1. Time-scale and Distance ( 시간 척도와 거리 )

2. SI 단위계에서 사용하는 접두어

3. Earth radius6400 km Moon-Earth distance3.8  10 5 km Sun-Earth distance1.5  10 8 km  1 AU (astronomical unit)

4. Parallax 시차 ( 視差 ) Parallax is the effect whereby the direction of an object appears to differ when viewed from different positions. Parallax = angle subtended by 1 A.U., the distance from Earth to the Sun. (1/2 of the diameter of Earth's orbit). As distance increases the parallax angle decreases. Ultimately limited by the smallest angles measurable. The distance at which 1 A.U. subtends 1" (one arc second) is called 1 parsec (pc). (parallax arc second). d pc = 1/p(”) 1 pc = 3.26 Light-years. Distance to nearest star,  Centauri p = 0.762" ---> d = 1.31 pc = 4.27 light-years

6. 1 parsec = 3.26 light year = 3.09×10 13 km 1AU

7. Parallax 시차 ( 視差 ) Parallax is the effect whereby the direction of an object appears to differ when viewed from different positions. Parallax = angle subtended by 1 A.U., the distance from Earth to the Sun. (1/2 of the diameter of Earth's orbit). As distance increases the parallax angle decreases. Ultimately limited by the smallest angles measurable. The distance at which 1 A.U. subtends 1" (one arc second) is called 1 parsec (pc). (parallax arc second). d pc = 1/p(”) 1 pc = 3.26 Light-years. Distance to nearest star,  Centauri p = 0.762" ---> d = 1.31 pc = 4.27 light-years

10. Virgo cluster ( 처녀자리 은하단, 室女座星系團 )

12. Big bang; formation of the elements H and He First stars and galaxies; first supernova explosions produce the heavy elements (C,N,O,Si,Fe,…) Formation of the milky way Formation of the solar system; at this point in time the interstellar medium has been enriched with 1% heavy elements Today 13.7 Gyr 13.4 Gyr 12 Gyr 0 Gyr Solid earth crust4.4 Gyr Layer structure of the earth4.45 Gyr Early ocean4.2 Gyr Plate tectonics4 Gyr Formation of oxygen-rich atmosphere; formation of ozone 2.3 Gyr Earth’s magnetic field Origin of life >3.5 Gyr Formation of the earth and the moon4.5 Gyr 4.567 Gyr Chronology of the Universe 우주의 연표 ( 연대기 )

13. Cosmic Calendar Jan 1: The Big Bang Feb. : The Milky Way forms August 13: The Earth forms December 13: Invertebrate ( 무척추 ) Life Evolves December 25: Rise of dinosaurs December 30: Dinosaurs extinct December 31: 9:00 pm Earliest human ancestors December 31: 11:59:47 pm Pyramids were built December 31: 11:59:58.4 pm King Sejong was born Cosmic Calendar: Scale 12 Billion year history of universe into one year.  1 month = 1 Billion years. 우주의 달력 : 우주의 탄생에서 현재까지를 1 년으로 두었다