醒了好几次

severalties───n.各别；各有各事；单独保有

sidereal times───[天]恒星时（利用恒星为准算出的时间）

universal times───世界时间；格林威治时；国际标准时间

In the experiment, they are wakened several times during the night, and asked to report what they have just been dreaming.───在这个实验中，他们在夜间被叫醒了好几次，并要求报告自己刚刚所梦见的东西。