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Lord Kelvin and the Age of the Earth

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William Thomson, 1st Baron Kelvin. Image: Smithsonian Libraries, via Wikimedia Commons. This image is in the public domain in the United States because its copyright has expired.

Today is the 189th anniversary of the birth of William Thomson, better known as Lord Kelvin. I don’t usually make a big deal about 189th birthdays, but I’ve been thinking a lot about Lord Kelvin recently. Yesterday I came across this quote of his on Pat Ballew’s blog, which reminded me that it’s his birthday: “When you measure what you are speaking about and express it in numbers, you know something about it, but when you cannot express it in numbers your knowledge about it is of a meagre and unsatisfactory kind.”

Kelvin is probably most famous for his contributions to thermodynamics, including the temperature scale that bears his name. My recent interest in Kelvin is due to his attempts to use thermodynamics to figure out how old our planet is. Earlier this year, I helped compile a Scientific American Classics issue called Determining the Age of the Earth. Classics issues are collections of articles from the Scientific American archives on one topic. In this case, I found several 19th- and early 20th-century articles about the advances in geology and physics that eventually led to our current understanding that the Earth is about 4.5 billion years old.

As chemist and author Paul Braterman (who, full disclosure, taught me chemistry for a semester in 1999 and is my Facebook friend) wrote in the introduction to Determining the Age of the Earth, “It is a drama consisting of a prologue and three acts, complex characters, and no clear heroes or villains. We, of course, know the final outcome, but we should not let that influence our appreciation of the story as it unfolds. Even less should we let that knowledge influence our judgment of the players, acting as they did in their own time, constrained by the concepts and data then available.”

One of the “three acts” Braterman refers to is Kelvin’s attack on the idea held by some 19th century geologists that the earth had been around forever. Primarily basing his estimates on heat transfer within the earth itself and from the sun to the earth, Kelvin believed that the earth was between 20 and 100 million years old. His estimates were only as good as the mathematical models he used to make them, and unfortunately these models were not aware of plate tectonics, the nuclear fusion that creates the heat of the sun, or radioactivity. Mario Livio includes Kelvin’s determination of the age of the earth as one of the greatest mistakes in the history of science in his recent book Brilliant Blunders.

Mathematician Gil Kalai discussed Kelvin’s mistakes in May on his blog Combinatorics and more, going deeper into the exact ways in which Kelvin’s calculations failed to yield correct results. After detailing the shortcomings of Kelvin’s work in the area, Kalai wrote, “It is rather impressive that this genius of physics was opposed by a bunch of geologists (high boots, shorts, field hammers, limited perspective) and that the latter turned out right, but it is also true that Kelvin showed two important points: The first is that the age of the earth is NOT INFINITE as many thought in the 19th century, and the second is that the age of the earth is calculable from physical principles. At that time, several geologists claimed that ‘physics cannot be applied to geology,’ and in this they were wrong! We owe him much for teaching us these two points.”

I thoroughly enjoyed working on the Determining the Age of the Earth issue. It is riveting to read about scientific progress as it unfolds, especially when Ernest Rutherford himself is writing about it! The two other Classics issues I’ve put together are also fascinating reads.

The Quest for the Periodic Table, as the title implies, chronicles the development of the periodic table as a way of organizing and understanding the properties of the chemical elements. Not only is it fascinating to see how many different ways Mendeleev was spelled in the late nineteenth century (I counted five), I love the way the periodic table almost sneaks up among the discoveries of new elements. The first mention is a mere paragraph from 1876 that notes that the newly discovered element gallium may fill a gap in “the system of known elements” recently proposed by “Mendeleef.”

Polio: Pushed to the Brink contains several articles from the 1950s about the study of polio and eventual development of the enormously successful polio vaccines. As we get closer to global polio eradication, it is fascinating to read about the early days of the struggle against the disease. The highlight of the issue is probably the 1955 article by Jonas Salk himself about the killed-virus vaccine he developed.

Along with Determining the Age of the Earth, these issues are available as pdf downloads for about $10 from Scientific American. I usually try to link to free stuff on this blog, but I’m rather proud of these compilations, and if you’re interested in the history of science, I think they are worthwhile additions to your library.

Evelyn Lamb About the Author: Evelyn Lamb is a postdoc at the University of Utah. She writes about mathematics and other cool stuff. Follow on Twitter @evelynjlamb.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Mendrys 2:25 pm 06/26/2013

    “It is rather impressive that this genius of physics was opposed by a bunch of geologists (high boots, shorts, field hammers, limited perspective) and that the latter turned out right…” If he was attacking the idea that Earth had been around forever then the latter was certainly not right. In my mind 100 million years is much closer to 4.5 billion years than to infinity.

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  2. 2. M Tucker 2:30 pm 06/26/2013

    No the Earth is not infinitely old but those who suggested an unknowable age for the Earth were fighting against religious dogma claiming a very young Earth. As field work began to influence their interpretations of the Earth it became clear that 6000 years was not enough time to allow for the geologic formations observed. This led Hutton to believe that the age of the Earth was incalculable, so very old that its age could not be determined. I do not believe anyone actually said the Earth “had been around forever” or was infinitely old. Hutton influenced Charles Lyell and he in turn influenced Charles Darwin. Darwin also needed Earth to be very old to allow for the development of life as we see it today.

    So when Lord Kelvin calculated Earth to be between 20 and 100 million years old that was just not long enough. Lord Kelvin was attacked by the geologists who held with the very old Earth proposed by Hutton/Lyell and he was attacked by Thomas Huxley, Darwin’s bulldog. It was because Kelvin was held in such high esteem. He was the “Einstein” of his age and 100 million years was just not old enough. Kelvin should have realized that he might not have enough information to make a reliable calculation but instead he continued to use his authority to promote his version of the young Earth. Kelvin new nothing of the geologic formations or of biology that influence his attackers. Kelvin behaved like an ass on this.

    “It is rather impressive that this genius of physics was opposed by a bunch of geologists (high boots, shorts, field hammers, limited perspective) and that the latter turned out right…”

    Let’s see:
    Bunch of geologists – yes but not ALL geologists, there were other competing theories.

    High boots – check
    Shorts – seriously? In the 19th century? Maybe knee pants and stocking for Hutton in the 18th.
    Field hammers – check
    Limited perspective – well those who agreed with Hutton/Lyell had a perspective of time so deep it could not be calculated. BUT it was older than 20 million years, older than 100 million years, older than 400 million years. They knew that much! So they knew that Kelvin had made a mistake. Kelvin could not recognize any of that. Kelvin in the end favored 20 million – that reeks of a very limited perspective.

    “it is also true that Kelvin showed two important points: The first is that the age of the earth is NOT INFINITE as many thought in the 19th century, and the second is that the age of the earth is calculable from physical principles.”

    I doubt you can find a quote from a geologist who argued against Kelvin who actually said the Earth was infinitely old. I doubt you can find a quote from Huxley saying that. Yes the age of the Earth can be calculated from physical principles but Kelvin did not know the first thing of what those principles were. Plate tectonics is not required. Kelvin did have some incorrect physical principles and calculations but in the end his knowledge proved to be of a “meagre and unsatisfactory kind.”

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  3. 3. S. N. Tiwary 2:59 pm 06/26/2013

    Lord Kelvin is famous for his Kelvin temperature and the measurement of the age of the planet earth.
    S. N. Tiwary

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  4. 4. Mendrys 8:24 pm 06/26/2013

    Thanks for the clarification Hutton and Lyell were certainly not in the camp of geologists who believed that the earth had been around forever. The article makes it appear that it was him against those who believed that the age of the Earth was infinite.

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  5. 5. David Marjanović 10:10 am 06/27/2013

    Lyell famously wrote “no vestige of a beginning, no prospect of an end”. You seem to have confused “no vestige of a beginning” with “a vestige of no beginning”.

    Sure, Lyell clearly thought the Earth was so old he couldn’t put a number to it; but that’s quite different from believing it had no beginning at all.

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  6. 6. M Tucker 1:23 pm 06/27/2013

    Kelvin was a relentless pompous ass on the subject of the age of the Earth and of the Sun. He was heavily influenced by religion. He was not willing to admit that there were some obvious limitations to his knowledge. He believed in the existence of things without any proof or data. Even after Rutherford suggested in 1903 that the age of the Earth might be incorrect, Kelvin maintained it did not matter because the age of the Sun could not be more than 20 million years. He based this on the gravitational collapse theory for the heating of the Sun. You see Kelvin did not like Darwin’s theory and his motive was to show that life developed on Earth in a very short period of time, around 20 million years. He believed in a type of theistic evolution where God could make life develop in a short period of time. His most vigorous detractors were the defenders of Darwin’s theory, Tyndall and Huxley, not some unspecified group of geologists.

    This post suggests that Kelvin taught us two important things: that the age of the Earth should not have been considered infinite and that it could be calculated if the correct physical principles were known and Kelvin is the one who taught us that.

    I maintain that you would be hard-pressed to find an influential group of geologists in the 19th century who actually said the age of the Earth was infinite. It was NOT a widely held belief among geologists. Further, neither Darwin nor Huxley nor Tyndall said the age of the Earth was infinite.

    As for Kelvin being the one to suggest that physical principles could be used to determine the age of the Earth…total poppycock. He was just one among many who attempted to determine the age based on some physical principle or experiment. I’m sure Kelvin was aware of the Count de Buffon’s experiments done about 100 years earlier. What physical principle did Edmund Halley use in the 18th century? No, Kelvin was not the first with the using physical principles idea, not by a long shot. But it was Kelvin’s standing in the scientific community of his day and his tremendous contribution to thermodynamics that brings attention to his erroneous calculation. Kelvin’s predecessors in determining the age of the Earth from physical principles are largely forgotten, unless you enjoy history, but Kelvin was just as incorrect as they were. He was influenced in his scientific beliefs by his religious beliefs and he used his standing and authority in the scientific community to promote erroneous theories unsupported by experimental evidence.

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