Dreams of Other Worlds

Summary

Dreams of Other Worlds explores how our concepts of distant worlds have been shaped and informed by space science and astronomy over the past forty years. The arc of the book is chronological and progresses from the proximate toward the remote. From comets to cosmology, and from the Mars rovers to the multiverse, the book spans eleven NASA missions that have given us a sense of our cosmic environment.

The book starts in the Solar System with Mars and the Viking landers. The Vikings dashed hopes that Mars might be habitable but they opened up the modern age of exploration of the red planet. Nearly three decades later, the Mars Exploration Rovers were embraced by the public as they traversed Mars and gathered evidence for a warmer and wetter planet in the distant past. Next come two spacecraft that made a Grand Tour of the outer Solar System during the 1970s. The Voyagers painted detailed portraits of the four gas giant planets and their moons. More recently, Cassini has explored Saturn and its fascinating moon system. Together, these missions have recast our understanding of the frigid realm beyond the asteroid belt.

The book continues with Stardust, the mission that caught not just one but two comets by the tail and in doing so told us how the Solar System was likely to have formed. The Solar and Heliospheric Observatory, by contrast, focused on the Sun itself and taught us what it means to live with a star. Belying its apparently steady light, the Sun has activity that manifests in invisible forms of radiation. Looking more broadly at the situation of the Solar System, the Hipparcos satellite refined the work of William Herschel by placing us accurately within the city of stars we call the Milky Way.

The two missions that follow illustrate the revolution in astronomy when astronomer’s blinders were removed after centuries of learning about the universe only through light. Spitzer and Chandra are two of NASA’s Great Observatories, straddling the electromagnetic spectrum and looking at regions of space that are hidden from view. Spitzer penetrates the gas and dust that permeates interstellar space and reveals new worlds being formed. Chandra, by contrast, has revealed the violence of dark objects like neutron stars and black holes, where tiny worlds distort space-time and accelerate particles beyond any capability of the largest accelerators.

Closing the book are two missions that explore the edges of space and time. The Hubble Space Telescope has embedded itself deeply into the consciousness of the general public and has contributed to every area of astrophysics. In particular it has quantified the limits of our vision, a region 46 billion light years in any direction, which contains roughly 100 billion galaxies. The Wilkinson Microwave Anisotropy Probe was a specialist mission to map the microwave sky and pin down physical conditions in the infant universe. By confirming the big bang model in great detail, this microwave satellite has shown that there are likely innumerable distant worlds out there whose light has not yet reached us in the time since the big bang.