Time-scale and Distance (시간 척도와 거리)

Earth radius 6400 km Moon-Earth distance 3.8105 km Sun-Earth distance 1.5108 km 1 AU (astronomical unit)

Parallax시차 (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). dpc = 1/p(”) 1 pc = 3.26 Light-years. Distance to nearest star,  Centauri p = 0.762" ---> d = 1.31 pc = 4.27 light-years Infinite === 무한 Isosceles triangle

1 parsec = 3.26 light year = 3.09×1013 km 1” = 1 arcsecond = 1/3600 degree 1AU 1 parsec = 3.26 light year = 3.09×1013 km

Parallax시차 (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). dpc = 1/p(”) 1 pc = 3.26 Light-years. Distance to nearest star,  Centauri p = 0.762" ---> d = 1.31 pc = 4.27 light-years Infinite === 무한 Isosceles triangle

Virgo cluster (처녀자리 은하단, 室女座星系團)

Chronology of the Universe 우주의 연표 (연대기) 13.7 Gyr Big bang; formation of the elements H and He 13.4 Gyr First stars and galaxies; first supernova explosions produce the heavy elements (C,N,O,Si,Fe,…) 12 Gyr Formation of the milky way 4.567 Gyr Formation of the solar system; at this point in time the interstellar medium has been enriched with 1% heavy elements Formation of the earth and the moon 4.5 Gyr Layer structure of the earth 4.45 Gyr Solid earth crust 4.4 Gyr Early ocean 4.2 Gyr Plate tectonics 4 Gyr Earth’s magnetic field Origin of life >3.5 Gyr Formation of oxygen-rich atmosphere; formation of ozone 2.3 Gyr 0 Gyr Today

우주의 달력 : 우주의 탄생에서 현재까지를 1년으로 두었다 Cosmic Calendar Cosmic Calendar: Scale 12 Billion year history of universe into one year. 1 month = 1 Billion years. 우주의 달력 : 우주의 탄생에서 현재까지를 1년으로 두었다 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