This did not rule out the investigation of events using experiment and mathematics, which are now the heart of the scientific method, but it did not particularly encourage them either. This is because Aristotelians saw the universe and everything in it primarily in terms of their meaning, rather than cause and effect. Aristotelians also inherited flawed assumptions about specific physical questions.
For example, if an object were in motion, they assumed something must keep it in motion, whether a mysterious quality in the object called impetus, the surrounding air, or something else. For many centuries this mindset confounded efforts to unravel the physics of motion. Despite many preconceptions, the Middle Ages and the Renaissance did produce some significant scientific developments. Manual workers such as joiners, builders, navigators, and shipbuilders accumulated knowledge about practical methods and materials.
Scholars advanced knowledge in several branches of mathematics, recovering the long-forgotten or poorly copied works of the Greek mathematicians Euclid born c. Descartes reasoned wrongly that neither atoms nor a vacuum could exist. Yet he prefigured the modern scientific approach by seeking a comprehensive, mechanical, rational interpretation of nature.
The sun, he theorized, like a spinning whisk at the center of a large bowl of cream, set the subtle matter twirling around it; since the twirling would naturally diminish with distance, this, according to Descartes, explained why planets more distant from the sun move more slowly than those that are closer. Descarte's vortex theory of planetary motion was popular in Europe at the time Newton published his own theory of the solar system in Philosophiae Natu-ralis Principia Mathematica Mathematical Principles of Natural Philosophy , usually referred to simply as the Principia Newton's mechanics explained both earthly and planetary motion, signaling the downfall of Descartes's vortex theory and his entire approach to knowledge.
Experiment combined with mathematics, rather than top-down philosophical speculations, would define all serious attempts to understand the physical world from that time onward. It was no accident that the motions of the planets concerned both Descartes and Newton. Before the advent of Newtonian physics, observational astronomy was the only science with mathematically precise knowledge or predictive power. Chemistry consisted mostly of unconnected bits of practical knowledge accumulated by trial and error. Modern concepts of the elements did not begin to develop until English scientist Robert Boyle 's — experiments disproved Plato's theory that all matter is composed of four elements—earth, air, fire, and water—in The existence of microorganisms was not known until , when Dutchman Antoni van Leeuwenhoek — built the first microscope.
Medicine, too, was rudimentary in Newton's day; the fact that the heart pumps blood through the body, for example, only became widely accepted after , when this theory was published in works by English doctor William Harvey — The s were a time of upheaval in all aspects of European society, including religion, science, politics, commerce, and the arts. The Protestant Reformation, starting in the early s, had split the centuries-old religious consensus of Europe along approximately geographic lines, with Protestant countries to the North and Roman Catholic countries to the South.
The Reformation called ancient patterns of thought into question and triggered wars that plagued the continent for decades. The Commercial Revolution, which ran from the early s to about , also helped break up old patterns of thought and motivate new discoveries in science and technology. Techniques for long-distance ocean navigation were needed, stimulating new precision work in astronomy and clock making. England, Newton's native country, suffered especially brutal upheavals.
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After the Puritans beheaded King Charles I — in , Oliver Cromwell — became first chairman of the Council of State, then Lord Protector from until his death in The British monarchy was restored under Charles II in A few years later, during an outbreak of plague, young Isaac Newton—a Puritan who was also fascinated not only by science but alchemy and the biblical book of Revelation—took refuge from pestilence in his mother's country house.
There, in a space of 18 months — , he conceived the basic elements of a new physics: the three laws of motion, the law of universal gravitation, and calculus.
He also did extensive work in optics, though he did not have the revolutionary effect there that he did in mechanics. Medieval astronomy was based on Claudius Ptolemy 's AD c.creatoranswers.com/modules/posey/conocer-hombres-mayores-de.php
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According to Ptolemy, the planets were embedded in vast crystal spheres centered around Earth and moving in changeless, perfect circles. Their motion was imparted by supernatural means from the outermost sphere of all, that of the fixed stars. This model was challenged by Nicolaus Copernicus — in the s.
In he published De revolutionibus orbium coelestium Six books concerning the revolutions of the heavenly orbs , in which he proposed that the sun, not Earth, is at the center of the universe. Copernicus's revision of the universe prompted a wave of new astronomical work. Tycho Brahe — made naked-eye observations of the motions of the sun, moon, and planets that were the most accurate to that date.
After Brahe's death, his assistant Johannes Kepler — , an advocate of the Copernican system , tried to fit Brahe's precise new observational data to equations describing planetary orbits, beginning with the planet Mars. At first he assumed a circular. Galileo Galilei — was an Italian physicist who perfected the modern scientific method. His work on accelerated motion was essential groundwork for Newtonian physics. Unfortunately, Galileo's defense of Copernican or heliocen-tric astronomy—the view that Earth rotates around the sun, not the other way around—ran afoul of established religious doctrine.
In the elderly Galileo was brought before the Inquisition and found guilty of heresy preaching incorrect belief and shown the instruments of torture that would be used on him if he did not retract his statements. Under duress, Galileo publicly retracted his belief in heliocentrism and spent the rest of his life under house arrest. Blind and disappointed, he died in , the same year Isaac Newton was born.
Because of Galileo's conviction, scientists were fearful of speaking truthfully in Southern Europe for decades afterward, and most of the work in the Scientific Revolution was thereafter done in England and Northern Europe. The church eventually admitted its mistake, but not until many years later.
In the church lifted its ban on books teaching the view that Earth goes around the sun; in Pope John Paul II — convened a new commission to study the Galileo case. Eventually he found that the best fit was given not by a circle but by an ellipse a curve like the outline of an egg. Kepler was the first to describe the motions of the planets in terms of mathematical laws. He stated three, two of which involved time as a variable.
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Using time to describe the world mathematically was a significant advance for physics; the European scientific tradition inherited from the Greeks was primarily static motion-less and geometrical. Its attention went primarily to the shapes of curves and rarely used mathematics to describe dynamic time-dependent processes. Kepler published two of his laws in and the third in They were purely descriptive, that is, they offered no explanation of why the planets acted as speci-fied, nor did they describe how any other objects such as falling apples might move.
After Brahe and Kepler, Galileo laid crucial groundwork for Newtonian physics. He mistakenly rejected Kepler's proof that the planets moved in elliptical orbits, but conducted precise experiments in the laboratory to characterize the movements of accelerating bodies—objects that are changing the direction or rapidity of their motion. Like Kepler, he searched for mathematical laws to describe the way physical systems change over time.
Galileo concluded that the distance covered by a steadily accelerating object is proportional to the square of the time it has been accelerating. He also discovered that objects accelerate steadily under the influence of gravity, which he treated as a constant force unaffected by distance which it is, approximately, near Earth's surface.
He found that objects accelerate with equal speed regardless of their weight—that is, a heavier ball does not fall faster than a light ball of the same size. Perhaps most fundamentally, he found that objects tend to maintain their straight-line motion unless acted upon by a force. This overthrew the Aristotelian view that a force is needed to maintain an object's state of motion. Newton's influence is due mostly to his major work, Philosophiae Naturalis Principia Mathematica, published in and best known by the shortened form of its Latin title, Principia.
This work was produced partly at the urging of Newton's friend, English astronomer Edmond Halley — , who also financed the project, helping to produce one of the most important works in the history of science. Of all the scientists working in his day, only Newton conceived that there could be a single universal system of mechanics—that is, a physics that would describe both earthly and celestial motions at the same time.
In the Principia, Newton established such a physics with his three laws of motion and his law of gravitation. A force acting on a body causes it to accelerate change its state of motion to a degree that is proportional to the body's mass. This law is most often stated as: For every action there is an equal and opposite reaction.
For example, when a gun fires, the force acting on the bullet as it accelerates through the barrel is equal to the recoil of the gun acting on the shooter's hand or shoulder. Larger masses mean larger gravitational force,. Even though three centuries have passed since Isaac Newton published his theory of gravitation in , scientists are still testing it.
Newton's law says that the gravitational attraction between any two objects decreases with the square of the distance between them; doubling the distance means one fourth the force. This type of relationship, called an inverse-square law, is accurate at the scale of baseballs, planets, or galaxies, but, according to quantum physics, should fail when objects are close together. In , a group of physicists led by D. They found that Newton's law was still valid even at this distance.
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