stuff to read for SF_Gold:
MOONDUST
DECAY OF MAGNETIC FIELD
FOSSIL RECORD
PROBABILITY
http://www.pcts.org/journal/young2002a.html
THERMODYNAMICS
VESTIGIAL FEATURES
FOSSIL FUEL FORMATION
THE SUN
DATING METHODS
(http://www.mnsu.edu/emuseum/archaeology/dating/radio_carbon.html)
http://pubs.usgs.gov/gip/geotime/radiometric.html
[damn, I'm too tired. I'll update next day. Can't think straight]
MOONDUST
Quote:
(http://www.talkorigins.org/faqs/hovind/howgood-yea.html#proof2)2. The most amazing thing about the cosmic dust argument is that it is still being used! It has coasted along on obsolete evidence, and nothing but obsolete evidence, for the last 25 years!! It nicely illustrates how creationists borrow from each other and never do any outside reading.
The obsolescence of this argument has been brought out in numerous debates and published in countless books, journals, and newsletters. It can be discovered by anyone who exercises his or her library card. It's not a state secret! What does it take to get through to the creationist brain??
The obsolescence of this argument has been brought out in numerous debates and published in countless books, journals, and newsletters. It can be discovered by anyone who exercises his or her library card. It's not a state secret! What does it take to get through to the creationist brain??
DECAY OF MAGNETIC FIELD
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(http://www.talkorigins.org/faqs/faq-age-of-earth.html#magnetic)2. Decay of the Earth's magnetic field
The young-Earth argument: the dipole component of the magnetic field has decreased slightly over the time that it has been measured. Assuming the generally accepted "dynamo theory" for the existence of the Earth's magnetic field is wrong, the mechanism might instead be an initially created field which has been losing strength ever since the creation event. An exponential fit (assuming a half-life of 1400 years on 130 years' worth of measurements) yields an impossibly high magnetic field even 8000 years ago, therefore the Earth must be young. The main proponent of this argument was Thomas Barnes.
There are several things wrong with this "dating" mechanism. It's hard to just list them all. The primary four are:
1. While there is no complete model to the geodynamo (certain key properties of the core are unknown), there are reasonable starts and there are no good reasons for rejecting such an entity out of hand. If it is possible for energy to be added to the field, then the extrapolation is useless.
2. There is overwhelming evidence that the magnetic field has reversed itself, rendering any unidirectional extrapolation on total energy useless. Even some young-Earthers admit to that these days -- e.g., Humphreys (1988).
3. Much of the energy in the field is almost certainly not even visible external to the core. This means that the extrapolation rests on the assumption that fluctuations in the observable portion of the field accurately represent fluctuations in its total energy.
4. Barnes' extrapolation completely ignores the nondipole component of the field. Even if we grant that it is permissible to ignore portions of the field that are internal to the core, Barnes' extrapolation also ignores portions of the field which are visible and instead rests on extrapolation of a theoretical entity.
That last part is more important than it may sound. The Earth's magnetic field is often split in two components when measured. The "dipole" component is the part which approximates a theoretically perfect field around a single magnet, and the "nondipole" components are the ("messy") remainder. A study in the 1960s showed that the decrease in the dipole component since the turn of the century had been nearly completely compensated by an increase in the strength of the nondipole components of the field. (In other words, the measurements show that the field has been diverging from the shape that would be expected of a theoretical ideal magnet, more than the amount of energy has actually been changing.) Barnes' extrapolation therefore does not really rest on the change in energy of the field.
The young-Earth argument: the dipole component of the magnetic field has decreased slightly over the time that it has been measured. Assuming the generally accepted "dynamo theory" for the existence of the Earth's magnetic field is wrong, the mechanism might instead be an initially created field which has been losing strength ever since the creation event. An exponential fit (assuming a half-life of 1400 years on 130 years' worth of measurements) yields an impossibly high magnetic field even 8000 years ago, therefore the Earth must be young. The main proponent of this argument was Thomas Barnes.
There are several things wrong with this "dating" mechanism. It's hard to just list them all. The primary four are:
1. While there is no complete model to the geodynamo (certain key properties of the core are unknown), there are reasonable starts and there are no good reasons for rejecting such an entity out of hand. If it is possible for energy to be added to the field, then the extrapolation is useless.
2. There is overwhelming evidence that the magnetic field has reversed itself, rendering any unidirectional extrapolation on total energy useless. Even some young-Earthers admit to that these days -- e.g., Humphreys (1988).
3. Much of the energy in the field is almost certainly not even visible external to the core. This means that the extrapolation rests on the assumption that fluctuations in the observable portion of the field accurately represent fluctuations in its total energy.
4. Barnes' extrapolation completely ignores the nondipole component of the field. Even if we grant that it is permissible to ignore portions of the field that are internal to the core, Barnes' extrapolation also ignores portions of the field which are visible and instead rests on extrapolation of a theoretical entity.
That last part is more important than it may sound. The Earth's magnetic field is often split in two components when measured. The "dipole" component is the part which approximates a theoretically perfect field around a single magnet, and the "nondipole" components are the ("messy") remainder. A study in the 1960s showed that the decrease in the dipole component since the turn of the century had been nearly completely compensated by an increase in the strength of the nondipole components of the field. (In other words, the measurements show that the field has been diverging from the shape that would be expected of a theoretical ideal magnet, more than the amount of energy has actually been changing.) Barnes' extrapolation therefore does not really rest on the change in energy of the field.
FOSSIL RECORD
Quote:
(http://www.gcssepm.org/special/cuffey_05.htm) As previously stated, a succession of transitional fossils exists that link reptiles (Class Reptilia) and mammals (Class Mammalia). These particular reptiles are classifie as Subclass Synapsida. Presently, this is the best example of th e transformation of one major higher taxon into another. The morphologic changes that took place are well documented by fossils, beginning with animals essentially 100% reptilian and resulting in animals essentially 100% mammalian. Therefore, I have chosen this as the example to summarize in more detail (Table 1, Fig. 1).
Quote:
(http://www.actionbioscience.org/evolution/benton2.html)Evidence of Evolutionary Transitions
By Michael Benton
One of the most startling discoveries of the past two centuries has been that all living organisms -- all the millions of species of microbes, plants and animals alive on Earth today -- share a common ancestry. However different an elephant, a dung beetle, an oak tree, and an AIDS virus may look, they can all be tracked back to common ancestors in the depths of geologic time. This insight was first articulated by Charles Darwin in 1859, and new lines of evidence have confirmed his discovery time and time again since then. There are two key lines of evidence:
* missing links
* shared characteristics
The role of missing links is most difficult to understand. Surely, argue the creationists and other religious fundamentalists, if evolutionists claim that all of life is related through a single huge family tree extending from the present day back millions of years to a single point of origin, we should find fossils that are midway between established groups. 'Where are the missing links?' they cry. Palaeontologists have them!
By Michael Benton
One of the most startling discoveries of the past two centuries has been that all living organisms -- all the millions of species of microbes, plants and animals alive on Earth today -- share a common ancestry. However different an elephant, a dung beetle, an oak tree, and an AIDS virus may look, they can all be tracked back to common ancestors in the depths of geologic time. This insight was first articulated by Charles Darwin in 1859, and new lines of evidence have confirmed his discovery time and time again since then. There are two key lines of evidence:
* missing links
* shared characteristics
The role of missing links is most difficult to understand. Surely, argue the creationists and other religious fundamentalists, if evolutionists claim that all of life is related through a single huge family tree extending from the present day back millions of years to a single point of origin, we should find fossils that are midway between established groups. 'Where are the missing links?' they cry. Palaeontologists have them!
PROBABILITY
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(http://www.talkorigins.org/faqs/abioprob/abioprob.html)Every so often, someone comes up with the statement "the formation of any enzyme by chance is nearly impossible, therefore abiogenesis is impossible". Often they cite an impressive looking calculation from the astrophysicist Fred Hoyle, or trot out something called "Borel's Law" to prove that life is statistically impossible. These people, including Fred, have committed one or more of the following errors...
Quote:
How to Evolve Specified Complexity by Natural Means
http://www.pcts.org/journal/young2002a.html
THERMODYNAMICS
Quote:
(http://www.talkorigins.org/indexcc/CF/CF001.html)# The second law of thermodynamics says no such thing. It says that heat will not spontaneously flow from a colder body to a warmer one or, equivalently, that total entropy (a measure of useful energy) in a closed system will not decrease. This does not prevent increasing order because
* the earth is not a closed system; sunlight (with low entropy) shines on it and heat (with higher entropy) radiates off. This flow of energy, and the change in entropy that accompanies it, can and will power local decreases in entropy on earth.
* entropy is not the same as disorder. Sometimes the two correspond, but sometimes order increases as entropy increases. (Aranda-Espinoza et al. 1999; Kestenbaum 1998) Entropy can even be used to produce order, such as in the sorting of molecules by size (Han and Craighead 2000).
* even in a closed system, pockets of lower entropy can form if they are offset by increased entropy elsewhere in the system.
In short, order from disorder happens on earth all the time.
# The only processes necessary for evolution to occur are reproduction, heritable variation, and selection. All of these are seen to happen all the time, so, obviously, no physical laws are preventing them. In fact, connections between evolution and entropy have been studied in depth, and never to the detriment of evolution (Demetrius 2000).
* the earth is not a closed system; sunlight (with low entropy) shines on it and heat (with higher entropy) radiates off. This flow of energy, and the change in entropy that accompanies it, can and will power local decreases in entropy on earth.
* entropy is not the same as disorder. Sometimes the two correspond, but sometimes order increases as entropy increases. (Aranda-Espinoza et al. 1999; Kestenbaum 1998) Entropy can even be used to produce order, such as in the sorting of molecules by size (Han and Craighead 2000).
* even in a closed system, pockets of lower entropy can form if they are offset by increased entropy elsewhere in the system.
In short, order from disorder happens on earth all the time.
# The only processes necessary for evolution to occur are reproduction, heritable variation, and selection. All of these are seen to happen all the time, so, obviously, no physical laws are preventing them. In fact, connections between evolution and entropy have been studied in depth, and never to the detriment of evolution (Demetrius 2000).
Quote:
(http://www.sciam.com/article.cfm?articleID=000D4FEC-7D5B-1D07-8E49809EC588EEDF&pageNumber=4&catID=2)This argument derives from a misunderstanding of the Second Law. If it were valid, mineral crystals and snowflakes would also be impossible, because they, too, are complex structures that form spontaneously from disordered parts.
The Second Law actually states that the total entropy of a closed system (one that no energy or matter leaves or enters) cannot decrease. Entropy is a physical concept often casually described as disorder, but it differs significantly from the conversational use of the word.
The Second Law actually states that the total entropy of a closed system (one that no energy or matter leaves or enters) cannot decrease. Entropy is a physical concept often casually described as disorder, but it differs significantly from the conversational use of the word.
VESTIGIAL FEATURES
Quote:
(http://www.csicop.org/si/2003-11/intelligent-design.html)Darwin was not only convinced by the success of evolution in explaining numerous instances of common descent, but also by its ability to account for vestigial organs, "parts in this strange condition, bearing the stamp of inutility." These organs are of little or no current use to an organism but are probable remnants of an earlier form from which the organism evolved. Intelligent Design has no explanation for these organs. As Stephen Jay Gould has put it, "Odd arrangements and funny solutions are the proof of evolution-paths that a sensible God would never tread but that a natural process, constrained by history follows perforce" (Gould 1980; Gould in Pennock 2001, 670). Let's look at some examples.
Cockroaches and other insects may grow an extra set of wings, as did their fossilized ancestors. Unlike most other snakes, boa constrictors possess small vestigial hind legs. Crabs possess small useless tails under their broad, flat bodies, remnants of some ancestral form. Flounders lie flat on the sea floor and in the adult both eyes are on the same side of the head, but when young the eyes are on opposite sides of the head and one moves to the other side! The earlier stage is a clue to an evolutionary path. The result is a wrenched and distorted skull.
The frigate, a non-aquatic bird, does not benefit from the webbing on its feet. In flightless birds the number of usable limbs is reduced from four to two with the presence of two non-functional limbs. Penguins possess hollow bones although they do not have the same need for minimal body weight as flying birds. Otherwise fully aquatic animals such as sea snakes, dolphins, and whales must rise to the surface to breathe air. Modern whales exhibit several non-functional vestigial traits. Fetuses of baleen whales bear teeth that are absorbed as the fetus matures; adult baleen whales do not have teeth.
Paleontologists proposed that whales had evolved from land mammals with legs, and therefore, in an example of its predictive power, the theory of evolution forecast that legs would be found on fossilized whales. In recent years the evolution of whales from now extinct land mammals has become well documented through newly found fossils from the Eocene epoch, about 50 million years ago (Wong 2002). The fossilized whales contain well-defined feet and legs. In modern adult whales, the front legs have evolved into flippers and the rear legs have shrunk so that no visible appendages appear. Hindlimbs still appear in the fetuses of some modern whales but disappear by adulthood. Externally invisible, vestigial diminished pelvic bones occur in modern adult whales. Evolution accounts for these useless vestigial elements as leftovers in the development of whales from land mammals, but they remain unaccounted for by Intelligent Design.
Cockroaches and other insects may grow an extra set of wings, as did their fossilized ancestors. Unlike most other snakes, boa constrictors possess small vestigial hind legs. Crabs possess small useless tails under their broad, flat bodies, remnants of some ancestral form. Flounders lie flat on the sea floor and in the adult both eyes are on the same side of the head, but when young the eyes are on opposite sides of the head and one moves to the other side! The earlier stage is a clue to an evolutionary path. The result is a wrenched and distorted skull.
The frigate, a non-aquatic bird, does not benefit from the webbing on its feet. In flightless birds the number of usable limbs is reduced from four to two with the presence of two non-functional limbs. Penguins possess hollow bones although they do not have the same need for minimal body weight as flying birds. Otherwise fully aquatic animals such as sea snakes, dolphins, and whales must rise to the surface to breathe air. Modern whales exhibit several non-functional vestigial traits. Fetuses of baleen whales bear teeth that are absorbed as the fetus matures; adult baleen whales do not have teeth.
Paleontologists proposed that whales had evolved from land mammals with legs, and therefore, in an example of its predictive power, the theory of evolution forecast that legs would be found on fossilized whales. In recent years the evolution of whales from now extinct land mammals has become well documented through newly found fossils from the Eocene epoch, about 50 million years ago (Wong 2002). The fossilized whales contain well-defined feet and legs. In modern adult whales, the front legs have evolved into flippers and the rear legs have shrunk so that no visible appendages appear. Hindlimbs still appear in the fetuses of some modern whales but disappear by adulthood. Externally invisible, vestigial diminished pelvic bones occur in modern adult whales. Evolution accounts for these useless vestigial elements as leftovers in the development of whales from land mammals, but they remain unaccounted for by Intelligent Design.
Quote:
(http://www.livescience.com/animalworld/top10_vestigial_organs.html)In Charles Darwin’s On the Origin of Species (1859) and his next publication, The Descent of Man (1871), he referred to several “vestiges” in human anatomy that were left over from the course of evolution. These vestigial organs, Darwin argued, are evidence of evolution and represent a function that was once necessary for survival, but over time that function became either diminished or nonexistent.
The presence of an organ in one organism that resembles one found in another has lead biologists to conclude that these two might have shared a common ancestor. Vestigial organs have demonstrated remarkably how species are related to one another, and has given solid ground for the idea of common descent to stand on. From common descent, it is predicted that organisms should retain these vestigial organs as structural remnants of lost functions. It is only because of macro-evolutionary theory, or evolution that takes place over very long periods of time, that these vestiges appear.
The term “vestigial organ” is often poorly defined, most commonly because someone has chosen a poor source to define the term. The Oxford English Dictionary (OED) defines vestigial organs as organs or structures remaining or surviving in a degenerate, atrophied, or imperfect condition or form. This is the accepted biological definition used in the theory of evolution.
The presence of an organ in one organism that resembles one found in another has lead biologists to conclude that these two might have shared a common ancestor. Vestigial organs have demonstrated remarkably how species are related to one another, and has given solid ground for the idea of common descent to stand on. From common descent, it is predicted that organisms should retain these vestigial organs as structural remnants of lost functions. It is only because of macro-evolutionary theory, or evolution that takes place over very long periods of time, that these vestiges appear.
The term “vestigial organ” is often poorly defined, most commonly because someone has chosen a poor source to define the term. The Oxford English Dictionary (OED) defines vestigial organs as organs or structures remaining or surviving in a degenerate, atrophied, or imperfect condition or form. This is the accepted biological definition used in the theory of evolution.
FOSSIL FUEL FORMATION
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(http://www.energyquest.ca.gov/story/chapter08.html)There are three major forms of fossil fuels: coal, oil and natural gas. All three were formed many hundreds of millions of years ago before the time of the dinosaurs - hence the name fossil fuels. The age they were formed is called the Carboniferous Period. It was part of the Paleozoic Era. "Carboniferous" gets its name from carbon, the basic element in coal and other fossil fuels.
Picture of carboniferous era swamp
The Carboniferous Period occurred from about 360 to 286 million years ago. At the time, the land was covered with swamps filled with huge trees, ferns and other large leafy plants, similar to the picture above. The water and seas were filled with algae - the green stuff that forms on a stagnant pool of water. Algae is actually millions of very small plants.
Some deposits of coal can be found during the time of the dinosaurs. For example, thin carbon layers can be found during the late Cretaceous Period (65 million years ago) - the time of Tyrannosaurus Rex. But the main deposits of fossil fuels are from the Carboniferous Period.
Picture of carboniferous era swamp
The Carboniferous Period occurred from about 360 to 286 million years ago. At the time, the land was covered with swamps filled with huge trees, ferns and other large leafy plants, similar to the picture above. The water and seas were filled with algae - the green stuff that forms on a stagnant pool of water. Algae is actually millions of very small plants.
Some deposits of coal can be found during the time of the dinosaurs. For example, thin carbon layers can be found during the late Cretaceous Period (65 million years ago) - the time of Tyrannosaurus Rex. But the main deposits of fossil fuels are from the Carboniferous Period.
THE SUN
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(http://www.infidels.org/library/modern/dave_matson/young-earth/specific_arguments/sun_shrinking.html)The shrinking-sun argument contains two errors. First, and by far the worst, is the assumption that if the sun is shrinking today, as might be detected over a period of years, then it has always been shrinking!
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(http://www.talkorigins.org/indexcc/CE/CE310.html)#1 This assumes that the rate of shrinkage is constant. That assumption is baseless. (In fact, it is the uniformitarian assumption that creationists themselves sometimes complain about.) Other stars expand and contract cyclically. Our own sun might do the same on a small scale.
#2 There is not even any good evidence of shrinkage. The claim is based on a single report from 1980. Other measurements, from 1980 and later, do not show any significant shrinkage. It is likely that the original report showing shrinkage contained systematic errors due to different measuring techniquies over the decades.
#2 There is not even any good evidence of shrinkage. The claim is based on a single report from 1980. Other measurements, from 1980 and later, do not show any significant shrinkage. It is likely that the original report showing shrinkage contained systematic errors due to different measuring techniquies over the decades.
Quote:
(http://www.asa3.org/ASA/PSCF/1986/PSCF9-86VanTill.html)From Puzzle to Proof: The Creation of a Legend
The puzzling report that there was evidence to suggest a rapid shrinkage of the sun over several centuries was quickly adapted by the "creation- science" community for use as a "scientific evidence," or .. proof," for a very young earth. Without the extended duration of cosmic history, the concept of cosmic evolution would appear to be untenable. And, according to the proponents of "creation science," if evolution over a multibillion-year period did not take place, then creation (restricted to acts of inception) must have occurred during a very busy week about 10,000 years ago. Let us explore for a time how the shrinking sun report has been employed to function as an "evidence" in support of the young earth hypothesis.
The puzzling report that there was evidence to suggest a rapid shrinkage of the sun over several centuries was quickly adapted by the "creation- science" community for use as a "scientific evidence," or .. proof," for a very young earth. Without the extended duration of cosmic history, the concept of cosmic evolution would appear to be untenable. And, according to the proponents of "creation science," if evolution over a multibillion-year period did not take place, then creation (restricted to acts of inception) must have occurred during a very busy week about 10,000 years ago. Let us explore for a time how the shrinking sun report has been employed to function as an "evidence" in support of the young earth hypothesis.
DATING METHODS
Quote:
(http://www.csun.edu/~vcgeo005/wise.htm)Radiometric dating (4)
Creationists argue that radiometric dates are invalid on a number of grounds, despite the massive and detailed explanation of all the dating methods by Dalrymple (1991). They argue that if the speed of light is changing, then all other fundamental constants could have changed, including rates radioactive decay. Some of these arguments are based on supposed changes in the speed of light using uncertainties in such measurements as of about 20 years ago. More recent refinements in the measurements have laid this idea to rest for all but the most committed (see discussion by Schadewald, 1984, and Lippard, 1989, 1990).
Creationists argue that radiometric dates are invalid on a number of grounds, despite the massive and detailed explanation of all the dating methods by Dalrymple (1991). They argue that if the speed of light is changing, then all other fundamental constants could have changed, including rates radioactive decay. Some of these arguments are based on supposed changes in the speed of light using uncertainties in such measurements as of about 20 years ago. More recent refinements in the measurements have laid this idea to rest for all but the most committed (see discussion by Schadewald, 1984, and Lippard, 1989, 1990).
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(http://www.gate.net/~rwms/crebuttal1.html#mag_field_decay_C14)The generation of C14 is affected by the earth's magnetic field. A strong increase in the magnetic field would deflect gamma radiation and reduce or halt the production of C14. Nonetheless, as the creationist idea that the earth's magnetic field has been constantly decaying has been rebutted immediately above, the claim regarding accuracy of C14 data is invalid. Interestingly, if it is true that an increasing magnetic would make C14 dating invalid after 1500 years, the fact that C14 has been used to accurately date historical objects older than this is further evidence that the earth's magnetic field has not been decaying in the matter claimed by creationists.
The accuracy of radiocarbon dating was tested on objects with dates that were already known through historical records such as parts of the dead sea scrolls and some wood from an Egyptian tomb. Based on the results of the Carbon 14 test the analysis showed that C14 agreed very closely with the historical information. ( Dating Exhibit )
The accuracy of radiocarbon dating was tested on objects with dates that were already known through historical records such as parts of the dead sea scrolls and some wood from an Egyptian tomb. Based on the results of the Carbon 14 test the analysis showed that C14 agreed very closely with the historical information. ( Dating Exhibit )
Quote:
Radioactive carbon, produced when nitrogen 14 is bombarded by cosmic rays in the atmosphere, drifts down to earth and is absorbed from the air by plants. Animals eat the plants and take C14 into their bodies. Humans in turn take carbon 14 into their bodies by eating both plants and animals. When a living organism dies, it stops absorbing C14 and the C14 that is already in the object begins to disintegrate. Scientists can use this fact to measure how much C14 has disintegrated and how much is left in the object. Carbon 14 decays at a slow but steady rate and reverts to nitrogen 14. The rate at which Carbon decays (Half-life) is known: C14 has a half-life of 5730 years. Basically this means that half of the original amount of C14 in organic matter will have disintegrated 5730 years after the organisms death; half of the remaining C14 will have disintegrated after another 5730 years and so forth. After about 50,000 years, the amount of C14 remaining will be so small that the fossil can't be dated reliably.
To discover how long an organism has been dead (to determine how much C14 is left in the organism and therefore how old it is), we count the number of beta radiations given off per minute per gram of material. Modern C14 emits about 15 beta radiations per minute per gram of material, but C14 that is 5730 years old will only emit half that amount, (the half-life of C14) per minute. So if a sample taken from an organism emits 7.5 radiations per minute in a gram of material, then the organism must be 5730 years old. The accuracy of radiocoarbon dating was tested on objects with dates that were already known through historical records such as parts of the dead sea scrolls and some wood from an Egyptian tomb. Based on the results of the Carbon 14 test the analysis showed that C14 agreed very closely with the historical information.
To discover how long an organism has been dead (to determine how much C14 is left in the organism and therefore how old it is), we count the number of beta radiations given off per minute per gram of material. Modern C14 emits about 15 beta radiations per minute per gram of material, but C14 that is 5730 years old will only emit half that amount, (the half-life of C14) per minute. So if a sample taken from an organism emits 7.5 radiations per minute in a gram of material, then the organism must be 5730 years old. The accuracy of radiocoarbon dating was tested on objects with dates that were already known through historical records such as parts of the dead sea scrolls and some wood from an Egyptian tomb. Based on the results of the Carbon 14 test the analysis showed that C14 agreed very closely with the historical information.
(http://www.mnsu.edu/emuseum/archaeology/dating/radio_carbon.html)
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(http://pubs.usgs.gov/gip/geotime/age.html)The Moon is a more primitive planet than Earth because it has not been disturbed by plate tectonics; thus, some of its more ancient rocks are more plentiful. Only a small number of rocks were returned to Earth by the six Apollo and three Luna missions. These rocks vary greatly in age, a reflection of their different ages of formation and their subsequent histories. The oldest dated moon rocks, however, have ages between 4.4 and 4.5 billion years and provide a minimum age for the formation of our nearest planetary neighbor.
Thousands of meteorites, which are fragments of asteroids that fall to Earth, have been recovered. These primitive objects provide the best ages for the time of formation of the Solar System. There are more than 70 meteorites, of different types, whose ages have been measured using radiometric dating techniques. The results show that the meteorites, and therefore the Solar System, formed between 4.53 and 4.58 billion years ago. The best age for the Earth comes not from dating individual rocks but by considering the Earth and meteorites as part of the same evolving system in which the isotopic composition of lead, specifically the ratio of lead-207 to lead-206 changes over time owing to the decay of radioactive uranium-235 and uranium-238, respectively. Scientists have used this approach to determine the time required for the isotopes in the Earth's oldest lead ores, of which there are only a few, to evolve from its primordial composition, as measured in uranium-free phases of iron meteorites, to its compositions at the time these lead ores separated from their mantle reservoirs. These calculations result in an age for the Earth and meteorites, and hence the Solar System, of 4.54 billion years with an uncertainty of less than 1 percent. To be precise, this age represents the last time that lead isotopes were homogeneous througout the inner Solar System and the time that lead and uranium was incorporated into the solid bodies of the Solar System.
The age of 4.54 billion years found for the Solar System and Earth is consistent with current calculations of 11 to 13 billion years for the age of the Milky Way Galaxy (based on the stage of evolution of globular cluster stars) and the age of 10 to 15 billion years for the age of the Universe (based on the recession of distant galaxies).
Thousands of meteorites, which are fragments of asteroids that fall to Earth, have been recovered. These primitive objects provide the best ages for the time of formation of the Solar System. There are more than 70 meteorites, of different types, whose ages have been measured using radiometric dating techniques. The results show that the meteorites, and therefore the Solar System, formed between 4.53 and 4.58 billion years ago. The best age for the Earth comes not from dating individual rocks but by considering the Earth and meteorites as part of the same evolving system in which the isotopic composition of lead, specifically the ratio of lead-207 to lead-206 changes over time owing to the decay of radioactive uranium-235 and uranium-238, respectively. Scientists have used this approach to determine the time required for the isotopes in the Earth's oldest lead ores, of which there are only a few, to evolve from its primordial composition, as measured in uranium-free phases of iron meteorites, to its compositions at the time these lead ores separated from their mantle reservoirs. These calculations result in an age for the Earth and meteorites, and hence the Solar System, of 4.54 billion years with an uncertainty of less than 1 percent. To be precise, this age represents the last time that lead isotopes were homogeneous througout the inner Solar System and the time that lead and uranium was incorporated into the solid bodies of the Solar System.
The age of 4.54 billion years found for the Solar System and Earth is consistent with current calculations of 11 to 13 billion years for the age of the Milky Way Galaxy (based on the stage of evolution of globular cluster stars) and the age of 10 to 15 billion years for the age of the Universe (based on the recession of distant galaxies).
http://pubs.usgs.gov/gip/geotime/radiometric.html
[damn, I'm too tired. I'll update next day. Can't think straight]
SnailIracing:n(500tpostshpereline)pants
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