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Period: 322 to
Aristotle
Aristotle was a greek philosopher who wrote entire cyclopidias , gathering together all he learnt about mathematics , biology and geography. He collected and recorded data or observations. this was another important step of the scientific method. he also invented a logical way of presenting an argument. Starting with agreed assumptions, a series of "if.... then.." steps lead to a final conclusion which was decisive. an example of his idea is that heavier objects fall faster than light ones -
Period: Feb 15, 1564 to
Galileo Galilei
Galileo Galilei was appointed the professor of mathematics at University of Pisa in 1589. Later on appointed the professor of mathematics at the University of Pedua, during his 18 years there he constructed telescopes, microscopes, air thermometers and the first pendulum clock. he used the telescope discover sunspots on the sun also discovered four moons of the planet Jupiter. This latter discovery supported his view that the sun is the center of the universe and not the earth. -
Period: to
Sir Isaac Newton
Sir Isaac Newton showed in his childhood early signs of talent in the design and construction of many gadgets: a water clock, water wheels, sundials, a pendulum clock, thermometers, microscopes, telescopes and a working model of a windmill. He rose to the top of the class as a teenager. Newton took his degree at Cambridge in 1665. Not yet 25 years he laid the foundation of his greatest work: the laws of motion and Universal gravitation, the calculus and the nature of white light. -
Period: to
Stephen Gray
Around 1730, Stephen Gray found that electric fluid (a current) could be transferred over fairly long distance by some materials but not by others. Thus, out of experimentation was born the distinction, ‘conductors and nonconductors”. The words “electric fluid” are used here, not because it was accepted theory but because the true nature of the electric phenomenon was not yet understood. The motion of the electric fluid or current was termed electricity. -
Period: to
Allesandro Volta
Allesandro Volta discovered and invented the “voltaic pile’. This permitted the production of a steady flow for an extended period of time. The full potential of this discovery could not be tapped because a real understanding was lacking. This, however, stimulated further work in this area. -
Period: to
Count Rumford
Count Rumford was responsible for the production of guns and cannons for the Bavarian army. The cannon generated between the cannon and the borer that they had to pour water in it to cool it down the amount of heat was enough to boil the water. -
Period: to
Hans Christian Oersted
The Danish physicist, Hans Christian Oersted, while performing a demonstration experiment before a small group of students, noticed that a compass needle was deflected when it was in the vicinity of a wire carrying an electric current. Since the compass is a freely rotating magnet, it could only mean that the current was producing a magnetic effect. The intermixing of both electricity and magnetism clearly could not be explained by fluid flow theories alone. -
Period: to
Michael Faraday
Michael Faraday wasthe son of a London blacksmith. His first job, at the age of 13, was an errandboy for a bookbinder. When he was 14 he became the bookbinder’s apprentice. A fewyears he began to attend lecturesat the Royal Institutions where, in 1812, he heardthe lecture of Sir Henry Davy .At the age of 22, Faraday became Davy’s apprentice andeventually he becameDirector of the Institution. Fromhis experimentation, and an attempt toexplain his observations, hedeveloped the concept of fieldlines -
Period: to
James Joules
James Joules worked as an English brewer but in his spare time, science was his hobby, He conducted many experiments. Joule spent many years taking careful measurements and came to the conclusion that a certain amount of mechanical produced the same amount of heat. He suggested, therefore, that heat was a form of energy and that mechanical energy was converted to heat energy. Joule’s experiment clearly indicates that the mechanical energy was converted to heat energy. -
Period: to
J.J. Thomson
J. J. Thomson showed that different materials when heated give off the same particles. These particles were negatively charged- later called electrons. he also showed that the mass of these particles was much less that the mass of an atom, hence it must be a component. Since the overall atom was neutral, it meant that there was an equal amount of positive charge also. -
Period: to
Ernest Rutherford
Baron Rutherford of Nelson was a British physicist in New Zealand. While investigating radioactivity Rutherford observed a peculiar phenomenon when some particles were allowed to hit a gold foil in a vacuum. With the help of Geigner and Marsden, Rutherford investigated this in detailed at Manchester University. The fate of the particles after striking the foil was detected by the scintillation they produced on a glass screen coated with zinc sulphide and fixed to a rotating microscope. -
Period: to
Albert Einstein
Albert Einstein was born in Germany. At school, he was lazy and slow at learning to read but was good at playing the violin. He failed man examinations but eventually got a degree. In the 20th century, an experiment called the “photoelectric effect” threw a new twist in the nature of light and other electromagnetic waves. The new twist was identified and explained by Einstein. When light waves fall on a metal surface they give energy to the electrons on the negative plate. -
Period: to
Niels Bohr
According to circular motion theory at the time, there were some contradictions with the atomic model proposed by Rutherford. If electrons are rotating around the nucleus they must be accelerating because they are continually changing direction.The electrons would be losing energy and would spiral into the nucleus. this does not happen. Niels Bohr tried to produce a theory without contradiction.From experiments, he observed that substances absorbed and emitted radiation of only certain frequency -
Period: to
James Chadwick
Chadwick discovered the neutron in 1932. This was a subatomic particle that had the mass of a proton but no charge. In order to be incorporated with the already existing model, these neutrons had to be located in the nucleus with the protons. The atomic model was therefore modified.