吉萨大金字塔的镜面反射
Specular Reflection from the Great Pyramid at Giza
摘要：
据说古埃及的金字塔曾在阳光下熠熠生辉。抛光的石灰石表面不仅会在各个方向上漫反射，而且还可能在特定方向上产生镜面反射。从很远的距离就可以看到朝向地平线上的点的反射。在特定的一天和时间，当太阳处于适当的位置时，一个站在远处的观察者会看到太阳的反射在金字塔表面移动时的瞬间闪光。反射到地平线上的太阳位置被限制在天空中的狭窄弧线上，金字塔的每一边都有一个弧线。我们模拟了胡夫金字塔的镜面反射，并得出了在重要的古代遗址上可见的年度日期和时间。这些事件中的某些可能与埃及日历上的重要日期相吻合，以及与太阳分点，冬至和跨季度日相吻合。Wepet-Renpet的庆祝活动，在金字塔建造的时候发生在春天的跨季度日附近，将以南部地平线上的镜面扫描为标志。在秋季和冬季的交叉季度的日子里，反射将被定向到赫利奥波利斯。我们认为，在那些日子里，在胡夫金字塔的截顶上方，可能已经可以通过镜面反射看到库鲁米底翁。
英文摘要：
The pyramids of ancient Egypt are said to have shone brilliantly in the sun. Surfaces of polished limestone would not only have reflected diffusely in all directions, but would also likely have produced specular reflections in particular directions. Reflections toward points on the horizon would have been visible from large distances. On a particular day and time when the sun was properly situated, an observer stationed at a distant site would have seen a momentary flash as the sun's reflection moved across the face of the pyramid. The positions of the sun that are reflected to the horizon are confined to narrow arcs in the sky, one arc for each side of the pyramid. We model specular reflections from the pyramid of Khufu and derive the annual dates and times when they would have been visible at important ancient sites. Certain of these events might have coincided with significant dates on the Egyptian calendar, as well as with solar equinoxes, solstices and cross-quarter days. The celebration of Wepet-Renpet, which at the time of the pyramid's construction occurred near the spring cross-quarter day, would have been marked by a specular sweep of sites on the southern horizon. On the autumn and winter cross-quarter days reflections would have been directed to Heliopolis. We suggest that on those days the pyramidion of Khafre might have been visible in specular reflection over the truncated top of Khufu's pyramid.
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