The Ages of the Earth and Universe


An overview


Our Earth is about 4.54 billion years old, while our universe is about 13.73 billion years old. Over the years, increasingly accurate dating methods have been developed to date with precision the ages of both the Earth and the Universe. Diverse methods of dating rocks, bones, and stars are now basic building blocks in several different scientific fields, including paleoclimatology, paleontology, paleobiology, cosmology, anthropology, archeology, geology, and dendrochronology. Thanks to the folks at RationalWiki for supplying quite a bit of the material below!


Determining the Precise Age of the Earth


Radiometric Dating

Radiometric dating is a technique used to date matter by measuring the correlation between a radioactive isotope and its decay product in the matter and extrapolating the age of the matter backwards by using known constant or decay rates. This technique is the most widely used method of dating rocks. Using different isotopes and different samples often gives consistent results for the age of rocks, which cannot be attributed to contamination or experimental error. Isochron radiometric dating methods eliminate assumptions about initial parent isotope conditions, further strengthening the validity of radiometric dating. Radiometric results have been confirmed by independent dating methods. Radiometric dating of Earth's oldest rocks and meteorites give the Earth the approximate age of 4.5 billion years old.

Some specific examples make it clear that radiometric dating is not random. For example, "The Hawaiian archipelago was formed by the Pacific ocean plate moving over a hot spot at a slow but observable rate. Radiometric dates of the islands are consistent with the order and rate of their being positioned over the hot spot. (Rubin 2001) "

More information and sources:
The Scientific Age of the Earth
Isochron Dating
Geochronology and initial conditions
Radiometric Dating


Lower Limits on the Ages of the Earth and Universe

Celestrial Cosmic Rays and Past Temperature Reconstructions Correlate

Data of cosmic ray changes and temperature going back 500 million years strongly correlate. If this geological data was created recently, this correlation would be essentially unexplainable. (Shaviv and Veizer 2003)

Cosmogenic nuclide dating

The influx of cosmic rays onto the earth continually produces a stream of cosmogenic nuclides in the atmosphere that will fall to the ground. By measuring the build-up of these nuclides on terrestrial surfaces, the length of time for which the surface has been exposed can be inferred. This technique can be used to date objects over millions of years old. (Mark Lorraine)


Iron-manganese nodule growth

Berryllium-10 produced by cosmic rays shows that iron-manganese nodule growth is one of the slowest geological phenomena. It takes several million years to form one centimeter (and some are the size of potatoes). (Somayajulu 2000)

Baptistina asteroid family

The Baptistina asteroid family is a cluster of asteroids with similar orbits. Evidence suggests this group was produced by a collision of an asteroid 60 kilometers in diameter with an asteroid 170 kilometers in diameter. Researchers from the Southwest Research Institute (SwRI) and the University of Prague have traced the orbits of these asteroids back from their current locations and have determined that the original collision happened 160 (±20) million years ago. (Sheriff 2007)


Amino acid racemization

Amino acid racemization dating is a technique that is used to date fossilized objects up to several million years in age. Amino acid molecules usually possess an asymmetric carbon atom which will occupy one of two configurations; D (right), or L (left). The ratio of these two isomers is initially unequal (with only one exception, naturally occurring amino acids used in polypeptide synthesis are in the L form) and will decay to a balanced state in a process called racemization. Measuring the degree of racemization and other known quantities can give you an estimated age of the sample. By measuring the racemization of the amino acid isoleucine, for example, objects can be dated up to several million years old. While it is true that there can be great variability on the rate at which amino acids undergo racemization, the changes in humidity, temperature, and acidity required to make the oldest known samples conform to a young earth (under 6000 years) view are completely unreasonable. (Petraglia and Korisettar 1998)


Distant Starlight

The fact that distant starlight can be seen on earth has always been a major problem for the young earth idea. Because the speed of light is finite, when you look at an object, what you are actually seeing is an image of that object from the past. On Earth, the delay caused by this phenomenon is incredibly minor — when you look at an object a mile away, you are seeing it as it was five microseconds ago. When you look at the sun, you are seeing it as it was 8.3 minutes ago.

But on the cosmic scale of things, this delay is far from minor. When astronomers look at the closest star to Earth (Alpha Centauri), which is roughly four light years away, they are seeing the star as it was four years ago. When astronomers look at objects in the region of space known as the "Hubble ultra deep field", they are seeing the stars there as they were over ten billion years ago.

Therein lies the problem for young earth creationism; if the universe is only 6,000 years old, how can objects billions of light years away — and therefore billions of years old — be seen?

Note that the creationist argument which goes along the lines of "God created the light already en route to Earth" does not explain the distant supernovae we see, the light from which would have taken millions to billions of years to reach Earth. If this light was created, does that mean these events did not happen? Would that not mean that the creationist God is deliberately deceiving humanity? More information


Global impact craters

Astronomical observations and advanced computer models have calculated the chances of a significantly sized asteroid striking the Earth to be around 2.5 x 10^−9 yr; this figure generally agrees with the number of impact craters we see on Earth if we take the Earth's age to be billions of years old.

However, the chances that the 176 known impact craters of significant size were created by impacts within the last 6,000-10,000 years are incredibly low. Additionally, each of the major impacts we know of would be able to independently wipe out the majority of life on the planet, and it would take thousands to millions of years for the atmosphere and biosphere to both fully recover. If the Chicxulub crater, for example, had been created by a massive impact within the last 10,000 years, life on this planet would still be recovering.


Paleo-climatic data confirmation

Paleoclimatic data measuring prehistoric temperature, dust, and CO2 strongly correlate in a record going back 400,000 years. This correlation would make little sense if the ice cores were recently created. They are powerful evidence of Earth's past written in ice. (NOAA data)


Fission track dating

Fission track dating is a radiometric dating technique that can be used to determine the age of crystalline materials that contain uranium. As uranium decays, it sends out atomic fragments, which leave scars or "fission tracks" in crystalline structures. Because decaying uranium emits fragments at a constant rate, the number of fission tracks correlates to the age of the object. (MNSU) This method is generally held to be accurate, as it shows a high degree of concordance with other methods such as potassium-argon dating. (Johns 1977)


Geomagnetic reversals

A geomagnetic reversal is a change in the polarity of the Earth's magnetic field. The frequency at which these reversals occur varies greatly, but they usually happen once every 50,000 to 800,000 years, and generally take thousands of years. This fact is obviously inconsistent with the young earth idea; around 171 reversals are geologically documented, which would make the earth at least several million years old. (Cox 1973)


Globular Star Clusters

Stars are constantly converting hydrogen to helium through fusion throughout their lifetimes. Using what is known about star cycles, the age of a cluster of stars can be estimated with a high degree of certainty by measuring the luminosity of stars within a cluster. Chaboyer et al. 1996 thus calculated a lower limit on the age of the universe of 12.07 billion years using this technique. Other estimates such as Gratton et al. 1997 also calculated the ages of star clusters to be about 12 billion years old.


Helioseismology

The composition of the sun changes as it ages. The differing composition changes the way sound waves behave inside the sun. Using helioseismic methods (models of pressure waves in the sun), the age of the sun can be inferred. Using this method, an Italian team came up with an age of 4.57 +/- 0.11 billion years. (Bonanno et al. 2002) This is consistent with independent methods of verifying the age of the Earth/Solar system.


Human Y-chromosomal ancestry

The Y-chromosome, unlike most DNA, is inherited only from the father, which means that all DNA on the human Y chromosome comes from a single person. This does not mean that there was only one person alive at that time, but that a single man's Y-chromosomal DNA has out-competed the other strains and is now - not taking into account smaller and less drastic mutations - the only one left. Because the only factor affecting the makeup of the DNA on the chromosome is mutation, measuring mutation rates and extrapolating them backwards can tell you when this man lived. Calculations by the geneticist Spencer Wells have shown that this man lived sometime between 35,000 and 89,000 years ago. (Underhill et al. 2000)


White Dwarfs

White dwarfs are the remnants of medium-sized stars. Using models of star cooling, the length of time for which current white dwarfs have existed can be inferred. Hansen et al. 2004 found an average age of 12 billion years for the white dwarfs in the star cluster M4.


Lack of DNA in fossils

Deoxyribonucleic acid (DNA), the universal carrier of genetic information, is present in all organisms while they are alive. When they die, their DNA begins to decay under the influence of hydrolysis and oxidation. The speed of this decay varies based on a number of factors. Sometimes, the DNA will be gone within one century, and in other conditions, it will persist for as many as one million years. The average amount of time detectable DNA will persist though is somewhere in the middle; given physiological salt concentrations, neutral pH, and a temperature of 15 °C, it would take around 100,000 years for all the DNA in a sample to decay to undetectable levels. (Hofreiter et al. 2001) If fossils of the dinosaurs were less than 6,000 years old, detectable fragments of DNA should be present in a sizable percent of dinosaur fossils, especially in the Arctic and Antarctic regions where the decay of DNA can be slowed down 10-25 fold.


Dendrochronology

Dendrochronology is a method of scientific dating which is based on annual tree growth patterns called tree rings. The rings are the result of changes in the tree's growth speed over the year (since trees grow faster in the summer and slower in the winter). The age of a tree can be found by counting the rings.

Now, any date derived from one individual tree is not in itself contradictory to the recent creation doctrine, since even the longest lived types of tree do not live longer than 5,000 years or so. However, it is possible to extend the chronology back over many different trees. Because the thickness of tree rings varies with the climate, a sequence of thick ring, thin ring, thin ring, thick ring, thick ring, thick ring, thin ring, thick ring is strong evidence that the corresponding rings formed at the same time. By observing and analyzing the rings of many different trees from the same area, including fossil trees, the tree ring chronology has been pushed back in some areas as far as 11,000 years.(Becker and Kromer 1993; Becker et al. 1991; Stuiver et al. 1986)


Length of the prehistoric day

Work by John W. Wells of Cornell University, New York has shown that certain pieces of extremely old coral show evidence of a growth rate which reflects a time when a year had 400 days of 22 hours each. Because the rate of change of the rotation of the earth is relatively predictable—about 0.005 seconds per year—one can calculate the last time a year had 400 days, which was about 370 million years ago (which is also about the same as radiometric dating of the coral). (Wells 1963)


Cetacean Paleobiology

Marx and Uhen 2010 found that cetacean diversity, diatom diversity, and stable oxygen isotope records strongly correlate over millions of years, an entirely unexplainable pattern if the Earth is young.


The Namib Desert

A brand new study in Nature Geoscience discusses the measured age of one of Earth's oldest deserts, the Namib. The study used decay of the cosmogenic nuclides 10Be, 26Al and 21Ne in the sand in order to date the desert to be at least one million years old. Cosmogenic nuclides are isotopes of elements which are created when cosmic rays interact with the nuclei of atoms, and which then decay into more stable isotopes. As can be seen in the graph below, the different nuclides confirm the results independently. (Vermeesch et al. 2010)



Lunar retreat

South African rocks studied by geologist Ken Eriksson contain ancient tidal deposits that indicate that at some point in time the moon orbited "25-percent closer to Earth than it does today." (Eriksson 2000) The distance between the earth and the moon is 384,403 kilometers, so for Ken Eriksson's work to fit with a YEC timescale the earth would have to have been receding at a speed greater than 15 kilometers per year. However, the moon is currently receding from the earth at a speed of 3.8 centimeters per year. (Dickey et al., 1994)


Nitrogen impurities in natural diamonds

Nitrogen is the most common impurity in natural diamonds, sometimes making up as much as 1% of their mass. Recently formed diamonds, however, have very little nitrogen content. A major way synthetic diamonds are distinguished from natural ones is on the basis of nitrogen permeation. It takes long periods and high pressures for the nitrogen atoms to be squeezed into the diamond lattice. Research on the kinetics of the nitrogen aggregation at the University of Reading have suggested that a certain type of diamond, Ia diamonds, spend 200-2000 million years in the upper mantle. (Evans and Qi 1981)


Oxidizable Carbon Ratio dating

Oxidizable Carbon Ratio dating is a method for determining the absolute age of charcoal samples with relative accuracy. This dating method works by measuring the ratio of oxidizable carbon to organic carbon. When the sample is freshly burned, there will be no oxidizable carbon because it has been removed by the combustion process. Over time this will change and the amount of organic carbon will decrease to be replaced by oxidizable carbon at a linear rate. By measuring the ratio of these two allotropes, one can determine ages of over 20,000 years ago with a standard error under 3%. (Frink 1995)


Permafrost

The formation of permafrost (frozen ground) is a slow process. To be consistent with the young earth creationist model, which states that all sediment was deposited by the global flood, there would have to be absolutely no permafrost present at the end of the flood, because any permafrost that was present at the moment of creation would have been melted during the flood.

Because earth is a good insulator and permafrost forms downward from the surface, it would have taken much more than the few thousand years allotted by creationism to produce some of the deepest permafrost. In the Prudhoe Bay oil fields of Alaska, the permafrost which extends over 600 meters into the ground has probably taken over 225,000 years to reach present depth. (Lunardini 1995)


Relativistic jets

A relativistic jet is a jet of plasma that is ejected from some quasars and galaxy centers that have powerful magnetic fields. It is conjectured that the jets are driven by the twisting of magnetic fields in an accretion disk (the plate like cloud of matter) found encircling many celestial objects. In super-massive bodies, immensely strong magnetic fields force plasma from the accretion disk into a jet that shoots away perpendicular to the face of the disk. In some cases, these columns of plasma have been found to extend far enough to refute the idea of a young universe.

For example, the quasar PKS 1127-145 has a relativistic jet exceeding one million light years in length. (Cowen 2002) Because the speed of light cannot be exceeded by any known form of matter, this column must be at least one million years old. Moreover, these jets are generally billions of light years from Earth, meaning they were at least a million years old several billion years ago due, again, to the speed of light.


Biological paleoclimatic confirmation

Prehistoric temperatures were obtained from two paleobiological sources which act as effective temperature records, and the results were fairly precise. This data and correlation makes absolutely no sense on a short term basis. (Pagani et al. 2006)


Rock varnish

Rock varnish is a coating that will form on exposed surface rocks. The varnish is formed as airborne dust accumulates on rock surfaces. This process is extremely slow; between 4 μm and 40 μm of material forms on the rock every thousand years, and instances of 40 μm of accumulation are very rare. (Liu and Broecker 2000) Because the rate of accumulation is generally constant, measuring the depth of the varnish can provide dates for objects up to 250,000 years old. (Liu 2007)


Seabed plankton layering

Fossils of dead plankton that layer on the ocean floor are used to gauge temperatures from the past, based on the chemical changes of Crenarchaeota, a primitive phylum of microbe. Much like ice layering and dendrochronology, researchers drill through the ocean floor to extract samples which indicate annual temperature fluctuations in the plankton fossils, or "chemical rings" as it were. A 2004 pioneering expedition to the Arctic Ocean near the North Pole collected samples dating back to over 56 million years of temperature dating. (Pagani 2006)


Sedimentary varves

Varves are laminated layers of sedimentary rock that are most commonly laid down in glacial lakes. In the summer, light colored coarse sediment is laid down, while in the winter, as the water freezes and calms, fine dark silt is laid down. This cycle produces alternating bands of dark and light which are clearly discernible and represent, as a pair, one full year. As is consistent with the old earth view, many millions of varves have been found in some places. The Green River formation in eastern Utah is home to an estimated twenty million years worth of sedimentary layers.

The creationist response is that, instead of once per year, these varves formed many hundreds of times per year. There is, however, much evidence against accelerated formation of varves.

  • Pollen in varves is much more concentrated in the upper part of the dark layer, which is thought to represent spring. This is what would be expected if varves formed only once per year because pollen is much more common at this time.(Source)
  • In Lake Suigetsu, Japan, there is a seasonal die-off of diatoms (calcareous algae) that will form layers in the bottom of the lake along with the sedimentary varves. If the 29,000 varves in the lake formed more than once per year, there should be several sediment layers for every layer of deceased algae. (Hitagawai and and van Derplicht 1998)
  • The varve thickness in the Green River formation correlates with both the 11-year sunspot cycle and the 21,000-year orbital cycle of the earth.(Source)

Space weathering

Space weathering is an effect that is observed on most asteroids. Extraterrestrial objects tend to develop a red tint as they age due to the effects of cosmic radiation and micrometeor impacts on their surfaces. Because this process proceeds at a constant rate, observing the color of an object can provide the basis for a generally reliable estimate. The ages provided by this dating technique exceed millions of years. (Jedicke et al. 2004)


Thermoluminescence dating

Thermoluminescence dating is a method for determining the age of objects containing crystalline minerals, such as ceramics or lava. These materials contain electrons that have been released from their atoms by ambient radiation, but have become trapped by imperfections in the mineral's structure. When one of these minerals is heated, the trapped electrons are discharged and produce light, and that light can be measured and compared with the level of surrounding radiation to establish the amount of time that has passed since the material was last heated (and its trapped electrons were last released). Although this technique can date objects up to approximately 230,000 years ago, it is only accurate on objects 300 to 10,000 years in age. This is, however, still about 4,000 years older than the creationist figure for the age of the earth. (Berger 2001)


Weathering rinds

Weathering rinds are layers of weathered material that develop on glacial rocks. The weathering is caused by the oxidation of magnesium and iron rich minerals, and the thickness of this layer correlates with the age of a sample. Certain weathering rinds on basalt and andesite rocks in the eastern United States are believed to have taken over 300,000 years to form. (Hubbard and Glasser 2005)


Lakebeds

Sediment deposits in lakebeds make distinct annual patterns, as different soil compositions form in the different seasons of each year. The annual layers in Lake Baikal go back 5 million years. (Williams et al. 1997)



Determining the Precise Age of the Universe


Age of the Elements

Radiometric dating of Uranium-238, which eventually forms Thorium-232, can give an age for the formation of the galaxy, as the uranium itself is very old and it has a very, very long half life. This method as used by Dauphas 2005 found an age for the universe of 14.5 +2.8/-2.2 billion years old, which confirms the results of other methods.


WMAP

WMAP was a NASA mission which has allowed us to accurately date the age of the universe instead of merely putting a close lower limit on it. As the early universe cooled and expanded, photons were suddenly able to travel long distances. After billions of years of continual universal expansion and cooling, the wavelength of this early light has been stretched out to microwaves since then. By observing the wavelengths of these particles in the universe today, scientists are able to calculate how long ago these particles formed, along with information about the conditions they formed in, returning an age of about 13.7 billion years old for the universe. This figure which roughly agrees with slightly less accurate previous methods.(WMAP)


Galaxy lenses time delay

Using galaxies as lenses of distant light, scientists were able to infer how far the light traveled in between galaxies. This information helped construct a picture of both the universe's size and age. This technique gave the universe an age of about 13.75 billion years old, which is highly similar to dates obtained from other evidences such as WMAP. (Saha et al. 2006)

Sources

Show sources

Hide sources.

P. Vermeesch, C. R. Fenton, F. Kober, G. F. S. Wiggs, C. S. Bristow & S. Xu. 2010. Sand residence times of one million years in the Namib Sand Sea from cosmogenic nuclides. Nature Geoscience 3, 862–865 (2010) doi:10.1038/ngeo985.

Becker, B. and B. Kromer, 1993. The continental tree-ring record -- absolute chronology, 14C calibration and climatic change at 11 ka. Palaeogeography Palaeoclimatology Palaeoecology 103 (1-2): 67-71.

Becker, B., B. Kromer and P. Trimborn, 1991. A stable-isotope tree-ring timescale of the late glacial Holocene boundary. Nature 353: 647-649.

Manz, Lorraine. "In-situ Cosmogenic Nuclides: Their Role in Studying the Age and Evolution of Landscapes, or what "as old as the hills" really means"

NOAA paleoclimatic data and Wikipedia Graph Link

Michael D. Petraglia, Ravi Korisettar (1998). "Early Human Behaviour in Global Context". Routledge Education. Page 63. ISBN 0415117631.

Nir J. Shaviv, NJ, Veizer, J, "Celestial driver of Phanerozoic climate?", pp4-10, GSA Today, vol 7, Issue 7 (July 2003) Date 22nd December 2008 ,WikiGraph

B. L. K. Somayajulu, 2000. Growth rates of oceanic manganese nodules: Implications to their genesis, palaeo-earth environment and resource potential. Current Sicence, VOL. 78, NO. 3, 10 Feb. 2000.

Stuiver, Minze et al., 1986. Radiocarbon age calibration back to 13,300 years BP and the 14C age matching of the German oak and US bristlecone pine chronologies. Radiocarbon 28(2B): 969-979.

Underhill PA, Shen P, Lin AA, Jin L, Passarino G, Yang WH, Kauffman E, Bonné-Tamir B, Bertranpetit J, Francalacci P, Ibrahim M, Jenkins T, Kidd JR, Mehdi SQ, Seielstad MT, Wells RS, Piazza A, Davis RW, Feldman MW, Cavalli-Sforza LL, Oefner PJ. 2000. Y chromosome sequence variation and the history of human populations. Nat Genet. 2000 Nov;26(3):358-61.

Sherriff, Lucy (September 6, 2007). "Dino-killing asteroid traced back 160m years". The Register.

Johns, Warren H. (1977). "THE IMPACT OF TEKTITES UPON AN ESTIMATED 700,000 YEAR HISTORY OF DEEP-SEA DEPOSITS"(Geoscience Research Institute). Retrieved on September 30, 2007.

http://www.mnsu.edu/emuseum/archaeology/dating/dat_fission.html

Cox, Allan (1973). Plate tectonics and geomagnetic reversal. San Francisco, California: W. H. Freeman. pp. 138–145, 222–228. ISBN 0716702584.

A. Bonanno, H. Schlattl, L. Paternò (2002). "The age of the Sun and the relativistic corrections in the EOS". Astronomy and Astrophysics 390: 1115. doi:10.1051/0004-6361:20020749.

Michael Hofreiter, David Serre, Hendrik N. Poinar,Melanie Kuch and Svante Pääbo (2001). "ANCIENT DNA" Accessed November 22, 2007.

Wells, John W. (1963). CORAL GROWTH AND GEOCHRONOMETRY. Nature 197: 948 - 950.

Eriksson, K.A. and Simpson, E.L., 2000. Quantifying the oldest tidal record: the 3.2 Ga Moodies Group, Barberton greenstone Belt, South Africa. Geology, 28, 831-834.

Dickey, J.O. et al. Lunar laser Ranging: A Continuing Legacy of the Apollo Program. Science 265: 482-490, July 22, 1994.

T. Evans, Zengdu Qi (1981). "The kinetics of the aggregation of of nitrogen atoms in diamond". Proceedings of the Royal Society, London. A 381, 159-178.

Douglas S. Frink (1995). APPLICATION OF THE OXIDIZABLE CARBON RATIO (OCR) DATING PROCEDURE AND ITS IMPLICATIONS FOR PEDOGENIC RESEARCH. Accessed November 2, 2007.

Virgil J. Lunardini (1995)."Permafrost Formation Time"(US Army Corps of Engineers). Accessed November 28, 2007.

Ron Cowen (2002)."X-Ray Universe: Quasar's jet goes the distance". Science News 161: 101.

Tanzhuo Liu and Wallace S. Broecker (2000). "How fast does rock varnish grow?". Geology 28: 183-186.

Tanzhuo Liu. "Rock Varnish Microlamination (VML) Dating"(VML Dating Lab). Accessed October 19, 2007.http://www.vmldatinglab.com/

Mark Pagani, Nikolai Pedentchouk, Matthew Huber, Appy Sluijs, and Stefan Schouten et al. (2006). Arctic hydrology during global warming at the Palaeocene/Eocene thermal maximum. Nature 442 (7103) p. 671-675 http://dx.doi.org/10.1038/nature05043

Mark Pagani, Nikolai Pedentchouk, Matthew Huber, Appy Sluijs, Stefan Schouten, et al. (2006) Nature 442 (7103) p. 671-675 http://dx.doi.org/10.1038/nature05043

Hiroyuki Hitagawai, Johannes van Derplicht (1998). "A 40,000-YEAR CHRONOLOGY FROM LAKE SUIGETSU, JAPAN: VARVE EXTENSION OF THE CALIBRATION CURVE". Radiocarbon 40: 505-515.

Robert Jedicke, David Nesvorny , Robert Whiteley, Z eljko Ivezic & Mario Juric.(2004) "An age–colour relationship for main-belt S-complex asteroids" Nature 429: 275-277

Thomas Berger (2001)."Thermoluminescence dating"(ATOMINSTITUT). Retrieved on September 30, 2007. http://www.ati.ac.at/~vanaweb/papers/archview.pdf

Bryn Hubbard, Neil F. Glasser (2005). "Field Techniques in Glaciology and Glacial Geomorphology". John Wiley and Sons, United States. Page 355. ISBN 0470844264.

Darrel R. Falk, Coming to Peace with Science: Bridging the Worlds between Faith and Biology (Downers Grove, IL: InterVarsity Press, 2004), 79-80.

Chaboyer, B., P. Demarque, P.J. Kernan, and L.M. Krauss. 1996. A Lower Limit on the Age of the Universe. Science 271: 957-961.

Raffaele G. Gratton et al 1997 ApJ 491 749 doi: 10.1086/304987

Ding, Z. L. et al., n.d. Rearrangement of atmospheric circulation at about 2.6 Ma over Northern China: Records of evidence from grain size loess-red clay sequences. http://fadr.msu.ru/inqua/nl-15/llz-abs.html#11

Russeau, D.-.D. and Wu, N., 1997. A new molluscan record of the monsoon variability over the past 130,000 yr in the Luochuan loess sequence, China. Geology 25(3): 275-278.

Sun, D., J. Shaw, Z. An, M. Cheng and L. Yue, 1998. Magnetostratigraphy and paleoclimatic interpretation of a continuous 7.2Ma Late Cenozoic eolian sediments from the Chinese Loess Plateau. Geophysical Research Letters 25: 85-88. http://www.agu.org/pubs/gap/DonghuaiS/DonghuaiS.html

Williams, D. F., J. Peck, E. B. Karabanov, A. A. Prokopenko, V. Kravchinsky, J. King, and M. I. Kuzmin, 1997. Lake Baikal record of continental climate response to orbital insolation during the past 5 million years. Science 278: 1114-1117.

WMAP Science Team Bibliography. NASA. http://lambda.gsfc.nasa.gov/product/map/dr3/map_bibliography.cfm

Saha, P., J. Coles, A. V. Macciò, and L. L. R. Williams. 2006. The Hubble Time Inferred from 10 Time Delay Lenses. The Astrophysical Journal 650: L17-L20.

Dauphas N. The U/Th production ratio and the age of the Milky Way from meteorites and Galactic halo stars. Nature. 2005;435(7046):1203-5. Available at: http://dx.doi.org/10.1038/nature03645.

Marx FG, Uhen MD. Climate, critters, and cetaceans: Cenozoic drivers of the evolution of modern whales. Science (New York, N.Y.). 2010;327(5968):993-6. Available at: http://www.sciencemag.org/cgi/content/abstract/327/5968/993.

Hansen B, Richer H, Fahlman G, et al. HST Observations of the White Dwarf Cooling Sequence of M4. 2004. Available at: http://arxiv.org/abs/astro-ph/0401443.