Science & People

Galileo Galilei | Biography, quotes, telescope, discovery, and facts

When Astronomer Galileo Galilei turned his newly built telescope into the sky on January 7, 1610, he saw a light spot that slowly traveled through the clear night over the city of Padua, Italy. This point he was looking at was the planet Jupiter. In amazement, he realized that "all four little stars" accompany the planet. These were actually the moons orbiting the giant planet.

Galileo's first telescope

The landscape he saw was against the traditional understanding of the Church, which assumed that all the objects in the sky revolve around the Earth. Galileo's discoveries would seriously confront the Church with a revolutionary new understanding of the universe.

Traditional beliefs about the nature of the universe were rigid and had been ruling for a long time. The Catholic Church and the universities had accepted the theories proposed by the Ancient Greeks for 300 years, especially Aristotle and Ptolemaios: the Earth remains stable in the center of the universe and other objects in the sky revolve around it. Since no one could see the roughness of the moon, planets, and stars, their models were considered to be perfect circles, the most flawless of shapes.

The church has adopted the perspective of the Ancient Age, in terms of supporting its mission to help sinful humanity turn towards divine perfection. Two beliefs supporting this view were vital. First, the sky should always be considered perfect. Second, the world in which humans live should have been the constant center of everything as the focal point of divine creation. Theories put forward by Aristotle and Ptolemy which are supporting this understanding gradually became religious dogma.

At the time Galileo lived, this dogma had lost some of its former strength. Polish pastor and mathematician Nicolaus Copernicus suggested in 1543 that the motion of the planets could be more easily explained if the Sun was considered to be the center of everything. Giordano Bruno was burned at the stake in 1600 due to his religious convictions (one of which was the insistence that the Earth was orbiting the Sun). In short, Galileo knew what he was facing.

The third telescope

Galileo Galilei against the church
The war that Galileo entered with the Church might have caused his death.

Galileo began his work at the age of 18 in 1582, which would later help shape various basic laws of motion. When he was a professor of mathematics in Padua in 1609, he heard the name of Dutch spectacle maker Hans Lippershey, who made two primitive telescopes by placing two lenses in a tube. Galileo made himself a telescope that can magnify objects only three times. He made a second telescope in a few months, and then magnified 32 times. It was this third telescope that he used to study the sky in 1609-1610.

The discoveries quickly followed one another, each a challenge against the teaching of the Church. The lunar surface wasn't perfect, there were craters, mountains, and plains. The Sun, which was regarded as "untainted" until then, had spots, and Jupiter also had moons that did not rotate around the Earth, and Venus could not be seen unless it revolves around the Sun, rather than Earth. And many previously unknown stars could now be observed.

In short, Galileo's telescope provided convincing evidence that we live on an Earth that revolves around the Sun, just a planet, and not at the center of creation. Copernicus was right, and the Church's doctrine on this subject was wrong, as Galileo clearly showed in Sidereus Nuncius (Starry Messenger), which he wrote in 1610.

The war lost by the Church

Dialogo sopra i due massimi system del mondo / Galileo
Galileo published his views in a "dialogue" that argues various states in which the Earth and the Sun stay at the center of our planetary system. But this smart move could not save him from the wrath of the Church.

Based on the detailed observations of German astronomer Johannes Kepler (1571-1630), a colleague of the Danish astronomer Tycho Brahe (1546-1601), it could be seen that the planets were not following an elliptical circle, but rather ellipses. Kepler designed three laws to explain the speed and orbit of a planet, thereby supporting the theories of Copernicus and Galileo. But it was still not easy for Galileo to prove that the Earth was moving. In 1615, the Church responded to the challenge.

The Pope stated that the doctrine that explains the Sun as the central and fixed figure was "false, absurd, formally contrary to religious belief and the Bible." Galileo was informed that he should change his views. He withdrew from public life until 1632, and that year he made a dangerous comeback with the book Dialogo sopra i due massimi system del mondo (Dialogue Concerning the Two Chief World Systems), which supported Copernicus' idea.

Galileo was ordered to return to Rome in 1633 and retract his words as he opposed religious belief. He did so because he was threatened with torture, but it was rumored by some that he murmured as "E pur si muove" (And yet it moves). Galileo was actually under house arrest until his death in 1642, but he could not prevent the spread of his ideas. The religious imposition was beginning to unravel in the face of science. But in 1992, it would take 359 years for Pope John Paul II to consider Galileo's conviction as "tragic mutual incomprehension". Now let's can move on to the section where we talked about the times before Galileo Galilei and the times when the inventions took place.

When did we start observing the sky?

Tycho Brahe's map
Tycho Brahe rejected Copernicus and remained true to the idea that the planets were turning around the Sun and the Sun around the Earth. Brahe mapped the stars and placed them on the 12 bands of the zodiac signs, which is thought to affect people's life.

From the ancient Babylonian civilization, that is, approximately 2000 BC, the sky has been explored not for objective information, but because it is believed to control people's lives. It was evident that the Sun and the Moon were linked to human life as they managed the seasons and the tidal event, therefore people worshiped them as gods. Other celestial bodies were also seen as divine beings with their own special powers on humans. Thus, it was thought that information of the stars must have been the information of the future. Mystical beliefs and practical knowledge were increasing together. Astronomy and astrology were the same things in the Old World.

Babylonians, Egyptians, Greeks, and the Chinese have long had a tradition of observing the sky. The Babylonians were able to calculate the length of a year with an error of four and a half minutes; but in all these cultures, astronomy was considered a means of supporting astrological prophecies. It was the Babylonians who designed the signs of the zodiac generation that are still in use today by astrologers. Ptolemy's geometric universe depiction based on circular movement was the main theory of his work Almagest. Ptolemy argued that behavior, height, appearance, and even national character traits of humans could be read from the stars.

The belief in the prophetic power of the stars survived after the emergence of Christianity and eventually experienced a great resurrection in Medieval Europe. Though his meticulously crafted catalog of stars would play a crucial role in proving that astrology was not a science, Tycho Brahe still believed in the reality of astrology. Tycho's student, Johannes Kepler, also made his living by preparing horoscopes.

However, the works that provided the proof needed to make astronomy a universe research science whose function is completely different from that of astrology, ironically came from Brahe, Kepler, and Galileo.

How did Galileo begin researching?

As a young boy, his father sent him to Pisa University to study medicine, but instead he studied mathematics.
As a young boy, his father sent him to Pisa University to study medicine, but instead he studied mathematics.

The origin of Galileo's research is based on an event that occurred while studying medicine at Pisa University. While looking at a lamp swinging from the ceiling of a church, he realized that even if the swinging distance was shortened, back and forth movements always seemed to be driving the same length. Seven years later, while teaching mathematics, he proved that the time it takes for a pendulum to complete its swing remains the same regardless of how much up or down it swings. The duration changes only when the length of the pendulum changes.

Galileo also found that altering the weight of a pendulum does not make a difference in timing, in complete contradiction with Aristotle's discreet "law" that heavy objects fall faster. In later experiments with balls rolling down prone surfaces, he discovered that falling objects always accelerated in the same way, which was not related to weight.

Discoveries made thanks to the telescope

Giovanni Cassini
Giovanni Cassini discovered the four moons and rings of the planet Saturn.

The new generation of people emerged after Galileo's death improved his two main scientific tools (telescope, and pendulum clock) and significantly expanded the revolution he started. Galileo's small telescope could magnify 32 times. In the middle of the XVII century, astronomers continued their experiments with 11.9ft (3.6m) long and 50 times magnifying equipment, and some even were 200ft (60m) long giant devices. Meanwhile, telescopes were inserted with new devices to calculate the position of the stars and the size of the planets. Galileo also suggested that pendulums could be used to adjust clocks. The use of pendulums resulted in a striking improvement in the management of the clocks. For the first time, clocks could measure both minutes and seconds and the duration of the movement of celestial bodies. More discoveries made later. Johannes Hevelius, a Polish scientist, mapped the moon. In the Netherlands, Christiaan Huygens discovered that it was Saturn's rings that change the way the planet appears. An Italian named Giovanni Cassini spotted a giant stain in the atmosphere of Jupiter, and discovered that it took 9 hours and 56 minutes for the planet to spin around its axis.

The telescope and the pendulum clock were combined in a brilliant experiment in 1670. Two astronomers, Cassini, who lives in Paris, and Jean Richer from French Guiana simultaneously measured Mars' position. Since there were about a distance of 4,000 miles (6,400 km) between the two people, the images appearing in both astronomers' telescopes were slightly different for the Mars' relative position to the fixed stars in the background. This difference made it possible for Cassini to calculate the distance between Mars and Earth.

Thus, Cassini had a measuring rod that made it possible to measure the distance from any planet or the Sun. He calculated the distance of the Sun as 87 million miles (140 million km) and his error was only 6%. For the first time, man was learning not only the structure of the Solar System, but also its incredible dimensions.

Development of science after Galileo

The telescope has revealed a new world to explore, and while this allowed us to find answers to some questions, it also created many new questions. The most important of these questions was: Why was the Earth, other planets, and moons following a rotation like this? Galileo's telescope and subsequent improved models showed that the sky was somewhat like Earth: the material objects directed by the same rules. This discovery was the basis for a major revolution in astronomy that would result in Isaac Newton's works, a generation after Galileo's death.

The atmosphere of thought that prevailed in England in the middle of the XVII century was very different from that in Italy. Since they did not have to fight the impositions of the Church, British scientists had great freedom to experiment and develop theoretical science.

In 1665 Newton analyzed the nature of light at his home in Lincolnshire Woolsthorpe. He then invented a powerful mathematical tool, an amazing calculation method that investigates the rate of change of quantities. It was the first time he began to understand the power that controlled the movements of celestial bodies, but it would take another 20 years for his findings to be published in his book Principia Mathematica (Principles of Mathematics).

Here he first described the force of gravity. Objects attract each other with a force proportional to their mass. This power decreases inversely proportional to the square of the distance between them. In other words, doubling the distance reduces gravity to a quarter. Behind Newton's mathematics lies an insight into the intriguing simplicity that was when Newton simply saw an apple falling in the garden by the force of gravity.

This phenomenon is so well known that its reality can be seen as suspicious. However, the story is true, even if it didn't actually fall on the scientist's head. The same rules govern apples and moons, pebbles and planets. The law of gravity is universal and can be defined by the language of mathematics. This was Galileo's true legacy.

Galileo and Leaning Tower of Pisa

A story that is always told tells that Galileo drops two spheres of different weights and sizes from the top of the Leaning Tower of Pisa, and he sees them fall at the same speed and reach the ground at the same time. But there is no record that this experiment was really done. Even so, it would be difficult to observe and correctly evaluate the results.

All objects tend to fall at the same speed in a vacuum environment. But in an environment with air, the rate of the decline reflects the complex relationships between the density and size of objects. Small objects fall slower than larger ones, even if they are made of the same material, because they have a larger surface area than their weight. A mouse can survive a fall, which can shatter a horse. Pendulums and inclined planes were undoubtedly more reliable scientific research tools.

Galileo Galilei quotes

  • “I have never met a man so ignorant that I couldn't learn something from him.”
  • "I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.”
  • “You cannot teach a man anything, you can only help him find it within himself.”
  • “In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.”
  • “All truths are easy to understand once they are discovered; the point is to discover them.”
  • “The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.”
  • “It is a beautiful and delightful sight to behold the body of the Moon.”
  • “Wine is sunlight, held together by water.”
  • “There are those who reason well, but they are greatly outnumbered by those who reason badly.”
  • “Measure what can be measured, and make measurable what cannot be measured.”
  • “Mathematics is the language in which God has written the universe”
  • “With regard to matters requiring thought: the less people know and understand about them, the more positively they attempt to argue concerning them.”
  • “By denying scientific principles, one may maintain any paradox.”
  • “Names and attributes must be accommodated to the essence of things, and not the essence to the names, since things come first and names afterwards.”
  • “It is surely harmful to souls to make it a heresy to believe what is proved.”
  • “See now the power of truth; the same experiment which at first glance seemed to show one thing, when more carefully examined, assures us of the contrary.”
  • “In the sciences, the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man.”
  • “Philosophy is written in that great book which ever lies before our eyes — I mean the universe — but we cannot understand it if we do not first learn the language and grasp the symbols, in which it is written”
  • “They seemed to forget that the increase of known truths stimulates the investigation, establishment and growth of the arts; not their dimination or destruction.”
  • “In time you may discover everything that can be discovered, and still your progress will only be progress away from humanity. The distance between you and them can one day become so great that your joyous cry over some new gain could be answered by an universal shriek of horror.”
  • “We cannot teach people anything; we can only help them discover it within themselves.”