The stars we see at night are really huge like our sun, but they are much farther away in space. Some of them have planets(行星)like our earth travelling around them.

    The stars are so hot that they give off great light and heat--more than the hottest, brightest fire you can imagine(想象). As we all know, light travels at the speed of 300, 000 kilometres per second. But the stars are so far away that their lights still take years to reach us. The light we see coming from some far-off stars started for the earth more than a hundred years ago.

    The moon is a ball of cold rock. It is smaller than the earth. It circles round(环绕)the earth as the earth circles round the sun. The whole journey(旅程)of the moon round the earth takes twenty-eight days. We see it changing from new moon to half to full and back to new moon every twenty-eight days. Our word "month" comes from the word "moon".

144的全部约数有多少个？这些约数的和是多少？

图（a）为测量滑块与水平木板之间的动摩擦因数的实验装置示意图．木板固定在水平桌面上，打点计时器电源的频率为50HZ，开始试验时，在托盘中放入适量砝码，滑块开始做匀加速运动，在纸带上打出一系列的点．

造成近代中国人物质生活和社会习俗发生变化的主要因素不包括(     )