This is a cool topic. Turns out, I have been reading several books on Kennewick Man and other ancient Paleo-American skeletons in North America. The latest is James Chatters' Ancient Encounters - Kennewick Man And The First Americans. James Chatters is the original anthropologist that examined the skeleton.

In his book, he has an excellent discussion on carbon dating. I'll present it word for word:

"Radiocarbon years and real years are not the same thing, hence the calibration. When Libby developed the radiocarbon dating method, he assumed that the proportion of carbon 14 to other carbon isotopes in the atmosphere had been constant throughout the 50,000- year period that can be dated by his method. This assumption has since proven to be false. Radiocarbon experts such as Minze Stuiver, professor emeritus at the University of Washington, have used tree rings and carbon trapped in annual layers in lakes, oceans, and polar ice caps to demonstrate that the proportion of radiocarbon in the atmosphere has varied through time. Radiocarbon dates thus can differ from actual ages by more than 1,000 years. The reason for this discrepancy is primarily that the cosmic radiation striking the earth has not remained constant. During periods of high solar activity, the flow of matter outward from the sun - known as solar wind - increases and effectively blows the cosmic radiation away from the solar system. During these times, less carbon 14 is produced, so dates from these times are correspondingly older than they should be. Likewise, when solar activity is low, radiocarbon ages are too young. By dating hundreds of samples of known ages, Stuiver and his colleagues have produced a calibration curve for radiocarbon ages that now extends more than 14,000 years into the past. The curve is not smooth, however, so that some radiocarbon ages correspond to more than one calendric age. Thus the radiocarbon age of Kennewick Man - which turned out to be 8,410+/-60 B.P. - is actually between 9,330 and 9,580 calendar years, or from about 7330 to 7580 B.C. Throughout the rest of this book, I will give ages in calendar years, not radiocarbon years."

Amazing!

Solar energetic particles are not cosmic rays and are much less energetic than cosmic rays which are extra-solar in nature and near the speed of light. Solar energetic particles (about 80% of speed of light) are mainly taken care of by the Earth's magnetic field.
Measurement standards had to be recalibrated as are any measurement standards are as new data are discovered. Standards are not arbitrary. Much work goes into them and they get more and more precise. Some, like the speed of light, are determined to be a constant or set to be a constant. Then other constants are recalculated using that value. They usually are composed of measured values of other constants. As better measurements are made the constants are adjusted. There is no absolute revealed data in science. It all has to be discovered and non-contradictory with all other data or it has to be discarded.

Probably not gamma rays. Should be neutron capture: neutron + nitrogen 14 gives carbon 14 + proton. Then the carbon 14 decays to nitrogen 14 + electron (a beta ray particle) + neutrino . That decay is interesting in that when neutrino detectors are made, great care must be taken that extremely small amounts of carbon 14 be in the any materials used in making the detectors, else carbon 14 would be producing stray neutrinos.

The rate of decay is constant. You do not have to measure more than a fraction of the output of an isotope in order to calculate its half-life. This is the same as not needing to measure the entire point-to-point travel of a car in order to know its velocity; you can measure a few feet of that distance and calculate the (assumed constant) velocity from that.

Jan

You are correct to question the constancy of the production of C14. Since, as you state, solar radiation initiates most of the C14 production, changes in solar output will alter the atmospheric C14 load. C14, as well as any of the other isotopic dating systems (there are a dozen major ones) need to be calibrated. C14 is generally calibrated my measuring the C14 content of tree rings and using that figure to calibrate the C14 reading taken from some other object, such as a deer bone.

Good article: http://c14.arch.ox.ac.uk/embed.php?Fi...

Jan

I don't think my assertion, aka conclusion, using two constants was cockamamie at all or speculation. Math can be used based on what I stated as long as you have those constants to act as a starting point.

You can use speculation,or you can use the mathematics of exponential decay. See this article:
https://en.wikipedia.org/wiki/Exponen...

A friend of times long ago used to say, "It stands to reason that ..." and then introduce some cockamamie theory he'd just invented. He was certain that because (1) he used the word "reason" and (2) HE had thought of it, that it was true. Was it Mark Mark Twain who said that only in science can you reap such a wholesale return of conjecture from such a tiny investment of fact?

The carbon isotope measured in carbon dating is created at a "contant" rate in the atmosphere. So, it is present in a known ratio in all new biomass (because all biomass C comes from the atmosphere). At the date of its death, biomass carbon content is no longer being replaced, as in living tissue, so that fixed ratio will start to decay at the known rate (defined by half-life).

Many errors can occur, for example if the biomass sample was found in any place which has (or has ever had) water contamination, then the water will have introduced fresh atmospheric carbon into the sample since its death. Any fresh carbon will then reduce the resulting age. Also, with any age more than a few multiples of the half-life, the result should be quoted with a very wide margin of error. If it does not, then don't trust the source.

My thinking....if you know the number of C14 atoms when you capture/harvest the C14 and you know the rate of decay (provided its constant) you can reasonably 1) determine its rate of exhaustion and 2) determine its starting point (creation). No?

Thanks for the info, its why I asked the question.

AJ, Unfortunately, we need to refresh your science education somewhat.

C14 is 'manufactured' starting from Nitrogen in the atmosphere. The rate of production is essentially constant within a small range.

The rate of decay is a statistical issue. We call it half life and it's a rule... Statistically a C14 atom has a 50% chance of decaying back into Nitrogen every ~5700 years.That doesn't guarantee that any particular atom will decay, just that after 5700 years about 1/2 of them will have decayed.

Carbon dating is only useful for dating living things after they've died. Living things take up carbon. Plants from the air, animals from the plants. While the thing is alive the ratio of C14 to normal Carbon is in equilibrium with the environment. When the thing dies the carbon it holds stops moving and the C14 that's trapped decays without being replaced with fresh atoms.

By measuring the amount of C14 in the unknown sample and comparing it to the amount in a series on KNOWN samples, a timeline of C14 intensities is established.

That's the important part that is usually glossed over. It's not one test, it's based on the tens of thousands of tests that various researchers have made! Every test adds to the database. making individual lookups VERY reliable.

For the most part, C14 dating is considered 'reliable' for measurements at least 50,000 years into the past, and indicative for twice as long. C14 dating is not used to measure the drift of continents, but it's a great tool to learn when a campsite was abandoned.

Carbon dating is a subset of radio isotope decay dating. The generally accepted validity of radio isotope dating is the result of both a lengthy chain of reasoning and experimental confirmation. Radio isotope decay is a consequence of the weak force which acts within the nucleus of the atom. The behavioral properties of this force and its consequences are well understood and are described with very high precision by QED (Quantum Electro Dynamics) and QCD (Quantum Chromo Dynamics). Carbon 14 is an isotope of carbon that has captured an additional neutron as a result of cosmic ray bombardment in the upper atmosphere. It is not the result of nucleosynthesis in massive stars. Because of the link to cosmic ray influx the uniformity of cosmic ray bombardment over time forms the most critical assumption in the carbon dating model. As a result, independent methods for measuring cosmic ray flux as a function of time have been sought. Studies of rocks on the Earth, Moon and Mars reveal no significant change in cosmic ray flux over lengthy time periods of several millions of years. As a result confidence in the process is strengthened. Experimental confirmation in the form of tree ring analysis is also positive. Non fossilized tree ring samples dating back thousands of years show carbon 14 to carbon 13 abundances that are consistent with the theory. Similar results have been obtained from ice core samples and analysis of ancient coral reefs. As a result confidence in the validity of carbon dating and radio isotope decay dating is justified.
However, new understanding is always possible. There have been some measurements that suggest that solar activity alters the weak force in some as yet not understood manner. It is suggested that somehow neutrino emission has some previously unknown influence on the behavior of the weak force and thus could alter radio isotope decay rates. While this remains to be confirmed it is an area of active study. If true it would require a significant modification to the standard model of quantum physics.

Whew! Thanks for that last sentence.
Thanks AJ - that is one of the questions that have been wandering around in my mind for some time as well, but I couldn't think of a good way to present it. When it gets answered (hopefully) I have a number of more questions to sneak in as time and patience permits.

The validity of half-life calculations is confirmed by observation of elements with extremely short half-life, and testing of created elements with moderate half-lives (like those found at nuclear weapon test sites). Polonium, which is a created element, has an extremely short half-life, and can be observed to decay to inert lead over a matter of months, as one example.

Given where our culture is right now, and where it is going, I think that attention to what happened 50,000 years ago is just not important to our lives.

Maybe if we were going in the right direction as a country there would be time and energy to work on things like this. Unfortunately a lot of things like this are relative wastes of time right now.

Carbon 14 is radioactive and decays back to Nitrogen 14. If you dig up something in the ground that is extremely old, it will have almost no C14, as it has long since decayed back to N14. So you might ask, "why does any modern plant or animal have any C-14"?

Well,...Gamma rays from the sun continually create new C14 by converting some of the Nitrogen in the atmosphere to Carbon-14 Plants and animal then ingest the mildly radioactive C14 and it becomes a part of them. The percent of C14 in the living plants and animals reflects the percent of C14 in the atmosphere. But once they die, they stop ingesting new C14 and the C14 in their system begins to decay away. The decay 1/2 life of C14 is 5730 years, so after an animal is dead for 5730 years it will have 1/2 the C14/C12 ratio of a living animal. Since we can measure the percent of C14/C12 very accurately in living and death organic matter, we can estimate the date of death fairly accurately. Does all that make sense?

So here is my question about C14 dating,...Are we sure the percent of C14 in the atmosphere has been constant over time? Because if 10000 or 20000 years ago it were higher or lower, than would create errors in the C14 dating results.

Sincerely,

Scientist of the Gulch.

... and counting the growth rings of the ancient bristlecone pine trees (some 5,000 years old, and alive, plus dead ones on the ground where overlapping growth rings extend the growth record back to about 10,000 years), along with their Carbon-14 decay profile has been used to
significantly enhance the accuracy of C-14 dating during this (last 10,000 years) period.

"half-life is 5,700 years (making its entirely life cycle 11,400 years)?"

No, no, that's not what 'half life' means. If you have a sample containing C14, then after 5700 years half of the C14 atoms will have decayed into N14. In another 5700 years half of those atoms remaining will also have decayed. The process continues until the number is statistically unverifiable by experiment.

How do we get the starting point from which the C14 decays? That's the incorporation of ambient carbon into the growth of a living thing. Once the carbon is stuck into some wood or a piece of leather or whatever, the fraction of the original C14 in the sample can be determined with an instrument that is sort of like a Geiger counter but sensitive to the particular 0.156476 MeV beta decay.

That's just touching the surface. Go hunt up material written by physicists to get the full details. The basic physics was done by Kamen and others over 60 years ago.

Half-life is a term with a precise meaning when used in science.

Half-life quantifies the rate of decay of a system that undergoes exponential decay. It is the time it takes for half of the sample to decay.
It is a statistical concept so an exact time for 'life' is not implied.
Radio carbon dating gives good results for up to about 50,000 years ago. It is used only on organic remains,

C-14 decays with a half-life of 5,730 years.
C-14 is an isotope of carbon, a constituent of all living things - as we understand life. organic, organism.

A mathematical formula can be used to calculate the half-life (of say C-14) from the number of breakdowns per second in a sample. At higher cost, accuracy is improved by using longer periods and larger samples.

A claim that half-life has varied over time is made by creationists to try to discredit radiometric dating. Measurements of radiation from supernova, 100,000 years distant, suggest no change in decay rates over 100,000 years.
Here, we call that a furthy, there are many others. An old colleague used to say 'One fool can throw more stupid objections than ten of the wise can quelch".

Different results between radiometric dating and other methods are known. Of those that were significant, the 'known history' method has given way, eg whether megalith building came later in Europe than in the middle east.

see also:
http://chem.tufts.edu/answersinscienc... and
https://www.boundless.com/physics/tex...

So, an appreciation of what exponential decay means, and knowing that half-life is not half of a life and does not depend on knowledge of some creation date, should resolve the difficulty.

The beginning of this article gives you a hint of the problem with 14C dating. It's not a constant, it's variable. Just ignore the rest of the article, it goes off the rails with a rebuttal of a small group of creationist that are just plain wacky and refuse to acknowledge that life and civilizations existed for 100's of thousands of years prior to the flood. 12 to 13K years ago...sorry, but the beginning of this article was spot on the issue, much better than the others, especially the Wikipedia ones which are vulnerable to unverified revisions.

http://phys.org/news/2010-08-radioact...
vary-sun-rotation.html

Still looking for a recent article- past 5 or 10 years that stated that 14C has increased substantially and the Periodic table had to be adjusted also. We expect that this may be a cycle. Also noted: Many things about the planets in our solar system changed also: Venus has increased it's rotational rate and many of the other planets have change their identifying signatures. We might understand that the current sun cycle, going into a grand solar minimum may have something to do with these occurrences.

Thanks, that lead me to this site for an explanation of Carbon 14 and why its used.
http://science.howstuffworks.com/envi...

It still raises the question, even though we know how C14 is created how can someone say conclusively that its half-life is 5,700 years (making its entirely life cycle 11,400 years)?

I suppose one could examine the last moments of a C14 life and then, knowing the rate of decay, mathematically work backwards until the C14 is at its fully potential (aka new). And if C14 is known to last 11400 years how can something be said to be 50-60K years old or more with any degree of certainly?

Also, I'm sure that there are factors that influence the rate of decay adding a variable to the theory.

Interesting stuff

As I understand it process works something like this.
1. An alternative method of dating is used to establish milestone markers. This means that an artifact or item is dated using a well-known well-established method to determine the age then the amount of carbon 14 in the sample is determined. This provides a marker. This process is repeated until several markers are made so that the basic carbon-14 dating process has a known basis.
2. A new sample or unknown sample is then examined to determine its carbon-14 levels. These carbon-14 levels are then compared to the “known sample” and the age established.
3. This method clearly has some issues because the further back you go the less certain the alternative scientific methods for determining age are.
Carbon-14 dating has known issues some of which you indicated. I have read that anything more than about 5000 years is moving into larger and larger uncertainty. Unfortunately I can’t remember where I read this. Hope this helps a little bit.
If I’m wrong and I certainly could be feel free to knock my silly ideas down.