[FinalBriefing]

Well, they can train the model on things we know _aren't_ alien signals.

Edit: From the article:

  > To train the AI system, Ma inserted simulated signals into actual data, allowing the autoencoder to learn what to look for. Then the researchers fed the AI more than 150 terabytes of data from 480 observing hours at the Green Bank Telescope.

The simulated signals were sounds that couldn't possibly be produced by any (known) natural astrophysical process. So, the model finds signals that have characteristics of artificially generated signals.

[mr_toad]

Or it will identify novel astrophysical phenomena. Which is not a bad thing.

[insane_dreamer]

yes, it can identify _unknown_ signals, but can't determine whether they are _alien_ or simply indeterminate natural phenomena