PSc 100 Survey of Astronomy Associate Professor M. Böttcher Clippinger Hall #339 Phone: Office Hours: Mo., Tu., We., Th., 3:00 p.m. – 4:00 p.m.

General Information Course Web Site: Check this web site regularly. All lecture powerpoints, updates, reading assignments, exam results, etc. will be posted on this web site Link

The TurningPoint Response System We will use the TurningPoint response system for questions + answers throughout the lectures (Mo. – We.). Class participation during regular lectures will be measured with the TurningPoint system (starting in the 2 nd week of classes) and enter with 10 % into the final class grade. TurningPoint will also be used for 6 Reading Assignment Quizzes almost every Thursday. Scores of Reading Assignment Quizzes will be combined to 30 % of your final class grade. If you do not have a TurningPoint clicker, please buy one from the Tech Depot on the ground floor of Baker Center. Tech Depot staff will be available to toruble-shoot clickers (if necessary) and replace batteries for free.

As a Matter of Courtesy Please turn your cell phones off or on vibrating mode during the lectures If you really need to leave during the lecture, do so quietly, through the rear door of the lecture hall.

The Scale of the Cosmos Astronomy deals with objects on a vast range of size scales and time scales. Most of these size and time scales are way beyond our every-day experience. Humans, the Earth, and even the solar system are tiny and unimportant on cosmic scales.

16 x 16 m A Campus Scene

1 mile x 1 mile A City View

100 miles x 100 miles The Landscape of Pennsylvania

Diameter of the Earth: 12,756 km The Earth

Guess: How many times would you have to travel around the Earth to travel the distance between the Earth and the moon? million

Distance Earth – Moon: 384,000 km Earth and Moon

Distance Sun – Earth = 150,000,000 km Earth orbiting around the Sun

In order to avoid large numbers beyond our imagination, we introduce new units: 1 Astronomical Unit (AU) = Distance Sun – Earth = 150 million km

How many miles are there in 1 AU? 1.245, million million billion trillion

Approx. 100 AU The Solar System

Approx. 10,000 AU (Almost) Empty Space Around our Solar System

Approx. 17 light years The Solar Neighborhood

New distance scale: 1 light year (ly) = Distance traveled by light in 1 year = 63,000 AU = km = 10,000,000,000,000 km (= zeros) = 10 trillion km Nearest star to the Sun: Proxima Centauri, at a distance of 4.2 light years Approx. 17 light years

1 AU (= 150 million = 150,000,000 km) equals 1.1.5*10 8 km 2.1.5*10 10 km 3.1.5*10 15 km 4.8*10 15 km 5.8* km

Approx. 1,700 light years The Extended Solar Neighborhood

Diameter of the Milky Way: ~ 75,000 light years The Milky Way Galaxy

The diameter of the Milky Way is 1.7.5*10 3 light years 2.7.5*10 4 light years 3.7.5*10 5 light years 4.5* light years light years

Distance to the nearest large galaxies: several million light years The Local Group of Galaxies Galaxies usually don’t exist alone, but in clusters of galaxies

Clusters of galaxies are grouped into superclusters. Superclusters form filaments and walls around voids. The Universe on Very Large Scales