I would like examples how estimates of the age of the universe (or the
the earth) have changed with time. There is a summary of some the 18th
and 19th century estimates in  Brysons, A Short History of Nearly
Everything, and I know that in this century estimates have changed
with the incresed understanding of comology. What intestest me is how
much estimates made by very different methods have roughly agreed at
any give time, but have changed with time (mostly upward). I am
imagining enough datapoint to to see this trend clearly  , if it
exists, or see that it does not.

<The type of correlation that you describe is shown in the article,
The Age of the Universe is a Function of time. Donald E. Simanek
describes how scientific estimates of the age of the earth and the
universe show a consistent tendency to increase at an increasing rate
as time goes on. The article gives a chronology of the ages of the
earth and universe and plots the figures on a graph showing that over
time the figure calculated for the age of the universe increases.
http://www.lhup.edu/~dsimanek/cutting/ageuniv.htm

The following is a list of dates, the method of calculation and links
to where more information can be found.



1642 
John Lightfoot (1602 ? 1675)
Constructed a chronology from biblical genealogies and calculated that
the world was created at the equinox in September of 3298 BC.
http://www.christianity.co.nz/science5.htm

1650 
James Ussher (1581 ? 1656)
Calculated a creation day of Sunday 23 October 4004 BC.
Correlated various texts.
http://www.christianity.co.nz/science5.htm

1928, 1929, 1930 ( I have come across various dates) ? 2 billion years
Edwin Hubble (1889-1953)
Red shift of different stars and galaxies.
http://hypertextbook.com/facts/1999/RachelHoover.shtml
http://www.govertschilling.nl/nieuws/archief/2002/0204/020424_stsci.htm

1947 ? 2-3 billion years
Uses Hubbles data.
George Gamow (1904-68)

1952 ? 1 to 10 billion years
Bart Jan Bok (1906-83)
Galactic clusters.

1987 - 8 billion years
Harvey Butcher 
Measured the ratios of thorium (Th) and neodymium (Nd) in the sun and
20 nearby stars spectroscopically.
Published in Nature
This site has references to various articles about the age of the universe.
http://www.ldolphin.org/univ-age.html




1995  ? 9.5 billion
Nial Tanvir
Nature 7 September 1995
http://www.ldolphin.org/univ-age.html

10 billion years
Barry Madore
Studied Cephoid variable stars
http://www.ldolphin.org/univ-age.html

1995 - 8-12 billion years.
Distance scale measurements and stellar evolution theory 8 ?12 billion years.
Distance to galaxy M100
http://liftoff.msfc.nasa.gov/academy/universe/age.html

Globular clusters and hubble time
http://csep10.phys.utk.edu/astr162/lect/cosmology/age.html


1997 ? 13 ? 14 billion years
HST Key Project on the Extragalactic Distance Scale
13 to 14 billion years. 
Used supernovae in distant galaxies to calculate the distances to
those galaxies to calulate the universe?s rate of expansion and, thus
its age.
http://www.stardate.org/resources/news/universe/200208.html

1999 ?13.4 billion years
Australian Charles Lineweaver of the University of New South Wales
calculated that the age of the universe is 13.4 billion plus/minus 1.6
billion. The calculation are based on young, independent observations
from which US researchers around Nehta Bahcall of the Princeton
university (new Jersey) newly calculated the form and extension speed.
Published in Science (US magazine). 23 May 1999.
http://www.eurobrasil.at/scientific_cage/archive/cool_reactor_9907.html


1999
12 billion years.
Cepheids
http://www.bbc.co.uk/science/horizon/1999/hubble_script.shtml
Wendy Freedman
http://science.nasa.gov/newhome/headlines/ast25may99_1.htm
http://www.cnn.com/TECH/space/9905/25/age.of.universe/
Cepheids Between 12 and 13.5 billion years.
http://www.angelfire.com/ga/Godandscience/morebang.html

2001 ? 12.5 billion years.
Clark, Stuart
Star date: The minimum age of the Universe is calculated using a new
radiometric approach. New Scientist. 7 February 2001.

2001 ? 12.5 billion 
February 7, 2001, Roger Cayrel et al  measured amounts of the radioactive
elements thorium and uranium in an ancient star named CS31082-001
using a technique called radioactive cosmochronometry. "The ages of the
oldest stars in the galaxy indicate when star formation began and provide a
minimum age for the universe," Cayrel said. They calculated that
CS31082-001 is about 12.5 billion years old, with an error factor of
about
three billion years.
Cayrel, R et al. Measurement of Stellar age from uranium decay. 
Nature. 8 February 2001. Vol 409, No. 6821.
http://physicsweb.org/article/news/5/2/5
http://www.afterabortion.com/universe.html


Kilkis 14.8 billion
http://www.perkel.com/nerd/relativity.htm

2002 - 12 to 13 billion years. 
Harvey Richer of the University of British Columbia in Vancouver. 
Studied the cooling of white dwarfs.
http://www.stardate.org/resources/news/universe/200208.html

2003 - 13.7 billion years
Schwarzschild Bertram
WMAP Spacecraft Maps the Entie Cosmic Microwave Sky with Unprecedented Precision.
Physics Today. Vol 56, No. 4. April 2003.
http://www.gsfc.nasa.gov/topstory/2003/0206mapresults.html
http://map.gsfc.nasa.gov/m_uni/uni_101age.html>



<Search strategy:>

<"the age of the universe" billion>
<://www.google.com/search?q=%22the+age+of+the+universe%22+billion&hl=en&lr=&ie=UTF-8&start=20&sa=N>


<"age of the universe" history>
<://www.google.com/search?sourceid=navclient&q=%22age+of+the+universe%22+history>



<Hope this helps.>

Just what I needed!

Unfortunately, the main article cited is a joke. I'm not making a
judgement - here's a quote from the end of the article "This material
is © 2001 by The Institute of Physics Publishing and appears in the
science humor collection Science Askew by Donald E. Simanek and John
C. Holden."

Ian G.

Yes, the main citation is joke, but the data and references are real,
and what I asked for.
The tip was for humorous conclusions. -Toluca

True - there's a lot of good stuff there, but it's carefully chosen to
fit the joke.

Ian G.

The idea that it carefully chosen suggests that there was important
data left out. If that is the case I would like to know about it. Were
there significant estimates  that bucked the tend?
-Toluca

I haven't read the full article, but the thing I missed from the
posted summary was the estimate made by Lord Kelvin by calculating how
long it would take the Earth to cool from a molten state.  He got
about 25 million years, which didn't make anyone happy, as it was far
longer than the Bible allowed for, but not long enough for the
observed geologic processes.

A fairly technical discussion of Kelvin's calculation is at:
http://www.me.rochester.edu/courses/ME201/webexamp/kelvin.pdf

I think the 2 main omissions are Walter Baade (1952) and Alan Sandage
(1958), both of whom did a lot to refine the value of the Hubble
constant. Sandage's value was between 50 and 100 km/s/Mpc. That's
pretty broad , but between then and the late 1990's, values have
stayed in that range, gradually homing in on the currently accepted
value of 70 km/s/Mpc.

If you allow that Hubble knew he had a problem with his own estimate
of the age of the Universe (it was already known that the Earth was a
lot older), I'd argue that Baade's 1952 estimate was the first
scientificaly acceptable one. Only 6 years later Sandage produced a
value that's been refined but not changed over the following 40 years.

Ian G.

Thank you both for the additional infomation. I found some summary
information on Baade and on Standage at

http://lcd-www.colorado.edu/astr2010/Lectures/part3/part3_11.html

As I understand it a Hubble constant of about 70 Km/s/Mpc suggest an
age of about 13 or 14  biillion years.
-Toluca