PSCI

• The Daily Motion


  • As the Earth rotates, the sky appears to rotate in the opposite direction
  • The sky appears to rotate around the N or S celestial poles
  • If you are standing at the poles, nothing rises or sets
  • If you are standing at the equator, everything rises and sets at 90° to the horizon
• Moon


  An object that orbits a planet or something else that is not a star. Besides planets, moons can circle dwarf planets, large asteroids, and other bodies
• Eclipse


  The partial or total blocking of light of one celestial object by another. An eclipse of the Sun or Moon occurs when the Earth, Moon, and Sun are aligned
• Constellations


  A group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure. Modern astronomers divide the sky into eighty-eight constellations with defined boundaries
• Sun


  • The star at the center of the Solar System
  • A massive, hot ball of plasma, inflated and heated by energy produced by nuclear fusion reactions at its core
• Geocentric


  Earth is the center. The Sun has an orbit that rotates around the Earth
• Heliocentric


  The Earth has an orbit that rotates around the Sun
• Geocentric Universe

  1. Eudoxus (409-356 B.C.): Model of 27 nested spheres

  2. Aristotle (384-322 B.C.): Universe can be divided in two parts - Imperfect, Changeable Earth, and Perfect Heavens (described by spheres)

  3. Aristotle expanded Exodus' Model to use 55 spheres
• Exodus


  An astronomer who created the first model of Geocentric Universe around 380. He designed his model of the universe as a series of cosmic spheres containing the stars, the sun, and the moon all built around the Earth as its center
• Aristotle's Geocentric Universe


  • The Earth at the center of the Universe
  • The sun, moon, and the planets move around the Earth on crystal spheres (the spheres was considered to be a perfect shape)
  • The stars are on a single sphere that was just beyond the orbits of the planets
  • The universe remains unchanged since it was created
• Aristarchus


  • He managed to place the Sun in the middle of the solar system and he also placed the planets in the right order from the Sun
  • He gave a model of the universe with a stationary Sun and planets rotating in circular orbits around the Sun
• Ptolemy


  • Placed the Earth at the center of his geocentric model
  • Using the data he had, Ptolemy thought that the universe was a set of nested spheres surrounding the Earth. He believed that the Moon was orbiting on a sphere closest to the Earth, followed by Mercury, then Venus and then the Sun
• Copernican


  • Copernican heliocentrism is the astronomical model developed by Nicolaus Copernicus and published in 1543
  • This model positioned the Sun at the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths, modified by epicycles, and at uniform speeds
• Tychonic


  • Tycho advocated as an alternative to the Ptolemaic geocentric system a "geoheliocentric" system (now known as the Tychonic system), which he developed in the late 1570s
  • In such a system, the Sun, Moon, and stars circle a central Earth, while the five planets orbit the Sun
• Galileo


  • Craters and mountains on the Moon: The Moon's surface was not smooth and perfect as received wisdom had claimed but rough, with mountains and craters whose shadows changed with the position of the Sun. Galileo was able to use the length of the shadows to estimate the height of the lunar mountains, showing that they were similar to mountains on Earth.
  • The phases of Venus: The planet Venus showed changing crescent phases like those of the Moon, but their geometry could only be explained if Venus was moving around the Sun rather than the Earth. This undermined the idea that everything in the heavens revolved around the Earth (although it was consistent with the Tychonic system as well as the Copernican one)
  • Jupiter's moons: The planet Jupiter was accompanied by four tiny satellites which moved around it. These are now known as the Galilean moons: Io, Ganymede, Europa and Callisto. Again, this showed that not everything in the heavens revolved around the Earth.
  • The stars of the Milky Way: Galileo saw that the Milky Way was not just a band of misty light, it was made up of thousands of individual stars
  • The first pendulum clock: Galileo designed a major component for the first pendulum clock, Galileo's escapement. This design, however, went unbuilt until after the construction of the first working pendulum clock by Christiaan Huygens
• Law of Inertia


  An object at rest, stays at rest. An object in motion, stays in motion unless acted upon by an unbalanced force
• Inertia


  • The tendency of an object to resist changes in its state of rest or motion
  • Inertia is directly proportional to the mass of an object
• Unbalanced Force


  When a force is greater than the other
• Law of Acceleration


  • Acceleration is directly proportional to force and is inversely proportional to the mass of an object
  • Greater Force = Greater Acceleration
  • Higher Mass = Lower Acceleration
• Acceleration


  A measurement of how quickly an object is changing speed
• Law of Interaction (Law of Action/ Reaction)

  • For every action, there is an equal but opposite reaction
  • When two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction
• Speed


  How fast an object is moving or how much distance is covered in a certain amount of time
• Velocity


  • The speed of a moving body in a given direction
  • How fast and which way
• Open System


  One in which both energy and mass cross the boundaries of the system
• Closed System


  One in which mass does not cross boundaries of the system, though energy may do so
• Isolated System


  One in which neither mass nor energy crosses the boundary of the system
• Law of Conservation of Energy


  Energy can neither be created nor destroyed; but can be transformed from one form to another
• • Energy of an object can be thought of as the sands in an hourglass
  • Energy always remain same or fixed in quantity
  • But this sand can change position, from the top to bottom and bottom to top!
  • Likewise energy can change in form eg. From KEP = ?
• Elastic Collision


  The colliding objects move separately after collision
• Inelastic Collision


  The colliding objects move together after collision
• Law of Conservation of Mass

  The mass can neither be created nor destroyed but is transformed from one form to another
• Law of Conservation of Energy


  The mass can neither be created nor destroyed but is transformed from one form to another. that energy can neither be created nor destroyed - only converted from one form of energy to another
• Law of Conservation of Momentum


  In an isolated system the total momentum of two or more bodies acting upon each other remains constant unless an external force is applied