2 billion? 3 billion? Exactly how old is the Earth? A lot of us never really knew about the age of the Earth. Hundreds of years of efforts made by scientists informed us about the age of the planet. Let us know more about how old is the Earth.
Rocks on the Earth’s surface were dated, including the rocks found in Earth’s neighboring planets or the moon, in order to determine Earth’s age. So, what is the age of Earth? Scientists estimated Earth’s age as 4.54 billion years old.
This age may represent Earth’s core formation. Soon after the formation of the calcium-aluminum-rich inclusions, the process of Earth’s core formation began.
We now know the age of the planet, but we are not aware of when exactly was Earth formed?
How Old is the Earth
Planet earth is the third planet from the sun and the only planet to host life. The curiosity and research of the scientists truly told us a lot about our home planet. The 4.5 billion years old planet earth is home to many beings.
In order to determine Earth’s age, scientists made many calculations based on the changing sea levels the aging of the rocks found on planet earth. As the technology advanced, it became difficult to find out how old is the Earth since there were many changes made.
The studies of strata may have given the reason thought for the naturalists that Earth has gone many changes over the years.
The efforts to find the age of Earth go back many centuries. Aristotle believed that the Earth was infinitely old. At the same time, the scholars of ancient India believed the Earth to be around 1.97 years old. Before science made developments, scholars and philosophers used mere observations to tell the age of the planet.
Lord Kelvin, in the year 1862, estimated the Earth to be 20 million – 400 million years old. How old is the Earth? He concluded this based on his calculation of how long did it take for planet earth to cool down after it began as a molten mass.
Even though the conclusion made by Lord Kelvin was wrong, his method of calculation based on observations was perfect.
Scientists then turned to find the age of Earth by finding the age of the rocks found on Earth’s surface. The revamping of the crust was caused due to plate tectonics; the oldest rocks have been recycled and reformed into new outcrops.
It is back-breaking to find the oldest piece of rocks since most of them have gone under erosion and have been recycled. Zircon crystal in Western Australia has recently been dated 4.4 billion years old by scientists. They are dated by uranium-lead techniques.
After a geological survey, it was revealed that zircon could survive the geologic processes of erosion, metamorphism, and transport. They are mainly found in the Jack Hills of Western Australia.
Prof. John Valley confirmed by his study that zircon is the oldest rock fragment on the surface of Earth. Progress was made, and Radiometric dating was developed.
After the development of radiometric dating, scientists looked deeper into the age of meteorites. With the process of radiometric dating of the material found in a meteorite, Earth’s age was determined by the scientists and is said to be the same age as the radiometric age of the oldest known terrestrial and lunar samples.
Considering that the planet earth and meteorites originate from the same system where the isotopic composition of lead changes owing to the constant process of decay of the radioactive element uranium, the best age of planet Earth can be calculated. This is how the scientists tried finding how old is the Earth.
Radiometric dating is a process to calculate the age of geologic materials by measuring the existence of short-life radioactive elements and long-life radioactive elements. All types of radioactive decay are also measured.
Radiometric dating was studied by many scientists but eventually given up on it since there was not a very prominent response to it. But, a scientist named Arthur Holmes continued to work on it. His efforts finally paid off when radiometric dating was considered credible.
The unstable isotopes decay into isotopes of other elements. Radiometric dating is feasible only because of this decay. The time that the rock takes for the radioactive material from one element to another is ‘half-life.’ There are some isotopes that have short half-lives. Hence, they were used to find how old is the Earth.
For example, U-235 is the unstable isotope of uranium which, after steps of decaying, breaks down to Pb-207, a stable form of lead. The scientists are well aware of the age of some rock samples. For instance, it is known that Potassium-40, which decays and breaks down to Argon-40, has a half-life of 1.3 billion years.
If the initial ratio of these elements is known, then it is easier to find out the age of the rock sample. Therefore, if a rock is found to have equal parts of Potassium-40 and Argon-40, it is said to have hardened 1.3 billion years ago.
These dated ages do tell us that the Earth is approximately 4.5 billion years in age but does not really tell us about the age of its formation. Ages of more than 70 meteorites were measured using the dating techniques.
History of Radiometric dating
Carried out since 1905, radiometric dating was invented by Ernest Rutherford and his colleagues. As advancements were made in science, there were additional discoveries in the field of radioactivity.
These advancements made the measurements more refined. This was the first step in finding how old is the Earth.
Arthur Holmes, in the year 1921, manifested that radiometric dating was a credible method and could be used to find the age of rocks.
With this, he further suggested that Earth was a few billion years old. Since then, radiometric dating has proved to be a prepotent way of finding not only the age of rocks but also the age of Earth.
After Rutherford, Robert Strutt started working on his helium method but later gave up. Arthur Holmes, Strutt’s student, then took over the research and put in a lot of effort. He stressed lead dating because he considered the helium method unfavorable.
After working on many rock samples, in 1911, he concluded that the oldest sample was about 1.6 billion years old. But, this measurement was inauspicious because he considered that there was the presence of only uranium in the samples and not lead.
Later, research showed the existence of elements in various different forms. This made Holmes work on his techniques. In 1921, his hard work paid off, and radiometric dating was considered reliable. It was concluded by Arthur Holmes’ report that radioactive dating was to be considered as the only reliable means to measure the geological time scales.
Modern technique of Radioactive Dating
Since the 1960s, geologists have been using radioactive dating to find the age of rocks. These different techniques used by them have made a close agreement with the age of the material, which makes it a reliable way to measure the age.
A variety of materials have been dated using about forty such techniques and have proved to be estimated closely with the actual age.
Use of meteorites for measuring how old is the Earth
Using the method of uranium-lead dating on several meteorites, that includes the Canyon Diablo meteorite, Clair Cameron Patterson determined the present age of Earth. The age of Earth is determined from the Canyon Diablo meteorite for multiple important reasons and is based upon cosmochemistry.
The Canyon Diablo meteorite is important because it has components that can be used to calculate age more prominently. After this study, geologists started studying other meteorites as well.
It has been observed that the rocks found on planets surrounding the Earth rarely disintegrate, unlike the rocks found on Earth. This enabled the geologists to find the age of not only the Earth but also the universe.
The Milky Way galaxy is aged about 13.2 billion years old, while the universe has been aged about 13.8 billion years old.
In order to find out how old is the Earth, scientists tried to give it an outward view. As you know, our planetary system is called the Milky Way Galaxy.
Our solar system consists of the sun, the 7 planets, dwarf planets, a lot of moons, and a plethora of comets, asteroids, and meteorites. The solar system is said to be formed when a large cloud of gas and dust collapses and forms a super nebula.
How was the solar system formed? To give a lower limit to the age of the solar system, the calcium-aluminum-rich inclusions, which are the oldest known constituents of meteorites, are aged 4.56 billion years.
Therefore, it is estimated that the Solar system formed 4.5 billion years back.
Age of Rocks
It has been 4.54 billion years since Earth formed. According to the data provided, we know that Earth’s crust goes under various geological processes. Therefore, it was always difficult to figure out rock’s age.
Acasta Gneisses in northwestern Canada are one of the oldest rocks found on Earth’s surface that are aged 4.03 years old.
The issue of Great Unconformity is also a huge battle for scientists. Great Unconformity is which where the sedimentary layers of rocks have been found missing over the years. For example, according to research done by the University of Arizona, there are 1.2 billion years old of rock missing on the Grand Canyon.
However, a study suggests that the global ice age caused the glaciers to crush the rock and gradually disintegrate, which then was thrown to the interiors of the Earth by plate tectonics.
To determine the age of the Earth, the determination of the age of rocks was very important. The rocks returned from the Moon have an estimated age of 4.51 billion years. Meteorites from Mars that may have landed on Earth have also been dated around 4.5 billion years old. Again, a step towards finding how old is the Earth.
Earth’s neighbors, such as the Moon, do not experience the geological process of resurfacing. Hence, there is the presence of old moon rocks. The rock samples returned from the Apollo missions revealed that there are rocks aged between 4.4 billion and 4.5 billion years old.
The moon rock from Apollo missions had a piece from Earth submerged in it. Other studies say that after an asteroid struck the surface of Earth, the snippets of the surface landed on the neighboring bodies in space. This helped the scientists figure out the age of Earth. So we understood how old is the Earth.
The oldest rocks and meteorites were studied to determine the age of Earth by scientists. Rocks from other bodies in space were also studied. These rocky visitors from space may have come due to humungous collisions. Other leftover pieces of the early solar system never coalesced to form one solid body.
The universe is almost 14 billion years old. The movements of galaxies were studied in order to find the age of the universe as a hundred million years younger than what was estimated by the Planck Collaboration. This was another step towards determining how old is the Earth.
By studying the age of the universe, it was also discovered that the universe was actually expanding very fast. The constant is known to us as the Hubble constant. This helped us understand more about how old is the Earth.
The rocks either brought back to Earth during the course of human exploration on Moon or cast off and landed Earth in the form of meteorites are Moon rocks.
With the help of radiometric dating, it was found that these rocks are dated in the range between 3.16 billion years to 4.44 billion years. The basaltic eruptions are said to have occurred 1.2 billion years ago. So, how old is the Earth?
The estimated ages were almost accurate because the Moon’s surface does not go under tectonic plates or rather does not have the atmosphere to cloak it. This is the reason the oldest rocks found there can still be dated. This is how we found out about how old is the Earth.
Many experiments, research reports, and calculations were made to find the age of Earth. A plethora of complications was faced too, yet, a consistent age was dated by the scientists/geologists. Thus, to conclude, Earth is dated 4.54 billion years old. We finally got the answer to our question – “How old is the Earth?”