Stardust (2000)
John Gribbin (1946)
198 pagesOne of the popular justifications in campaigns promoting recycling is that material can be reused to create new products. In his book Stardust, astrophysicist and writer John Gribbin takes this concept to a whole other level, describing, as his subtitle states: The cosmic recycling of stars, planets and people. In an engaging mix of science and history we learn how the universe recycles the remains of stars to form the basic building blocks of solar systems and, finally, of life itself.
Gribbin introduces his topic by summarizing theories put forward on how life could have first appeared on Earth, before concluding that
[although] we still don’t know exactly how life began … we do know, very precisely, what mixture of chemicals is required for the existence of life as we know it. And we know exactly where those chemicals come from --- as a natural by-product of the processes of star formation and evolution. (17)
Identifying Carbon, Hydrogen, Oxygen and Nitrogen (CHON) as the fundamental elements to life, he focuses in particular on the properties of Carbon and Hydrogen, including their critical ability to easily form chemical links with other elements, and so to create such all-important structures of life as amino acids and DNA. This leads then to the central question of his book: “can we explain where the stuff we are made of, dominated by CHON, comes from?” (42) The key word for Gribbin being explain, as both the title of the book and the introduction give away the answer: “stardust.” Gribbin describes his motivation for writing the book as a desire to explain how scientists came to recognize the importance of stardust, to characterize its content, and to discover the processes of its creation.Though Gribbin has targeted the book at a lay audience by avoiding the more complex details of the physics and chemistry involved, it helps for following his explanations to have some level of comfort with high school level science. To make the book more accessible, he does early on provide a brief but effective review of key scientific concepts, dusting them off for readers and so preparing a strong foundation for the rest of his text. He augments these explanations with clarifying sketches to illustrate the ideas introduced.
Gribbin’s presentation of the scientific history of stardust necessarily follows two scales of discovery that occurred roughly in parallel: the very large --- understanding the origins and development of the cosmos; and the very small --- understanding the constituent parts of matter and how they interact. He begins with the ancient Greeks and their understanding of what they saw in the night sky; in particular he highlights the philosopher Democritus, who proposed both that “the Milky Way might indeed be made up of countless numbers of stars … [and who] was also a leading early proponent of the atomic theory.” (44) (For more on Democritus, see Carlo Rovelli’s excellent work investigating the intersection of science and history Reality is not What it Seems; my review here.)
Using Democritus as an example, Gribben highlights a key element of the scientific process, pointing out that “[Democritus] had no way to test his ideas because he lacked the appropriate technology. They remained hypotheses, not theories, until the technology to test them was invented.” (44) This fundamental relationship between technological development and its relationship to theoretical understanding is central to Gribbin’s presentation in the rest of the book; he traces the intimate connection of the evolution and refinement of scientists understanding of the nature of the universe, including of stars and their systems of planets, to the availability of ever more advanced technology with which to make observations. And he doesn’t shy away from addressing the inevitable mistaken assumptions and dead-ends that scientists made along the way, and that often delayed progress until the technology became available to clarify and correct them.
As ever better tools came on-line, scientists were able to determine that the elements that had been discovered on Earth were also present throughout the universe, in stars and nebula. They also came to understand that our present universe had originated “from a superhot, superdense state --- the Big Bang --- about … 15 billion years ago,” (99) but that what “emerged [from the Big Bang]… was a mixture of 75 per cent hydrogen, just under 25 per cent helium, and a smattering … of very light elements.” (111) The key question became then, how that “very light primordial stuff turned into the stuff we are made of?” (111) The answer ultimately lay within an understanding of the processes involved in the creation, life, and, particularly, end-of-life of stars.
Gribbin describes how scientists came to understand that the earliest stars --- necessarily made from the only elements available, hydrogen and helium --- had short lives, at the end of which many expelled material into the cosmos as either red giants or, for some subset of stars, more dramatically as novae or supernovae. The processes that occurred as the dying stars ejected this material created a cosmic dust of heavier elements --- stardust. Supernovae in particular lead to vast amounts of these heavier elements, and Gribbin provides a fascinating review of the two types of supernovae that have been identified, and how they lead to the creation of different sets of elements.
The heavier elements contained in the nebulae of stardust created by that first generation of stars became a small but significant part of the next generation of stars that formed, which further enriched the interstellar material with an even larger proportion of heavier elements as these stars in turn completed their lifecycle. Each subsequent generation then continued this process of enriching the material available for the formation of new stars and their planetary systems.
As some scientists developed and demonstrated these theories for the end-of-life stellar processes that created heavier elements, others worked out an ever more refined understanding of how stars and planets form from this material. Gribbin describes what has been learned by using the formation of our own solar system as an example, and in particular the development of Earth and how it came to have the ingredients for life. Based on the latest evidence and understanding about the broad variety of molecular material contained in stardust (revealed and proven out using the latest technology), he summarizes current theories on how the fundamental building blocks of life may have arrived on Earth.
In an Appendix, Gribbin moves on from his main topic of stardust --- which he describes as now increasingly well-understood --- to the forefront of speculative science, at least as it stood when he was writing this book at the turn of the millennium. He notes that, while his book provides an explanation of the current understanding of how the universe we observe today arose from the Big Bang, it does “not necessarily [represent] the whole story of life and the universe.” (179) At the cutting edge of astrophysics, the latest theories describe the potential origins for singularities such as that which caused the Big Bang; they postulate the existence of multiple universes, each with a potentially different set of physical characteristics, and one of which --- ours --- having the particular set of coincidences necessary for life as we know it. Thus, scientists continue to push forward, while remaining inseparably tied to what the latest technological developments make observable to them.
Stardust reads a lot like a detective or mystery story, though one in which the solution is revealed early on. The thrill comes from learning how successive generations of scientist-detectives, supported by ever more expertly engineered equipment, slowly but inexorably piece together answers to the mysteries of the universe. Gribbin’s engaging writing brilliantly achieves the right balance of conceptual overview, technical detail and scientific history to make his book comfortably accessible to those interested in understanding more about our cosmic origins.
Other reviews / information:
In an interesting note, Gribbin points out that it is incorrect to think of the Big Bang as having exploded to fill space:
The Big Bang was not an explosion that took place somewhere in empty space, with fragments from the explosion (galaxies) flying apart through space like shrapnel form an exploding shell. Rather, what happens is that space itself expands, and takes galaxies along for the ride. (100)
I tripped across this wonderful video showing The Entire Life of the Universe.
Have you read this book, others by this author, or even similar ones by other authors? I’d enjoy hearing your thoughts.
Other of my book reviews: FICTION Bookshelf and NON-FICTION Bookshelf
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