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演示昼夜更替及其原因
以电灯或一只电代表太阳,使之与地球仪的球仪心在同一平面上.地球仪绕地轴(地轴北端指向正北方)自西向东转动。地球自转的周期(转一周3600)为一个恒星日,即23小时56分4秒。地球仪自西向东自转时,在北极上空看地球仪呈反时针方向旋转;从南极上空看地球仪呈顺时针方向旋转;从赤道上空看地球仪自西向东旋转,这三种表述是一致的。由于地球(仪)是一个不透明的球体,同一时间太阳(电灯或手电)只能照亮地球的一半,即向日为昼,背日为夜。被太阳(电灯或)照亮的半球,称为昼半球,半夜照亮的半球,称夜半球。向个斗球之间的分界线(两条)合为一个圆圈,叫晨昏线(圈)。地球(仪)不停地自西
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景观雕塑的观赏效果必须事先做预测分析,特别是对其体量的大小、尺度研究,以及必要的变形和错觉的校正。人们较好的观赏位置一般选择处在观察对像高度两倍至三倍以远的位置上比较适当,如果要求将对象看得细致些,那么人们前移的位雕塑刀塑造黏土造型。好好的用泥巴做雕塑,干嘛非要用软件?这是广大雕塑家们心中疑问。当你真正了解了软件能做到无数种可能性是泥巴这种现实材料无法做到的时候,就不会再有这样的疑问了。比如对称着做,泥巴能做到么
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张衡创制地动仪的诱因可能来自灯笼和风铃。候风地动仪直径8尺,可能反映张衡惯于向上观天象,精于天文的形象,我国原始天文仪器标准尺寸是8尺,大约为一个的身高(古代用的尺),张衡设计过的指南车、三轮、自飞木雕等,涉及观天文的仪器如圭表、浑仪、浑象尺寸一律8尺,地动仪制成之后与几件天文仪器一起安装在高高的观天灵台上,这是张衡科学灵感之物在高处显灵的表达,或者是东汉古人对悬挂物,对天象、星辰和大自然的敬畏与崇拜。这与现代人判断地动时观察吊灯晃动,判定地动
张衡利用物体的惯性来测定地动,都柱悬挂在***,为人类探索地动奥秘迈出,其贡献理当在世界科学占有光辉的一页。为了永远纪念他,国际天文学会于1970年、1977年先后以张衡的名字对一座月亮环形山和一颗太阳系小行星作了命名,这不能不是中华民族的骄傲。
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