Newton, the apple and the Moon
Transcription
Newton, the apple and the Moon
http://modellus.fct.unl.pt Newton, the apple and the Moon This is an activity about the invention of gravitation by Isaac Newton, during the XVII century. Newton created a theory of gravitation, based on mathematical reasoning, that unified all motions, on the earth or on the heavens. Previous work by Galileo Galilei and Johannes Kepler was essential for Newton ideas. In a very short summary, Newton has shown that the motion of any falling object, like a simple apple falling from a tree, was of the same nature of the motion of any planet, such as the Moon around the Earth... Let’s see what was his line or argument. Geometrical and visual thinking was essential in Newton explanations. The motion of a cannon ball (a projectile!) that can start orbiting the Earth, if its initial velocity is sufficient high, is a classic of scientific thinking and imagination (on the background of this text). Notes and answers by... Place and date... http://en.wikipedia.org/wiki/Isaac_newton Some texts on this document are adapated from the Wikipedia. Most of the images are also from the same source. Teacher/tutor comments... http://modellus.fct.unl.pt Newton, the apple and the Moon 1. Gravitation before Newton: Aristotle 2. Gravitation before Newton: Ptolomey 3. Medieval thought and religious views of the world “Newton,” by William Blake; here, Newton is depicted as a “divine geometer” 4. Planets and retrograde motion 5. Explorations of Ptolomey´s Cosmology 16.Grav 6. Gravitation before Newton: Ptolomey 17.Grav 7. Making a model of planetary motion accordingly to Ptolomey 18.Grav 8. Gravitation before Newton: Galileo, Tycho Brahe and Johannes Kepler 20.Grav 9. Kepler 1st law: orbits are ellipses with the Sun at a focus 10.Kepler 2nd law: the law of the areas 11.Kepler 3rd law: the law of the periods 12.How fast does the Moon move, assuming it has an uniform circular motion? 13.Gr 14.Grav 15.Grav 19.Grav 21.Grav 22.Grav 23.Grav Newton, the apple and the Moon 1 http://modellus.fct.unl.pt Gravitation before Newton: Aristotle 1 The Greek philosopher Aristotle (384 BC – 322 BC) developed many theories on the nature of physics that are completely different from what are now understood as the laws of physics. These involved what Aristotle described as the four elements, as well as a variety of principles, most of which modern science has now disproved, and which provide no significant roots to any area of modern physics. 2 The Aristotelian theory of gravity was a theory that stated that all bodies move towards their natural place. For some objects, Aristotle claimed the natural place to be the center of the earth, wherefore they fall towards it. For other objects, the natural place is the heavenly spheres, wherefore gases, steam for example, move away from the centre of the earth and towards heaven and to the moon. Plato (left) and Aristotle (right), a detail of The School of Athens, a fresco by Raphael. Aristotle gestures to the earth, representing his belief in knowledge through empirical observation and experience, while holding a copy of his Nicomachean Ethics in his hand, whilst Plato gestures to the heavens, representing his belief in The Forms. 3 What were the main ideas of Aristotle about the natural world? 4 How was Artistotle theory of gravitation modified during the Middle Age? Notes, answers and comments... Teacher/tutor comments... Newton, the apple and the Moon 2 http://modellus.fct.unl.pt Gravitation before Newton: Ptolomey 1 The Notes, answers and comments... Teacher/tutor comments... Newton, the apple and the Moon 3 http://modellus.fct.unl.pt Medieval thought and religious views of the world 1 The Dante Notes, answers and comments... Teacher/tutor comments... Newton, the apple and the Moon 4 http://modellus.fct.unl.pt Planets and retrograde motion 1 The Notes, answers and comments... Teacher/tutor comments... Newton, the apple and the Moon 5 http://modellus.fct.unl.pt Explorations of Ptolomey´s Cosmology 1 The tr Notes, answers and comments... Ptolomey’s Cosmology Ptolomaic System Simulator Teacher/tutor comments... Newton, the apple and the Moon 6 http://modellus.fct.unl.pt Gravitation before Newton: Ptolomey 1 The Alternative Solar Systems Notes, answers and comments... Teacher/tutor comments... Newton, the apple and the Moon 7 http://modellus.fct.unl.pt Making a model of planetary motion accordingly to Ptolomey 1 The equant of Mars moves around the Earth. How long it takes to give a complete turn? Explain. 2 Mars moves around its equant. How long it takes to give a complete turn? Explain. 3 The Sun moves around the Earth. How long it takes to give a complete turn? Explain. 4 Use the animation to find how long it takes to Mars to be again at the smallest distance to Earth. 5 Build a model similar to the one on the right. Don’t forget to attach the origin of the circular motion of Mars to the equant. Notes, answers and comments... Teacher/tutor comments... Newton, the apple and the Moon 8 http://modellus.fct.unl.pt Gravitation before Newton: Galileo, Tycho Brahe and Johannes Kepler 1 The tr Notes, answers and comments... Teacher/tutor comments... Newton, the apple and the Moon 9 http://modellus.fct.unl.pt Kepler 1st law: orbits are ellipses with the Sun at a focus 1 The tr Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 10 http://modellus.fct.unl.pt Kepler 2nd law: the law of the areas 1 The tr Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 11 http://modellus.fct.unl.pt Kepler 3rd law: the law of the periods 1 The tr Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 12 http://modellus.fct.unl.pt How fast does the Moon move, assuming it has an uniform circular motion? 1 The trajectory of the Moon around the Earth is approximately circular, with constant speed. 2 The period of this uniform circular motion is 27.3 days. 3 The radius of the orbit is 384 000 km. 4 How fast is the Moon travelling around the Earth, in m/s? And in km/h? Hint... 5 In 1 s, what is the distance travelled by the Moon? 6 Make a model of the Moon travelling around the Earth for three lunar months (don’t forget to use the AutoScale button and to choose appropriate time step and time interval...) Hint... Click on the image to see the movie... Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 13 http://modellus.fct.unl.pt Newton’s law of gravitation 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 14 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 15 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 16 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 17 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 18 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 19 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 20 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 21 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 22 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments... Newton, the apple and the Moon 23 http://modellus.fct.unl.pt Grav 1 The Comments and answers... Teacher/tutor comments...