Age of the Earth
| The poetry of reality|
|We must know. |
We will know.
|A view from the|
shoulders of giants.
“”…within a finite period of time past the Earth must have been, and within a finite period of time to come the Earth must again be, unfit for the habitation of man as at present constituted, unless operations have been, or are to be performed, which are impossible under the laws to which the known operations going on are subject.
The consensus view of scientists in relevant fields is that the age of the Earth and the solar system is roughly 4.54 billion (4.54 × 109 ± 1%) years , an age primarily derived by radiometric dating. Because of the molten state of the early Earth, erosion, and subduction of tectonic plates moving surface material into the Earth's mantle, radiometric dating of materials originating on Earth provides a range of lower limits for the age of the Earth of approximately 3.8 to 4.2 billion years.
Early scientific attempts at determining the age of the Earth
Sir Isaac Newton speculated that because "comets occasionally hit the Sun", perhaps the Earth formed from the scattered debris and as such began in a molten state and has been cooling ever since. Spurred by this suggestion, Georges Louis Leclerc (Comte de Buffon) conducted a series of experiments in which he measured how long it took for iron balls glowing red hot to cool to approximately room temperature. He then used a rough-and-ready technique to extrapolate the data, estimating that the Earth must be about (at least) 75,000 years old. (Newton pointed out that it must be older than 50,000 years.) A while later, Jean-Baptiste Fourier refined Buffon's investigation. Drawing from empirical measurements and observations, he formulated his own analytical theory of heat diffusion. Once again, he treated the young Earth as a molten sphere, but also took into account the insulating crust. In light of volcanic eruptions, this is natural after all. His formula yielded an age of (at least) 100 million years.
In the second half of the 19th century, William Thomson (Lord Kelvin) brought newly discovered laws of thermodynamics to bear. Hermann von Helmholtz hypothesized that the energy of the Sun comes from gradual gravitational collapse. Kelvin calculated that the Sun must be between 50 to 500 million years old and, reassuringly, obtained similar figures for the Earth. Such a time scale was consistent with discoveries in geology and evolutionary biology of the time. (For whatever reason, perhaps religious, Kelvin later reduced his estimated to 24 million years, which was widely criticized. But we shall not bother with that here.)
While these early attempts at determining how old Earth is seem rather quaint and inaccurate compared to more modern ones, they play a historically important role in science since people were then beginning to try to answer questions initially thought to be beyond the scope of science. Nuclear physics, which no one knew about at the time, was the missing ingredient in their calculations. In addition, even these primitive calculations conflict with Christian doctrine, something most were too afraid to question directly at the time.
Formation of the Solar System
The original formation of the Earth was a violent process that resulted in an early Earth that was in effect, constantly molten. Therefore, we do not and perhaps cannot know exactly how old the Earth is. However, scientists have determined that our Solar System was formed roughly 4.54 billion years ago. This age is based on radiometric evidence from meteorites found on Earth. Lunar rock, which is collected from a body that does not have a fluid mantle or crust and so has therefore remained constant, dates to 3.8 - 4.2 billion years. Other evidence includes meteorites that have landed on Earth, which date to a slightly older 4.5 - 4.6 billion years. Though not yet perfected, recently developed technology to study the sun, helioseismolgy, provides excellent independent verification of the age of the solar system 
Use of meteorites to date the Earth relies on assumptions required by various hypotheses of the formation of the Earth and other planets from the accretion disk created by the Jeans collapse of the material that formed our Sun. On its own, analysis of any particular meteorite may depend on the assumption of uniform rates of decay of radioactive isotopes, which creationists attack as unsound based on the necessary consequence of their dogmatic view that the Bible must trump science, and the uniform distribution of lead isotopes in the solar system. Taken together, analysis of various meteorites correlates ages of the early Solar System, and therefore the Earth, to a high degree of statistical significance.
A common creationist criticism of radiometric dating is that it provides inaccurate results. The claim is frequently due to attempts to analyze contaminated specimens or the use of methods inappropriate to the analysis of specific materials. The claim may also be due to a misunderstanding and inaccurate interpretation of scientific literature on the subject. When used properly, radiometric dating provides results that are known to be accurate from their close correspondence with other methods of dating the Earth and solar system.
Formation of the Earth
Due to the nature of our own Earth, and the fact that the mantle is fluid and the crust has in fact undergone many stages in its formation, it is nearly impossible to find rocks that were actually created when the Earth was formed. However, recently a few samples of lead, believed to be formed during the Archaean Eon (c. 4 - 2.5 billion years ago), have been dated to 4.40 billion years, fitting perfectly into a theory of formation at the same time as the rest of the Solar System, at 4.5 billion years.
Incorrect religious views
Simply because the concept of deep time is quite hard to wrap your head around, few cultures that existed prior to modern scientific scholarship have specifically posited an age of the Earth that expanded much beyond the longest time they could imagine – generally, thousands or perhaps tens of thousands of years.
Early Christian and modern Young Earth Creationist Views
There has always been a strand of Christianity that held idea that the Earth is only thousands of years old.
The two Genesis creation stories and the supposedly detailed listing of generations (also known as the "begats") reinforce the idea that the Earth must have been created within the last 10,000 years or so. Similarly, Talmudic commentaries over the last 2000 years place Creation at roughly 7,000 years, give or take many thousands of years.
In the 17th century era of a new "rational" approach to the world, Christians, both theologians and scientists, attempted to define the Day of Creation more precisely. Isaac Newton, using the Bible as a template, worked out the year of creation of the Earth to be 4000 BC, Johannes Kepler, 3992 BC, and Bede at 3952 BC.
The most famous date for the Day of Creation is the one proposed by James Ussher who determined that he could figure out the date of creation by compiling a chronology of all the events in the Bible, together with Persian & Chaldean histories for the inter-testamental period. Working back from a presumed date of Jesus' birth of 0 AD/BC Ussher arrived at a date of Creation of exactly Sunday, October 23, 4000 BC. Learning that there was a miscalculation in the Gregorian calendar, and that Christ's birth is roughly 3 years off, he amended his date to Sunday, October 23, 4004 BC.
It is not at all surprising that all these dates spin near or around the 4000 BCE mark, as they are based on a popular Christian idea around the 17th century that the Earth only had a 6000 year life span.
Though most of modern Christianity has now set aside the clearly unscientific notion of "a few thousand years," there persists a group of Christians called "Young Earth Creationists" who set the date of Creation as some time within the last 10,000 years. They originally followed Ussher's dates; however, indisputable archaeological evidence of civilizations older than 6,000 years, generally pushes "YEC" types to say "up to 10,000 years."
Islam, as per the Quran, says that the Earth was created in 6 days by Allah. However it should be noted here that the word yaom which is literally translated as "days" has different spans of time, as in time is not of a fixed length but that it stretches and compresses as Allah wills. This is evident when in one verse a "day" is equated to "fifty thousand years" while in another verse a "day" is "one thousand years". This directly corresponds with the use of the Hebrew word "yom" in the Judeo-Christian Tanakh, where "yom" is said to be on par with a thousand years.  Many people wrongly assume that Islam's teaching of creation is entirely unlike that of the Bible's. In truth, as a result of the Quran's basis being the Bible, the two are thoroughly comparable. As such, many Muslims believe the Earth to be 6,000 years old. Other Muslims, however, take the view that Islam does not specify how long it has been since the creation of the Earth, as a result of the ambiguity of the word "yaom". 
The Zoroastrian religion is one of the few religions that provides a specific age in which the Universe and the Earth were made. The life of the Universe is 4 units of 3,000 years each, for a total of 12,000 years. The universe as we know it ("all of Creation" is the term, so we will assume the Earth is part of Creation) was made after 3000 years of perfect balance. Thus making the age of the Earth somewhere between 6000-9000 years, depending on when it fell in the Age of Creation.
On the other hand, according to Hinduism the Earth is much older. Hinduism states that the Earth came into being with the god Brahma, and after doing some calculations with units of time found in Hinduism we come up with an age of 155.5 trillion years.
Dick Teresi in his book, Lost Discoveries: The Ancient Roots of Modern Science, reviews the Vedas and writes that "Twenty-four centuries before Isaac Newton, the Hindu Rig-Veda asserted that gravitation held the universe together, though the Hindu hypothesis was far less rigorous than Newton's. The Sanskrit-speaking Aryans subscribed to the idea of a spherical earth in an era when the Greeks believed in a flat one. The Indians of the 5th century CE calculated the age of the Earth as 4.3 billion years; scientists in 19th century England were convinced it was 100 million years." However, unlike the English scientists who based their estimates of Earth's age on observations and their (limited) knowledge of the ability of energy sources to last for billions of years, the Hindu ideas were based on religious cosmology. Likewise, the Greeks changed their cosmology as regards the shape of the Earth due to observations made by Eratosthenes.
Science researchers, such as Carl Sagan and Fritjof Capra have stated similarities between the latest scientific information of the age of the Universe, and the Hindu concept of a "day and night of Brahma", which is much like the current known age of the Universe than other creation views. Sagan describes as:-
“”The Hindu religion is the only one of the world's great faiths dedicated to the idea that the Cosmos itself undergoes an immense, indeed an infinite, number of deaths and rebirths. It is the only religion in which time scales correspond to those of modern scientific cosmology. Its cycles run from our ordinary day and night to a day and night of Brahma, 8.64 billion years long, longer than the age of the Earth or the Sun and about half the time since the Big Bang.
- 101 evidences for a young age of the Earth and the universe
- Evidence against a recent creation
- Old Earth creationism
- A paper on helioseismology
- More helioseismology
- 100 Reasons the Earth is Old Age of Rocks by Jonathan Baker
- as quoted in Lewis C. Heat and Thermodynamics: A Historical Perspective. Westport, CT: Greenwood Press; 2007.
- Gribbin J. Science, a history, 1543-2001. London: Allen Lane; 2002.
- Lewis C. Heat and Thermodynamics: A Historical Perspective. Wesport, CT: Greenwood Press; 2007.
- Helioseismology, or the study of acoustic waves and their propagation in the sun, gives a more general date of 4.0 - 5.5 billion years. While not as precise as those provided by radiometric dating, these dates provide independent confirmation that radiometric dating is not providing wildly inaccurate dates.
- See, Radiometric dating.
- Zircons found in the Jack Hills area of Australia have returned an age of 4.4 billion, interpreted through crystallization. These same samples seem also to suggest that there was water on the Earth as early as 4.4 billion years ago. See the Wikipedia article on Oldest dated rocks.
- Meaning, if you follow, we were all supposed to be dead just back in the year 2000 CE.
- The "Era of Zoroaster", S. H. Taqizadeh, The Journal of the Royal Asiatic Society of Great Britain and Ireland, No. 1 (Apr., 1947), pp. 33-40.
- Bhakti Yoga Meditation — Hinduism: Age of the Earth according to Vedic chronology
- Sagan, Carl (1985). Cosmos. Ballantine Books. ISBN 978-0-345-33135-9. p. 258.
- Capra, Fritjof (1991). Tao of Physics. Shambhala. ISBN 978-0-87773-594-6. p. 198
- Sagan, Carl (1985). Cosmos. Ballantine Books. ISBN 978-0-345-33135-9. p. 258.