Most scientists accept the Earth to be approximately 4.5-4.6 billion years old. Evidence for this age comes from * Radiometric dating of rocks in Greenland, Australia, and the Great Lakes region of North America, * Radiometric dating of zircon crystals in Australian rocks, * Dating of moon rocks and meteorites, and * Measurements of lead isotopes, leading to the "model lead age." For more a more detailed treatment of the Earth's age, please see these websites: http://www2.nature.nps.gov/geology/usgsnps/gtime/ageofearth.pdf http://www.talkorigins.org/faqs/faq-age-of-earth.html http://en.wikipedia.org/wiki/Age_of_the_Earth

Honestly, my belief on it, probably about 6,000-10,000 years old.

If we knew that then we could date everything exactly.

i don't know, but i guss it should be very old(kidding)

Here is a bit from wiki, it should be helpful.   Modern geologists and geophysicists consider the age of the Earth to be around 4.54 billion years (4.54 × 10^9 years). This age has been determined by radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunar samples. Following the scientific revolution and the development of radiometric age dating, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old. The oldest such minerals analysed to date – small crystals of zircon from the Jack Hills of Western Australia – are 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 that 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 Earth. It is hypothesised that the accretion of Earth began soon after the formation of the Ca-Al-rich inclusions and the meteorites. Because the exact accretion time of Earth is not yet known, and the predictions from different accretion models range from a few millions up to about 100 million years, the exact age of Earth is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages. The Acasta Gneiss of Northern Canada may be the oldest known exposed crustal rock. http://en.wikipedia.org/wiki/Age_of_the_Earth

Nobody knows for sure. Other factors can affect the production rate of 14C in the atmosphere. The earth has a magnetic field around it which helps protect us from harmful radiation from outer space. This magnetic field is decaying (getting weaker). The stronger the field is around the earth, the fewer the number of cosmic rays that are able to reach the atmosphere. This would result in a smaller production of 14C in the atmosphere in earth’s past. The cause for the long term variation of the C-14 level is not known. The variation is certainly partially the result of a change in the cosmic ray production rate of radiocarbon. The cosmic-ray flux, and hence the production rate of C-14, is a function not only of the solar activity but also of the magnetic dipole moment of the Earth.4 Though complex, this history of the earth’s magnetic field agrees with Barnes’ basic hypothesis, that the field has always freely decayed.... The field has always been losing energy despite its variations, so it cannot be more than 10,000 years old.5 Earth’s magnetic field is fading. Today it is about 10 percent weaker than it was when German mathematician Carl Friedrich Gauss started keeping tabs on it in 1845, scientists say.6 If the production rate of 14C in the atmosphere was less in the past, dates given using the carbon-14 method would incorrectly assume that more 14C had decayed out of a specimen than what has actually occurred. This would result in giving older dates than the true age. 4.M. Stuiver and H. Suess, On the relationship between radiocarbon dates and true sample ages, Radiocarbon, Vol. 8, 1966, 535. Back 5. R. Humphreys, The mystery of earth’s magnetic field, ICR Impact, Feb 1, 1989. www.icr.org/article/292. Back 6. J. Roach, National Geographic News, September 9, 2004. Back

Not as old as John McCain....