Lecture 2 Notes - History of Astronomy

Lecture 2 Notes - History of Astronomy Pre-Lecture Notes: ● In order to understand how the existing awareness of the universe has been developed, it is vital to comprehend history of astronomy. - Astronomy has been inevitably developing for centuries and, at the same time, enriched with new discoveries and incredible inventions by people of different ages and civilizations. ● ● Staring at the sky has been something that people have done since the existence of man. Many early societies like the Babylonians, Egyptians, and Greeks kept thorough records of the stars’ motion. These observations were used for farming, orientation and timetelling or making a calendar. Babylonians: Developed some of the first catalogs of stars, and came up with mathematics methods to determine future occurrences in the sky. Egyptians: Synchronized their pyramids with stars and made use of the heliacal rising of sirius in drawing out the annual flooding of the river Nile. Greeks: Other philosophers such as Aristotle and Ptolemy came up with what is referred to as geocentric models of the universe were Earth was considered middle of the universe. Nicholas Copernicus was a Renaissance -period mathematician and astronomer who proposed a heliocentric system of the world. Thanks to his work, the worldview, described in the book De revolutionibus orbium coelestium, Copernicus had an exceptional opportunity to deny the geocentric theories of Aristotle and Ptolemy. ☞ Heliocentric Model: Proposed that the Sun, not the Earth, was the center of the universe, fundamentally shifting our understanding of celestial mechanics. ☞ Impact: Laid the groundwork for future astronomers, despite his ideas being controversial and initially rejected by the Church. One of Italy’s most famous polymaths is the humanist of the Renaissance age, Galileo Galilei who brought about significant changes in the observational astronomy. - He is normally considered to have been the father of modern observational astronomy. Telescope Observations: Advanced the construction of the telescope and discovered many facts such as the four largest moons of the Jupiter which is now called as the Galilean moons, phases of Venus and the rings of Saturn. ☞ Support for Heliocentrism: supported by observation, with which he proved Copernicus’ heliocentric theory and became an enemy of the Church. Johannes Kepler was a German mathematician and astronomer is renowned for his laws of planetary motion. He expanded on Copernicus, who offered an approximate technique of the orbits of planets. Kepler's Laws: ➊ First Law: Planets orbit the Sun in elliptical paths, with the Sun at one focus. ➋ Second Law: A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. ➌ Third Law: The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit. ● Impact: Kepler's laws provided a mathematical basis for the heliocentric model and were crucial for Newton's later work on gravity. Sir Isaac Newton was an English scientist of great repute, being a mathematician, physicist, and astronomer who contributed to many fields among them astronomy. - Newton was responsible for the laying down of foundations of what is known today as classical mechanics. Law of Universal Gravitation: ● Suggested with the discovery that every mass in the universe pulls every other mass towards it with force that is directly proportional to the product of the two masses of the objects and inversely proportional to the square of the distance between the two objects’ centers. Principia Mathematica: ● In one of the greatest works, Newton has introduced the laws of motion and universal gravitation which gave a clear foundation of the celestial and terrestrial movements. Reflecting Telescope: ● Created the world’s first workable reflecting telescope known as Newtonian telescope that used mirror to gather and bend light to provide better observation of astronomical objects.