There is a metaphor in the film that hits the spot: if the sun suddenly darkens, the earth will still be bright for 8 minutes, and during these 8 minutes, we do not know that the sun is dead. The boy used these 8 minutes as a metaphor for his disbelief in his father's death. He stayed in place for a long time during these 8 minutes, and slowly accepted it in his own way. "Lost" is as difficult a topic as "existence". The latter relies on human reason to answer, while the former relies on emotion.
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