geology at a Glance
After differentiation, a Mars-sized
planetoid collides with Earth
blasting out a large part of its
mantle.
Debris from the collision
coalesces to form the Moon.
© 2011, W. W. Norton Geology at a Glance
The atmosphere accumulates
from volcanic outgassing.
When the Earth is cool enough
for water vapor to condense, the
oceans come onto existence.
© 2011, W. W. Norton
Useful Web Resources
• NASA Solar System Exploration
– http://solarsystem.nasa.gov/index.cfm
• NASA / JPL Solar System Missions
– http://www.jpl.nasa.gov/solar-system/index.cfm
• BBC Big Bang Theory Program
– http://www.bbc.co.uk/science/space/universe/questions_and_ideas/big_bang/
• Scientific American Article: “Misconceptions about the Big Bang”
– http://www.scientificamerican.com/article.cfm?id=misconceptions-about-the-
2005-03
© 2011, W. W. Norton
Photo Credits
• Ronald L. Parker, slides 3, 25.
W. W. Norton & Company
Independent and Employee-Owned
This concludes the Norton Media Library
Enhanced Art Slide Set for Chapter 1
Earth: Portrait of a Planet
4th Edition (2011)
by Stephen Marshak
GLG1A10 - Minerals, Rocks, and Earth Dynamics
Michael Knoper
Lecturer,
Department of Geology, UJ
