We assume that other intelligent civilizations would broadcast radio signals like we do, she said — but we've been radio-loud for a short time, and we're actually getting quieter as our technology improves. And it's more complex than that anyway. We assume other intelligent civilizations would want to talk to us at all, or that they would even know to look. But what if other planets play host to hyper-intelligent space dolphins, who, in an attempt to evade dangerous stellar radiation, never left the sheltering waters of their world? They wouldn't even know there were other stars, Walkowicz said. Our interest in whether life is out there stems from our ability to see the stars, and recognize that we are a planet orbiting just one of them.