THE SCIENTIFIC REVOLUTION:

The Birth of Modern Science

UNIT SUMMARY:

After the Middle Ages, the Renaissance began in Europe and led to great changes in thinking that resulted in spectacular advancements in art, science, engineering, exploration, and government. This period is considered to be the beginning of modern times and forever altered the way we look at the world.

The Scientific Revolution was part of the new thinking the Renaissance brought about. While men like Leonardo da Vinci and Michelangelo focused on ideas and art and Martin Luther attempted to change the Catholic Church, others were more focused on understanding the physical world around us. Like Copernicus before them, men such as Kepler, Galileo, Newton, Bacon, and Descartes created methods of study and new understandings that changed the way we would look at our world and the universe forever.

During this unit you will focus on four different aspects of the Scientific Revolution and use the information you gather to help prepare for the unit assessment at the end. Our focus will include:

• Major ideas and changes that led to the Scientific Revolution, including: religious influence, the Renaissance, humanism, and more.

• The breakthrough theories of Scientific Revolution thinkers that changed our view of nature and their importance.

• New inventions that were created during the Scientific Revolution and what their purpose was.

• The scientific method and how we still use it today.

The Scientific Revolution

How did the Scientific Revolution change the way people understood the world?

Introduction

Between 1500 and 1700, modern science emerged as a new way of gaining knowledge about the world. This major shift in thinking became known as the Scientific Revolution. Before this time, Europeans relied on two main sources for their understanding of nature. One was the Bible and religious teachings. The other was the work of classical thinkers, especially the philosopher Aristotle.

During the Scientific Revolution, scientists challenged traditional teachings about nature by asking fresh questions and answering them in new ways. Inventions like the telescope exposed a universe no one had imagined before, while careful observation revealed errors in accepted ideas about the physical world.

A good example is Aristotle's description of falling objects. Aristotle had said that heavier objects fall to the ground faster than lighter ones. Although this idea seemed logical, the Italian scientist Galileo Galilei (gal-uh-LEE-oh gal-uh-LAY) questioned it.

According to his first biographer, Galileo performed a demonstration in the city of Pisa, where he was teaching. He dropped two balls of different weights from the city's Leaning Tower. The results shocked the crowd of students and professors since they expected the heavier ball to land first. Instead, the two balls landed at the same time.

Galileo's demonstration is an application of the scientific method. As you will learn, the scientific method uses both logic and observation to help people understand the natural world.

In this lesson, you will learn about the origins of the Scientific Revolution and how it changed the way people understood the world. You will meet some of the key scientists of the period and find out about their major discoveries and inventions.

Roots of the Scientific Revolution

Humans have asked questions about nature since ancient times. What was different about the Scientific Revolution of the 16th, 17th, and 18th centuries? What factors helped it arise?

During the Middle Ages, two major sources guided most Europeans' thinking about the natural world. The first was the Bible because, for Christians, the Bible was the word of God. Therefore, whatever the Bible seemed to say about nature must be true.

The second source was the teachings of Aristotle, a Greek philosopher who had written about logic in the 300s B.C.E. In the late Middle Ages, philosophers like Thomas Aquinas combined Aristotle's thinking with Christian faith by arguing that reason, or logical thought, could be used to support Christian beliefs. He held that the existence of God, for example, could be proven by reason.

During the Renaissance, many thinkers began to question the conclusions of earlier thinkers. For example, Renaissance scholars rediscovered the cultures of ancient Greece and Rome. Arab, Christian, and Jewish scholars in the Muslim world translated many classical works and made advances of their own in such fields as medicine, astronomy, and mathematics.

From the works of these scholars, Europeans learned about a greater variety of ideas. Many European philosophers were influenced by Greek rationalism, which was the belief that reason, or logical thought, could be used to discover basic truths about the world. Renaissance thinkers also observed nature directly. The Renaissance physician Vesalius dissected corpses to test ancient ideas about the body. Trust in reason and observation became a key part of modern science.

Additionally, the Age of Exploration helped inspire the growth of science. For instance, in the 2nd century C.E., Ptolemy had stated that there were only three continents: Europe, Africa, and Asia. However, explorers who visited the Americas proved him wrong. Such discoveries encouraged Europeans to question existing knowledge.

Gradually, scientists developed a new method for probing nature's mysteries. Their work led to many dramatic discoveries.

Famous Figures of the Scientific Revolution

Copernicus and Kepler: A New View of the Universe

The Scientific Revolution began with the work of the Polish astronomer Nicolaus Copernicus. His work led to a new view of the universe.

For nearly two thousand years, most people considered Earth the center of the universe. According to this geocentric theory, the sun, stars, and planets - everything believed to be the universe - traveled around a motionless Earth. Aristotle had taught this theory. The Bible also seemed to support it since, in one Bible story, God stops the sun from moving across the sky. Additionally, the geocentric theory seemed to make obvious sense because the sun and stars do appear to travel around Earth.

Aristotle had also taught that all heavenly bodies move in circles. Unfortunately, this belief made it difficult to explain the observed movements of planets, such as Mars and Jupiter. In the 2nd century C.E., Ptolemy created a complicated theory to account for this.

Both ancient and medieval writers, including Muslim scientists, found problems with Ptolemy's theory. In the early 1500s, Copernicus tackled these issues when he used observations and mathematics to propose a very different idea. According to his heliocentric theory, Earth and the other planets travel in orbits around the sun, which is at the center of this solar system. Earth also turns on its own axis every 24 hours, explaining why heavenly objects seem to move around Earth.

Like Ptolemy, Copernicus had trouble predicting the movement of planets with perfect accuracy, but he still believed his theory was simpler and more satisfying than Ptolemy's. In 1543, he described his idea in a published book. However, the book convinced very few people and was even attacked by some Church officials and scientists.

Then, in the early 1600s, German scientist Johannes Kepler expanded on Copernicus's theory. After studying detailed observations, Kepler realized that the orbits of the planets were ovals, not circles. With this insight, he wrote precise mathematical laws describing the planets' movements around the sun.

Kepler's laws coincided beautifully with actual observations, proving that the Copernican theory was correct. Once the theory was accepted, people would never again hold the same view of Earth's place in the universe.

Galileo and the Copernican Theory

Galileo Galilei lived at the same time as Johannes Kepler. Galileo explored many questions, but he was especially interested in problems of motion. As you have read, he disproved Aristotle's theory that heavy objects fall faster than lighter ones. He made other discoveries about motion, as well. For example, he used mathematics to describe the path of a projectile, or something that is thrown or shot.

Galileo's most notable discoveries came when he turned his curiosity toward the sky. What he learned there made him a champion of the Copernican theory.

Galileo's Discoveries

In 1609, Galileo heard about an invention from the Netherlands: the telescope. A telescope uses glass lenses to make distant objects appear much closer.

Galileo decided to build his own telescope, so he learned how telescopes worked and how to grind glass for lenses. Soon he was building more and more powerful telescopes.

Galileo began studying the sky through a telescope and noticed things no one had seen before. He saw that the moon's surface was rough and uneven, and he discovered four of the moons that revolve around the planet Jupiter.

Galileo also observed the planet Venus. To the naked eye, Venus resembles a bright star, but Galileo noticed something new.You know from looking at the moon that it goes through phases. It takes on what appear to be different shapes, from a thin sliver to the full moon. With his telescope, Galileo could see that Venus also passed through phases. Sometimes it was brightly lit, while at other times it was partially dark.

Galileo's discoveries contradicted the traditional view of the universe. For example, Aristotle had taught that the moon was perfectly smooth, but Galileo observed that it wasn't. Although Aristotle had said that Earth was the only center of motion in the universe, Galileo saw moons moving around Jupiter. Aristotle believed that Venus and other planets traveled around Earth.However, Galileo realized that the phases of Venus meant that it was traveling around the sun.

Conflict with the Church

Galileo's discoveries supported the Copernican heliocentric theory and led him into a bitter conflict with the Catholic Church. Church leaders viewed the Copernican theory as wrong and dangerous because the idea that Earth was at the center of the universe was part of their system of religious belief.

Church officials feared that attacks on the geocentric theory could lead people to become skeptical of the Church's teachings. In 1616, the Catholic Church warned Galileo against teaching the Copernican theory.

Galileo refused to be silenced and, in 1632, he published a book called Dialogue on the Two Chief World Systems. The book described an imaginary conversation about the theories of Ptolemy and Copernicus. Although Galileo did not openly take sides, the book was really a clever argument for the Copernican theory. The character who upheld the geocentric theory was portrayed as foolish, while the one who believed the heliocentric theory was logical and convincing.

Galileo's Dialogue caused an uproar. In 1633, the pope called Galileo to Rome to face the Catholic court, known as the Inquisition.

At Galileo's trial, Church leaders accused him of heresy and demanded that he confess his error. Initially Galileo resisted, but eventually the court forced him to swear that the geocentric theory was true, and he was forbidden to write again about the Copernican theory.

Galileo's Influence However, the Church's opposition could not stop the spread of Galileo's ideas. Scientists across Europe read his Dialogue, which helped convert many to the Copernican theory.

Galileo's studies of motion also advanced the Scientific Revolution. Like Kepler, he used observation and mathematics to solve scientific problems. Galileo's theory of motion describes how objects move on Earth, while Kepler's laws describe the movements of the planets. The next scientist you will meet united these ideas in a single great theory.

Isaac Newton and the Law of Gravity

Isaac Newton was born in England in 1642, the same year Galileo died. Newton was a brilliant scientist and mathematician whose greatest discovery was the law of gravity.

In later life, Newton told a story about his discovery. He was trying to figure out what kept the moon traveling in its orbit around Earth. Since the moon was in motion, why didn't it fly off into space in a straight line? Then Newton saw an apple fall from a tree and hit the ground and realized that when objects fall, they fall toward the center of Earth. He wondered if the same force that pulled the apple to the ground was tugging on the moon. The difference was that the moon was far away, so Newton reasoned that the force was weaker there but still strong enough to bend the moon's motion into an oval orbit around Earth.

This was Newton's great insight. A single force explained a falling apple on Earth, as well as the movements of heavenly bodies. Newton called this force gravity.

Newton stated the law of gravity in a simple formula. All physical objects, he said, had a force of attraction between them. The strength of the force depended on the masses of the objects and the distance between them. Mass is a measure of the amount of matter in an object. For example, the moon and Earth tug on each other. At a certain point in space, these “tugs” cancel each other out. The result is that the moon is trapped in its orbit around Earth. In contrast, an apple has a small mass compared to Earth and is very close to Earth, so gravity pulls it toward Earth's center.

In 1687, Newton published a book known as the Principia, or Principles, which presented the law of gravity and described three laws of motion. Newton's laws provided an explanation for what earlier scientists had observed. For example, others had shown that the planets moved around the sun, but Newton's laws explained why. Just as gravity kept the moon traveling around Earth, it kept the planets traveling around the sun.

Newton's laws dramatically changed people's view of the universe. Many people began to view the universe as a beautifully designed machine. Some compared it to a well-built clock. People needed only to discover how it worked.

Key Inventions

The Scientific Revolution spurred the invention of new tools for studying the world. These tools, such as the telescope, helped scientists discover new facts and measure data more accurately.

Microscope

Scientists use microscopes to make small objects appear much larger. The microscope was invented by Dutch lens makers in the late 1500s. In the mid-1600s, Dutchman Antonie van Leeuwenhoek (LAY-ven-hook) designed his own powerful microscopes and became the first person to see bacteria. Leeuwenhoek was amazed to find a tiny world of living things and exclaimed, “All the people living in our United Netherlands are not so many as the living animals that I carry in my own mouth this very day!”

Thermometer

Galileo likely made the first thermometer. In the early 1700s, however, a German scientist, Daniel Gabriel Fahrenheit, made thermometers more accurate. He put mercury in a glass tube, and as the mercury grew warmer, it expanded and rose up the tube. The height of the mercury provided a measure of temperature. Additionally, Fahrenheit designed a new temperature scale. In the United States, we still measure temperature using Fahrenheit degrees.

Barometer

Another important tool developed in this period was the barometer, which measures changes in the pressure of the atmosphere. Evangelista Torricelli (tawr-ih-CHEL-ee) invented the barometer in the 1640s. He filled a glass tube with a liquid metal called mercury, and then placed the tube upside down in a dish.

Over the next few days, Torricelli watched the tube and observed that the height of the mercury did not stay the same. The column of mercury moved up and down vertically as the pressure in the atmosphere changed. The barometer soon proved to be a valuable tool in studying and predicting the weather.

The Scientific Method

A key outcome of the Scientific Revolution was the development of the scientific method. Two philosophers who influenced this development were Francis Bacon and Rene Descartes (reh-NAY dey-KAHRT).

Francis Bacon was born in England in 1561. Bacon distrusted much of the traditional learning of the Middle Ages and argued that people could gain knowledge only if they rid their minds of false beliefs. He outlined a method of scientific investigation that depended on close observation.

Rene Descartes was born in France in the year 1596. Descartes prized logic and mathematics. To gain knowledge that was certain, he suggested, people should doubt every statement until logic proved it to be true. Descartes also saw the physical universe as obeying universal mathematical laws.

These ideas helped create a new approach to science. Eventually, scientists developed this approach into the scientific method, which combines logic, mathematics, and observation into five basic steps:

1. The scientist states a question or problem.

2. The scientist forms a hypothesis, or assumption, that might explain the problem.

3. The scientist designs and conducts an experiment to test the hypothesis.

4. The scientist measures the data, or information, produced by the experiment and records the results.

5. The scientist analyzes the data to determine whether the hypothesis is correct.

Galileo's demonstration with falling objects illustrates how this method works. Galileo wondered whether objects of different weights fall at the same speed. He formed a hypothesis that they did, then designed and conducted an experiment to test it. He dropped a heavy and a light ball together from the same height off a tower and observed that they landed at the same time, which showed that his hypothesis was correct.

Scientists still use this basic method today. An advantage of the scientific method is that any trained scientist can repeat what another has done. In this way, scientists can test each others' ideas.

In one way, the spread of the scientific method marked a separation from the past. Fewer and fewer people looked to traditional authorities for the answers to scientific problems, but that did not mean they discarded all their old beliefs. For example, thinkers such as Descartes and Newton were deeply religious. For many, science was a way to better understand the world God had made.