Radio serial on astronomy Episode 2: What is astronomy? [Note for script writer: This brief has been prepared keeping the average non-specialist viewer in mind. The attempt has been to develop the subject in a logical sequence that could bring out the excitement of the process of making new discoveries and relating them to the gradual understanding of the nature of the Universe. It is not designed to be a popular account of the development of astronomy as a scientific discipline and its impact on our understanding of the cosmos. Since the treatment is not rigorous, many details are not included. The script has to be developed along the outline suggested using simple colloquial language as far as possible. The dialogues and conversations need to be lively without any suggestion of pedagogy.] Points to be covered: - Introduction to astronomy - Basics of sky watching - The objectives of astronomy Outline of content: Early ideas about the Universe were primarily based on everyday observations and common sense. To us Earth-bound observers, the Universe is all that we see around us – our Earth, the Sun, Moon, the planets and the stars. We can hardly visualise things beyond what our eyes can see or our senses can feel. For example, although it is spinning around its axis and at the same time also going around the Sun at a break-neck speed, we cannot feel the Earth move. So it is common sense to think that the Earth is standing still, as our ancestors believed. Similarly, early humans could only see the Sun, the Moon, five planets and a few thousand stars with the naked eye. So this was their Universe. They could not imagine that there could be three more planets beyond Saturn or billions of galaxies outside our own galaxy that make up the real Universe. They did not have the slightest idea about the vastness of the Universe. One of the most surprising observations for early humans was the changing appearance of the Moon in the sky. Unlike the Sun, neither did it rise and set at any fixed times during the day nor did its shape remain the same. It waxed and waned over a period of about a month, disappearing totally in between. Sometimes, the Full Moon appeared to darken and then regain its brightness again after some time. But more frightening was the disappearance of the Sun behind a dark shadow, which occurred only on some New Moon days. When it happened, the day suddenly turned into night, birds returned to nest, animals behaved strangely and everything appeared eerie. Of course, the Sun always came out in its original glory in the end. But it was always a terrifying experience. The position of the Sun in the sky also does not remain the same throughout the year. The Sun appears high up in the sky from the northern hemisphere during northern summer, while it appears low in the southern sky during winter. Similarly, the days are longer during summer and shorter during winter. What made the Sun change position in the sky and what made the days longer or shorter? Answers to all these puzzles are provided by astronomy – the study of the movement of Sun, Moon, stars and planets in the sky. Astronomy is the study of the universe beyond the Earth’s atmosphere. Using principles of physics, astronomy explains the evolution of the universe and through sound 1 Radio serial on astronomy mathematical simulations forecasts its development. Although astronomy has been around for thousands of years and is perhaps the oldest science, it is only in the last century and particularly the last few decades that we have developed the technology to study the universe in greater detail. Anyone can enjoy doing astronomy. One only needs to have keen eyesight, a good sense of direction, and a lot of patience. A pair of binoculars or a small telescope can add a lot to the joy of sky watching. Although a few thousand stars are visible on a clear, Moonless night, one needs to know only a hundred or so that make up the constellations to be able to find one’s way across the night sky. However, before venturing to explore the night sky one must know the north, south, east and west directions, because if one does not stand facing in the right direction one may not be able to identify a particular constellation, and correctly indentifying constellations is the first step in astronomy. Of course, modern astronomy is much more than simple sky watching. Today astronomers use sophisticated telescopes and instruments to study not only the stars and planets but also a host of other objects like quasars, pulsars, supernovas, and strange objects that emit radio waves, infrared rays, Xrays, and gamma rays by violent processes. In the mid-20th century, it was discovered that the universe was expanding. This, along with other evidence, led to the theory of the Big Bang according to which the entire universe began as a point particle of extreme density. Later observations of the cosmic microwave background confirmed this, and the Big Bang continues as the primary theory of cosmological origins to this day. Every day new data on everything from galaxy formation to black holes to the Big Bang itself are being gathered using a staggering array of multi-wavelength telescopes on the ground and in space. Orbital observatories such as the Hubble Space Telescope have produced the best images, including extremely high-resolution photographs of other galaxies. In other words, astronomy is helping us to understand our Universe better. 2