Does the Universe have a "day"?

A day is the time for the earth to go around the sun. I don't know what you mean a "universe day"? an era? Don't use day then, use some other terms. Don't confuse me.

所有跟帖： 

• 天上一天，地下一年，是形容在不同参照系里，测量的结果不是一样的。 -蓝山雀- ♀ (47 bytes) () 09/25/2015 postreply 12:08:22

• "天上一天，地下一年", why not two years? -Calypso- ♂ (306 bytes) () 09/25/2015 postreply 12:16:28

• Are you telling me that -Calypso- ♂ (100 bytes) () 09/25/2015 postreply 12:32:21

• 天上一天，地下一年，是西游记里的 -Calypso- ♂ (50 bytes) () 09/25/2015 postreply 14:07:36