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Register a new userUlugh Beg, Prince of Stars
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Added by
Jean-Pierre Luminet
Publication date
2018
fields
Physics
and research's language is
English
Authors
J.-P. Luminet
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Who was Ulugh Beg? A prince who governed a province in the central Asian empire built by his grandfather Tamerlane. Above all, he was a scholar who founded the Samarkand astronomical observatory, whose work predated that of the best astronomers in Europe one and a half centuries later.
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We survey early Indian ideas on the speed of light and the size of the universe. A context is provided for Sayanas statement (14th century)that the speed is 2,202 yojanas per half nimesha (186,000 miles per second!). It is shown how this statement may have emerged from early Puranic notions regarding the size of the universe. Although this value can only be considered to be an amazing coincidence, the Puranic cosmology at the basis of this assertion illuminates many ancient ideas of space and time.
In the ancient Egypt seven goddesses, represented by seven cows, composed the celestial herd that provides the nourishment to her worshippers. This herd is observed in the sky as a group of stars, the Pleiades, close to Aldebaran, the main star in the Taurus constellation. For many ancient populations, Pleiades were relevant stars and their rising was marked as a special time of the year. In this paper, we will discuss the presence of these stars in ancient cultures. Moreover, we will report some results of archeoastronomy on the role for timekeeping of these stars, results which show that for hunter-gatherers at Palaeolithic times, they were linked to the seasonal cycles of aurochs.
Indigenous peoples across the world observe the motions and positions of stars to develop seasonal calendars. Additionally, changing properties of stars, such as their brightness and colour, are also used for predicting weather. Combining archival studies with ethnographic fieldwork in Australias Torres Strait, we explore the various ways Indigenous peoples utilise stellar scintillation (twinkling) as an indicator for predicting weather and seasonal change, discussing the scientific underpinnings of this knowledge. By observing subtle changes in the ways the stars twinkle, Meriam people gauge changing trade winds, approaching wet weather, and temperature changes. We then explore how the Northern Dene of Arctic North America utilise stellar scintillation to forecast weather.
A century ago, Srinivasa Ramanujan -- the great self-taught Indian genius of mathematics -- died, shortly after returning from Cambridge, UK, where he had collaborated with Godfrey Hardy. Ramanujan contributed numerous outstanding results to different branches of mathematics, like analysis and number theory, with a focus on special functions and series. Here we refer to apparently weird values which he assigned to two simple divergent series, $sum_{n geq 1} n$ and $sum_{n geq 1} n^{3}$. These values are sensible, however, as analytic continuations, which correspond to Riemanns $zeta$-function. Moreover, they have applications in physics: we discuss the vacuum energy of the photon field, from which one can derive the Casimir force, which has been experimentally measured. We further discuss its interpretation, which remains controversial. This is a simple way to illustrate the concept of renormalization, which is vital in quantum field theory.
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