It seems that the cosmology constant has something to do with the energy density of empty space , and it may change with time , or may even do the opposite one day - compel the universe to contract 我们对宇宙常数的认识实在太少了,它似乎跟真空空间中的能量密度有关,也可能随时间不断改变,又或甚至终有一天反过来迫使宇宙收缩。