Our solar system is an extraordinary place where asteroids careen off course and solar winds hurl charged particles across billions of miles of space. Yet we seldom consider how these events, so immense in scale, influence our own fragile blue planet. In Ripples on the Cosmic Ocean, Dagomar Degroot traces the surprising threads linking humanity to the rest of the solar system. He reveals how the shifting sands of other planets have shaped geopolitics, spurred scientific and cultural innovation, and encouraged new ideas about the emergence and fate of life. Martian dust storms altered the trajectory of the Cold War and inspired fantastical stories about alien civilisations. Comet impacts on Jupiter led to the first planetary defence strategy. And volcanic eruptions spewed sulfuric acid into Venus's atmosphere, exposing the existential risks of global warming. But just as we expand the boundaries of space exploration, cosmic environments are becoming increasingly vulnerable to human activity. Yet, they may also hold the key to slowing down the climate crisis back on Earth. Ripples on the Cosmic Ocean urges us to develop an interplanetary environmentalism across a vast mosaic of entangled worlds and to consider the profound connections that bind us to the cosmos and each other.