Replies

4.567 billion years (years based on the current present rotation rate) this of course was far different in the past.

http://en.wikipedia.org/wiki/Age_of_the_Earth

Based on extensive and detailed scientific evidence, geologists have determined the age of the Earth to be around 4.567 billion years (4.567×109 years). This age represents a compromise between the oldest-known terrestrial minerals – small crystals of zircon from the Jack Hills of Western Australia – and astronomers' and planetologists' determinations of the age of the solar system based in part on radiometric age dating of meteorite material and lunar samples.

The radiometric age dating evidence from the zircons further confirms that the Earth is at least 4.404 billion years old. Comparing the mass and luminosity of the Sun to the multitudes of other stars, it appears that the solar system cannot be much older than those rocks. Ca-Al-rich inclusions (inclusions rich in calcium and aluminium) – the oldest known solid constituents within meteorites which are formed within the solar system – are 4.567 billion years old, giving an age for the solar system and an upper limit for the age of the Earth. It is assumed that the accretion of the Earth began soon after the formation of the Ca-Al-rich inclusions and the meteorites. Since the accretion time of the Earth is not exactly known yet, and the predictions from different accretion models vary between several millions up to about 100 million years, the exact age of the Earth is difficult to define.

In the centuries preceding the scientific revolution, the age of the Earth was determined from the accounts of creation by religious authority. Today some religious groups continue to accept only theological accounts regarding the age of the earth, rejecting scientific evidence which contradicts their beliefs.

However no matter how much evidence or theory is presented, for some, it is "turtles all the way down".
To each his own.

"A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the Earth orbits around the sun and how the sun, in turn, orbits around the centre of a vast collection of stars called our galaxy.
"At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise."
"The scientist gave a superior smile before replying, "What is the tortoise standing on?"
"You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down."

Radiocarbon Assumptions and Problems

Like other radiometric methods, radiocarbon dating faces technical problems and operates under some questionable assumptions.

Perhaps the most critical assumption of radiocarbon dating is that the rates of carbon-14 production and decay are in a state of balance or equilibrium, and have been so for millions of years. If this were true, the carbon-12/carbon-14 ratio in living organisms will be the same as the ratio in an organism that lived thousands of years ago. However, we have reason to think that this is not true, as we will see in a later section.
Radiocarbon dating assumes a constant decay rate for the breakdown of carbon-14. At present, we have no firm evidence for any systematic change in this rate.
Contamination by groundwater, soil, or foreign matter is always a potential problem. However, people working with radiocarbon dating feel confident that good sample collection can overcome this problem.
Some organisms may exclude the heavier carbon-14 isotopes preferentially, making them look too old (e.g., living shellfish that have a radiocarbon “age” of several hundred years). Comparison of carbon-12 and carbon-14 with the stable isotope carbon-13 is supposed to correct this problem (see Aitken, 1990, pp. 62-64). Environmental factors, such as forest fires and volcanic eruptions, which increase the local concentrations of carbon dioxide, may also have an effect on the carbon-14/carbon-12 ratio.
Looming over all these assumptions is the idea that cross-checking with other archaeological information will confirm whether the radiocarbon date is “reasonable.” This introduces the specter of subjectivity.