A dazzling display of colorful fireworks can always delight a crowd and put everyone in attendance in good spirits. The shrieking boom of a cannon delivers the opposite reaction. That is the paradox of gunpowder, the invention that is responsible for both of these powerful and spectacular activities.
Discovery and Spread
Gunpowder
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
Chinese Fire Arrow (Credit: Wikimedia Commons)
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
Several Types of Gear Designs
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.
Wheels appear everywhere in today’s world. It is impossible to imagine civilization as we know it without them. The idea seems quite simple and given the number of wheels we see in the world today, almost obvious. However, wheels are a rather recent actor to appear on the worlds stage. Whereas many ideas’ stem from things found in nature, there are no wheels in the natural world. Evolution by natural selection would never select for it. The Earth’s natural landscape rigid and rough, not paved and flat.
The idea of the wheel developed in ancient Mesopotamia, which in time proved highly effective and rolled on throughout the Old World. There is no evidence of the wheel being used in the America’s prior to European contact despite the highly advanced civilizations of the Mayans, Aztecs, and Incas.
Stone Carving of a Chariot
The Wheel’s Unexpected First Use
Illustration of a Foot-turned Potters Wheel
Most people think of the wheel as a component in a transportation device. Less people associate the wheel with pottery, its actual origination. The wheel was invented and first used by ancient Sumerian potters (the same Sumerians who invented writing) during the late Neolithic period at around 3500 BCE. This exact date of its original use is a little uncertain, as is with many things in ancient history. It’s possible the idea was hit upon centuries earlier, but since nobody was around keeping detailed records we can’t be absolutely sure when it was first invented. However by 3500 BCE it was certainly in use in that region of the world. The device was extremely practical and quickly spread through cultural diffusion, however the Chinese also came across the idea of the wheel around 2800 BCE.
As valuable to civilization as the wheel is, one might think that it was of the first invention of human civilization But this isn’t the case, as this simple invention occurred well into the Bronze age. By this time more complex technologies like metallurgy were already established as an increasingly sophisticated, 2000-year-old science. Even pottery as a craft had been around for tens of thousands of years. So this is where the story of the invention of the wheel begins, as an artifact assisting in making pottery. The potter’s wheel was not a wheel used for rolling or moving things. It laid horizontally on its side while pottery was spun on top of it. The potter’s wheel was typically made from solid wood or stone and attached to a fixed axle, allowing for smooth, slow and controlled rotation.
The potters wheel quickly found new uses and it adapted those used to the urgent needs of civilization. During the late Neolithic period human societies were increasingly settling into agricultural communities and the need for more effective methods of labor and transportation became apparent. After the invention of the potters wheel, it only took another few centuries of innovation before the next generation of people assembled two wheels, rotated 90 degrees and placed an axle through the center of each. This process did not happen overnight, as in one swift stroke of genius. It was a gradual process that began with a rolling log and culminated with a rudimentary wheel and axle device.
However by around 3400 BCE the wheel was likely being used for transportation, at least in one part of the world. The first depictions of a wheeled vehicle were found in 1974 during an excavation of a neolithic village near the present day village of Bronocice, Poland. Found in a pit among animal bones was an artifact that has come to be known as the bronocice pot. The bronocice pot is a ceramic vase showing what appears to be a wheeled vehicle. The discovery shows that wheeled wagons were in use in Central Europe by this time. They were likely drawn by aurochs, the wild ancestor of domestic cows, as auroch remains were found in the same area. Clay tablets found in around 3200 BCE in Urak – present day Iraq – also show depictions of wheeled vehicles.
A Drawing of the Wheeled Vehicle from the Bronocice PotThe Bronocice Pot Showing the First Known Depiction of a Wheeled Vehicle
Once the wheeled vehicle arrived on the scene, the innovations continued. It could be connected to carts and eventually larger transportation vehicles called chariots. The transformation of the potter’s wheel to a transportation device was now complete. The transformation from a solid wooden wheel to today’s rubber tire was just beginning.
The Evolution of the Wheel
The wheel has evolved substantially over its 5000 year history. It has become thinner and stronger, and has developed into different types. One of the first such evolution’s of the wheel was a plank wheel. The plank wheel is made from wooden planks rather than being one solid log of wood. As societies advanced the wheel continued to evolve to meet the needs and demands of society. Some wheels had parts of it that were able to be removed, making it lighter. The next major steps were hollowing out the center of the wheel and adding spokes radiating from the axle. The use of spokes reinforced the structure of the wheel and reduced its weight. It is believed to have originated in ancient Sumer around 2000 BCE. The spoked wheel eventually became used in chariots.
Additional features of the wheel continued to be modified or added to improve its performance. The concept of the rim, an outer edge of a wheel that holds it in place, dates back to ancient times as well. Rims provide structural support to make the wheels more durable. Early rims were made of wood or metal, and as metal-working become more sophisticated various other materials such as iron and steel were used. The wheel and axle also went through some changes. Originally the two were fixed, meaning that they rotated as a single unite. The design is simple but does not allow for much maneuverability. The fixed axles were modified into pivoting axles where the wheels can move independently of each other, increasing the vehicle’s maneuverability.
The biggest change in the evolution of the wheel came many thousands of years after its first use as a form of transportation, during the Industrial Revolution. The manufacture of wheels improved as cast iron, and later steel wheels greatly enhanced their performance, durability, and load capacity. This era also found many new uses, such as for trains or for components in factory machinery. The modern wheel of the 21st century continued to evolve as manufacturing techniques continue to improve and technology advances at a breakneck pace. Wheels were now mass produced for a variety of new vehicles such as cars and airplanes, and made from a variety of materials such as aluminum and rubber. The digital age has transformed wheeled vehicle technology and features such as traction control, anti-lock breaking systems, and advanced driver-assistance systems are becoming commonplace in vehicles. Currently, we are seeing the concept of “smart wheels” that incorporate electronic systems using sensors that monitor conditions such as tire pressure, tread wear, and temperature. New technologies like robotics are making wheeled robots a common sight in manufacturing plants and warehouses, and even in advanced space agencies such as NASA. As human civilization continues to push the limits of technology, the wheel will undoubtedly continue to be an integral part of that process.
Evolution of the Wheel (Credit: www.123rf.com)
The Power Behind the Wheel
There are two main reasons why wheels make moving loads easier than pushing or pulling loads.
Decreased friction – Only a small part of the wheel is in contact with the ground leading to increased efficiency and reduced wear and tear. Decreased friction also increases maneuverability making it easier to change directions. There are many methods to decrease the friction of the wheel such as optimizing the wheels design and materials used in construction, using lubricants, and minimizing the roughness of the surface that the wheel is being used on.
Increased leverage – Wheels elevate the load reducing the angle at which force is required to move the load. Additionally, the rim of the wheel turns more distance than the axle of the wheel. Turn the wheel at the rim and more force is applied to the axle. Turn the wheel at the axle to create more speed.
The Wheel’s Impact on Early Civilizations
The wheel has played a significant part in shaping history and had a variety of early uses and forms. The first use was for pottery making – the pottery wheel. Although the most important use was for transportation. For thousands of years people dragged heavy things on sledges. Wheels changed this, and subsequently altered our terrain. Wheels work best when they have a smooth surface to roll on. The Romans were the first to institute large scale road construction to connect their large empire. They constructed thousands of miles of straight roads, some of which are still in use today.
The agricultural process also benefited from wheels in the form of improved food production, transportation, and distribution. The invention of wheeled plowing and tilling revolutionized the preparation of soil for planting. Carts and wagons allowed farmers to transport crops, seeds, and other agricultural goods over long distances with ease. With transportation now easier than ever, farmers had access to larger markets and an expansion of trade markets. The significant boost the invention of the wheel gave to agricultural production allowed for larger food surpluses, thus increasing population in urban centers.
People continued to find new and innovative uses for the wheel. They harnessed the energy of water and wind in the form of the waterwheel and the wind turbine. They added teeth to the wheel and created gears, an essential component in many mechanical devices.
A Waterwheel at Babcock State Park in West Virginia (Credit: Jim Vallee)
For such a simple device, the evolution of the wheel keeps on spinning. Bicycles, trains, and automobiles all rely on the wheel for movement. But the wheel can be adapted for uses other than movement. Automobile engines depend on many wheels. One part of the engine is a crankshaft – a wheel with an off-center axle. This is spun to power the engine that spins the road tires. The wheel – found nowhere in nature – is certainly human’s greatest yet simplest innovative achievement.
The importance of metallurgy to human culture is so vital that scholars typically divide ancient time periods by metalworking ages such as the Stone Age, the Bronze Age, and the Iron Age. Metallurgy is the process of extracting metals from their ores and modifying them for human use. These early usages resulted in the production of hardened weapons and armor, tools, utensils, pottery and more. The role of metallurgy is even more important in the industrialized present-day. It has essential uses in machines, buildings, electronics, and in our transportation systems.
The Origination of Metallurgy
Early Metallurgy
Years before metals were valued for their usage they were valued for their natural beauty. In time it was found that metals could be molded into different forms to serve some practical use. The earliest evidence for smelting, the process of extracting an metal by heating an ore, was found in the Balkans and Western Asia around 7500 years ago. The first metals smelted were tin and lead, followed by copper.
Eventually metals were mixed together to create stronger alloys. Alloys are new metals containing greater strength and durability that are made of two more more metals. Combining tin with lead in the right proportions produced bronze which was significantly harder than copper. Exactly how this was discovered is unknown, but happened probably by accident or through trial and error. However it is certain that the intentional mining of tin to produce bronze was happening by around 2000 BCE.
Metallurgy technology provided significant advantages to the peoples who figured it out. Civilizations that mastered this technology obtained a competitive advantage over their neighbors, and created essential industries such as mining and blacksmithing.
The First Metals Used by Humans
There were seven metals used by ancient human civilizations. These were gold, silver, tin, lead, copper, iron, and mercury. Of those seven metals only gold is found in a natural state. There rest were mixed in with ore’s and had to be melted out, a process called smelting. The first metals to be smelted were lead and tin. A simple campfire was hot enough for this to work although neither metal was strong enough to provide much practical usage in buildings or weapons. The same is true for gold and silver which were used for adornment in jewelry and ornaments.
Metallurgy Timeline
Copper is stronger than both tin and lead, but it requires higher temperatures than an open fire to be smelted. The heat needed to be insulated by a kiln, which is basically like an oven. The earliest known discovery of copper smelting occurred around 5500 BCE in the Fertile Crescent. While copper is stronger than tin and lead it still was not very useful in making weapons and structures. Copper weapons were soft and dulled very quickly. Like gold and silvery it was first used for its aesthetic value but later used for pottery to make items such as pots, cups and trays.
Bronze Age Weapons and Tools (Credit: Wikimedia Commons)
After using copper for about a thousand years early civilizations discovered ways to improve the metal. They created bronze alloys. Bronze made by combining copper other materials, but it was typically arsenic or tin. Bronze alloys of arsenic were used first, followed by a stronger and more durable alloy of tin. The proportions of copper to tin varied but the most common proportion was 8-1, or about 87.5% copper to 12.5% tin. Bring stronger, bronze was quickly used in the creation or improvement of additional tools, weapons, currency, and building structures. It was the dominate metal used during 2300 BCE until 1200 BCE iron became widespread.
Iron was relatively rare until about 1200 BCE when large scale iron production began. The Hittites of Anatolia (present day Turkey) are recognized as being the first civilization to smelt iron, although like most things in ancient history this is debated. After they were conquered the technology quickly spread around the Mediterranean and Northern Africa then into India and Asia. Iron is significantly stronger than bronze however it requires a much higher temperature to melt and mold. Smelting iron therefore required specially designed furnaces to melt and cast the metal. Metallurgy in human culture did not stop with iron and the Iron Age, it was only the beginning.
Metallurgy Today
The improvement of metals for human benefit continues to this day. Steel combines iron with charcoal and is one of the most important material used in the modern worlds large building structures. Many new processes have been invented to cut, mill, grind, and join metals into stronger, lighter and more durable materials.
At some point in history there had to be one initial crucial step that separated humans from the other animals in our journey to becoming the dominant species on this planet. I will call that point the beginning of science and label it by humans ability to control fire. The ability to control fire was a turning point in human evolution.
The Benefits of Controlling Fire
Fire Power
Sometime in our ancestor’s very ancient past, and certainly by 400,000 years ago, fire came under human control. By this time the archeological record is full of heat altered artifacts. Control of fire in human evolution was beneficial for a variety of novel reasons. These benefits include:
Provided protection from predators and assisted in hunting prey.
Provided warmth which allowed people to live in cooler regions of the planet
Assisted in tool making
Ceremonial usages
Allowed people to see at night
Provided us with the ability to cook food
Provided groups with a “nest” – the campsite
Protection from predators and used in hunting prey
In the struggle for survival, fire was used both defensively and offensively. Fire can be used as a deterrent because it often scares away animals. Additionally, there is evidence that first accidental and then controlled fires were used to scorch large areas of land for food. During the blaze many animals inevitably perished in the inferno. Our early humans ancestors could then walk in and “fire harvest” many of the small animals and eggs for food. These large scale fires would also create chance cooking, a prequel of intentional cooking as it led to the food being more easily digestible. Fires would also cause larger animals to flee out into the open making them easier to kill.
Fire provides warmth
Humans are well adapted to living in warmer climates but are much less well adapted to living in colder regions. The obvious reason is that we have lost much of the hair on our body. Without fur we needed another way to stay warm. Staying close to a fire allows us to survive during cooler nights and in cooler regions during the winter season.
Homo Erectus Using Fire to Make Tools (Credit: Christian Jegou/Public Photo Diffusion/SPL)
Fire assists in tool-making
Fire allowed the forging of tools. The is evidence that Neanderthals used fire in shaping wood tools. Although wood from hundreds of thousands of years ago would not last to the present day it is likely that our ancestors would have done the same. Stone and bones last much longer than wood. There is evidence for deliberate heat altered stone and bone artifacts as far back as 1,000,000 years ago in caves across Africa. The artifacts would have been used for weapons such as a spear, or a digging stick for a food gatherer.
Fire in ceremonial usage
The raw power of fire would have been inspiring to our ancient ancestors. There is evidence that it was used in ceremonials services of sacrifices, offerings, or devotion. We still see candles displayed in many ceremonies today.
Night vision
Controlling fire allowed people to see at night. Being able to see at night adds to the time that people can be productive. It also meant people could travel much more safely at night.
Cooking food
Cooking food may have been a significant step in leading humans to the top of the food chain and even to increasing brain size, although hominid brain size was increasing before cooked food became common in early humans. In any case, what is indisputable is that cooking food killed the parasites that infested food, allowing for easier digestion. This enabled our human ancestors to make due with smaller teeth and shorter intestines. It is hypothesized that a smaller intestine was the factor in allowing for a larger, jumbo brain of sapiens and Neanderthals, since both the brain and the digestive tract are two are the largest energy consuming organ systems in the body. By shortening the digestive tract it enabled the energy economy of the body to devote more resources to a jumbo human brain.
The campsite
The campsite is also believed to have functioned as a “nest” for our ancestors and therefore played a pivotal role in the evolution of our sociability. All animals that exhibit sociability have a nest, which allow for a common place for the species to gather and stay at. Evidence of campsites exists from about 400,000 – 300,000 years ago in varying sizes and contexts.
Control of fire was a turning point in human evolution. The process happened gradually through increasing interaction with natural fires. Accidentally cooked meat provided a new sources of calories and protein that was easily digestible. A fortuitously shaped burnt stone in the shape of a sharp point would have been used for hunting or digging. Eventually our ancestors learned to control fire and made these things deliberately. We used the power of fire to forge the metals that made our tools and building structures. The benefits to our species of fire use cannot be overstated in the physical, social, and cultural realms.
Scientific discoveries often progress step by step with technological improvements. The invention of the telescope in 1608 by Dutch spectacle makers provided the tool need to transform astronomy. Word spread quickly of this new invention, and by April 1609 one could be purchased in eyeglass shops in Paris. Later that same year it spread into Italy, where word of it came to the Italian polymath Galileo Galilei. Galileo did not actually see a telescope, but based on its description he went ahead with the task of creating his own. He vastly improved the instrument allowing for some of the most revolutionary and groundbreaking discoveries in the history of science.
It didn’t take very long for Galileo to make his discoveries known. Published by Galileo in 1610, Sidereus Nuncius (or Starry Messenger) revealed to the world his observations as he viewed the night sky through his improved telescope. These new observations and discoveries changed how we viewed the composition of the universe and our place among the cosmos. Unfortunately for Galileo at the time, they came in direct contradiction with Aristotelian cosmology, Ptolemaic astronomy, and the most significantly the theological teachings of the Roman Catholic Church. The evidence presented in the book sided more with the Copernican System of the universe, placing the Sun at the center of the Solar System.
The Starry Messenger and its Findings
The Starry Messenger is a short book of about 60 pages written in Latin by Galileo, published on March 13, 1610. It is historically important not only for its shocking content, but it was the world’s first scientific publication derived from telescope observations. The book consists of an introduction, some observations made by Galileo through his telescope, and his conclusions based on those observations. Galileo also included dozens of supplementary drawings of his observations. Despite its brevity, the impact of the work was profound.
Let’s take a look at some of the profound observations and conclusions of the Starry Messenger:
Sketch of the Moon with its visible craters from Sidereus Nuncius.
Craters and Mountains on the Moon: Galileo’s observations showed mountain and valleys present on the moon. He could even estimate the height of the mountains based on the length of their shadows. These observations contradicted the accepted wisdom of Aristotle and the cosmology of Ptolemy that taught that the moon and other heavenly bodies were perfect spheres. It proved there could be other worlds similar to Earth.
The Discovery of Four of Jupiter’s Moons: Galileo noticed four points of light following and orbiting around Jupiter, which he deduced as moons. This further reinforced that the Earth is not the center of everything.
Many additional stars in the night sky: Galileo was able to observe hundreds of stars behind the stars visible by the naked eye. This showed unequivocally that the stars were not fixed, and that the universe was far larger than most people had previously imagined.
Galileo also made some other startling discoveries around this time that were not published in his book. These observations included:
Sunspots: Galileo observed many dark spots on the Sun that moved and changed in shape and size over time. He was able to see that the Sun itself was rotating. These were published later in a different work titled “Letters on Sunspots” in 1613.
The Phases of Venus: The order of phases and changes in diameter of Venus proved conclusively that Venus orbited the Sun. This proved that the Earth is not the center of the universe and that the Sun was also a center of motion. These were also published in his work “Letters on Sunspots” in 1613.
Questioning the Established Dogma with Empirical Evidence
The publication of this book began the process of upending the long-held ideas of Aristotelian cosmology and Ptolemaic astronomy by providing evidence for heliocentrism and the Copernican System. Clearly the Earth was not the center of the universe. Clearly the revered heavenly bodies were not perfect spheres. And clearly the universe was far larger than anyone had previously imagined. These discoveries quickly made Galileo famous across Europe. Indeed, Galileo sought out fame. He dedicated the four satellites orbiting Jupiter to Cosimo de Medici II, Grand Duke of Tuscany, naming them the “Medicean Stars” after Cosimo’s family name. But the fame coupled with his arrogant personality also also brought him enemies. It marked the beginning of his famous troubles with the Catholic Church as heliocentrism was at the time in direct conflict with Christian theology.
In 1616 Galileo was called before Cardinal Robert Bellarmine and warned to cease his teachings of heliocentrism. It was determined at this meeting that the Sun being placed at the center of the universe was heretical and that mobility of the Earth was in contrast to theology. For a time, Galileo stayed away from teaching and promoting the Copernican System. However, eight years later Galileo published a book defending the Copernican System titled A Dialogue on the Two Chief World Systems. This work further infuriated Church as it seemed to mock the Pope as a simpleton and in 1633 Galileo was brought before the Roman Inquisition to stand trial for his supposed heresies. Threatened with torture and ridicule, Galileo was ultimately forced to plead guilty and spent the rest of his life on house arrest at his villa near Florence. Only centuries later, in 1992, was Galileo finally vindicated by the Catholic Church when Pope John Paul II officially declared him innocent.
