The exact start date of Ramadan changes because it's based on clerics seeing a crescent or new moon as the Islamic calendar follows the lunar cycle.

斋月的确切开始日期会变化，因为它是基于伊斯兰历的月相或新月而定的，伊斯兰历遵循月亮的周期。

Led by the Chinese Academy of Sciences, the study suggests that " impact glass beads in lunar soils are a prime water reservoir candidate able to drive the lunar surface water cycle."

由中国科学院牵头的研究表明，“月球土壤中的冲击玻璃珠是能够驱动月球表面水循环的主要候选水库。”

On earth, we use the moon to define this length of time as it takes 29 and a half days to complete the lunar cycle which conveniently breaks the year down into roughly 12 equal parts.

在地球上，我们用月球来定义这个时间长度，因为完成一个月球周期需要 29 天半，这方便将一年分成大约 12 个相等的部分。

And because the ancient Egyptians were using the lunar cycle in combination with this heliacal rising, some years ended up having 12 lunar months, while others had 13 lunar calender months, if Sirius didn't rise in the 12th month.

因为古埃及人将月球周期与这种日升相结合，如果天狼星没有在第 12 个月升起， 一些年份最终有 12 个阴历月， 而其他年份有 13 个阴历月。

And because the ancient Egyptians were using the lunar cycle in combination with this heliacal rising, some years ended up having 12 lunar months, while others had 13 lunar calender months, if Sirius didn’t rise in the 12th month.

而且由于古埃及人将月球周期与这种日升相结合，如果天狼星没有在第 12 个月升起，一些年份最终有 12 个阴历月，而其他年份则有 13 个阴历月。