Kate was reviewing the results of a full ship diagnostic when Paul and Mary entered the conference room wearing the dry clothes she had provided.
"Two Atlantean scientists came here one hundred fifty thousand years ago to study the early humans on this planet. As part of their routine procedures, they deployed a beacon. It filters the light we can see and blocks any signals either to or from Earth."
Kate explained that the Atlantean homeworld had fallen fifty thousand years ago, and the sole survivors of the war had sought refuge here on Earth, under the protection of the beacon, where their enemy couldn't find them.