How old are your rocks?
Several attempts to scientifically date the planet have occurred over the past 400 years. Scientists attempted to predict the age based on changing sea levels, the time it took for Earth or the sun to cool to present temperatures, and the salinity of the ocean. As science progressed, these methods were proven to be unreliable; for instance, the rise and fall of the ocean was shown to be an ever-changing process rather than a gradually declining one.
In an effort to calculate the age of the planet, scientists turned to the rocks that cover its surface. However, because plate tectonics constantly changes and revamps the crust, the first rocks have long since been recycled, melted down and reformed into new outcrops.
In the early 20th century, scientists refined the process of radiometric dating. Earlier research had shown that isotopes of some radioactive elements decay into other elements at rates that can be easily predicted. By examining the existing elements, scientists can calculate the initial quantity, and thus how long it took for the elements to decay, allowing them to determine the age of the rock.
A fist-size sample of the Acasta Gneisses, rocks in northwest Canada that are the oldest known rocks on Earth.
The oldest rocks on Earth found to date are the Acasta Gneisses in northwestern Canada near the Great Slave Lake, which are 4.03 billion years old. Rocks older than 3.5 billion years can be found on all continents. Greenland boasts the Isua Supracrustal rocks (3.7 to 3.8 billion years old), while rocks in Swaziland are 3.4 to 3.5 billion years. Samples in Western Australia run 3.4 to 3.6 billion years old.
Research groups in Australia found the oldest mineral grains on Earth. These tiny zirconium silicate crystals have ages that reach 4.3 billion years, making them the oldest materials found on Earth so far. Their source rocks have not yet been found.
The rocks and zircons set a lower limit on the age of Earth of 4.3 billion years, because the planet itself must be older than anything that lies on its surface.
Meet the neighbors
In an effort to further refine the age of Earth, scientists began to look outward. The material that formed the solar system was a cloud of dust and gas that surrounded the young sun. Gravitational interactions coalesced this material into the planets and moons at roughly the same time. By studying other bodies in the solar system, scientists are able to find out more about the early history of the planet.
The nearest body to Earth, the moon, does not suffer from the resurfacing problems that cover Earth's landscape. As such, rocks from early lunar history should be present on the moon. Samples returned from the Apollo and Luna missions revealed ages between 4.4 and 4.5 billion years, helping to constrain the age of Earth.
In addition to the large bodies of the solar system, scientists have also studied smaller rocky visitors to that fell to Earth. Meteorites spring from a variety of sources. Some are cast off from other planets after violent collisions, while others are leftover chunks from the early solar system that never grew large enough to form a cohesive body.
Although no rocks have been deliberately returned from Mars, samples exist in the form of meteorites that fell to Earth long ago, allowing scientists to make approximations about the age of rocks on the red planet. Some of these samples have been dated to 4.5 billion years old, supporting other calculations of the date of early planetary formation.
More than 70 meteorites have fallen to Earth to have their ages calculated by radiometric dating. The oldest of these have ages between 4.4 and 4.5 billion years.
Fifty thousand years ago, a rock hurled down from space to form Meteor Crater in Arizona. Shards of that asteroid have been collected from the crater rim and named for the nearby Canyon Diablo. In 1953, Clair Cameron Patterson measured ratios of lead isotopes in samples that put tight constraints on Earth's age.
The Canyon Diablo meteorite is important because it represents a class of meteorites with components that allow for more precise dating. Samples of the meteorite show a spread from 4.53 to 4.58 billion years. Scientists interpret this range as the time it took for the solar system to evolve, a gradual event that took place over approximately 50 million years.
By using not only the rocks on Earth but also information gathered about the system that surrounds it, scientists have been able to place the age of the Earth at approximately 4.54 billion years. For comparison, the Milky Way galaxy that contains the solar system is approximately 13.2 billion years old, while the universe itself has been dated to 13.8 billion years.
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How Old Is The Earth According To The Bible?
The Institute for Creation Research has always taught, as an integral part of its ministry, the concept of the young earth. We have never put an absolute date on the age of the earth. We feel that the Bible doesn't provide all the information necessary for certainty, as shown by the fact that almost every Bible scholar who has ever tried to discern the exact date has come to slightly different conclusions. Maybe all the information is there but we just don't understand it fully yet.
However, lest we be too concerned, every honest attempt to determine the date, starting with a deep commitment to the inerrancy of God's Word, has calculated a span of just a few thousand years, most likely close to 6000 years, since creation. The largest figure I've ever seen from a trustworthy scholar is approximately 15,000 years, but even this seems to stretch the Biblical data too far.
To calculate the date one must first employ the genealogical data given in Genesis, I & II Chronicles, the Gospels, and elsewhere. Information gleaned from Judges, I & II Kings, Daniel, Acts, and other books must be included as well. Since dates are fairly well established archaeologically beginning at about the time of David, these can be a big help. This is because so many Biblical events are referenced to the reigns of individual kings. Obviously, the job is difficult.
Of course the genealogies only begin with the creation of Adam, so the question of time before Adam remains. As has been well noted on these pages, the six days of Creation Week must be of the same length as our days. We recognize, however, that the Hebrew word yom, translated "day," can have a variety of meanings, including an indefinite period of time. Thus, some have suggested that these six days might then be equated with the billions of years claimed by geologists.
Whenever a word in Scripture can have a variety of meanings, we must go to the context to determine what it does mean and not be content with what it might mean. And when we do, we find that the first time yom is used, it is defined as a solar day (Genesis 1:3), and then a total day/night cycle (1:3).
Furthermore, yom is modified by "evening and morning," which in Hebrew can only mean a literal day. It is also modified by an ordinal number (first, second, etc.), a construction limited in Hebrew to that of a literal day. Elsewhere the six days of creation are equated with the six days of our work week (Exodus 20:11), a formula incorporated in the fourth of the Ten Commandments regarding the Sabbath rest. We should mention that the use of a numeral to modify "days," in this case "6," is again reserved for a literal day in Hebrew, as is the use of the plural word "days."
Suffice it to say that no one could conclude that Scripture specifically places Creation any longer ago than a few thousand years, and to my knowledge no one does. Many do hold to an older position, but not for Scriptural reasons. They are convinced by radioisotope dating, perhaps, or maybe the molecular clock of mutation rates, or some other line of thinking, but not from Scripture.
Scripture teaches a young earth, and the time has come for Christians to stop twisting Scripture to fit the evolutionary and uniformitarian speculations of some scientists about the unobserved past. We suggest it's time for such Christians to stop calling themselves "Bible-believing" Christians and start using some such name as "world-believing" Christians.
How Do We Know the Earth Is 4.6 Billion Years Old?
The Earth is very old. But how old, exactly? And how can we know with any degree of confidence? As Henry Reich describes in the video above, the process of scientifically estimating the age of the Earth revolves around, essentially, finding the oldest piece of the planet we can, then figuring out how old that piece is.
Finding super old rocks is conceptually straightforward, but practically difficult. The processes of plate tectonics mean that the Earth is constantly recycling its rock, breaking it down into magma in the interior before pumping it back up to the surface once more. But old rocks do exist, says Reich, and the oldest rock we know is a tiny piece of zircon found in western Australia.
The process of figuring out a rock’s age often falls to the scientific techniques of radiometric dating, the most famous of which is radiocarbon dating. This process focuses on the ratio between the number of carbon-14 and carbon-12 isotopes in any once-living being: that ratio indicates how long it’s been since that being was alive. But carbon is not the only element that can be dated—a whole host of others exist. In uranium-lead dating, for instance, the radioactive decay of uranium into lead proceeds at a reliable rate.
Based on the very old zircon rock from Australia we know that the Earth is at least 4.374 billion years old. But it could certainly be older. Scientists tend to agree that our little planet is around 4.54 billion years old—give or take a few hundred million.