2014-Space, Time & Cosmos Lecture 1 Prof. Ken Tsang SCIT 4020: Space, Time and Cosmos • • • • • Instructor: Prof. Ken Tsang Office: E-409-R9 Phone: 3620606 Email: [email protected] TA: ?? Assessment • Continuous Assessment (60%) – Quizzes (10%) – Assignments (10%) – Mid-term test (10%) – Project (30%) • Final Examination (40%) Web-page for this class • http://www.uic.edu.hk/~kentsang/cosmos14/ SCIT4020cosmos2014.htm • Link from Ispace as well Cosmos • originates from a Greek term κόσμος (kosmos) meaning "orderly or harmonious arrangement“, opposite to chaos. • In many Slavic languages such as Russian, Bulgarian, and Serbian, the word Космос (cosmos) also means "outer space". • In Mandarin Chinese, cosmos and universe (from Latin universum) are both translated as 宇宙 (yǔzhòu), which literally translated means spacetime. Cosmology • Pythagoras ( ~570 - 495 BC) is said to have been the first philosopher to apply the term cosmos to the Universe, reflecting his belief that the universe is an orderly arrangement that can be understood. • “Cosmology” is a recent word (first used in 1730 in Christian Wolff's Cosmologia Generalis). But the study of Universe has a long history involving science, philosophy, esotericism, and religion. Creation according to Christian & Jewish Bible The size of the Moon • By comparing the size of the Earth’s shadow cast upon the Moon during a lunar eclipse, it was possible to estimate the size of the Moon compared with the Earth. Diameter of Moon ~3200 km • Eratosthenes estimated the distance to the Moon as well, ~100 times of its diameter, 320,000 km. How did the Greek philosophers know the size of the Sun? In third century BC, Aristarchus argued that moonshine was reflected sunshine, and the half moon must occur when the Moon, Sun & Earth formed a right-angled triangle. He measured the other angle (~87°, the correct value is 89.85°) in this right-angled triangle and used trigonometry to work out the ratio between the EarthMoon & Sun-Moon distances. This means the Sun is 400 times further away than the Moon. Finally, the size of the Sun is determined during a solar eclipse, by comparing the relative size of the Sun and the Moon to an observer on Earth. Modern measurements Moon orbital radius: 363,295 - 405,503 km Radius: 1,737.10 km Earth’s orbital radius: 147,098,290 152,098,232 km Radius: 6,371.0 km Sun diameter: 1.392684×106 km Geocentric cosmology Aristotle postulated a geocentric cosmology which was widely accepted up until the 1500s. This view was perfected by Ptolemy (~AD 90 – 168). From the 3rd century to the 1500s, the dominant view held that the Earth was the center of the universe. Apparent retrograde motion of Mars in 2003 as seen from Earth The Universe of Aristotle and Ptolemy The Ptolemaic order of spheres from Earth outward is: Moon Mercury Venus Sun Mars Jupiter Saturn Fixed Stars Sphere of Prime Mover Figure of the heavenly bodies — An illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568 (Bibliothèque Nationale, Paris) A brief history of ancient Western Civilization 800 BC (Greek epic poem) Iliad & Odyssey Socrates 470? ~ 399 BC; Plato 424? ~ 348 BC Aristotle 384? ~ 322 BC Greek First Roman Emperor: Augustus 63 BC-14 AD Roman Empire Constantine I legalized Christianity in Roman Empire, 330 AD moved the capital to Constantinople 395 AD Christianity became official state religion Byzantine Empire 330-1453 AD 476 AD End of the western Roman Empire Germanic Roman general Odoacer deposed Emperor Romulus Augustulus Homer's Iliad and the Odyssey: Trojan War The Trojan War was waged against the city of Troy by the Achaeans (Greeks) after Paris of Troy took Helen from her husband Menelaus, king of Sparta. The ancient Greeks thought that the Trojan War was a historical event that had taken place in the 13th or 12th century BC, and believed that Troy was located in modern-day Turkey. Alexander the Great (356 –323 BC) Shakespearean tragedy: Antony and Cleopatra The last pharaoh of Ancient Egypt, Cleopatra, consummated a liaison with Julius Caesar that solidified her power. After Caesar's assassination in 44 BC, she aligned with Mark Antony (Roman general and important supporter of Julius Caesar) in opposition to Caesar's legal heir, Gaius Julius Caesar Octavianus (Augustus). After losing the Battle of Actium to Octavian's forces, Antony & Cleopatra committed suicide. The Printing Press • The world's first movable type printing technology was invented and developed in China by Bi Sheng (毕升 ？-1051) between the years 1041 and 1048. [沈括《梦溪笔谈》] • Re-invented and improved by a goldsmith from Mainz, Germany, Johannes Gutenberg, ~1450. Wine Press Screw Carolingian Script Paper Moveable type The Printing Press • First book ever printed on a printing press using moveable type: • The Gutenberg Bible ~1450 Why Printing Press is so important to the Scientific Revolution • Books became more affordable to ordinary people (cost producing a book becomes 300 times cheaper). • No more transcription errors, making knowledge accumulation much easier. – “nothing new under the sun”, ancient discoveries soon became forgotten. Books produced per Year Economic Impact of the Printing Press The Historical Revolt • Consequence of the invention of movable type printing press – In 1517, Martin Luther started the Protestant Reformation (宗教改革) – In science, the spread of Heliocentric cosmology and the inductive method of reasoning with experimental data Pre-Copernicus heliocentric models Early traces of a heliocentric model are found in several anonymous Vedic Sanskrit texts composed in ancient India before the 7th century BCE. In the sixth century the Indian astronomer and mathematician Aryabhata anticipated elements of Copernicus's work. Aristarchus of Samos in the 3rd century BCE proposed what was the first scientific model of a heliocentric solar system: the Earth and all other planets revolving around the Sun, the Earth rotating around its axis daily, the Moon in turn revolving around the Earth once a month. His heliocentric work has not survived. History of Copernicanism In 1514 Copernicus made available to friends a short handwritten manuscript describing his ideas about the heliocentric hypothesis. Thereafter he continued gathering data for a more detailed work. In 1533, Johann Albrecht Widmannstetter, secretary of the pope, delivered in Rome a series of lectures outlining Copernicus' theory. The lectures were heard with interest by Pope Clement VII and several Catholic cardinals. Copernicus' work was in its final form in 1536, and rumors about his theory had reached educated people all over Europe. Despite urgings from many, Copernicus delayed the publication of his book, perhaps from fear of criticism. Roman Catholic Church's decree Copernicus died in Frombork on 24 May 1543. Legend has it that the first printed copy of De Revolutionibus was placed in his hands on the very day that he died. It has been much debated why it was not until six decades later that the Catholic Church took any official action against Copernicus's work. In March 1616, the Roman Catholic Church's Congregation of the Index issued a decree suspending De Revolutionibus until it could be "corrected“. Main points of Copernicus' theory •There is no one center of all the celestial circles or spheres. •The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere. •All the spheres revolve about the sun as their midpoint, and therefore the sun is the center of the universe. Kepler's laws of planetary motion Kepler studied the data from Tycho Brahe’s observation. Around 1605, Kepler found that Brahe's observations of the planets' positions followed three relatively simple mathematical laws. Kepler's laws challenged Aristotelean and Ptolemaic geocentric view. His asserted that the Earth moved in ellipses, and his proved that the planets' speeds varied. Almost a century later Isaac Newton was able to deduce Kepler's laws from Newton's own laws of motion and his law of universal gravitation. Contribution of Galileo Galilei The key to all of Galileo's discoveries was the accurate measurement of time. Galileo used the uniform motion of the pendulum to measure time Galileo experimented with various sorts of motions and falling bodies. He formulated the basic law of falling bodies, which he verified by careful measurement. Galileo’s contribution to Astronomy Improved telescope (~1608). Discovered (1610) Jupiter's four largest moons: Io, Europa, Callisto, and Ganymede and obtained remarkably accurate estimates for their periods. Observed that Venus exhibited a full set of phases similar to that of the Moon. First European to observe sunspots, the first one to report lunar mountains and craters, the planet Neptune (1612), and the planet Saturn (but he was confused by its ring). Observed the Milky Way, previously believed to be nebulous, and found it to be a multitude of stars packed so densely that they appeared to be clouds from Earth. Located many other stars too distant to be visible with the naked eye. By 1616 the attacks on the ideas of Copernicus had reached a climax, and Galileo went to Rome to try to persuade Catholic Church authorities not to ban Copernicus' ideas. In the end, a decree of the Congregation of the Index was issued, declaring that the ideas that the Sun stood still and that the Earth moved were "false" and "altogether contrary to Holy Scripture“. Galileo was ordered to stand trial on suspicion of heresy in 1633. and was found guilty of heresy. He was ordered imprisoned; the sentence was later commuted to house arrest, until his death in 1642. Cristiano Banti's 1857 painting Galileo facing the Roman Inquisition Rehabilitation of Galileo • Galileo was accused of heresy in 1633 for his support of Copernicus' heliocentrism and it was not until 1992 that Pope John Paul II announced that the Catholic Church's denunciation of Galileo's work had been a tragic error and officially conceded that the Earth was not stationary. • Pope Benedict XVI later (21 December 2008) praised Galileo, at events marking the 400th anniversary of Galileo's earliest observations with a telescope. After Galileo’s Death The weight of papal authority which had succeeded in halting the growth of the new science in Italy. Following Galileo's death in 1642 that the greatest advances in science would come from outside Italy in Protestant countries (with a tradition of protest and toleration) like England, Holland and Germany. 1642 as a Significant Year Isaac Newton (1642-1727雍正五年), the man most responsible for producing modern science was born. 1620. Francis Bacon published Novum Organum Scientiarum 1644. René Descartes: (Principles of Philosophy) “I think, therefore I am” 1644. The Manchu conquer China ending the Ming Dynasty. ~1760: Beginning of Industrial Revolution Newton's laws of motion Newton's First Law (the Law of Inertia) states that an object at rest tends to stay at rest and that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. Newton's Second Law states that an applied force on an object equals the time rate of change of its momentum, or with constant mass: F= ma Newton's Third Law states that for every action there is an equal and opposite reaction. Newton's law of gravity Pierre-Simon Laplace (1749 –1827): …if we conceive of an intelligence that at a given instant comprehends all the relations of the entities of this universe, it could state the respective position, motions, and general affects of all these entities at any time in the past or future. The Newtonian Worldview Reductionism to understand any complex phenomenon, you need to take it apart; properties of a system are explainable by explaining the individual behavior of its smallest parts. Materialism all phenomena, whether physical, biological are ultimately constituted of matter The Newtonian Worldview • Determinism/mechanism – If you know the initial positions and velocities of the particles constituting a system together with the forces acting on those particles (which are themselves determined by the positions of these and other particles), then you can in principle predict the further evolution of the system with complete certainty and accuracy. The Newtonian Worldview Dualism The Newtonian worldview considers the physical and spiritual realms to be entirely separate. while material objects obey mechanical laws, the mind does not This way physics can avoid conflicting with religion. The Clockwork Universe • The Universes is like a giant clock that was assembled and wound up by “God”, but no longer needs anything else to keep functioning according to its rule of operation. Influence of Newtonian Worldview Newtonian thinking has had a profound influence on society: the concept of natural law inspired democracy The mechanistic and deterministic view of nature also inspired communism. Dualism has had a profound impact on the way we see ourselves in relation to nature.