By Alexander von von Humboldt, Nicolaas A. Rupke
The first quantity of Cosmos, his five-volume survey of the universe, seemed in 1845, even though Humboldt had worked at the whole paintings for almost part a century. He scrupulously despatched sections of the paintings to different specialists for feedback and corrections. The final quantity, prepare from his notes after his demise, seemed in 1861. The volumes have been translated virtually as speedily as they seemed. This paperback variation reprints the Harper & Brothers variation, released in big apple in 1858-59.
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Anyone alive within the eighteeth century could have recognized that "the logitude problem" used to be the thorniest medical quandary of the day--and were for hundreds of years. missing the facility to degree their longitude, sailors during the nice a long time of exploration were actually misplaced at sea once they overlooked land. hundreds of thousands of lives, and the expanding fortunes of countries, held on a resolution.
The medical institution of Europe--from Galileo to Sir Issac Newton--had mapped the heavens in either hemispheres in its sure pursuit of a celestial solution. In stark distinction, one guy, John Harrison, dared to visualize a mechanical solution--a clock that might retain percise time at sea, anything no clock had ever been capable of do on land. Longitude is a dramatic human tale of an epic clinical quest and Harrison's forty-year obsession with development his excellent timekeeper, identified at the present time because the chronometer. packed with heroism and chicanery, it's also a desirable short historical past of astronomy, navigation, and clockmaking, and opens a brand new window on our world.
In Longitude, Dava Sobel chronicles the world's quest to tame time. In 1714, the English Parliament handed the longitude act. It tested the Board of Longitude and provided a prize of 20,000 kilos to somebody who may perhaps discover a uncomplicated and sensible procedure for the ideal decision of a ship's longitude. specifically Sobel highlights John Harrison's pursuit of the prize. She lines the arc of his profession, and information the ideas of every of his next entries (H1-H5) regrettably, even supposing his Chronometers many times proved their worthy in Sea trial after sea trial, and the watch fast received adherents between sea captains, Harrison used to be thwarted at each flip in his try and declare the prize. Jealous competitors at the board used their impression to alter the foundations of the competition a number of instances. His family with the board turned so acrimonious that finally his buddies went over the board's head and appealed on to the King himself. George III requested exact act of Parliament be handed and Harrison eventually acquired his prize.
Despite it's brevity, Longitude is an exceptionally enticing and academic e-book. Sobel writes in a manner that makes the technological know-how and math obtainable to the final reader.
First released 1995
ebook ISBN13: 9780802779434
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Extra resources for Cosmos: A Sketch of the Physical Description of the Universe (Foundations of Natural History) (Volume 1)
37. 9 - la tensione T esercitata dalla fune; la reazione R esercitata dalla parete. 9. La puleggia diﬀerenziale `e una macchina costituita da: due pulegge connesse rigidamente con l’asse di rotazione ﬁsso in comune, una puleggia mobile al cui asse viene appeso il corpo di peso P da sollevare, una fune avvolta come in Fig. 37 c attorno alle pulegge. Indichiamo con r e R i raggi delle due pulegge ad asse ﬁsso. Si determini la forza T che `e necessario applicare al punto A della fune per tenere in equilibrio il corpo di peso P nei due casi: a) il peso della fune `e trascurabile; b) il peso della porzione di fune liberamente appesa (nella ﬁgura, il tratto ABC) `e p.
La forza con cui l’uomo grava sulla piattaforma `e pertanto P − F . 44) τi = 0 . 43), d` a: P = F + T1 + T2 ⇒ P = 4F ⇒ F = P/4 . 46) L’intensit` a di F `e cos`ı determinata. 44) `e necessaria ma non sufﬁciente per l’equilibrio. 45), cio`e la condizione sui momenti. Calcoliamo i momenti rispetto al punto O di appoggio dell’uomo sulla piattaforma: 2 R T2 = R T 1 ⇒ T1 = 2 T 2 . 43). 45) `e pertanto soddisfatta. ` possibile mantenere l’equilibrio nel caso le due carucole abbiano raggi B) E diversi ?
25 c,d). Sui due cilindri inferiori il cilindro superiore esercita le forze R12 e R13 . Per il principio di azione e reazione R12 = −R21 , R13 = −R31 . 32) assicura che R12 = R13 . Per determinare l’incognita R2 = R3 `e pertanto suﬃciente considerare la condizione di equilibrio delle forze agenti su uno solo dei due cilindri inferiori, ad esempio il n◦ 2 (quello di sinistra) e proiettarla sull’asse x: √ R2 = | R12x | = | R21x | = P/2 3 . ) Perch´e nel diagramma di corpo libero del cilindro 2 non si `e considerata la reazione esercitata dal cilindro 3 (e viceversa) ?