Transcript Observing
Observing Astronomy 315 Professor Lee Carkner Lecture 3 Our Point of View Think about the motions of the heavens from different points of view Remember that everything is moving at once The Changing Sky North Pole of the Earth is pointed at Polaris (the North or Pole star), which stays stationary as the other stars move around it Caused by the rotation of the Earth on its axis Caused by the motion of the Earth around the Sun Diurnal Motion Annual Motion The Observer’s View Observing Can measure distance on the sky in degrees (360 degrees = complete circle) Horizon -Zenith -Meridian -- Time and the Stars Stars make one complete circuit around the sky in 24 hours Example: if stars move 1/12 of the way around the sky, 2 hours have passed Big Dipper is circumpolar (never sets) The Solar Year The Seasons When the northern hemisphere is pointed at the Sun, it is summer here Seasons are not caused by Earth being more or less distant from the Sun!!! Direct and Indirect Sunlight Solstice and Equinox Solstice When the Sun is highest or lowest in the sky Equinox When the Sun is overhead at the equator Times of year Vernal Equinox -March First day of spring Summer Solstice -June First day of summer Autumnal Equinox -September Day and night equal in length Winter Solstice December Shortest day of the year Changing Day Length Lines on a Globe Equator -- Sun is overhead at equinox Tropic of Capricorn -- Tropic of Cancer -- Arctic and Antarctic Circles -- 23 1/2 degrees south or north of the pole, Sun never sets or rises at solstice time Latitude (degrees North of the Equator) Longitude (degrees East or West of the Prime Meridian running through Greenwich England) Navigation The Celestial Sphere Project the lines on a globe into space to form a coordinate system North Celestial Pole -- Celestial Equator -- Celestial Coordinates Right Ascension -- Declination -The coordinates do not move or vary with location on the Earth, they are fixed to the stars The Ecliptic For observers the ecliptic is a line on the sky where the Sun, Moon and planets can be found Constellations of the Zodiac Precession The Earth “wobbles” as it spins, causing the Earth’s axis to point at different parts of the sky This changes where the equinoxes are in the sky Astrology The belief that the positions of heavenly bodies at the time of your birth foretells your future For example: March 8th = Pisces, but Sun is in Aquarius. All star signs are about 1 month off Science and Pseudoscience Astrology is a pseudoscience, it uses some of the terminology of science, but its basic tenets are not subject to proof Next Time Meet back in Science 102 Read Chapter 3.1-3.4