SETI Explained - How We Search for Alien Civilizations

“A civilization might choose not to talk, it might be cautious, indifferent, or simply uninterested in announcing its presence, but any civilization that grows beyond its home planet must manipulate energy and matter on increasingly large scales. And those activities have physical consequences that cannot be perfectly hidden.”

“A perfectly compressed signal looks like noise unless you know how to decompress it. To an unprepared observer, the most advanced messages may be the least recognizable.”

“A star that looks dimmer in visible light but unusually bright in infrared may not be strange, it may be busy.”