Fw: [問卦] 宇宙有多大丫?
※ [本文轉錄自 Gossiping 看板 #1Enr4wR3 ]
作者: hvariables (Carl) 看板: Gossiping
標題: Re: [問卦] 宇宙有多大丫?
時間: Sat Nov 19 14:48:19 2011
一維:長度有限的線段兩邊會有盡頭.
長度有限的線圈沒有盡頭.
二維:面積有限的平面四周會有盡頭.
面積有限的球面沒有盡頭.
三維:體積有限的歐幾里德體周圍會有盡頭.
體積有限的橢圓幾何體沒有盡頭.
歐幾里德幾何和非歐幾里德幾何最基本的不同是
歐幾里德幾何三角形內角和是180度.
橢圓幾何三角形內角和大於180度.
雙曲幾何三角形內角和小於180度.
一般來說三角形內角和 A+B+C = π+三角形面積*K K是曲率
歐幾里德幾何曲率等於0
橢圓幾何曲率大於0
雙曲幾何曲率小於0
根據廣義相對論,宇宙是四維非歐幾里德時空,可用實驗測量曲率以確定宇宙的時空結構.
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◆ From: 114.24.93.110
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首尾相連就是沒盡頭,意思就是直線往前走最後會回到原來的地方.
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※ lovefordidi:轉錄至看板 sky 11/19 14:52
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※ 編輯: hvariables 來自: 114.24.93.110 (11/19 16:40)
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※ 發信站: 批踢踢實業坊(ptt.cc)
※ 轉錄者: lovefordidi (61.222.20.145), 時間: 11/19/2011 16:47:16
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