Cosmic Evolution and Impermanence

The cosmological theory that best describes the current observations of the universe is that of the Big Bang. It is now believed that the universe began its existence some 15 billion years ago with an enormous explosion from an initial state that was extremely tiny, hot and dense and that spawned space and time. Since then, there has been a relentless ascent towards increasing complexity. Beginning with a vacuum filled with energy, through the primordial soup of elementary particles, the universe has woven an immense cosmic tapestry composed of hundreds of billions of galaxies, each made in turn of hundreds of billions stars. In one of these galaxies named “Milky Way”, on a planet near a star about 2/3 of the way from the Galactic center toward the edge, humanity appeared, capable of marveling at the beauty and harmony of the cosmos and of asking questions about it.

One of the most remarkable changes of paradigm that has occurred with the advent of the big bang theory is that the universe has acquired a historical dimension. We can now speak of the history of the universe, with a beginning and an end, with a past, present and future. That the universe has a history was not always accepted. Some 24 centuries ago, the Greek philosopher Aristotle thought that the Heavens, because they were perfect, had to be unchanging and eternal in contrast to the changeable and imperfect world of the Earth and the Moon. Newton’s universe in the 17th century was static, unchanging and devoid of history. As late as the 1950s, the Steady State Theory, which says that the universe is on the average unchanging both in space and time, was considered a serious rival to the Big Bang Theory. The Big Bang Theory thus introduces the fundamental idea of cosmic evolution. Stars are born, live their lives, and die. In the course of their death throes, the massive stars eject gas that shall serve as seed for the birth of a new generation of stars. Those life and death cycles last from a few million years to several billion years. The universe itself may go through cycles of births and deaths, Big Bangs followed by Big Crunches, although it is not yet clear if the universe contains enough dark matter for its gravity to halt its present motion of expansion and reverse it. The idea of ceaseless change, of constant evolution due to the never-ending chain of causes and effects, is also central to Buddhism. It is called “impermanence.”

Contributed by: Trinh Xuan Thuan