Perhaps the outside world really was something akin to a quantum state, and did not exist unless he observed it. - Liu Cixin

At the end, an adult and a child stand in front of the grave of a Red Guard who had died during the faction civil wars. The child asks the adult, ‘Are they heroes?’ The adult says no. The child asks, ‘Are they enemies?’ The adult again says no. The child asks, ‘Then who are they?’ The adult says, ‘History.

it was not a good idea for the human race as a whole to make contact with extraterrestrials. The impact of such contact on human society would be divisive rather than uniting, and would exacerbate rather than mitigate the conflicts between different cultures. In summary, if contact were to occur, the internal divisions within Earth civilization would be magnified and likely lead to disaster.

Life needed smoothness, but it also needed direction. One could not always be returning to the point of origin.