The Scientific Revolution

Beliefs about the Solar System during the Middle Ages 

  • Geocentric theory (earth centered view of the universe) 

    • Aristotle (Greek philosopher) started the idea in the 4th century B.C. 

    • Ptolemy (Greek astronomer) expanded upon it in the 2nd century A.D.

    • Earth - is unmoving & located at the center of universe

      • everything (sun, moon, and stars) revolves around the earth


  • The Church assumed this idea to be true during the Middle Ages

The Scientific Revolution – a new way of viewing the natural world based on careful observation with a willingness to question accepted beliefs

  • European scholars translated the writings of Muslim astronomers

  • Renaissance scholars learned more from classical ancient manuscripts - such as the writing of Aristarchus 

  • The Renaissance and Reformation, the Printing Press, and the new discoveries found during the Age of Exploration challenged old ideas

Polish Astronomer
Nicolaus Copernicus

  • Discovered that the sun was the center of universe (today we call it our Solar System)

    • Heliocentric theory (sun-centered = Solar System)

  • Fearing persecution – he didn’t publish his findings until 1543, at the end of his life

  • He wrote: On The Revolutions of the Heavenly Bodies

Astronomy

  • Reasons why Aristarchus' model did not gain wide acceptance and was in effect lost for 18 centuries until Copernicus redeveloped it. 

  • First his original writings were lost in the destruction of the Great Library of Alexandria in AD 415.

  • Second, it defies common sense. We do not feel the Earth spinning or moving through space. 

  • The final objection - failure of observers to detect any stellar parallax.  Closer stars should show a periodic shift in position to and fro against more distant stars over the course of a year as the Earth orbited the Sun. In fact this was not detected until 1838 following careful telescopic observations. 

Johannes Kepler
Expanded upon Heliocentric Theory to include elliptical planetary orbits around the sun

  • He studied Tyco Brahe a Danish astronomer

  • Found that mathematical laws govern planetary motion 

Galileo Galilei

  • Discovered the law of the pendulum, an indication of the earth’s rotational motion 

  • Realized that all objects accelerate at a fixed and predictable rate regardless of mass (weight) ex. Large heavier stones fall at the same rate as smaller lighter stones

  • Built a telescope 

    • From this he was able to describe the moon and Jupiter and other planets 

    • He published his findings in 1632 supporting Copernicus’ belief of the heliocentric theory 

    • He wrote: Dialogue Concerning the Two Chief World Systems 

      • Of two fictional people debating the laws of planetary motion

Galileo’s conflict with church 

  • The Church felt  threatened by his ideas

    • He was called to stand trial in 1633

  • Under threat of torture, Galileo agreed that Copernicus’s findings were false 

  • He lived under house arrest until his death in 1642 

Scientific Method

  • The Scientific method: 

    • Scientists form a hypothesis 

    • Then use observation, mathematic calculation, and measurements to test their hypothesis

    • When repeat attempts of the same steps under the same conditions achieve a consistent result then scientific laws may be formed. 

The development of the Scientific Method 

  • Francis Bacon – and English politician / writer - rejected Medieval laws of nature and Aristotle

    • He believed that scientists should observe the world

    • gather information first, then draw conclusions about the natural world

The development of the Scientific Method

  • Rene Descartes – of France developed analytical geometry -which linked algebra and geometry

  • He relied on mathematics and logic

  • believed that everything should be doubted (the skeptic approach) until proven by reason

  • The only thing that he knew for certain was his existence – “I think, therefore I am.”

Isaac Newton

  • Newton – added to Copernicus, Kepler, and Galileo.  

  • He explained how the planets  move around the sun – through gravitational forces

  • He proposed the Law of Universal Gravitation:

  • every object in the universe attracts each other 

Newton’s work

  • His book was published in 1687, Mathematical Principles of Natural Philosophy

  • The universe acts as a giant clock 

    • all of its parts working perfectly together 

    • and can be expressed mathematicall

  • He believed that God was the creator of this orderly universe

Other Scientists began to study the  secrets of nature on earth

  • Janssen – (Dutch eyeglass maker) made the first compound microscope

  • Leeuwenhoek – (Dutch drapery merchant) first observed bacteria and red blood cells under a microscope - his discoveries led to the development of the Cell Theory

  • Torricelli – (Galileo’s student) built a mercury barometer measuring atmospheric pressure

  • Fahrenheit – (Dutch physicist) made a mercury thermometer – where water freezes at  32̊ 

  • Celsius – (Swedish astronomer) made another mercury thermometer where water freezes a 0̊ 

Robert Hooke - the first to see cells

  • In 1665 Robert Hooke looked through a microscope at a thinly sliced piece cork and discovered many cells

  • He saw a series of walled boxes that reminded him of tiny rooms occupied by monks living in monasteries, and was the first to coin the word “cells” 

Vesalius and Harvey studied the  human body 

  • Vesalius – a Flemish physician - dissected humans

    • He wrote the book “On the Fabric of the Human Body” 

    • He illustrated human muscles, bones, and organs 

  • William Harvey – and English doctor

    • Wrote a book proving that the heart acts as a pump to circulate blood throughout the body 

    • He wrote: On the Motion of the Heart and Blood in Animals

    Discoveries in Chemistry

    • Robert Boyle – his book The Skeptical Chymist

    – challenged Aristotle’s idea that the earth’s four basic 

        elements were earth, air, fire, and water

    • Boyle’s contribution to Chemistry, was his proposal that 

       matter consists of tiny particles that join together to form 

       everything we see,

    • It was a form of “Atomism”, a philosophy practiced during his 

       day; he applied this philosophy to the natural sciences.

    • Boyle’s Law - the volume, temperature, and pressure of gas affect each other

Smallpox vaccination

  • Edward Jenner (British physician) introduced a smallpox vaccine.

  • His inoculation contained:

    • germs of the Cowpox (cattle disease) which gave “permanent” protection to humans from the Smallpox disease. 

  • Cowpox, a much milder disease; it’s risks of  deadly side effects were much lower.