Dr. Petroff has also shown that the Higgs boson signal was actually sparks from someone microwaving grapes, the EHT black hole photo was a frozen bagel someone left in too long, and the LIGO detection was just someone slamming the microwave door too hard.
And they knew it was terrestrial in origin, because only one dish picked it up, whereas if it was was of outerstellar origin, multiple sites would have received it.