Born in England on Christmas day 1643. Overview Chapter 2b Copernican Revolution Bubonic Plague 1665 While home for 2 years with nothing to do he made his most profound discoveries and proposed his most startling theories. 1.Newton s Three Laws 2. Gravitation 3. Discovery of the outer Planets Newton's marble tomb and monument in Westminster Abbey Sir Edmond Halley (1656-1742) English astronomer known for his study of comets, noticed that the comets of 1531, 1607, and 1682 seemed similar and hypothesized that they were the same comet and predicted the comet would return in 1758; when it was observed as predicted, the comet was named Halley's Comet in his honor. 1684 Newton was in a discussion with Edmund Halley, when Halley remarked But why do planet s move the way they do? Newton astounded everyone with the answers from his work 20 years earlier. Isaac Newton (1643-1727)) 1) Invented calculus to solve mathematical problems related to motion 2) Discovered the three laws of motion 3) Discovered the universal law of gravitation Newton s Three Law of Motion Principia The Mathematical Principles of Natural Philosophy 1687 Newton s Three Law of Motion 1. An object at rest tends to stay at rest, and an object in uniform motion tends to remain in that state of motion, unless an external force is applied to it (the Law of Inertia). 2. A force causes acceleration (a change in the velocity) of an object (F=ma). 3. For every action there is an equal and opposite reaction.
Newton s First Law of Motion: Newton s 2nd Law of Motion: An object continues in a state of rest or in a state of uniform motion at a constant speed along a straight line unless compelled to change that state by a net force. The amount of acceleration (a) produced by a force (F) depends on the mass (m) of the object being accelerated. F= m a An astronaut floating in space will continue to float forever in a straight line unless some external force is accelerating him/her. Newton s Third Laws of Motion For every action, there is an equal and opposite reaction. The same force that is accelerating the boy forward is accelerating the skateboard backward. Newton s Law of Gravity 1686
Force Moon m1 No Force r Gravity m2 Force of Gravity Moon s Orbit Force of Gravity Sec 2 Comets Newton s Law of Gravity 1686 Two bodies attract each other with a force that is proportional to the mass of each body and inversely proportional to the square of the distance between them.! G is the gravitational constant! r is the distance between the objects!m1 and M2 are the masses Types of Orbits Comets 100 lb Planets 1/4 (100 ) =25 lb Sec 2 To help determine the paths of the planets and the forces upon them, Newton needed a more sophisticated mathematics than was then available. So he invented calculus
Meaning of Kepler s 3rd Law and Gravity other planets discovered. Msun =a3/p2 Uranus Same value for all planets The year 1781 The first planet discovered. William Herschel Neptune The year 1846 First observed by Galle and d'arrest (based on calculations by Adams and Le Verrier). Pluto The year 1930 Discovered by Clyde Tombaugh Sec 2 Discovery of Uranus by Sir William Herschel (1738-1822) Discovered Uranus on March 13, 1781 "Discovered accidentally while Herschel was surveying the stars. One "star" seemed different and within a year was shown to have a planetary orbit 18 times farther from the Sun than Earth. " The new planet was named Uranus after the father of Saturn in Roman mythology. " The planet had been observed numerous times by other astronomers as early as 1690, but it was thought to Uranus was discovered using be another star. this 15-centimeter (6-inch) telescope designed and built by Herschel. Sec 3 5 Discovery of Neptune 1846 Discovered as the result of irregularities in the motion of Uranus and was the first planet to be discovered on the basis of theoretical calculations. Sun s Gravity J. C. Adams of Britain and U. J. Leverrier of France independently predicted the position of Neptune it was discovered by J. C. Galle in 1846, the day after he received Leverrier's prediction.
Pluto: Discovered 1930 by C. Tombaugh. First proposed by Percival Lowell on the perturbations in the orbit of Uranus. He began searching for the planet in 1905. Independent calculations were published by W. H. Pickering and others. In 1929, the search for a new planet was resumed at Lowell Observatory. On Feb. 18, 1930, Clyde W. Tombaugh discovered a trans- Neptunian planet. Pluto is named for the mythical Greek god of the underworld First two letters of Pluto stand for Percival Lowell Lowell's calculations now appear to have been incorrect and predicted location was accidentally accurate---pluto is far too small to have detectable influence on Neptune or Uranus No longer considered to be a planet-- reclassified as a dwarf planet Clyde W. Tombaugh: 1906-1997 Sec 3 Summary of Chapter 2, cont. Laws of Newtonian mechanics explained Kepler s observations Gravitational force between two masses is proportional to the product of the masses, divided by the square of the distance between them Summary: Major Early Scientist Claudius Ptolemy (140) Nicolaus Copernicus (1473-1543) Tycho Brahe (1546-1601) Johannes Kepler (1571-1630) Galileo Galilei (1564-1642) Isaac Newton (1642-1727)
End of Chapter 2b The Copernican Revolution Go to Chapter 6