Introduction to the Cosmos
On Tuesday 14th July I offered Suffolk Humanists & Secularists an “Introduction to the Cosmos”. I’m from Coddenham Astronomical Observatory, and I used images from the Hubble Space Telescope and other space and ground based telescopes to describe the Universe in which we live. The talk began in our local neighbourhood and introduced the sizes and distances of the planets in our own solar system. As the Earth shrunk in relative size the journey took us out from the rocky inner planets to the cold gas giants most distant from the Sun. The planets were contrasted in size to the Sun, our nearest star. At this stage the Earth was quickly becoming smaller and less significant.
The situation was further emphasised as larger and larger stars were discussed. Some were so large that the Sun and its entire family of planets could orbit inside them. The distances here were even larger. If the sun were to be represented as a grain of sugar then the next nearest star would be another grain of sugar just over 4 miles away. From the room where we watched the show the grain of sugar would be typically, at Capel St Mary to the south or, towards the north, the bus station at M&S in Ipswich. Pictures of the Hubble â€˜Deep Fieldâ€™ were shown. These showed the most distant galaxies ever photographed.
More Hubble photographs showed pictures of the birth and death of stars. These included the violent death of the largest stars and a supernova, which was observed by the early Chinese astronomers in the year 1054 to the more gentle deaths of the smaller stars like our Sun. Our Sun is a dwarf star and smaller stars live longer. It is because of this that life has had time to evolve on Earth. Pictures of nebulae (gas clouds) were shown similar to the one our Sun would eventually produce in 6 or 7 billion years time. The discussion of the life and death of stars was just an excuse to introduce some of the most wonderfully photographed objects in the heavens and to explain their beautiful colours. The reds, greens, blues and oranges were contrasted with the dark silhouettes of the dust and gas clouds from which new stars would eventually be born. Each colour represented an element. The heavier ones were made inside stars themselves. Indeed everything that we can see or touch around us, including the elements in our bodies, was made in stellar interiors. As Carl Sagan said, â€˜We are all made of stardust,â€™ or, depending on your point of view, â€˜from nuclear wasteâ€™ as the stars shine using nuclear fusion reactions in their hot cores.
We moved on and discussed the discovery of planets around other stars and how astronomers managed to detect them. We realised that our Sun is not the only star with planets around it. There are over 100 billion stars on average in each galaxy and more galaxies in the Universe than there are grains of sand on every beach on Earth. The Earth is indeed an insignificant speck in the vast Universe. We looked at the shape of our galaxy and the Earthâ€™s unremarkable position inside one of its spiral arms. We felt humbled by the sizes and distances involved and realised that we hold no special place in the Universe.