Ibn Sina wasn’t the only Persian polymath who dabbled with rocks and fossils.

(Cover Image Credit: all-Biruni (left), FAL1.3, Ibn Sina (right), By Adam Jones CC BY-SA 2.0.)

Hundreds of years ago, two of the top scientists in the world bickered back and forth over a series of letters.¹

At stake was a set of questions about how the world and the universe worked. Specifically, they wondered about how the “heavens” functioned, where did the heat that warmed the world ultimately come from (the sun or somewhere else?), and how was the world itself made?

The two had passionate but conflicting viewpoints. Their arguments were heated and often personal.

They debated as two archrivals, but they may have been student and teacher.²

One point of contention was the history of the Earth. Was it created whole and complete, or had it changed over time? 

The first scientist asserted that the Earth was dynamic.

He cited evidence of vast seaways long gone and the marine shells they left behind. He observed the massive rocky mountains, thrust high overhead, that contained evidence of past shorelines and rivers that had long since dried up. The Earth, he explained, had to change, and likely did so slowly and gradually through vast expanses of time.

The second scientist questioned this claim. The written consensus of the day was certain; the world had been created as is and was unchanged. How could the first scientist, given his status as one of the top theologists of his time, argue against religious texts that asserted the Earth was created in its current state?

The two cited a mix of geological and theological evidence to make their points until they came upon a mutually agreeable compromise, that the Earth was created by a higher power who allowed it to change steadily through time.²

The first of these scientists is already familiar to you: Ibn Sina. The second was his rival, and possible teacher, Abu Rayhan al-Biruni (or al-Biruni). 

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The letters between Ibn Sina and al-Biruni are very modern. They sound like two tenured professors squabbling in a journal. They even get personal. 

Ibn Sina, exasperated by al-Biruni’s continued questions, wrote: “I have tried hard to refute this theory but I am amazed at the reasons offered by the ‘man of logic.’”¹  

Ibn Sina suggested, with a hint of snark, that al-Biruni would have been more persuasive if he used “gentler language for [his] purposes.”¹

Ibn Sina debated against the existence of a vacuum, that the sun was not a source of heat, and that the “heavens” should not have the same gravity as what we experience on Earth (less the bodies in the sky fall to the ground). 

Al-Biruni questioned him on all of these counts noting evidence that suggested otherwise (and accusing Ibn Sina of relying too much on ancient Greek philosophers instead of his own scientific evidence).¹

Al-Biruni asked Ibn Sina why ice floats on water and why a clay jar with water breaks when it freezes (due to the expansion of water when it solidifies).

Ibn Sina’s answer was that Al-Biruni was just mistaken. The jar did not break outwards but inwards as the water solidified. Ice floats on water because it traps air bubbles that make it buoyant. Surely the “man of logic” had missed these details. After all, if water expanded when it froze, Aristotle would have written about it!¹

Al-Biruni wrote back with more clear evidence. The jar had expanded and cracked, not imploded. There were no observable air bubbles in the ice. He then told Ibn Sina to “illustrate [his] points better rather than just write about them.”¹

The arguments between Ibn Sina and al-Biruni are important because they show that Ibn Sina was not a lone ranger in a location bereft of science. Instead he was a part of a much larger scientific movement in the Islamic world. Some authors have termed this the “Islamic Golden Age.”²

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The Islamic Golden Age and Geosciences

Following the Islamic conquests of much of the territory of the Byzantine Empire, countless Greek scientific and philosophical texts were captured and transplanted to centers of power in modern day Syria, Iraq, and Iran. The collection of these texts led to an explosion of scientific advancement in the Islamic world that would go unmatched until the Scientific Revolution in Europe hundreds of years later.²

The Islamic interest in geoscience was spurred by this proliferation of Greek work and renewed interest in understanding the natural world.

Both Ibn Sina and al-Biruni cite Greek philosophers in their points and counterpoints. However they both accuse the other of using less than trustworthy sources.

Al-Biruni specifically calls out Aristotle. He noted that many of the ancient Greek philosopher’s claims were not backed up by a more modern understanding of science. He then suggested that Ibn Sina’s judgment was clouded by his overreliance on the Greek thinker.¹

Al-Biruni’s criticism illustrates how heavily Ibn Sina relied on the transplanted Greek works to build his ideas. I already mentioned how much a fervent fan of Aristotle Ibn Sina was, but he read many other Greek writers. He was clear that his ideas on paleontology and geology came from these ancient Greek sources.

Ibn Sina’s interest in, and avid study of, geoscience was matched by his former teacher.

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Al-Biruni, Geology, and Paleontology

Al-Biruni was an accomplished scientist in his own right.

He has been credited with many discoveries in physics, astronomy, and geography. He determined and carried out a novel way to measure the Earth’s radius.³ He theorized that, in the ocean between Europe and Asia, there existed a massive landmass, foretelling the discovery of the Americas by several hundred years.⁴ Al-Biruni is considered by some to be the first anthropologist as he studied the customs and religions of India.⁵

Importantly for this blog, al-Biruni was a geoscientist.

He may have been the first person to suggest a standard ordering of geologic time with different eras that followed one another. In this way, he identified the concepts of stratigraphy, which I wrote about at length in my last post.⁶

Al-Biruni correctly concluded that gravity and density drive the accumulation of sediment in water. We know know that density-driven settling of sand, silt, and clay is one of the primary processes of sedimentation

He surmised changes in the rock record were caused by shifts in the Earth’s gravity that led to large-scale changes in the position of the seas.⁷ While his reason was incorrect, he had correctly identified past sea level change from geologic evidence.

“With the passing of time, the sea becomes dry land, and the dry land the sea, but if such changes took place on Earth before the appearance of man, we are not aware of them.”

Al-Biruni⁷

Al-Biruni may have been the first geoscientist to identify that the Arabian peninsula was once undersea. He made this conclusion based on his discovery of “stones which if broken apart, would be found to contain shells, cowry-shells and fish ears [sic].”⁷

He reasoned that the modern arid landscapes of the peninsula were once a broad shallow marine sea.⁷ His conclusion mirrors those made in other parts of the world by Shen Kuo, who was nearly contemporary with al-Biruni, and ancient Green writers, who likely inspired al-Biruni in the way they had Ibn Sina.

So, if al-Biruni made these surprisingly modern geologic discoveries, why did I choose to write a series on Ibn Sina instead of al-Biruni?

I think it could be fun to argue who deserves the credit for being the “best” geologist of their day. Both men were intelligent and derived several important conclusions about how the world works, even if they vehemently disagreed with one another.

However, while al-Biruni made these observations, he did not build them up into geologic laws and principles in the same way that Ibn Sina did.

Al-Biruni observed that steady, uniform processes resulted in the geologic record, and even suggested a way to subdivide the record into geologic time. However, he never codified these processes into a theory of how the world was formed in the same way Ibn Sina had.

Ibn Sina concluded that the rock record holds key information about how the world itself was formed and how it changed through time. To me, this shows that extra level of geologic understanding, which is why Ibn Sina, and not al-Biruni, made it to my “Founding Five.”

That is not to say al-Biruni does not deserve credit for what he did, or recognition for his contributions to geology. Instead both Ibn Sina and al-Biruni prove that the Islamic world has made significant contributions to Earth sciences for almost a thousand years.

It is important that we acknowledge this fact when we talk about the history of geoscience and especially when we teach it to the next generation of geoscientists.

Ibn Sina and al-Biruni demonstrate how we have erased the contributions of non-western scientists from the history books. Even though both men wrote about geology in a modern language (Arabic), we still largely are unaware of their contributions. If we are going to make geology and paleontology more diverse, we can start by acknowledging the diverse history of geologists and paleontologists.

They may not have done science in the same way we do today, but they nonetheless deserve credit for what they did.

References

1. Berjak, R. 2005. Ibn-Sina – Al Biruni Correspondence: A series of correspondence containing questions from Abu Rayhan Muhammad b. Amad al-Biruni to Abu ‘Ali al-Husayn b. ‘Abd Allah ibn Sina. Centre for Islam & Science. Link
2. Starr, F. 2015. Lost Enlightenment: Central Asia’s Golden Age from the Arab Conquest to Tamerlane. Princeton University Press
3. Pingree, D. 2010. Biruni, Abu Aayan. vi. History and Chronology. http://www.iranicaonline.org. Link.
4. Starr, S. F. 2013. So, who did discover America? History Today. Link.
5. Ahmed, A. S. 1984. Al-Beruni: the first anthropologist. Rain, 60: 9-10.
6. Sparavigna, A.C. 2013. The science of al-Biruni. https://arxiv.org/ftp/arxiv/papers/1312/1312.7288.pdf
7. Ahaman, S. M. 2003. Geodesy, geology and mineralogy, geography and cartography. History of Civilizations of Central Asia, 4(2).