In the midst of the early turmoil over the distance scale and the internal structure of stars, a few vague attempts were made to examine a whole new aspect of astronomy. Until this time, astronomers had been observing only in the optical part of the spectrum, that part ranging from about 300 to 1000 nm. […]
Bubble had shown definitively that spiral nebulae were external galaxies. In the 1930s he continued work on these objects with the Mount Wilson 2.5-m reflector, which was then the world’s largest telescope. Studies over the next decade revealed that the extra-galactic nebulae could be divided into four main classes: irregular, elliptical, normal spiral and barred […]
The Nature of Nebulae Certain nebulous patches, such as the Magellanic Clouds in the south and the Andromeda Nebula in the north, are clearly visible to the naked eye and have undoubtedly been observed from early times. Comments on the Andromeda Nebula date back to the Arabs in the middle of the tenth century. Similarly, […]
The discovery at the turn of the nineteenth century that the light from the Sun dispersed through a spectroscope produced not only a continuous spectrum, as Newton had shown in 1666. But one crossed by dark lines – the Fraunhofer lines as they came to be known – provoked much concern among astronomers, physicists and […]
In the midst of these cosmological expansions, several events culminated in the abolition of the concept of solid, classical spheres required by mechanistic models of the universe. Copernicus Universe deprived the stellar sphere of its earlier function as the driving force behind celestial motions. A succession of uncommon celestial events showed that the spheres were […]
Mediaeval astronomical measurements assumed the model of a two sphere Universe. This model postulated the segregation of Earth and sky: the laws of motion and the constitution of the heavens were considered quite separately from the physical relationships governing the behaviour of matter on the Earth. Philosophers considered the heavens to be perfect and unchangeable: […]
Early Measurements of The Universe A spherical Earth was accepted very early, although the first conclusive physical argument in favour came from Aristotle. He pointed out that during a lunar eclipse the shadow cast by the Earth on the Moon was circular, which would not be the case unless the Earth were spherical. Aristotle alluded […]
Towards the middle of the eighteenth century, European rather than British mathematicians began to investigate the remaining problems in the lunar and planetary theories. Although Newton had provided a solid foundation for the theory of the motions of the Moon and planets, he was not able to account for all the inequalities in their orbits. […]
Astronomy, being the oldest of the exact sciences, has a very long historical tradition going back many thousands of years. For the greater part of this time, the study of the skies has been inseparable from astrological and religious traditions. Indeed, in the past, astronomy was more intricately woven into the fabric of civilization than […]
Suppose that we are not the sole intelligent life-form in the Universe. Discovery of another life-form and subsequent communication with it would be one of the most important events in the history of the human race. But how should we go about searching for such a life-form, let alone communicate with it? The question of […]