Science Teachers’ Workshop 2006 R. Hollow 1 Concepts for The Cosmic Engine Robert Hollow CSIRO Australia Telescope National Facility Robert.Hollow@csiro.au Introduction This workshop will provide you with some simple ideas, demonstrations and analogies that consolidate a conceptual grasp of the theory and skills in module 8.5 The Cosmic Engine of the NSW Stage 6 Physics syllabus. Concepts addressed, in varying depths, include historical perspectives, the expansion of space and the Big Bang, colour and temperature of stars, luminosity and the Hertzsprung-Russell diagram. Despite the seeming lack of practical investigative work in the revised version of the Cosmic Engine unit, there are many simple demonstrations and analogies that are effective in engaging and challenging students. This paper aims to provide teachers with a range of ideas and activities plus some useful data with which to cover the syllabus requirements. It is not intended to provide a detailed theoretical background on the concepts as this is better covered in the various references but rather it aims to clarify some key teaching points and misconceptions about them. Some of the material included in this paper may be found in The Cosmic Engine section of the Australia Telescope Outreach and Education website; http://outreach.atnf.csiro.au/education/senior/cosmicengine/ . Other material has been incorporated and updated from papers presented at previous Science Teacher Association of NSW workshops by the author. Syllabus Requirements This paper uses the amended NSW Board of Studies Stage 6 Physics Syllabus of October 2002. The three areas targeted in this paper approximately relate to the syllabus outcomes in bold points 1, 2, and 3 in module 8.5 The Cosmic Engine (pages 35 – 37 of the printed edition). It is recommended that you read the paper with access to a current copy of the syllabus. It can be obtained online from the Board of Studies at http://www.boardofstudies.nsw.edu.au/syllabus_hsc/ . Historical Models Astronomy is the oldest of sciences. Numerous ancient sites such as many of the megalithic stone circles of north- western Europe show evidence of astronomical alignment. The growth of agricultural communities required an understanding of seasons and time keeping. Ancient Egyptian and Babylonian records provide evidence of systematic observations of the night sky. Figure 1: Stonehenge at around Midwinter sunrise © R. Hollow Five planets, Mercury, Venus, Mars, Jupiter and Saturn plus the Sun and Moon were visible to the unaided eyes of the ancient astronomers. The planets could be distinguished from stars in that through regular observation they were seen to move relative to the stars. The very word planet derives from the classical Greek term for wandering star. Unlike stars, planets also varied their brightness over time. A final complication in the observed behaviour of planets was that of retrograde motion. This is where a planet seemed to back track on its path across the sky through the constellations before reverting to its normal direction. Figure 2 on the next page clearly shows this for the planet Mars in late 2003.