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Sunset Conjecture
The Sunset Conjecture shows why two people can experience the same universe from different perspectives. Picture yourself on the beach at sunset. The sun's golden reflection appears to point directly toward you, while a friend beside you sees it pointing toward them. This phenomenon occurs because (1) everyone is at the center of their own observable universe where everything they see arrives from the past, and (2) at that center lies the observer's idea space, the private field through which the incoming universe is experienced.