For 17 years, astronomers at a massive radio telescope in Australia at the Parkes Observatory have been searching for the source of an alien signal of “perytons.” With a new retrofit, they finally were able to isolate the source: their microwave in the kitchen.
The perytons have been detected a couple times a year and were extremely nearby. Their new receiver isolated the signal at 2.4 GHz. That is when a light went off for one of the scientists who remembered that was the level of a conventional microwave.
They went to the kitchen and took readings. It turns out that, when food was warming, the signal would be released when you opened the door to check the dish.