The question (v2) that was closed as non-mainstream read:
Title: How would a tachyonic antitelephone work?
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So here's my question. Let's say that in the year 2067, a highly advanced alien race decides to send a message back in time 50 years to Earth in 2017. How could they send such a signal so that it could be detected by 2017 technology? I understand this isn't possible under mainstream physics, but let's assume mainstream physics is wrong. Hypothetically, how could it happen?
The question was later edited by OP, and is currently (Sept 27, 2017) in the review queue.