The carbon14 to carbon12 ratio can be used to date fossils appox. how old.?
365812
Carbon-14 is only reliable for dating objects up to about 60,000 years old.  The website below explains the equation in detail if your interested.
414512
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. \nA formula to calculate how old a sample is by carbon-14 dating is: \n\n\nt = [ ln (Nf/No) / (-0.693) ] x t1/2 \nwhere 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). \n\nSo, if you had a fossil that had 10 percent carbon-14 compared to a living sample, then that fossil would be: \n\n\nt = [ ln (0.10) / (-0.693) ] x 5,700 years \nt = [ (-2.303) / (-0.693) ] x 5,700 years \n\nt = [ 3.323 ] x 5,700 years \n\nt = 18,940 years old \n\nBecause 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).
995783
W. F. Libby, 1947. Carbon dating has been compared to a core sample from tree rings and it is a little imprecise. It understates the dates by 5 to 10%. Carbon dating is accurate only to about 70,000 years. We believe it because of the scientific principles upon which it is based.
541684
Carbon 14 dating cannot be used to determine the age of the Earth itself.  It has a half-life of only 5730 years, and can only be used on organic materials.  Current techniques can produce accurate results up to about 100 000 years old with Carbon 14, but this is not nearly old enough for the origins of the Earth.\n\nOther methods, such as U-238, or Potassium/Argon (K/Ar) dating can be used on igneous rocks (like volcanic ash, obsidian or granite) to find out when it formed, and have been used to date some of the oldest rocks in the world:  Precambrian granites exposed as part of the Canadian Shield when glaciers scraped all the top layers away during the most recent ice ages (the last of which was a mere 10,000 years ago) have been dated to about 4.2 billion years old, and some Australian zircons have been found to be at least 4.4 billion years old.\n\nHowever even these oldest rocks don't really give us the age of the Earth.  They show us that the Earth must be at least that old, but not exactly when the Earth itself formed.\n\nThe Earth has undergone constant vulcanism and reforming, with oceanic plates sliding under continental plates and being melted and reformed, and even continental plates dividing, subducting, transforming, eroding and being buried under new lava flows.  The oldest ocean beds are Triassic in age, perhaps a mere 300 million years old or less.\n\nHowever meteorites have not undergone this same reworking.  Presumably, most of them would have been formed at the dawn of the solar system, as the sun and planets were accreting from the gas cloud into more solid, spinning forms.  A meteorite from Canyon Diablo has been used as the sort of benchmark test, it is a very large metallic nickel-iron meteorite with sulfide materials, and ideal for most forms of radiometric dating.\n\nThe Canyon Diablo meteorite comes out to 4.567 billion years old.  Other extra-terrestrial rocks, such as the moon rocks, Mars rocks, and other meteorites come out to about the same ages, between 4.53 to 4.58 billion years old.  This range has been determined through a number of different techniques on a wide number of different samples, and they always come out in the same range, thus indicating that it probably accurate.\n\nSo the age of the Earth is generally taken to be about 4.5 to 4.6 billion years.
1118534
No.  The only way of confirming its accuracy is to date objects that we already know how old they are.  These fall into the scope of the last 5000 years, a period which they already say is less accurate than when measuring older objects.  Scientists always seem to be arguing about the age of things regardless of what the carbon dating says.
1057852
It takes a very long time.  The oldest fossils are about 3.5 billion years old, but many are not nearly that old.  The youngest are probably only about 23 million years old or even less.\n\nThese links are helpful.
675720
The currently accepted estimate is 4.5 to 4.6 billion years old.  Radiometric dating of Earth rocks can't get us there because the surface of the Earth has undergone so much upheaval.\n \nInstead, moon rocks and meteorites are used to estimate the age of the Earth, because it appears that all of the solar system formed at about the same time.\n\nCarbon dating is of no use here; it only works for organic material and it can't date back further than 50,000 years or so. Long-lived radioactive elements such as uranium are used instead.
424443
you mean appart from all the carbon dated bones that have been found over the last centuries?
968818
Shanna and Geo06 have got this just about right.  The only thing I can add is that radiocarbon dating can not be used for more than about 70,000 years ago, and is more accurate for living things that died within the last 8,000 years.\n\nMost geologists measure rock ages in millions, or even billions, of years, so the age of the earth and the age of almost all igneous rocks is well beyond the range of carbon dating.  On top of that, igneous rocks contain very little if any carbon,  so carbon dating is not applicable here.  \n\nSo the only thing carbon 14 can be used for is to determine the time that an exchange of carbon with the atmosphere stopped, ie, the death of a living thing - the third item on your list of choices for your homework.\n\nThe half life of C-14, the radioactive isotope of carbon, is about 5730 years.  Therefore, if you know the ratio between C-14 and C-12 in the atmosphere when the organism died, and you know the ratio now, the difference in the ratio can be calculated backwards, using the half life, to estimate when the organism died. \n\nAtmospheric C-14 has not been in a constant ratio with C-12, as previously thought, so there are some serious problems with the accuracy of C-14 dating.  The problem is that the natural ratio of the carbon isotopes in the atmosphere (carbon dioxide) varies because cosmic ray bombardment of the outer atmosphere produces C-14 but not C-12.  The ratio can be predicted accurately using the ratios in old trees, where the tree rings can be used to accurately determine the age of each ring with its annual ratio, with a maximum of about 8,000 years -that's how old the oldest trees are which can establish a reference ratio.\n\nDating of artifacts is a best guess, the best method is to measure the amount of lichens growing on them, or the age of carbon in ashes found in the same spot.
53656
Around 4.57 billion years old.
1023108
The fossil history is false. The scientists don't know what they are talking about. Radiometric dating is flawed. Everything is a lie except the Bible. I am trying out the other side of this argument. It's pretty weak I must say.
664667
All fossils should have some Carbon-14, but hypothetically, if one didn't, a different radioactive isotope could be used to determine the age of a fossil.
1006777
You'd have to build a time machine and go back a few billion years. Sadly organisms like amoeba are too small and soft to leave fossil records, the best we have to go on is evidence of the chemical reactions microbes perform.
976654
Looking at astoriods because the whole solar system was formed from the same stuff and the rocked in the Earth is being renewed by subduction a creation zones so you can never tell how old that rock is because it will have been remade many times since the formation of the Earth.\n Radioactive dating not the most accurate but radioactive particles are in everything and they all decay so you can tell how old something is by looking at how much the radioactive particles have decayed \nalso there is carbon dating. You have to set things on fire for this so obviously you cnt do this on everything so it's not terribly accurate \nALSO I'M ONLY 12 YEARS OLD
112629
Very roughly 2 billion years ago.  But you should be aware of two points. \n\nThe first is that the date is a matter of considerable debate and it could easily be half a billion years either side of that.\n\nThe second is that the transition was extremely slow, starting with the addition of oxygen by inorganic processes and then taking a massive leap with the evolution of oxygen producing autotrophs.
941865
It is quite reliable when properly applied.  It can't be trusted when:\n\n(1) it is applied so far in the past that it is extreme extrapolation of limited data.\n\n(2) the sample and its food source were radiation-protected.\n\n(3) the sample came from a situation or time where the C14/C12 ratio was different from what it is today, or is unknown.\n\nFor all these reasons, the farther back in time you try to read, the less reliable the dating.
1068442
There are a lot of different dating techniques.  (The second link talks about some) Usually, when dating something, you don't just use one technique one one sample--you try to find a few different ways, and use them to build up a case for the age of something.\n\nSome dating systems are relative, in that they can only tell you which came first.  This is useful because it lets people assemble a chronology of things, even though it won't have absolute dates.  Once you have this chronology, you can use absolute dates to start finding approximate ages for things. For example, there's a distinctive layer of iridium in many rocks. If you find something below that layer, it's a good bet that it's older than the layer is.  Once you know that the layer was put down about 65 million years ago, you can start to narrow down the date of the things beneath it.\n\nRelative techinques are also useful as a test for the absolute techniques--if you know what order things happened in, you can use that to check that other techniques are giving sensible results.\n\nThere are also a lot of different absolute techniques--see the third link for a disscussion. Some, like counting tree rings, are very accurate, but only go back a few hundred or thousand years. Others, like carbon-14 dating, work on things that were once alive.  Still others, like Uranium-Thorium dating or archaeomagnetism, only work on certain kinds of rocks. Carbon-14 and U-T dating work by looking at how much radioactive materials in the sample have broken down, and archaeomagnetism works because the Earth's magnetic field has changed over the ages, leaving signs in some minerals.\n\nFinally, you can just look at the things that are near a sample.  So, if an archelogical dig contains a kind of pottery that you know was used 3000 years ago, that's a clue that the site is about that old.  If a layer of rock is full of fossils of animals that lived 300-200 million years ago, the rock was probably formed around then.