August 9, 2017 - Missing the Forest for the Tree: A Worldview Grounded in Science

Discovery and Spread

Gunpowder was discovered in China around the year 900 during the Tang Dynasty. As with so many civilizations of the time, alchemy was a thriving occupation. The Chinese alchemists were working on an elixir of life when they stumbled upon the formula for an elixir of death. They called their formula fire medicine and soon found a variety of uses for the explosive material such as in fireworks and in military weaponry.

A powerful military technology could not stay isolated for long, but it did take the knowledge of gunpowder around 350 years to spread to the Middle East. Soon after arriving in the Middle East it quickly made its way into Europe by 1300, now nearly 400 years after its invention. William of Rubruck is likely responsible for bringing gunpowder back to Europe after his encounters with the Mongols, although there is little direct evidence for this. The earliest European reference to gunpowder is found in Roger Bacon’s great work Opus Majus (Opus Majus literally means Great Work in Latin) in 1267.

Its impact in warfare was substantial and almost immediately felt on the battlefield through infantry weapons, having a devastating effect on the knightly class. Although this was a setback for the nobility they still had their walled castles. Even those castles would soon succumb to the power of gunpowder.

Impact on Warfare

Fire arrows were the initial military weapon for gunpowder. A small pouch of gunpowder was attached the arrow resulting in open fires upon impact. Other incendiary devices such as bombs and fire lances were soon widely deployed. Many proto-gun and proto-cannon designs were experimented with in the 12th and 13th century. During the later part of the 13th century, the Mongols were using a hand cannon, something we can definitively call a firearm. It took until the 1320s for guns to catch on in Europe as a form of weaponry but they soon rapidly spread across the continent. Within twenty years larger artillery weapons were arriving on the battlefield. The strategies of warfare were on the verge of being revised.

Artillery weapons powered by gunpowder, initially unreliable but once perfected, made once impenetrable walled castles vulnerable. Sieging a castle in the Middle Ages was a long and arduous process. Techniques involved tunneling under walls, ramming down walls, starving out the inhabitants, all of which could take weeks or even months. However with the invention of cannons firing their devastating projectiles from a safe distance, a castle could be taken within a single day.

No other example illustrates the power of cannons than the fall of the city of Constantinople to the Ottoman Turks in 1453. Certainly the city’s downfall was the result of many factors – a weakened Byzantine state and Western Europe’s reluctance to provide assistance to name a few. But one undeniable factor was the effective Ottoman use of cannons.

A Cannon Used by the Ottoman Turks to Pummel the Walls of Constantinople
(Credit: Wikimedia Commons)

The walls of Constantinople were considered to be impenetrable. Five meters thick and 20 meters high, they stretched over four miles long from the Golden Horn to the Sea of Marmara. Much of it was double walled with some area’s having up to five walls deep. These walls had held off dozens of sieges for over 1,000 years. The Ottomans employed around 60 cannons which battered and weakened the walls for the duration of the siege. The final assault by the Ottoman’s was focused on the section of the wall most damaged by cannon fire and was eventually breached by the invading Turks.

The Chemistry of Gunpowder

Gunpowder consists of a mixture of saltpeter (potassium nitrate), charcoal, and sulfur. Early on this proportion was experimented with until a 75% saltpeter, 15% charcoal, 5% sulfur solution was determined to be most effective. The sulfur and charcoal act as the fuel, with saltpeter acting as an additional oxidizer creating a stable chemical reaction with the rapidly expanding gases resulting in the propelling motion. This was the only known chemical explosive until the middle of the 19th century. Since that time gunpowder has been replaced by other means in military weaponry but it is still used in fireworks today.

Antikythera Mechanism, National Archaeological Museum, Athens
(Credit: Wikimedia Commons)

One valuable technology in assisting people do to work was the invention of gears. Gears consist of a system of cogs that takes energy from an input source, such as flowing water, and convert it to an output source, such as a pump. The oldest archeological evidence for gears dates to about 230 BCE in China, however evidence of geared technology prior to that time is referenced from ancient Imperial Chinese manuscripts.

A Brief History of the Invention of Gears

Reconstruction of the Antikythera Mechanism
(Credit: Wikimedia Commons)

The invention of gears are a natural extension from the invention of the wheel. They appear to have been invented in China but it was the Greeks who demonstrated their widespread use. Archimedes is believed to have used gears in his constructions and in the 4th century BCE Aristotle provided one of the earliest descriptions of gear-like devices. By 100 BCE they were being used across much of Greek civilization.

The discovery of the Antikythera mechanism, dubbed the worlds first analogue computer, is one of the earliest examples of a complex mechanism using a combination of gears. This device was discovered in 1901 from a shipwreck off the coast of the Greek island Antikythera. The instrument was used to predict astronomical positions. It is a complex, hand-wound device consisting of 30 bronze gears. Like a clock, it had a circular face with several hands that displaced times of celestial objects such as the Sun, Moon, and known planets. Winding the device forward or backward would move the hands at various speeds thought the interconnecting gear train. Not all of the pieces have been fully recovered so the precise mechanisms and exact purpose of the device is not fully understood, but it does unequivocally show that gears were being used in complex devices by 100 BCE.

A Remarkable Level of Flexibility Leads to a Remarkable Level of Functionality

There are many ways to design and combine gears making them extremely versatile. The various different types of gears can be broadly classified by the orientation of their axes. There are other characteristic differences such as gear tooth design and gear shape.

The first category is parallel axes. Spur gears and helical gears have parallel axes. This design is easy to manufacture and produces efficient power and motion transmission. The next category is intersecting axes. Gears such as plain bevel and spiral bevel have intersecting axes. These also have high transmission efficiencies. A final category that is non-parallel and non-intersecting such as worm gears. These typically have lower motion and power efficiencies than the prior two categories. Each type provides a unique set of advantages and disadvantages. Some operate more smoothly and quietly while others provide strength and durability where needed. Ease of manufacturing, which is related to costs, also varies across the different types of gears.

Putting Gears to Use

The earliest gears had a few broad applications. They were used in large machinery such as water mills and irrigation systems where they were needed to transmit considerable power. Water mills were increasingly used from the time of the Romans all the way through the Middle Ages of Europe. A secondary application of gears were also used in small, precise devices usual focused on astronomy and the calendar.

Some gears were constructed of wood and others constructed with various types of metals. The material used depended on its use. As the centuries passed gears continued to find uses in new inventions. The first clocks incorporated very precise systems of gears. During the Industrial Revolution a multitude of machines would not be able to operate with out properly working gears.

Gears feature predominately in today’s world, especially in transportation. One modern transportation invention using gears was the bicycle, whose modern form was developed in 1885. The bicycle caused a bicycle craze in the late 19th century and many people became wealthy manufacturing bicycles. The Wright Brothers constructed their gliders and the first airplane, The Wright Flyer, from the bicycle factory they owned in Ohio. After the widespread use and adoption of the bicycle gears became used in a newer type of transportation, the automobile. The automobile uses a system of gearboxes in the transmission system to transmit power from the engine to the wheels. Today gears are used in nearly all transportation systems including railroads and airplanes, as well as other common appliances and industries such as pumps, power plants, energy systems, lifts, and elevators.

Continue reading more about the exciting history of science!

900: Gunpowder