"Everything is sad," wrote the Ancient poets. But is this sadness merely a human experience, projected onto the world, or is there a gloom attributable to the world itself? Could the universe be forever weeping the "tears of things"? In this series of meditations, Dominic Pettman and Eugene Thacker explore some of the key "negative affects" - both eternal and emergent - associated with climate change, environmental destruction, and cosmic solitude. In so doing they unearth something so obvious that it has gone largely unnoticed: the question of how we should feel about climate change. Between the information gathered by planetary sensors and the simple act of breathing the air, new unsettling moods are produced for which we currently lack an adequate language. Should we feel grief over the loss of our planet? Or is the strange feeling of witnessing mass extinction an indicator that the planet was never "ours" to begin with? Sad Planets explores this relationship between our all-too-human melancholia and a more impersonal sorrow, nestled in the heart of the cosmic elements. Spanning a wide range of topics - from the history of cosmology to the "existential threat" of climate change - this book is a reckoning with the limits of human existence and comprehension. As Pettman and Thacker observe, never before have we known so much about the planet and the cosmos, and yet never before have we felt so estranged from that same planet, to say nothing of the stars beyond.