By Dr Anthony Lewis
Anthony is Chair of Windsor Humanists and Chair of the South Central England Humanists Network. In this article he explores humanity's relationship with the abundant and versatile chemical element known as silicon.
Silicon is one of the great unsung heroes of the modern era. It has quite literally driven both the Industrial Revolution and the ongoing Information Age Revolution. We are surrounded by silicon both indoors and outside. Twenty eight percent of the Earth's crust is made up of silicon by mass. Our modern societies could not function without it. It's used in all of our buildings and virtually all of our machines including car engines, and silicon-based materials play an essential role in construction and infrastructure. It's central to the operation of every electronic device including computers, mobile phones and watches. We now effectively live in The Great Age of Silicon. It's the foundation of our modern lives!
As a geoscientist, I've had a lifelong relationship with silicon in its many rock forms. But all humans have had an intimate relationship with silicon from earliest times some two million years ago when we first started to make stone tools. Since then, we've found an incredible array of different uses for it by exploiting its chemical, electrical and mechanical properties in increasingly sophisticated ways. According to the Royal Society of Chemists, silicon is one of the most useful elements to humanity (link below). So let’s celebrate and explore our enduring and symbiotic relationship with silicon.
The Book of Life and the Chemical Brothers
Carbon and silicon have similar chemical properties, as they both sit in the same family of elements in the periodic table. Both have four electrons in their outer electron shell and therefore both can form a dizzying array of comparable complex molecules. As a result, when organic matter is buried under the right conditions, the original carbon atoms can be replaced atom by atom with silica through the slow process of fossilisation. This process has left us an incredible natural fossil record of the evolution of life stored in the Earth’s sedimentary rock strata. This wonderful natural legacy, a ‘book of life’, is literally embedded in the rocks all around us, and it has enabled geoscientists to work out the whole history of life on Earth. All it needed was a hammer, a magnifying glass or a microscope, and a geologist, together with some evidence-based thinking, to work out how life on earth had evolved. We all owe a great debt of gratitude to the fact that silicon and carbon are such close chemical brothers. Otherwise, we might not have worked out the theory of evolution two hundred years or so ago, until perhaps we had discovered DNA and genomics.
Between a rock and a hard place
In its natural state as stone, silica (a compound composed of mainly silicon and oxygen) is hard wearing, durable and resistant to most of the Earth’s weather conditions. Early humans used rocks composed mainly of silica to create the first stone tools such as axes, clubs and rudimentary cutting implements using obsidian and flint. Throughout the history of constructing dwellings, silicon in the form of sand, gravel, and stone such as granite has been integral in our buildings. Silicates are used today in pottery, enamels and ceramics. At every meal, we eat off crockery composed mostly of silicates.
Tough as cement
The Romans invented cement, but its use ceased almost completely when the Roman Empire collapsed. The Pantheon in Rome, completed in its current form around 126 CE during the reign of the Emperor Hadrian, still stands today as a testament to the durability of cement. Sand rich in silica and clay minerals (hydrous aluminium phyllosilicates), together with calcium carbonates, are key ingredients for making modern cement. We now know that the Romans unwittingly used a type of cement that ‘cures’ with age, becoming tougher as it is exposed to the elements. Engineers now exploit the complex chemical interaction of silica with carbonates to manufacture different cements with different mechanical properties for a wide variety of different uses. Our high-rise cityscapes are monuments to the toughness and physical properties of these advanced cement formulations. Cement is the foundation of our modern urban landscapes.
Hard and slippy
Silicons ability to bond with most other elements has also been exploited to create complex hard-wearing silicon-based alloys such as aluminium-silicon and ferro-silicon. Most of the raw silicon that humans mine is used to manufacture these silicone alloys which are used to make dynamo and transformer plates, engine blocks, cylinder heads and machine tools. They are also used to deoxidise steel in steel plants. Silicon carbides are used as important abrasives in many factory processes and are also used in lasers. However, the complex chemistry of silicon can be very slippery. When two methyl molecules (or other organic carbon molecules) are attached to silicon atoms, the properties of silicon are transformed into oils and rubbers to form complex silicon-oxygen chains or silicone polymers and siloxanes. The resultant silicon-based oils are used extensively as lubricants in machinery with moving parts and also in many cosmetics and hair conditioners. In addition, different formulations create silicone rubber which is widely used as a waterproof sealant in every modern building. It's used as a sealant around every window and you may have used it in your bathroom, or your swimming pool if you have one. Every car and aeroplane depends on the toughness and durability of silicon alloys to function at the required high temperatures and torque speeds inside the core of every engine. They also depend on the lubricant properties of silicone oils and rubber to operate efficiently.
Through the looking glass
Sand composed of nearly pure silica is mined and used to manufacture glass of various qualities. It has been used extensively to manufacture windows since the advent of the rudimentary stained glass used during the Middle Ages in Europe. Glass has been a major driver of the scientific revolution, owing to its optical properties and being chemically inert. No scientific laboratory could function without glass in the form of glassware such as the ubiquitous test tube. Most measuring devices such as telescopes, microscopes, electron microscopes, and lasers use high-quality glass lenses. Italian astronomer, physicist, and mathematician Galileo perfected the telescope within months of its invention, in 1609, by the Dutch-German spectacle-maker Hans Lippershey. Galileo used it to look up at the night sky and what he observed changed the world. Microscopes allowed us to observe cells and the fine structures of the natural world which were, until then, hidden to our naked eyes. Spectacles allowed those of us with failing eyesight to see clearly again. In his early studies of optics, the English scientist Sir Isaac Newton used glass lenses to split light into its rainbow colours . It's fair to say that most of the transformative measurements that have advanced science since the 17th and 18th centuries have relied on glass technology. Silicon has literally enabled us to see the universe and connect with the reality around us.
Solid states of humanity
As if all of that were not enough, silicon is now driving the Information Age Revolution which, in some ways, should really be called the Silicon Revolution. Hyper-pure processed silicon is used extensively as a semiconductor in every solid-state device and across the microelectronics industries. It is selectively doped with tiny amounts of boron, gallium, phosphorus or arsenic to control its electrical properties for specific purposes. Every electronic device around us is driven by the complex electrochemical properties of silicon. Some electronic devices consist of single crystals of super-pure silica which has been ‘grown’ for specific purposes. As we head towards an electric future based on cleaner energies without fossil fuels, it is very likely that the importance of silicon to our lives will only increase further.
The Age of Silicon
It is remarkable how one of the most abundant elements around us has been exploited in ever more sophisticated ways to transform our lives through innovation, science, engineering and technology. As pointed out by Marian Tupy and Gale Pooley and in their book Superabundance: The Story of Population Growth, Innovation, and Human Flourishing on an Infinitely Bountiful Planet (2022), the same silicon resources were available to our Stone Age ancestors. The difference in the quality of our modern lives is due to the cumulative increase in our knowledge about how to exploit the natural resource around us, including the element silicon, in progressively inventive ways. The Royal Society of Chemistry points out that we have only just started out on our journey of exploiting the elements of the periodic table. Silicon is just one example of the impact material sciences will have on the future of humanity. Hopefully, you will now agree that we really do live in the Age of Silicon.
Royal Society of Chemists Interactive Elements Chart - https://www.rsc.org/periodic-table/
Superabundance by Gale Puly and Marian Tupy 2022 - https://www.superabundance.com