Astronomy principles and practice

Các kiến thức về vũ trụ

[...]... heavenly and human events in close harmony: not only did celestial events guide and control men, in particular the Emperor and his court but the decisions and actions of such powerful rulers influenced the state of Heaven As mathematical knowledge grew and more accurate astronomical instruments for measuring altitudes and angles were developed in succeeding centuries, the movements of the Sun, Moon and planets... well At Alexandria, at the same longitude as Syene, the obelisk at the same solar solstice, cast a shadow at noon, showing by its length that the Sun’s altitude was 82 1 2 degrees (figure 2.1) He also knew the distance between Syene and Alexandria Eratosthenes then made the assumptions that the Sun was very far away and that the Earth was spherical The Sun’s rays arriving at Syene and Alexandria could... or α) and declination (Dec or δ) RA and Dec can be compared to the coordinate system of longitude and latitude for expressing a particular position on the Earth’s surface The central part of figure 5.1 depicts the Earth and illustrates the reference circles of the equator and the Greenwich meridian The position of a point on the Earth’s surface has been marked together with the longitude (λ W) and latitude... bright and well-known, being Vega or α Lyrae It also appears in all other catalogues and may, for example, be known as 3 Lyrae (Flamsteed’s number), Groombridge 2616 and AGK2 + 38 1711 (from Zweiter Katalog der ¨ Astronomischen Gesellschaft f¨ r das Aquinoktum 1950) u Returning to the quotation from Norton’s Star Atlas: Bode’s constellation boundaries were not treated as standard, and charts and catalogues... passage through the Earth’s atmosphere and corrections must be applied because of the particular position of the observer’s site and the individual properties of the observing equipment It may be noted here also that with the advent of computers, more and more observational work is automated, taking the astronomer away from the ‘hands-on’ control of the telescope and the interface of the data collection... reducing the observations, gleaning the last iota of information from them and pondering their relevance in our efforts to understand the Universe The development of astronomical theories often involves long and complicated mathematics, in areas such as celestial mechanics (the theory of orbits), stellar atmospheres and interiors and cosmology Happily in recent years, the use of the ubiquitous computer... transmitted directly through the atmosphere and collected by telescope 4.2 Macroscopic bodies As the macroscopic bodies penetrate the Earth’s atmosphere, the air resists their motion and part of their energy is lost in the form of heat The heat generated causes the ablated material and the atmospheric path to become ionized and, when the atoms recombine, light is emitted and the rapid progress of the body through... observations prior to the Incas However, very few of the ideas and notions of astronomy and cosmology from any of these civilizations have had an influence on the development of our understanding of the astronomical Universe Our starting points find their origins mainly in ancient Greece A completely new departure in mankind’s contemplation and interpretation of the heavens came with the flowering of Greek... in both the optical and radio regions, are useful in gaining information about the Earth’s atmosphere, upper winds and the ionosphere Although allowances can be made successfully for the effects of atmospheric extinction, it is obvious that absolute brightness measurements, brightness comparisons and colour measurements could be made more easily, with less risk of large random and systematic errors,... the spring and autumnal equinox He measured the Sun’s distance and went a considerable way towards providing theories to account for the motions of Sun and Moon Finally, as Greek civilization decayed, the last and perhaps the most influential thinker of them all embodied the work of many of the predecessors in the Almagest Ptolemy, who lived during the second century AD, not only collected and discussed