How Do We Not Know Where the Earth Is?

If the earth happens to be in another situation where it slows down bob's time, then alice can finish her experiment first. So who finishes the experiment first and who can send a message to the other one about their results depends on who is closer to the gravitational object that's slowing down time. Yet this sounds like short anish prisoner as dilemma. Sounds catastrophic exactly. We don't know then what has happened inside the box. Was it alice and then bob, or was it bob and then alice? And so in this situation, because the position of the light cones is uncertain, sality is uncertain. In this kind of experiment, which happened? Was at a before b