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Mathematics behind Prague's Horologe 2014 June. 20 th GROUP 6 Presentation Hu Mengge Wang Miaomiao Wang Linfan Shi Wanting

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Prague,the capital of the Czech Republic,located in central Europe.many mathmatics and physicists and astronomers have spent here very fruitful and creative years, and left unforgettable traces in Prague. tion duc tro In

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in particular, Bruno, Kepler, Bolzano, Cauchy, Abel, Doppler and Einstein were the most excellent person. During their stays in Prague the above mentioned scientists developed several fundamental mathematical and physical theories and engaged in related activities. tion duc tro In

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tro Now we are discussing some unexpected mathematics associated with a prominent building at the heart of the Old Town Square of Prague. In the center of Old Town in Prague there is an astronomical clock— an interesting rarity often visited by many tourists, not only mathematical tourists. tion duc In

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tro The clock has two large dial- plates on the south wall of the tower. the astronomical clock of Prague is placed inside an almost 60m high tower of the Old Town City Hall. Over the centuries the construction of the clock has been renovated several times. tion duc In

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tro The upper dial-plate of the astronomical clock is an astrolabe controlled by a clockwork mechanism. It represents a stereographic projection of the celestial sphere from its North Pole onto the tangent plane passing through the South Pole. tion duc In The center of the dial-plate thus corresponds to the South Pole of the celestial sphere. The smallest interior circle around the South Pole illustrates the Tropic of Capricorn, whereas the exterior circle illustrates the Tropic of Cancer. The concentric circle between them corresponds to the equator of the celestial sphere.

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important Any circle on the sphere which does not pass through the North Pole is mapped onto a circle as well. Therefore, the ecliptic on the celestial sphere is projected on a circle, which is represented by the gilded ring with zodiac signs along the ecliptic. However, its center is not the South Pole, but the ring eccentrically rotates around this pole. property An

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tro The black circular area at the bottom of the dial-plate corresponds To the astronomical night,when the Sun is lower than 18° below horizon. The brown area stands for twilight. Sunrise is denoted by ORTVS and sunset by OCCASVS. tion duc In

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B E L L R O W 1. A large gear with 24 slots at increasing distances along its circumference; 2.A small gear whose circumference is divided by 6 slots into segments of arc lengths 1,2,3,4,3,2. S=1+2+3+4+3+2=15 KS how the clock

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The Bellworks Documents Websites The number of bell strokes is denoted by the numbers...,9,10,11,12,13,...along the large gear.The small gear placed behind it is divided by slots into segments of arc lengths 1,2,3,4,3,2. The catch is indicated by a small rectangle on the top. When the small gear revolves it generates by means of its slots a periodic sequence whose particular sums correspond to the number of strokes of the bell at each hour: 1,2,3,4,5=3+2, 6=1+2+3, 7=4+3, 8=2+1+2+3,9=4+3+2, 10=1+2+3+4, 11=3+2+1+2+3, 14=2+3+4+3+2, 15=1+2+3+4+3+2,...

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The Bellworks At the beginning of every hour a catch rises, the 12 apostles appear and transit through two windows in sequence, and finally the bell chimes. The gears stop when the catch falls back into the slots on both gears at the same time. The bell strikes 1+2+3+...+24=300 times every day.

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The Bellworks Moreover, one stroke of the bell at one a.m. is due to the movement of the small gear (there is no tooth between the first and second slot of the large, since such a tooth would be extremely thin and thus, it could break),therefore, in this case the catch is in contact only with the tooth of arc length 1 of the small gear,which makes the use of the small gear essential.

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The clock sequence We can continue in this way until infinity. However, not all periodic sequences have such a nice summation property. For instance: a.1, 2, 3, 4, 5,4, 3, 2 6<4+3; b.1, 2, 3, 2 2+1<4<2+1+2. Sloane: 1,2,3,4,3,4,... The clock sequence

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connections with triangular numbers and periodicsequences In this section wo briefly mention how the triangular numbers are related to the astronomical clock.We shall look for all periodic sequences that have a similar property as the clock sequence 1,2,3,4,3,2,i.e.,that could be used in the construction of the small gear.Put The periodic sequence is said to be a Sindel sequence if for any positive integer k there exists a positive integer n such that where the triangular number on the left-hand side is equal to the sum of hours on the large gear, whereas the sum on the right-hand side express the corresponding rotation of the small gear.

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The upper numbers denote lengths of segments on the small gear, whereas the lower number indicate the number of strokes at the k-th hour.

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The above condition can be replaced by a much weaker condition based on only a finite number of k 's:namely, the sequence with period length is a Sindel sequence if there exists a positive integer such that equation holds for This enables us to perform only a finite number of arithmetic operations to check whether a given period yields a Sindel sequence.

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fu rt he r ts gh si

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1,1,2,3,5,8,13,21,34,55,89…… a n+1 = a n-1 + a n a n+1 /a n

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1/2,2/3, 3/5,5/8,8/13,13/21,21/34,... 21/34= 0.6176 34/55= 0.6182 55/89= 0.6180 golden ratio

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e plam ex on enrth Pa Golden Ratio a r t h i t e c t u r e p a i n t i n g n a t u r e m u s i c d e s i g n

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