Question about carbon dating and the laws of physics?

Question

Ok... does carbon dating take into account that all the elements that are on the earth are the same elements that were originally created or "banged" or whatever? (per the law of thermodynamics which says (I think it's the first) "matter can neither be created nor destroyed")

I guess what I am trying to ask is how can you tell one tree is older than another through carbon dating if they are both made of carbon and oxygen and hydrogen atoms that have been around for the same millions of years?

Do I have the wrong idea about carbon dating in general? Does it only apply to certain things... and also when you like, do it to a skelton, does it tell you how old the bones are or how long the person has been dead?

I am very confused.

Answer 1

As already mentioned, carbon-14 dating depends on assumptions of the proportion of carbon-14 in the living organism and its food supply. That depends on assumptions of the amount of incoming gamma radiation, and generally assumes it is constant. But a living seal would indeed test at 1300 years old if it lived its life under a few feet of water, shielding the gamma radiation. The HVL (half value layer, the thickness of a material needed to reduce gamma radiation by half) is

* 9 cm (3.6 inches) of packed dirt or
* 6 cm (2.4 inches) of concrete,
* 1 cm (0.4 inches) of lead,
* 0.2 cm (0.08 inches) of depleted uranium,
* 150 m (500 ft) of air.
so a little shielding makes a dramatic difference in the indicent gamma radiation.

I don't know about the other ancient historical accounts, but the Biblical account of conditions before the flood mentions 'the canopy above'. If that had a shielding effect, carbon-14 dating would be useless before the flood. Similarly, any change in the magnetosphere would affect gamma radiation reaching the surface of the earth, as well as the depth of the atmosphere.

Carbon-14 dating is a useful tool, but only if used properly.

Answer 2

You are half correct that matter can not be created or destroyed, but more accurately it is matter/energy can not be created or destroyed. Energy and matter are manifestations of the same thing, and elements can be change through radioactivity, fusion, fission, neutron capture, etc. Mass and energy are conserved, but the elements do not necessarily remain the same.

Carbon dating relies on making an assumption on the ratio of C-14/C-12 the sample once had, and then looking at the current ratio. If you make the incorrect assumption about the initial ratio, your dating will be wrong.

In the case of testing a skeleton, the testing will tell you how long the person has been dead, not how old the bones are. The reason is because the C-14/C-12 ratio remains roughly the same while a creature is living because it continually takes up new Carbon from either the atmosphere (in plants), or from eating.

By the way, if you try to date the age of a polar bear, because it eats fish from the ocean, its carbon source will have a different C-14/C-12 ratio than it would if it had been eating plants. So, when dating a sample there are pitfalls that can throw off your assumptions about the initial C-14/C-12 ratio, and hence the resulting date that you get.

And Carbon dating is only good for dating certain things. For example, Carbon dating can be used to date ancient scrolls, but it is not useful to date the age of most rocks.

Answer 3

1st part: The big bang released only subatomic particles. They coalesced and formed stars. The star formation, operation, and death produced heavier atoms like carbon, iron, oxygen, etc.

2nd part: Carbon dating measures how long since something has collected carbon. While alive, organisms collect carbon. Carbon comes in two forms, 12 and radioactive 14. Chemically, they react the same. In the environment, they are present in a certain ratio. A living thing collects carbon at this ratio. Once collected, the carbon 14 slowly turns into carbon 12 at a known rate and changes the ratio. Carbon dating measures the new ratio and uses the decay rate to calculate the time since the organism collected its carbon.

3rd part: Usually a skeleton has some other stuff associated with it like scraps of cloth, pieces of flesh, wooden tools. That's what is dated. Carbon dating has some error. Not knowing when the particular sample was formed in the body usually increases the error by the lifetime of the subject. I also think the technology of carbon 14 measurement can presently really only get down to accuracies of 1000 years or so.

Answer 4

According to a page titled Dating Techniques from the Minnesota State University web site, radiocarbon dating, also known as Carbon-14 (or C-14) dating, is a type of absolute dating technique used to determine the age of organic material. Introduced in 1947 by Willard F. Libby, C-14 dating was a real breakthrough for scientists, who up to this point, had to rely on relative dating techniques.
Basically, all living things are mostly made of carbon. A small portion of this carbon is in the form of Carbon-14, an unstable radioactive isotope. Once an organism dies, the C-14 in the organism begins to disintegrate. Because it disintegrates at a steady, known rate, scientists can measure the amount of C-14 remaining and use a scientific formula to determine the age of the sample.

The University of Waikato, New Zealand web site offers an in-depth explanation and, for the less scientifically-inclined, a simple summary that's a bit easier to understand. Another good place to start is Yahoo's Archaeometry category, a sub-category of Archaeology that deals with methods of dating artifacts.

While C-14 dating has its limitations, it remains a significant scientific discovery and has been used to date some of the most important archaeological finds, including the Dead Sea Scrolls, the Iceman, and the controversial Shroud of Turin.

According to British prehistorian Desmond Clark, without Carbon-14 dating "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation." Sounds pretty frightening, doesn't it?

Answer 5

The only thing you can be sure about is that carbo dating has been proven numorous times to be wrong! Some examples: "The lower leg of the Fairbanks Creek mammoth had a carbon age of 15,380 RCY, while its skin and flesh were 21,300 RCY." - Harold E. Anthony, "Natures Deep Freeze" Natural History, Sept. 1949,p. 300.; A freshly killed seal was carbon dated as having died 1300 years ago! Antarctic Journal vol. 6, p. 211; "One part of the Vollosovitch mammoth carbon dated at 29,500 years, and another part @ 44,000." Troy L. Pewe, Geologic Survay Professional Paper 862.
Those are just a few examples. SO I sure don't trust the carbon dating - & now you see why.

Answer 6

You have a couple confusion points in your question, but I'll try to answer them. First of all, thermodynamics is not tied to Big Bang Theory. It is a part of Physics, mostly a difference between heat and temperature. Heat is an amount of energy, but temperature is the measurement of the hotness or coldness of a substance. Thermodynamics is mostly heat transfer between objects of different mass, or heat transfer/loss in fluids.

For example, a pool of water at 70 Fahreinheit has more energy than a glass of water at 70 degrees Fahreinheit. Same temperature but different mass. It's M*Change in Temperature. So if I was to spin a turbine with water from a swimming pool, I could, but not from a glass of water. So I would transfer heat energy of water, into mechanical energy into electrical energy. Does that make sense?

Second of all matter not being created or destroyed is not part of thermodynamics either.

Thirdly, carbon dating, is tied to what is called radio-active decay or the half life of a substance. It's mathematically 1/e^t. Or it's the inverse of e to power of "t", where "t"is time, and e=2.77. Think of it like this: if I told you something falls of 1/x^2, that would be inverse porabola graph, right? One over the distance squared. So if the distance is 3 meters, and I'm measuring gravity, it would fall by 1/9th, right? One over 3 squared. So if the distance is 9 meters, it would fall by 81, or 1 over 9 squared. Now then, imagine the same idea, but the "x" is not distance, but instead is "e".

So basically, let's say the "half life" of a substance is 100 years. That means its radio-activity level will one half of the number of Curries (measurement of radiation) that it is today. So if today, it is 90 Curries, and has a half life of 100 years, it means one hundred years from now, it will have a radioactivity of only 45 Curries. That means that 200 years from now, it will have zero radiation. Make sense?

Ok, now, let's get back to carbon dating. Most carbon is chemically called C12. But there is a radioactive version called C13. Everything radioactive, uranium, plutonium, iridium, C13, and so forth, has a half life. That means, we know how many years it will take for the radioactivity of something to drop by half. So, if I measure Uranium, it has a different half life than plutonium, but I can still figure out how long it has been around on this earth based on its CURRENT radioctivity level as compared to what it was sometime in the past. I can plot my measurement against a graph of the equation above. So just like I can predict how much time it takes for radioactivity to drop , I can use the radio-activity as measured today, to mathematically go back and date something.

So going back to my earlier example, if I know the half life of something is 100 years for it to reach 45 Curries and it starts off at 90 Curries, how old is the substance if it currently is 60 Curries? Simple: 90 curries=now, 45 curries=0.5 T. So 60/90 is 66%, or 2/3rds. So, if radiation is 2/3rd, the time is 2/3rd as well! So, if 100 years is half life and 200 years is full life, how many years have elapsed if the substance is currently 60 Curries? Get the idea?

Carbon dating can be used to accurately tell how old something is. You can't use Uranium, because most biological substances are made of carbon, and so, you need a radioactive carbon dating approach. I hope I clarified.

Answer 7

You probably have seen or read news stories about fascinating ancient artifacts. At an archaeological dig, a piece of wooden tool is unearthed and the archaeologist finds it to be 5,000 years old. A child mummy is found high in the Andes and the archaeologist says the child lived more than 2,000 years ago. How do scientists know how old an object or human remains are? What methods do they use and how do these methods work? In this article, we will examine the methods by which scientists use radioactivity to determine the age of objects, most notably carbon-14 dating.

Carbon-14 dating is a way of determining the age of certain archeological artifacts of a biological origin up to about 50,000 years old. It is used in dating things such as bone, cloth, wood and plant fibers that were created in the relatively recent past by human activities.


How Carbon-14 is Made
Cosmic rays enter the earth's atmosphere in large numbers every day. For example, every person is hit by about half a million cosmic rays every hour. It is not uncommon for a cosmic ray to collide with an atom in the atmosphere, creating a secondary cosmic ray in the form of an energetic neutron, and for these energetic neutrons to collide with nitrogen atoms. When the neutron collides, a nitrogen-14 (seven protons, seven neutrons) atom turns into a carbon-14 atom (six protons, eight neutrons) and a hydrogen atom (one proton, zero neutrons). Carbon-14 is radioactive, with a half-life of about 5,700 years.


For more information on cosmic rays and half-life, as well as the process of radioactive decay, see How Nuclear Radiation Works.

Carbon-14 in Living Things
The carbon-14 atoms that cosmic rays create combine with oxygen to form carbon dioxide, which plants absorb naturally and incorporate into plant fibers by photosynthesis. Animals and people eat plants and take in carbon-14 as well. The ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things at any given time is nearly constant. Maybe one in a trillion carbon atoms are carbon-14. The carbon-14 atoms are always decaying, but they are being replaced by new carbon-14 atoms at a constant rate. At this moment, your body has a certain percentage of carbon-14 atoms in it, and all living plants and animals have the same percentage.


Dating a Fossil
As soon as a living organism dies, it stops taking in new carbon. The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced. The carbon-14 decays with its half-life of 5,700 years, while the amount of carbon-12 remains constant in the sample. By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely.

A formula to calculate how old a sample is by carbon-14 dating is:

t = [ ln (Nf/No) / (-0.693) ] x t1/2

where ln is the natural logarithm, Nf/No is the percent of carbon-14 in the sample compared to the amount in living tissue, and t1/2 is the half-life of carbon-14 (5,700 years).

So, if you had a fossil that had 10 percent carbon-14 compared to a living sample, then that fossil would be:

t = [ ln (0.10) / (-0.693) ] x 5,700 years

t = [ (-2.303) / (-0.693) ] x 5,700 years

t = [ 3.323 ] x 5,700 years

t = 18,940 years old

Because the half-life of carbon-14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old. However, the principle of carbon-14 dating applies to other isotopes as well. Potassium-40 is another radioactive element naturally found in your body and has a half-life of 1.3 billion years. Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).

The use of various radioisotopes allows the dating of biological and geological samples with a high degree of accuracy. However, radioisotope dating may not work so well in the future. Anything that dies after the 1940s, when Nuclear bombs, nuclear reactors and open-air nuclear tests started changing things, will be harder to date precisely.

Answer 8

Suppose you have a wooden sample. In the wood you find carbon atoms.
Most carbon is 'normal' and stable. It is C12.
A small amount of the carbon is the radioactive isotope. It is C14
This one desintegrates. Every 5730 year half of it is gone.
In living plants the C14 concentration is constant, thanks to absorbing CO2 from the air and thanks to production of C14.
When the plant dies it stops taking new CO2.
During years the concentration of C14 goes down by radioactivity.
By measuring the concentration of C14 (in a mass spectrometer), you can calculate the number of years since the plant died.

Answer 9

CARBON DATING IS TOTALLY BASED ON THE CARBON -14 WHICH IS A RADIOACTIVE ELEMENT.AS WE KNOW THAT A RADIOACTIVE ELEMENT ALWAYS EMUTS RADIO ACTIVE SUBSTANCE.IN THE SAME WAY THIS ALSO EMITS BETA PARTICLE.THIS EMISSION OF BETA PARTICLE TOOK PLACE THROUHOUT THE LIFE AND DEATH.IT DOES NOT STOP TILL OUR BODY IS DESTORYED .IN AFIXED TIME A FIXED AMOUNT OF BETA PARTICLE EMITS OUT OF BODY THUS BY CALCULATING WE CAN FIND IT OUT THAT HW MUCH LD THE BODY IS.

Answer 10

yeah...you really are confused..
see..when trees decay their carbon compounds begin to disintegrate.this isnt the same stuff created millions of years ago but food material formed by the trees due to photosynthesis.