Astrophysics

Introduction: The Cosmological Puzzle of Existence The question of how the universe began—where all the matter, energy, space, and time...

Introduction: The Ancient Question of Other Worlds For millennia, humanity has looked up at the night sky and pondered a...

Introduction: The Triumphs and Limits of General Relativity The study of the cosmos has been utterly transformed by Albert Einstein's...

Introduction: A New Window on the Universe For over three decades, the Hubble Space Telescope (HST) provided humanity with breathtaking...

Introduction: The Universe's Great Cosmic Mystery For centuries, astronomy has relied on the simple principle that what we observe through...