Presentation on theme: "Based on “The structure of Scientific Revolutions“ by Thomas S. Kuhn Speakers: Carola Elsner, Meike Reichle Tuesday, 11 May 2004."— Presentation transcript:
based on “The structure of Scientific Revolutions“ by Thomas S. Kuhn Speakers: Carola Elsner, Meike Reichle Tuesday, 11 May 2004
Overview Introduction Definitions Geocentric – Heliocentric System Newtonian – Relative System Kuhn‘s theories Transfer Discussion
Paradigm: A paradigm is a point of view, a model in which you perceive the world, a weltanschauungModel: A model is an imaginary analogy that helps you to understand complex coherences. Our whole weltanschauung consists of models, most of which we are not aware of Paradigm Shift: Discarding a paradigm in favour of another, often a radical change.
Geocentric System versus Heliocentric System
The Earth is at the centre of the Universe. Sun and all other planets move around the earth All motion in the heavens is uniform circular motion. The objects in the heavens are made from perfect material, and cannot change their properties (e.g., their brightness or form) The geocentric system
Problem: Planets seem to move in one direction most of the time, but sometimes, there is a strange retrogradation, meaning they go into the other direction.. The solution: In the geocentric system, planets move in circular epicycles while the centers of the epicycles move in circular orbits around the Earth.
Nicolaus Copernicus Astronomer, Mathematician, Church Canon, Jurist, Doctor Books: 1.Commentariolus, „Little Commentary“ (published in 1514) 2. De Revolutionibus (either published in 1530 or 1540 or after his death)
Copernicus‘ theories The center of the Earth is not the center of the Universe, but only the center of the mass and of lunar orbit (the moon moves around earth) The Sun is the center of the World The daytime movement of the Sun is only apparent, because the earth rotates around its axis within 24 hours The Earth moves around the Sun, so the movements that the Sun seems to be making are only effects of the Earth's real movements. These movements of the Earth and of the other planets around the Sun, can explain the stations, and all the particular characteristics of the planets' movements. (No Epicycles)
Aftermath Copernicus knew that those revolutionary thoughts would have caused great problems, so he hesitated to present them to a wider audience. He spent 30 years writing his book „de revolutionibus“, and without pressure by some friends, he wouldn‘t have published it at all. The heliocentric system contradicted the Church‘s point of view. He was right to do so, as people like Galileo, who openly defended this new system had to suffer from the Inquisition‘s prosecution. It took at least a generation until this heliocentric system was accepted.
Newton's three laws of motion 1.A body remains at rest, or moves in a straight line (at a constant velocity), unless acted upon by a net outside force. 2.The acceleration of an object is proportional to the force acting upon it. 3.Whenever one body exerts force upon a second body, the second body exerts an equal and opposite force upon the first body. (Aka: For every action, there is an equal and opposite reaction. )
Most important properties of Newton's universe Time and space are constant and absolute A body always and constantly emits the same amount of gravitational energy ( the g constant)
Problems of Newton‘s model 1.It assumes that changes in the gravitational force are transmitted instantaneously when positions of gravitating bodies change. However, this contradicts the fact that there exists a maximum velocity at which signals can be transmitted (speed of light in vacuum). 2.It does not explain gravitational waves or black holes in space
The Ether Theory Every kind of wave has a medium, so does light Ether is rigid at very high frequencies and fluid at lower speeds Ether isn‘t dense, it can permeate all kinds of matter.
The Michelson- Morley Experiment 1/3
The Michelson- Morley Experiment 2/3 Light is parted by the half silvered mirror Both rays looked at the detector If they don't arrive at the same time there will a visible interference pattern
The Michelson- Morley Experiment 3/3 The was no measurable difference between the two rays Even heavy adjustments of the interferometer didn't show any success What now??
The Theory of relativity 1/2 Albert Einstein *March 14, 1879 April 18, 1955 Theoretical physicist 1921 Nobel Prize of Physics for his explanation of the photoelectric effect
The Theory of relativity 2/2 Two theories, the special and the general theory of relativity Special: Considers observers in inertial reference frames which are in uniform motion with respect to each other General: Considers all observers to be equivalent, not only those moving at a uniform speed
The Special Theory of Relativity 1/2 First introduced in In „On the Electrodynamics of Moving Bodies „ a theory of time, distance, mass and energy There is no ether Light does not travel through a medium but has a constant speed of km/s
The Special Theory of Relativity 2/2 Redefinition of time, distance, mass, energy and momentum!! Moving Clocks run slower The speed of light is the maximum speed for matter and information
The Special Theory of Relativity Mass and energy are equivalent E=mc² Two events judged to be simultaneous by one observer may be seen as non- simultaneous by other observers which are in motion with respect to the first one The theory does not account for gravitational effects
Simultaneity in the special theory of relativity
The General Theory of Relativity Published in 1916 introduction of an equation that replaced Newton's law of gravity
Thomas Kuhn July 18, 1922-June 17, 1996 Started with a Ph. D in Physics, Later turned to history of sciences and finally philosophy of science. Most important book: The Structure of Scientific Revolutions
Conclusion & Transfer why is this topic relevant for us today?
Conclusion Past paradigms are often denied. Instead, the history of science is told as if one paradigm had always built on the previous one, and all of them had led to the current theory. Why is that? We think that this is a way to strengthen the current paradigm and to discourage scientists to come up with their own ideas.
Transfer Paradigm Shifts happen gradually, new Ideas are often primarily rejected. People should not stick to their ideas, but open their minds for new inventions, pushing them forward instead of pushing them away
Can paradigms coexist? Why is social science more likely to accept competing likely to accept competing paradigms than natural science?