Cosmic evolution can be defined, in the simplest terms, as the scientific study of change as it has occurred since the beginning of this universe. The age of the universe is now estimated to be approximately 14 billion years. The concept of the arrow of time has been employed to record the major changes that have resulted in the universe’s increasing complexity. Cosmic evolution focuses on the interconnectedness of all parts of the universe. This orientation can be noted at least as early as the 16th century in the writings of Nicolaus Copernicus and Galileo Galilei. The idea of the centrality of planet Earth was abandoned only in the past several hundred years. The movement toward more critical thinking about humans and the universe was a prominent element of the Renaissance.
Julian Huxley, a 20th-century British biologist, is associated with a scientific approach to the study of cosmic evolution. Pierre Teilhard de Chardin, a 20th-century French geopaleontologist and Jesuit priest, emphasized the religious aspects of cosmic evolution. Mainstream scientists have generally taken an objective orientation, claiming that it is crucial to continually gather and test data to further our general understanding of the order and nature of this universe. Implicit in these attempts is an implication that humans, however important and advanced at present, should not be considered as unique or as the center of the universe. The study of cosmic evolution is becoming increasingly interdisciplinary in that it includes scholars in astronomy, physics, chemistry, geology, biology, and anthropology. Recently, physicist Eric Chaisson has written extensively on the seven major stages of cosmic evolution: particulate, galactic, stellar, planetary, chemical, biological, and cultural.
The particle epoch refers to the first few minutes after the big bang that scientists generally agree created our universe. The big bang itself probably took only a few seconds and could be described as the beginning of the arrow of time, or of time itself. At that point, the intense energy kept matter from forming even elementary particles. The weakening and cooling of energy initially resulted in the production of hydrogen, the lightest and most common element in our universe. Research on the galactic epoch represents special challenges to scientists. Though galaxies have been observed throughout the universe, there are still questions about exactly how they were formed. It is generally concluded that most were formed during the universe’s first billion years, and that conditions conducive to their formation are no longer present. The conditions that first produced stars during the stellar epoch still exist at the present time. Astronomers have observed new stars being formed in the Milky Way. For stars to form, stellar gas must combine with large amounts of matter. The sun is an example of a star with medium mass that has lasted around 5 billion years and is expected to last at least that long into the future.
The planetary epoch is generally assumed to have developed as the result of the stellar epoch, since planets appear to form as the result of the explosion of stars with a large mass. At the time that the sun was forming, around 5 billion years ago, other planets appear to have been formed by the fragmentation of a large ball of gas and dust. Earth is an example of a planet closer to the sun, which accounts for its smaller size and rocky surface. Under the original harsh conditions, it seems likely that life did not yet exist. Earth is also held to be approximately 4.6 billion years old. During the chemical epoch the available energy resulted in the growing complexity of simple chemicals that would eventually make life itself possible. Perhaps 4 billion years ago, the biological epoch began with the formation of the earliest and simplest forms of life. Fossil records have indicated that a particularly diverse set of new life forms appeared during the Cambrian period, about 550 million years ago. Compared to other forms of life and complex organisms, humans have existed for only a few million years, with more advanced humans appearing only about 150,000 years ago.
The cultural epoch, the seventh and final stage, includes the present day. The most rapid period of advancement of civilization took place within the last 10,000 years, including the rise of technology, the development of symbolic language as articulate speech, and even the desire and ability to measure time itself more accurately. This fertile period represents just 1% of human history. As humans evolved, an actual increase in brain size occurred. Those changes increased their capacity to acquire and store information and to pass it on to others, as well as to have the curiosity and ability to tackle a topic as complex as cosmic evolution.
Chaisson emphasizes the importance of energy in the evolutionary process. Though the amount of energy in the universe is fixed according to the conservation principle, cosmic expansion has resulted in an ever-increasing energy flow per mass over the past 10 billion years. Galaxies, stars, planets, and various life forms can be described as open systems. They are able to exchange energy and matter with their surroundings. The increased energy that results may explain the growing complexity of the universe and the increased order of its various structures. In this sense, a kind of natural selection occurs when a specific system survives because it has been able to process energy at the most efficient level. Chaisson describes the arrow of time as linear and not reversible, with the sequence of the various epochs that occur being more important than identifying how much time actually passed during each epoch. It can be useful to imagine the arrow of time as flexible and able to be modified as scientists gather more data. Fortunately, modern scientists have the advantage of increasingly sophisticated technological resources for finding new data. An important example is the Hubble Space Telescope, a major tool used in the 2007 Cosmic Evolutionary Survey (COSMOS) at the California Institute of Technology. The survey revealed that this universe consists of only 4% ordinary matter. The remainder, not directly observable, consists of 22% dark matter and 74% dark energy.
Cosmic evolution can be described as a historical study as well as a scientific discipline. Scientists strive to avoid being judgmental in their observations, and the interdisciplinary nature of the field can only increase the scope of what scientists and other scholars may discover. In addition to satisfying humankind’s natural curiosity, the study of cosmic evolution is an important way of linking the past with the present and speculating on the future. What we learn could also allow us to monitor our impact on evolution in the most constructive way possible.
Betty A. Gard
See also Copernicus, Nicolaus; Cosmogony; Cosmology, Inflationary; Galilei, Galileo; Hawking, Stephen; Time, Emergence of; Universe, Closed or Open; Universe, Contracting or Expanding; Universe, Evolving; Universes, Baby
Chaisson, E. J. (2001). Cosmic evolution: The rise of complexity in nature. Cambridge, MA: Harvard University Press.
Chaisson, E. J. (2006). Epic of evolution: Seven ages of the cosmos. New York: Columbia University Press.
Tyson, N. deG., & Goldsmith, D. (2004). Origins: Fourteen billion years of cosmic evolution. New York: Norton.