What are the various methods of finding the age of the earth?

Answer 1

Well, carbon dating has NEVER been used to date the age of the earth, since carbon-14 decays almost completely in roughly 60,000 years, the method can only be used for relatively recent dating. The half-life of carbon-14 is 5,700 years, so every 5,700 years half of the original quantity decays to nitrogen-14 which is stable. After 10 half-lives, there is only about 0.0002% of the original amount remaining.

The two major methods of dating the earth has been comparison of Uranium-Lead series dating of both meteorites and primeval deposits of lead in the mineral galena on earth. A model known as the Holmes-Houtermans Model accounts for the isotopic composition of any given sample of common lead in terms of its history. Radiogenic lead is produced by decay of Uranium and Thorium, and is then incorporated into galena, where the isotopic composition remains constant because that mineral does not contain either uranium or thorium that would add to the lead content. Since there are several different isotopes of lead (208, 207, 206, and 204- refering to the atomic weight of the atom) and these have different decay periods, the ratios can be used to determine an age. Comparison of results from lead in the earth and from meteorites have very similar ages.

Here is some further explanation:
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/clkroc.html

Here is an example of an application of U-Pb dating:
http://www.berkeley.edu/news/media/releases/2004/09/16_uranium.shtml

Answer 2

It is not true that all dating methods are based on unprovable assumptions about the past. Radioactive dating (for example) is based on quantum mechanics, which has been repeatedly tested in the lab and in the field and has never been shown to fail.

Various "young earth" dating claims are based on processes that are known to be variable, and therefore unreliable clocks. Here's one example: It was 65 degrees at six o'clock this morning, and 85 at three this afternoon. Therefore, it must have been below absolute zero two weeks ago, which is the maximum age of the earth. If you can see through the flaw in this kind of silliness, you will be able to see through the same flaw in most of the young-earth arguments creationists use.

The recession of the moon is known to occur at variable rates, depending on the location of continents due to tectonic activity.

The earth's magnetic field is known to increase and decrease over intervals of 100,000 years or so, therefore the current decrease cannot be extrapolated to determine the age of the earth.

Sea salinity is also an unreliable clock, since salt can be removed from the sea in some places and times in vast quantities -- which is what causes large rock salt deposits in places like Kansas.

Erosion of the continents occurs at constant rates, but mountains are much younger than the earth, and are created by processes that have occurred recently compared to the age of the earth.

Human remains: fossilization is very rare to begin with, and finding the few that do exist is even rarer. No surprise there.

Spirals in galaxies are density waves that are self-sustaining.

The Oort cloud is a valid explanation for why the aphelion of so many comets lie in the same region of space; and there is no other theory that explains this phenomenon.

Helium in rocks is created by radioactive decay, and in constantly being replentished. So this too is an unreliable clock.

The BIG LIE that creationists continue to tell you is that there is scientific controversy about the age of the earth. There is no scientific controversy. There IS, however, THEOLOGICAL controversy between the Biblical literalists and those who do not interpret the Bible literally. It is not only sad, but totally DISHONEST of Fundamentalist Christians to manufacture a nonexistant controversy in order to proseletize their narrow theology to the rest of us.

Answer 3

It's based on several things:

1) dating meteorites. When we find a meteorite from this solar system that has a similar composition to earth, you get many young ages, but the oldest and most common date to 4.6 Ga (billion years).

2) isotope trends. When you look at certain radiogenic isotope ratios that change with time, like Rb/Sr or U/Pb, you find that many rocks with differnt ratios of many ages form a line, and the line traces back to an origin of 4.6 Ga as well.

The oldest life is 3 1/2 Ga, the oldest rock is about 4 Ga, and the oldest date ever found is on the highly durable mineral Zircon from Australia, it's date is 4.2 Ga. So, there is no direct method, it is based on inferences. However, many different inferences lead to the same number 4.559 Ga (to be specific).

And by the way, carbon dating only goes back at most 60,000 years. You need K/Ar or U/Pb to date the earth.

Answer 4

Carbon dating can only date to about 50000 years ago since the half life is about 5700 years and the amounts become too small to measure beyond that.

The estimates of great antiquity (millions/billions) of years are based on uniformitarian assumptions - things have always been as we see now. In this way rocks are alleged to be millions of years old since we do not see them being laid down quickly now. The possibility of a Global flood that laid down sedimentary rocks quickly all over the world, burying billions of creatures, is dismissed by some a fairy story since it conflicts with their philosophical (religious) worldview.

The idea that the earth is millions of years old is a recent one and was pushed to support the hypothesis of darwiniam evolution, which requires vast ages for the alleged evolutionary changes to occur. Most dating methods indicate that the earth and universe is young. All dating methods are based on unprovable assumptions about the past. But if outnof hundreds of dating methods, 99% suggest youth... well it would surely be perverse to ignore them all!

There are other radiometric dating methods that are used to give an estimate of age, but these rely on unprovable assumptions: that the amount of parent and daughter isotopes originally present is known; that the decay rate has been constant; that there has been no contamination.
These dating methods are not reliable - volcanic rock known to be just hundreds of years old was dated as millions!
If a date does not 'fit' ancient expectations then contamination is assumed to make it fit.

However there are many dating methods that indicate a young earth and universe (thousands of years). For example:
The recession of the moon - the moon is receding from the earth and extrapolating back indicates youth since if very old and close the earth and moon's gravitational forces would torn each other apart.
The decrease in earths magnetic field - measured over the last few hundred years.
The salinity of the sea - would be much saltier if ancient.
Ditto dozens of minerals.
Erosion of the continents - at current erosion rates the continents would have been eroded many times over if the earth was millions of years old.
Not enough human remains - human activity goes back just a few thousand years - should be the remains of countless billions of our ancestors.
Spiral galaxies would no longer be spiral if they were ancient.
Comets should not exist in old galaxy since they get burnt up quickly - oort cloud was invented to try and explain where 'new' comets are coming from.
Too much helium in rocks - very light gas and if rock were ancient the helium would have escaped by now.

And plenty more - check out some of the links below for more info - don't take my word for it. Plenty of fairly technical articles there too.

Answer 5

The value of 4.5 billion years is derived from several lines of evidence. It cannot be measured directly.

The oldest rocks found are dated at 3.8-3.9 billion years old, containing minerals that have been dated at 4.1-4.2 billion years. These establish a minimum age of the earth.

The most direct means for calculating the Earth's age is a Pb/Pb isochron age, derived from samples of the Earth and meteorites. This involves measurement of three isotopes of lead (Pb-206, Pb-207, and either Pb-208 or Pb-204). A plot is constructed of Pb-206/Pb-204 versus Pb-207/Pb-204.

If the solar system formed from a common pool of matter, which was uniformly distributed in terms of Pb isotope ratios, then the initial plots for all objects from that pool of matter would fall on a single point.

Over time, the amounts of Pb-206 and Pb-207 will change in some samples, as these isotopes are decay end-products of uranium decay (U-238 decays to Pb-206, and U-235 decays to Pb-207). This causes the data points to separate from each other. The higher the uranium-to-lead ratio of a rock, the more the Pb-206/Pb-204 and Pb-207/Pb-204 values will change with time.

Answer 6

There are 2 ways to find the age of the Earth: carbon and radioactive dating. Also, the age of the Earth is 4.6 Billion years.

Answer 7

Carbon dating is not totally accurate and the other methods are based on hypotheticals....no telling how old the Earth is, but I doubt it is millions or even billions of years old.

Answer 8

the only one I learnt about was carbon dating