If an observer waits in the western sky for a planet like Venus, what will they witness just before the planet disappears?
Answer
The planet setting
The direction in which an object is observed determines whether it is arriving or departing from visibility for the night or day. If an observer positions themselves facing the western horizon, they are looking toward the point where objects conclude their transit across the celestial sphere. Therefore, waiting in the West for a planet that has already risen in the East means one will catch the planet just before it sinks below the horizon, which is defined as setting. It is crucial to distinguish this normal setting event from the highly anomalous event of a West rising.
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