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9/19/2013
1
EVOLUTIONBiology 145
Lecture 3 –The age of the Earth
Theological approaches
James Ussher (1581‐1656)
Summed generations in Old Testament
Creation: 4004 B.C.
(October 26th)
Origin of Earth is therefore ~ 6000 B.P.
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An archaeological approach
Nicholas Steno
Etruscan city of Volterra ~ 3000 years old in AD 1669
“Build on sediments of The Flood”, hence Flood subsided no later than 1331 BC
Historical records show Lydia 1000 years older than Volterra; hence 2331 BC.
Malta: not much time for events!
Geological Arguments
James Hutton (1726 – 1797) Uniformitarianism
“The result, therefore, of our present enquiry is that we find no vestige of a beginning, no prospect of an end”.
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Geological arguments (2)
Charles Darwin
Erosion of the WealdenValley, England
300 million years!
Geological arguments (3)
John Joly 1857 ‐ 1933
Salination of the Oceans
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Arguments from Physics
William Thompson (Lord Kelvin) 1824 ‐ 1907
The geothermal gradient (~ 1 degree F / 100 ft)
100 million +/‐ factor of 4
Clarence King –USGS – 24 million.
Uranium – lead dating
Ernest Rutherford ( 1871‐ 1937) 1909‐1930
Ca(UO2)2(PO4)2
1907
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Uranium – lead dating
4.468∙109 a
238U 4.468∙109 a 218Po 3.1 mins
Uranium – lead dating
Boltram: 1640 ma, Archean of Ceylon
Boltwood eventually achived dates of 2.2 billion from elsewhere)
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RADIOCARBON DATING
Formation of 14C
10n +
147N
11H +
146C
Result: 1 part 14C per trillion parts 12C
Willard Libby ‐ 1960 Nobel prize.
RADIOCARBON DATING
Decay of 14C
146C
147N + B
‐ + v + 0.156 MeV
Specific activity in modern atmosphere is 13.56 +/‐ 0.07 disintegrations/minute per gram C
Half‐life is 5730 +/‐ 40 years
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RADIOCARBON DATING
Decay of 14C
0
2
4
6
8
10
12
14
16
0 10000 20000 30000 40000 50000 60000 70000
14C
RADIOCARBON DATING
Decay of 14C
Limit ~ 10 half‐lives, i.e. 1/210= ~ 0.002
Atmospheric abundance ~ 1 part per trillion
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RADIOCARBON DATING
RADIOCARBON DATING
3000 BP = 1050 BC
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Age of the Universe
Edwin Hubble – 1929
Age of the Universe
Value of Hubble constant changes through time, according to a deceleration parameter, q
If q = 0, then H= 1/t where t is time since the Big Bang
4.35×1017 s or 13.8 billion years
=
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