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July 3, 2017

Everyone knows the famous question of the tree falling in the forest,
"If a tree falls in a forest and no one is around to hear it, does it make a sound?"
While philosophers have many reasons to argue the point, physicists are fairly certain that sound is produced in all classical mechanical situations such as this, independent of an observer. However, if the "tree" exists in the quantum realm, it will not have fallen until observed.

The Roman philosopher, Lucretius (99 BC - c. 55 BC), actually explored this idea in 50 BC in relation to the origin of the universe in his book, De Rerum Natura (On the Nature of Things). Lucretius traced the origin of the universe to the point at which human history was first recorded, and he wrote that the universe would have its end when men ceased to exist. If paleontology had existed as a science in Lucretius' time, he might have had a different opinion.

Figure caption

Lucretius (99 BC - c. 55 BC) was among the atomists, although his writing were much later than the early atomists, such as Democritus (c. 460 - c. 370 BC). (Lucretius image, a 1682 engraving by Michael Burghers, via Wikimedia Commons. Latin text and English translation by William Ellery Leonard from Tufts University Project Perseus.[1] Click for larger image.)

At the other extreme, we have the idea of a universe with neither beginning nor ending. This is the steady-state theory of the universe that I discussed in a previous article (Clinging to Theory, August 18, 2016). While the steady state universe had a basis in scientific theory, rather than philosophy, the progress in cosmology made the theory far less tenable than the current Big Bang cosmology.

Since universal expansion is now viewed as a certainty, it's a requirement of a steady-state universe that matter is continually created as the universe expands. Such matter need only be created at a rate of just one hydrogen atom per cubic meter per billion years, a process that's quite undetectable. The number of cosmologists who still believe in the steady-state universe might just fit in a single, very small, conference room.[3]

Helge Kragh of the Niels Bohr Institute, the University of Copenhagen (Copenhagen, Denmark), has just published a paper on arXiv that reviews these, and other theories of cosmogony.[4] This paper is an English version of a book chapter that is expected to be published later in the year. This book, entitled, Orígenes, is edited by Ángel Díaz de Rada of the Open University, Spain, and it will appear in Spanish. I wrote about Kragh's work in three previous articles (Bohr Model of the Atom, January 3, 2012; Vegard and the Periodic Table, January 24, 2012; and, Radioactivity, November 5, 2014.

These contrary conceptions of the universe as being either eternal or having an origin have existed throughout history. In the cosmogony of the ancient Egyptian and Mesopotamian civilizations, everything was created from an undifferentiated chaos that was separated into the heavens and the Earth. This is true, also, in Hesiod's Theogony. Whether this chaos could be considered to be the universe before such differentiation is not considered.

Aristotle (384 BC-322 BC) was a proponent of a steady state universe of limited spatial extent, but temporally infinite in both the past and future; that is, it had no creation, and it was indestructible. In De Caelo (On the Heavens), Aristotle argued that the universe's appearing from some other state at a particular time was illogical,
"Why, after an infinity of not being, was it generated, at one moment rather than another? If there is no reason and the moments are infinite in number, it is clear that a generated or destructible thing existed for an infinite time."[4]

Many of the early astronomers still believed in a literal interpretation of the Bible, so they addressed the creation problem through biblical chronology rather than through science. Johannes Kepler (1571-1630) calculated that God had created the universe in 3,983 BC. As I wrote in a previous article (Newton's Chronology, March 6, 2013), Isaac Newton's chronology, "The Chronology of Ancient Kingdoms," was published, posthumously, in 1728.

Newton's objective was not to discover a start to the universe, but a start to history. In his chronology, Newton makes use of an astronomical phenomenon, the precession of the equinoxes, to date world events. The earliest recorded date he could verify was a reference to an Egyptian Pharaoh, possibly Ramesses IX, in 1125 BC. This is about a hundred years after the Trojan War.

Isaac Newton

A 1689 portrait of Isaac Newton (1642-1727) by Godfrey Kneller (1646-1723).

(Via Wikimedia Commons.)

The prolific German philosopher, Immanuel Kant (1724-1804), published his Allgemeine Naturgeschichte und Theorie des Himmels (Universal History and Theory of the Heavens) in 1755. In Kant's theory of the universe, it all began with a chaos of particles that then ordered themselves according to classical mechanics to condense into the universe. The laws of physics are as important as matter itself in Kant's universe, and the universe is creating new versions of itself as time progresses.

After the time of Kant and the emergence of the scientific revolution, cosmogony slowly came under the purview of science. In 1858, the German astronomer, Johann von Mädler (1794-1874), was the first to apply the finite speed of light to observations of the universe. In addressing Olbers' paradox, he reasoned that the darkness of the celestial sphere arose from the idea that the stars had not always existed, and the universe is finite in extent.[4] Von Mädler's idea received attention after the discovery of universal expansion in the 1930s.

More convincing an argument for a finite universe came from the second law of thermodynamics. According to this law, the universe should evolve into an equilibrium state of uniform temperature; and, eventually, it will succumb to a "heat death." As a consequence of thermodynamics, the universe must have existed for a finite time, since we would presently be in its heat death stage if it had existed for an infinite period.

The discovery of universal expansion sparked a renewed interest in cosmogony among scientists. The notion that the universe started in a Big Bang was proposed in a letter to Nature on May 9, 1931, by Belgian astrophysicist, Georges Lemaître (1894-1966), who proposed that the entire mass of the universe was initially contained in an "atom" of chaotic material.[5] Subsequently, in 1948, Russian-American physicist, George Gamow (1904-1968), and his colleagues, Ralph Alpher (1921-2007) and Robert Herman (1914-1997), reasoned that this initial state of the universe was high energy radiation and not matter. They further proposed the idea of an oscillating universe, contracting in a "Big Crunch," then expanding, to contract, again and again.

The triumph of modern cosmology is that we're quite certain that our universe began with a Big Bang 13.799±0.021 billion years ago with a long future for us to contemplate.

Figure caption

The 13.799±0.021 billion year history of the universe, as determined by the Wilkinson Microwave Anisotropy Probe. (NASA/WMAP Science Team image, via Wikimedia Commons.)


  1. T. Lucretius Carus, "Of the Nature of Things," Thomas Creech, Trans., J. Matthews (London: 1714), via archive.org.
  2. Titus Lucretius Carus, "De Rerum Natura," William Ellery Leonard, Trans., E.P. Dutton and Co., J.M. Dent and Sons (New York: 1916), 301 pp., via Tufts University Project Perseus.
  3. Mario Livio, "Brilliant Blunders: How the Big Bang Beat Out the Steady State Universe," NOVA blog from PBS, June 27, 2013.
  4. Helge Kragh, "Cosmology and the Origin of the Universe: Historical and Conceptual Perspectives," arXiv, June 2, 2017.
  5. Yaël Nazé, "Astronomical arguments in Newton's Chronology," arXiv, December 20, 2012.
  6. Isaac Newton, "The Chronology of Ancient Kingdoms" (Project Gutenberg).
  7. G. Lemaître, "The Beginning of the World from the Point of View of Quantum Theory," Nature, vol. 127, no. 3210 (May 9, 1931), p. 706, doi:10.1038/127706b0.

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