Age of the earth

The Earth seen from the space

It is, at least for the moment, the only planet on which there is life. It is just the right distance from the sun so that there can be water in liquid form and a temperature comfortable enough for millions of plants and animals to grow. The earth.

How old are you? His journey to being what he is today has been very long and fraught with danger. Outer space is not a safe place. But, What is the age of the earth and how has it been calculated?

How old is the Earth?

Planet Earth seen from space

Although there is no exact number, our planet is known to be about 4.500 billion years old. Geologists and geophysicists have been able to calculate age by measuring the rate at which elements in the radioactive metal uranium decompose into lead. Also, using radiometric dating techniques, they have found out how old meteorites are, which is similar to that of the Earth and the Moon.

The oldest known mineral is zirconium from the Jack Hills area of ​​Western Australia. They are estimated to be 4.404 million years old. The oldest meteorites found in the solar system, that is, the calcium-aluminum-rich inclusions, are 4.567 million years old. This means that the Solar System began to form 4.567 million years ago.

One hypothesis states that the Earth began to form shortly after the meteorites did, but it is not yet possible to pinpoint its exact age.

First theories

Rock mountain

For a long time it was thought that the planet had been here forever, until naturalists began to understand the different changes that the planet had undergone by studying the layers of it. Nicolas Steno was one of the first to realize the connection between the fossil remains and the aforementioned strata. Around 1790, the British naturalist William Smith hypothesized that if two layers of rock at different sites contained similar fossil remains, it was highly likely that both layers came from the same time. Years later a nephew of his, John Phillips, calculated using these techniques that the age of the Earth would be about 96 million years.

The naturalist Mikhail Lomonosov thought that the Earth had formed independently of the rest of the universe, several hundred thousand years earlier. In 1779 the French naturalist Comte Du Buffon carried out an experiment: he created a reduced-size globe whose composition was similar to that of the planet and then measured its cooling rate. Thus, he estimated the age of the earth at about 75 thousand years.

However, It wasn't until 1830 that a geologist named Charles Lyell suggested that the planet is constantly changing. This, although today it is something natural and completely logical to us, at that time it was a very novel theory, since they thought that the planet was something static, that it only changed through natural catastrophes.

Calculations

The physicist of Glasgow William Thomson published in 1862 a series of calculations that estimated the age of our planet to be between 24 million and 400 million years. Lord Kelvin, who would later be called that, assumed that the Earth formed as a ball of molten rock, and calculated the time it took for the cooling process to reach the current average temperature (14 ° C). Despite everything, the geologists were not very convinced that this hypothesis was valid.

Charles Darwin, who studied Lyell's works, proposed his theory of natural selection, a process by which a series of changes in organisms and, of course, time were necessary for them to occur.. Therefore, he thought that 400 million years was insufficient.

In 1856 the German physicist Hermann von Helmholt and in 1892 the Canadian astronomer Simon Newcomb, presented their own calculations. The first was 22 million years old, and the second 18 million. Scientists had arrived at these figures by calculating the time it would have taken for the Sun to evolve to its current diameter and intensity from a nebula of gas and dust from which it formed.

The development of radiometric dating

Sediments and fossils

We can now get an idea of ​​how old rocks and minerals are thanks to radiometric dating, which is a procedure that Arthur Holmes developed at the beginning of the XNUMXth century and that is based on the proportions of an isotope called the father and of one or more descendants whose half-life is known.

Radiometric dating was first published in 1907 by Bertran Boltwood and today it is the main source of information about the age of rocks, or planet Earth itself. There are different methods of dating, which are:

  • Carbon 14 method: It is useful for dating in archeology, anthropology, climatology, oceanography, soil science, and recent geology.
  • Potassium-argon method: it is used in geology.
  • Rubidium-etrontium method: it is used in the dating of ancient terrestrial rocks as well as of lunar samples.
  • Thorium 230 methods: used in very old ocean sediment dating.
  • Lead methods: used in geology.

Thus, Holmes made measurements on rock samples and in 1911 concluded that the oldest was 1600 million years old.. But these calculations were not very reliable. Two years later, results were published showing that the elements had isotopes, which are various variants with different masses. In the 30s, isotopes were shown to have nuclei made up of different numbers of neutral particles or neutrons.

Holmes's work was ignored until the 1920s, when In 1921 at the annual meeting of the British Association for the Advancement of Science the members established that the age of the planet was a few billion years, and that the radiometric dating was credible. In 1927 he published his work »The Age of the Earth, an Introduction to Geological Ideas in which he estimated that it was between 1600 and 3000 million years old.

Around 1931 the National Reserach Council, of the National Academy of Science of the United States, appointed a committee to find out how old the Earth was. Holmes, being one of the few people who knew radiometric dating techniques, was invited to join the committee. The report they produced stated that radiometric dating was the only reliable method that could be used to determine the sequences of geologic times.

Finally, CC Patterson calculated the age of the Earth in 1956 using isotope dating of the uranium lead decay chain of meteorites.

Planet earth from space

Our planet still has many millions of years of life ahead of it. If in the end the theory that the Sun will "swallow" the Earth when it turns into a red giant, we can be almost certain that it will still orbit around the Sun for about 5 billion years.


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  1.   Anonymous said

    They are only assumptions, it is still clearly known if these information are correct. But they are the ones that are closest to reality.

  2.   Daniel Rincon said

    The most important conclusion was missing, and it is the calculation of the age of the earth according to the most recent study by CC Patterson in 1956 using isotopes of the uranium lead decay chain of meteorites.