The Big Bang

1
The Big Bang!

• ESCI 511
• Spring 2005

2
Origins

• How and when did the
• universe form?
• solar system / Earth form?
• Moon form?
• What were early Earth conditions?
• How Do We Know?

3
Origin of the Universe

• Big Bang
• occurred 15 billion years ago
• model for the beginning of the universe

4
Building a Universe
- infinitely dense point not governed by our
physical laws or time - all matter and
energy contained in one point
http//rainbow.ldeo.columbia.edu/courses/v1001/7.h
tml
5
Building a Universe
- instantaneous filling of space with all
matter
http//rainbow.ldeo.columbia.edu/courses/v1001/7.h
tml
6
Edwin Hubble

• Universe is continuously expanding
• Galaxys velocity is proportional to its distance
  (galaxies that are twice as far from us move
  twice as fast)
• taken every galaxy the same amount of time to
  move from a common starting position to its
  current position

7
Hubbles Evidence

• Doppler shifting - wavelength emitted by
  something moving away from us is shifted to a
  lower frequency
• Sound of a fire truck siren - pitch of the siren
  is higher as the fire truck moves towards you,
  and lower as it moves away from you
• Visible wavelengths emitted by objects moving
  away from us are shifted towards the red part of
  the visible spectrum
• The faster they move away from us, the more they
  are redshifted. Thus, redshift is a reasonable
  way to measure the speed of an object (this, by
  the way, is the principal by which radar guns
  measure the speed of a car or baseball)
• When we observe the redshift of galaxies outside
  our local group, every galaxy appears to be
  moving away from us - universe is expanding.

8
Evidence for Big Bang

• Red shift - as light from distant galaxies
  approach earth there is an increase of space
  between earth and the galaxy, which leads to
  wavelengths being stretched
• In 1964, Arno Penzias and Robert Wilson,
  discovered a noise of extraterrestrial origin
  that came from all directions at once - radiation
  left over from the Big Bang
• In June 1995, scientists detected primordial
  helium in the far reaches of the universe -
  consistent with an important aspect of the Big
  Bang theory that a mixture of hydrogen and helium
  was created at the beginning of the universe

9
Building a Universe

• 10-43 s - gravity separates from other forces -
  10-28 centimeters
• 10-35 to 10-32 s - fundamental particles -
  quarks and electrons - softball
• 10-6 s - quarks combine into protons and neutrons
  - solar system
• 1 s - electromagnetic and weak nuclear forces
  separate
• 3 minutes - protons and neutrons combine into
  atomic nuclei
• 105 years - electrons join nuclei to make atoms
  light is emitted
• 105-109 years - matter collapses into clouds,
  making galaxies and stars

Orion Nebula - http//stardate.utexas.edu/resource
s/ssguide/planet_form.html
10
When Did the Universe Form?

• 10 to 20 billion years ago (15)
• How do we know?
• spreading (Red Shift)
• know distances, rates of retreat, relative
  positions
• pervasive background radiation of 2.7C above
  absolute zero
• afterglow of the Big Bang

Orion Nebula - http//stardate.utexas.edu/resource
s/ssguide/planet_form.html
11
How old is the universe?

• Speed x time distance
• (distance of a particular galaxy) / (that
  galaxys velocity) (time)
• or
• 4.6 x 1026 cm / 1 x 109 cm/sec 4.6 x 1017
  sec
• 15 billion years

12
Origin of Our Solar System

• Solar nebula theory

• cloud of gases and dust

• formed a rotating disk
• condensed and collapsed due to gravity

• forming solar nebula
• with an embryonic Sun
• surrounded by a rotating cloud

13
Embryonic Sun and Rotating Cloud

• planetesimals have formed in the inner solar
  system
• large eddies of gas and dust remain far from the
  protosun

14
Precambrian Earth and Life History

• The Teton Range
• is largely Archean gneiss, schist, and granite
• younger rocks are also present but not visible

Grand Teton National Park, Wyoming
15
Precambrian The First 4 Billion Years

• 88 of geologic time

16
Rocks Difficult to Interpret

• The earliest record of geologic time preserved in
  rocks is difficult to interpret
• many Precambrian rocks have been
• altered by metamorphism
• complexly deformed
• buried deep beneath younger rocks
• fossils are rare
• Subdivisions of the Precambrian have been
  difficult to establish

http//www-rohan.sdsu.edu/rhmiller/fossilrecord/F
ossilRecord.htm
17
Eons of the Precambrian

• Two eons for the Precambrian
• are the Archean and Proterozoic
• Hadean is an informal designation
• for the time for which we don't have a rock record

18
What Happened During the Hadean?

• No rocks of Hadean age present on Earth
• except for meteorites
• Yet, we do know some events that took place
• Earth accreted from planetesimals
• differentiated into a core and mantle, and at
  least some crust
• Earth was bombarded by meteorites
• volcanic activity was ubiquitous
• atmosphere formed, quite different from todays
• oceans began to accumulate

19
Hot, Barren, Waterless Early Earth

• about 4.6 billion years ago

• Shortly after accretion, Earth was
• a rapidly rotating, hot, barren, waterless planet
• bombarded by comets and meteorites
• no continents, intense cosmic radiation
• widespread volcanism

20
Oldest Rocks

• Oldest known rocks on Earth are
  3.96-billion-year-old Acasta Gneiss in Canada and
  other rocks in Montana
• some continental crust must have evolved by 4
  billion years ago
• Sedimentary rocks in Australia contain detrital
  zircons dated at 4.2 billion years old
• so source rocks at least that old existed
• These rocks indicted that some kind of Hadean
  crust was certainly present
• but its distribution is unknown

21
Hadean Crust

• Early Hadean crust was probably thin, unstable
  and made up of ultramafic rock
• rock with comparatively little silica

Where does this occur now?

• This ultramafic crust was disrupted
• by upwelling basaltic magma at ridges
• and consumed at subduction zones
• Later Hadean continental crust may have
• formed by evolution of felsic material
• only felsic crust, because of its lower density,
  is immune to
• destruction by subduction (sialic)

22
Second Crustal Evolution Stage

• Second stage in crustal evolution began as
  Earths production of radiogenic heat decreased
• Subduction and partial melting of earlier-formed
  basaltic crust
• resulted in the origin of andesitic island arcs
• Partial melting of lower crustal andesites, in
  turn, yielded silica-rich granitic magmas
• Several sialic continental nuclei had formed by
  the beginning of Archean time

23
Dynamic Processes

• During the Hadean, various dynamic systems became
  operative
• Once Earth differentiated into core, mantle and
  crust,
• internal heat caused interactions among plates as
  they diverged, converged , and slid past each
  other

• Continents began to grow
• by accretion along
• convergent plate boundaries

http//www.geosc.psu.edu/People/Faculty/FacultyPag
es/Fisher/Web/Taiwan.htm
24
Continental Foundations

• Continental crust
• composition similar to that of granite
• thicker and less dense than oceanic crust
• Precambrian shields
• consist of vast areas of exposed ancient rocks
• found on all continents

25
Distribution of Precambrian Rocks

• Areas of exposed Precambrian rocks constitute the
  shields
• Platforms consist of buried Pre-cambrian rocks

• Shields and adjoining platforms make up cratons

26
Canadian Shield

• The craton in North America is the Canadian
  shield
• occupies most of northeastern Canada
• parts of the Lake Superior region
• in Minnesota, Wisconsin and Michigan
• and the Adirondack Mountains of New York

27
Canadian Shield Rocks

• Gneiss, a metamorphic rock, Georgian Bay Ontario,
  Canada

28
Canadian Shield Rocks

• Basalt (dark, volcanic) and granite (light,
  plutonic) on the Chippewa River, Ontario

29
Archean Rocks Beyond the Shield
Rocky Mountains, Colorado

• Archean metamorphic rocks found
• in areas of uplift in the Rocky Mtns

30
Archean Rocks Beyond the Shield

• Archean Brahma Schist in the deeply eroded parts
  of the Grand Canyon, Arizona

31
Precambrian The First 4 Billion Years

• 88 of geologic time

32
The Archean

• Most geologists are convinced that some kind of
  plate tectonics took place during the Archean
• but it differed in detail from today
• Plates must have moved faster
• more residual heat from Earths origin
• more radiogenic heat
• magma was generated more rapidly

33
The Origin of Cratons

• Several small cratons existed by the beginning of
  the Archean
• and grew by periodic continental accretion during
  the rest of that eon
• They amalgamated into a larger unit during the
  Early Proterozoic

By the end of the Archean, 30-40 of the present
volume of continental crust existed
http//spacebio.net/modules/lu_resource/ArcheanLan
dscape.jpeg
34
Atmosphere and Hydrosphere

• Earths early atmosphere and hydrosphere were
  quite different than they are now
• Todays atmosphere is mostly
• nitrogen (N2)
• abundant free oxygen (O2)
• oxygen not combined with other elements
• such as in carbon dioxide (CO2)
• water vapor (H2O)
• ozone (O3)
• common enough in the upper atmosphere to block
  most of the Suns ultraviolet radiation

35
Earths Very Early Atmosphere

• Earths very early atmosphere was probably
  composed of
• hydrogen and helium, the most abundant gases in
  the universe
• If so, it would have quickly been lost into space
  
• Earths gravity is insufficient to retain them
• Earth had no magnetic field until its core formed
• without a magnetic field, the solar wind would
  have swept away any atmospheric gases

So how did the modern atmosphere originate?
36
Outgassing

• Once a core-generated magnetic field protected
  the gases released during volcanism (outgassing),
  they began to accumulate to form a new atmosphere
• Water vapor is the most common volcanic gas today
• volcanoes also emit carbon dioxide, sulfur
  dioxide, carbon monoxide, sulfur, hydrogen,
  chlorine, and nitrogen

37
Hadean-Archean Atmosphere

• Hadean volcanoes probably emitted the same gases,
  and thus an atmosphere developed
• but one lacking free oxygen and an ozone layer
• It was rich in carbon dioxide and gases reacting
  in this early atmosphere probably formed
• ammonia (NH3)
• methane (CH4)
• This early atmosphere persisted throughout the
  Archean

38
How do we know the early atmosphere was
oxygen-free?

• Early atmosphere was chemically reducing, rather
  than an oxidizing one
• Some of the evidence for this conclusion comes
  from detrital deposits containing minerals that
  oxidize rapidly in the presence of oxygen
• pyrite (FeS2)
• uraninite (UO2)
• But oxidized iron becomes increasingly common in
  Proterozoic rocks, indicating that at least some
  free oxygen was present

39
How did we get free oxygen?

• Two processes account for introducing free oxygen
  into the atmosphere,
• one or both of which began during the Hadean
• 1. Photochemical dissociation involves
  ultraviolet radiation in the upper atmosphere
• radiation disrupts water molecules and releases
  their oxygen and hydrogen
• could account for 2 of present-day oxygen
• but with 2 oxygen, ozone forms, creating a
  barrier against ultraviolet radiation
• 2. More important were the activities of organism
  that practiced photosynthesis

40
Photosynthesis

• Photosynthesis is a metabolic process
• carbon dioxide and water combine into organic
  molecules
• oxygen is released as a waste product
• CO2 H2O organic compounds O2
• Even with photochemical dissociation and
  photosynthesis,
• probably no more than 1 of the free oxygen level
  of today was present by the end of the Archean

41
Oxygen Forming Processes

• Photochemical dissociation and photosynthesis
• added free oxygen to the atmosphere

• once free oxygen was present an ozone layer
  formed
• and blocked incoming ultraviolet radiation

42
Earths Surface Waters

• Outgassing was also responsible for the Earths
  surface water - the hydrosphere
• most of which is in the oceans - more than 97
• Some, but probably not much, of our surface water
  was derived from icy comets
• Probably at some time during the Hadean, the
  Earth had cooled sufficiently so that the
  abundant volcanic water vapor condensed and began
  to accumulate in oceans
• Oceans were present by Early Archean times

43
Ocean water

• The volume and geographic extent of the Early
  Archean oceans cannot be determined
• Nevertheless, we can envision an early Earth with
  considerable volcanism and a rapid accumulation
  of surface waters
• Volcanoes still erupt and release water vapor
• is the volume of ocean water still increasing?
• perhaps it is, but if so, the rate has decreased
  considerably
• the amount of heat needed to generate magma has
  diminished
• Much of volcanic water vapor today is recycled
  surface water

44
Decreasing Heat

• Ratio of radiogenic heat production in the past
  to the present

• width of the colored band indicates variations in
  ratios from different models

• Heat production 4 billion years ago was 4 to 6
  times as great as it is now

• with less heat, outgassing decreased

45
First Organisms

• Today, Earths biosphere contains
• millions of species of bacteria, fungi,
  protistans, plants, and animals,
• only bacteria are found in Archean rocks
• We have fossils from Archean rocks
• 3.3 to 3.5 billion years old
• Carbon isotope ratios in rocks in Greenland
• 3.85 billion years old
• convince some investigators that life was present
  then

46
How Did Life First Originate?

• To originate by natural processes, life must have
  passed through a prebiotic stage
• in which it showed signs of living organisms
• but was not truly living
• In 1924, the great Russian biochemist, A.I.
  Oparin, postulated that life originated when
  Earths atmosphere had little or no free oxygen
• oxygen is damaging to Earths
• most primitive living organisms

comparatively simple organic (carbon based)
molecules known as microspheres
47
How Did Life First Originate?

• With little or no oxygen in the early atmosphere
• and no ozone layer to block ultraviolet
  radiation,
• life could have come into existence from
  nonliving matter
• The origin of life has 2 requirements
• a source of appropriate elements for organic
  molecules
• energy sources to promote chemical reactions

48
Primordial Soup

• Amino acids in the primordial soup
• might have washed up onto a beach or perhaps
  cinder cones
• where they were concentrated by evaporation
• and polymerized by heat
• The polymers then washed back into the ocean
  where they reacted further

http//www.jmcgowan.com/abscicon.html
49
Next Critical Step

• Not much is known about the next critical step in
  the origin of life
• the development of a reproductive mechanism
• The microspheres divide
• may represent a protoliving system
• but in todays cells nucleic acids, either RNA or
  DNA, are necessary for reproduction
• The problem is that nucleic acids
• cannot replicate without protein enzymes
• appropriate enzymes cannot be made without
  nucleic acids
• or so it seemed until fairly recently

50
RNA World?

• Now we know that small RNA molecules can
  replicate without the aid of protein enzymes
• the first replicating systems may have been RNA
  molecules
• Some researchers propose an early RNA world in
  which these molecules were intermediate between

inorganic chemical compounds  and the
DNA-based molecules of organisms How RNA was
naturally synthesized remains and
unsolved problem
http//www.jmcgowan.com/abscicon.html
51
Much Remains to Be Learned

• The origin of life has not been fully solved
• but considering the complexity of the problem
• and the fact that scientists have been
  experimenting for only about 50 years
• remarkable progress has been made
• Many researchers believe that the earliest
  organic molecules were synthesized from
  atmospheric gases

- but some scientist suggest that life arose
instead near hydrothermal vents on the seafloor
http//web.uvic.ca/sciweb/pics/hydrothermal-vents.
html
52
Precambrian Life

• Prior to the mid-1950s, scientists had little
  knowledge of Precambrian life
• They assumed Cambrian life must have had a long
  early history
• but the fossil record offered little to support
  this idea
• A few enigmatic Precambrian fossils had been
  reported
• but most were dismissed as inorganic structures
  of one kind or another
• The Precambrian, once called Azoic (without
  life), seemed devoid of life

53
Oldest Know Organisms

• Charles Walcott (early 1900s) described
  structures from the Early Proterozoic Gunflint
  Iron Formation of Ontario, Canada
• that he proposed represented reefs constructed by
  algae

• Now called stromatolites
• not until 1954 were they shown to be products of
  organic activity

Present-day stromatolites Shark Bay, Australia
54
Stromatolites

• Different types of stromatolites include
• irregular mats, columns, and columns linked by
  mats

55
Stromatolites

• Present-day stromatolites form and grow
• as sediment grains are trapped on sticky mats of
  photosynthesizing blue-green algae
  (cyanobacteria)
• they are restricted to environments where snails
  cannot live

Shark Bay, Australia
http//www.mlssa.asn.au/journals/1999Journal.htm
56
Stromatolites

• The oldest known undisputed stromatolites

are found in rocks in South Africa that are 3.0
billion years old but probable ones are also
known from the Warrawoona Group in Australia
which is 3.3 to 3.5 billion years old
http//www.3d-fossils.com/photos/fossils/stromatol
ites.jpg
57
Other Evidence of Early Life

• Carbon isotopes in rocks 3.85 billion years old
  in Greenland indicate life was perhaps present
  then
• The oldest known cyanobacteria were
  photosynthesizing organisms
• but photosynthesis is a complex metabolic process
  
• A simpler type of metabolism must have preceded
  it
• No fossils are known of these earliest organisms

58
Earliest Organisms

• The earliest organisms must have resembled tiny
  anaerobic bacteria
• they required no oxygen
• They must have totally depended on an external
  source of nutrients
• they were heterotrophic
• as opposed to autotrophic organisms
• that make their own nutrients, as in
  photosynthesis
• They all had prokaryotic cells
• they lacked a cell nucleus
• lacked other internal cell structures typical of
  eukaryotic cells

59
Earliest Organisms

• The earliest organisms, then, were anaerobic,
  heterotrophic prokaryotes
• Their nutrient source was most likely adenosine
  triphosphate (ATP) from their environment
• which was used to drive the energy-requiring
  reactions in cells
• ATP can easily be synthesized from simple gases
  and phosphate
• so it was doubtless available in the early Earth
  environment

60
Photosynthesis

• A very important biological event occurring in
  the Archean was the development of the
  autotrophic process of photosynthesis
• This may have happened as much as 3.5 billion
  years ago
• These prokaryotic cells were still anaerobic,
• but as autotrophs they were no longer dependent
  on preformed organic molecules as a source of
  nutrients
• These anaerobic, autotrophic prokaryotes
• belong to the Kingdom Monera
• represented today by bacteria and cyanobacteria

61
Fossil Prokaryotes

• Photomicrographs from western Australias3.3- to
  3.5-billion-year-old Warrawoona Group
• schematic restoration shown at the right of each