Telescopic observations of Venus, as it goes through its phases, would be one of the most exciting of views that we can share with children, to convey the excitement and significance of these observations, for the acceptance of Heliocentric theories, four hundred years ago.
A Nearly crescent phase of Venus captured by Ashmeet Singh, member of the Amateur Astronomers Association, Delhi and also a 12th standard student.
Even before we get down to telescopic observations, there is a lot of excitement related to simple naked eye observations of Venus that children can be alerted about. The changes in its brightness and rising or setting azimuth as its elongation changes, for instance. The changes in setting azimuth, during its evening apparition between September 2008 to February 2009, can be easily measured with simple handmade instruments by children. Measurement of its changing elongation is a little tricky for the very young, but, can be made by senior school students through independent Altitude and Azimuth measurements of the Sun and Venus. The Jantar Mantar instruments can also be used for making these measurements, as had been done by us in March 2004 as part of educational activities related to the 2004 Transit of Venus.
Students of Sanskriti School measuring the Altitude and Azimuth of the Sun using the Jaiprakas instrument of the Delhi Jantar Mantar, preparatory to measuring the elongation of Venus, during March 2004
Would observations of maximum elongation of Venus enough on their own merit, to have nudged people towards thinking away from a geocentric and towards a heliocnetric point of view? Obviously not, as the maximum elongation observations for Venus and Mercury must have existed for many centuries before the Copernican revolution. Complicated geocentric theories involving epicycles explained both the retrogarde motion of the planets as well as the maximum elongations of Venus and Mercury within the geocentric framework.
And then came observations of the phases of Venus, through Galileo's telescope! Phases, correlated with changes in angular diameter of Venus.
As students' discussion on many websites shows, many are aware that observations of phases of Venus, by Galileo with his telescope, said something about the fact that Venus was orbiting the Sun, rather than the Earth. However, there are a lot of confusions amongst students as to exactly how these observations do show that. To clarify completely, one needs to build a step by step observational background for students – 1.) Noting the maximum elongation of Venus and Mercury. 2.) Noting the phases and changes in angular diameter (if any) of the Moon correlated with the phases and finally 3.) Telescopic observations of Venus and measuring its changing angular diameter and their correlation with its phases. All these observations combined together with some hands on activities using torches and balls will give a physical understanding of the significance of the phase related observations of Venus, to Heliocentric theories. Venus activities for middle school and senior school children will be looking at these aspects.
Activities for senior school and college groups, will look into summarising in an easily understandable way, the Venus Science results obtained by the Messenger Venus flyby and the Venus Express.
