What if alien transmitters compensate for their own motion?
Most of the SETI pipelines we run on Earth are tuned to a clever assumption: that any narrowband signal not drifting in frequency is probably terrestrial interference. Real interstellar transmitters should drift, because the Earth is spinning and orbiting and so is whatever’s transmitting at the other end. We look for that drift, and we throw out the things that don’t move.
The problem is — that filter is only as good as the assumption behind it.
I started thinking about this last fall: what if a transmitter on the other end is deliberately compensating for the relative motion between its planet and the receiving system? It’s not a wild assumption — we already correct spacecraft signals for our own motion. A civilization that knows where Earth is, and roughly how Earth moves, could in principle pre-bias its transmitter to land at a fixed frequency in our frame. From here, it’d look like interference. We’d discard it.
The paper I just put up on Zenodo proposes a small tiered framework for thinking about this — distance-aware signal models, what kinds of compensation are plausible at different ranges, and what a pipeline that tolerates Doppler-invariant candidates would have to look like in practice.
It’s not a claim that anyone is doing this. It’s a question about whether our filters are biased against them if they were.