Cosmos

Sagan devotes a significant amount of time to the presence of comets and the birth (and death) of stars.

Comets occupy a prominent place in Chapter 4, entitled “Heaven and Hell,” wherein the author discusses the ways in which comets—and other cosmic detritus, like meteors—have affected evolution. Comets—literally chunks of space rock that orbit larger stellar objects and sometimes crash into them—can have world-ending influence: “But in the history of Nature, the record is clear. Worlds have been devastated” (73) by collisions with comets and other cosmic objects. Comets have also been incorporated into traditional belief systems, often viewed as harbingers of change—or doom: “Comets have always evoked fear and awe and superstition” (78), shorthand for the fears of Earthbound populations unable to explain observed phenomena via the lens of science.

The author devotes even more time to the significance of stars. Chapter 9, “The Lives of the Stars,” is dedicated almost entirely to the way their births, declines, and deaths define the cosmos. Without our sun—a rather mediocre star, according to Sagan—there would likely be no life on Earth, and certainly no intelligent humanity able to navigate the skies. The matter that makes up the composition of life, whether vegetable or animal, is clearly indebted to the stars: “Where do these atoms come from?” Sagan asks. “Except for hydrogen, they are all made in stars” (218). As he emphasizes, “The origin and evolution of life are connected in the most intimate way with the origin and evolution of the stars” (233). It is through these scientific facts that humanity, and Earth itself, is most intimately connected to the Cosmos.

Mars, the fourth planet from the sun in our solar system, has loomed large in our imagination. It is the nearest planet to Earth, and considered to have the most potential for extraterrestrial life. Mars has long been a repository for the expectations of astronomers and for the dreams of writers and philosophers, “a kind of mythic arena onto which we have projected our Earthly hopes and fears” (106). Writers throughout history have imagined inhabitants of Mars as alternately hostile and potentially welcoming, from H. G. Wells’s The War of the Worlds (1898) to Andy Weir’s The Martian (2011). The author points out that, even when viewed from the perspective of science, “The real Mars is a world of wonders” (106). The Red Planet, it seems, will continue to captivate this blue one for years to come.

The author also observes the features of other planets of the solar system, most notably Venus—a notorious hellscape—and Jupiter, with its giant red spot and gargantuan size. These other planets are important to Cosmos because they provide context for Earth’s place in the universe. Venus is much smaller and considerably hotter. Jupiter is much, much larger and remarkably different; its gaseous makeup is grounds to assume that, if life has evolved elsewhere in the universe, it might be fundamentally other from what has evolved on Earth, given the environmental conditions. The cold rings of Saturn and its many moons—some of which have been shown to have conditions conducive to life—have also captured the imagination of scientists and writers alike.