From the Big Bang to Infinite Expansion

From the Big Bang to Infinite Expansion

Carlo Maria Polvani

Explosive beginning and silent end

In the 1977 Pulitzer Prize Winner for General Non-Fiction, The Dragons of Eden: Speculations on the Evolution of Human Intelligence, Cornell University astronomer Carl E. Sagan (1934-1996) proposed an intriguing pedagogical tool: the cosmic calendar. If the 13.8 million years that comprise the history of the universe were reduced to a scale of a single year of 365 days, it would produce the following points of reference: the Big Bang would have occurred at midnight on 1 January; the Milky Way would have begun to form on 16 March (11 billion years ago); the solar system on 2 September (4.6 billion years ago); until 9 November the only forms of life on earth would have been very simple, with fish appearing on 17 December (500 million years ago), dinosaurs on 25 December (250 million years ago) and hominids on 31 December (12 million years ago) at around 2:30 in the afternoon.

Although a provocative approximation, the cosmic calendar deftly illustrates the idea of time in the transformation of the universe. In the thought-provoking work, Solo un miliardo di anni? Viaggio al termine dell’universo [Just a Billion Years? Voyage to the End of the Universe] (Bologna, il Mulino, 2016), Prof. Paolo De Bernardis proposes, in a certain sense, an even bolder approach: to imagine a cosmic calendar of the future. His vivid description of the times and ways in which life on Earth will end and through which the universe itself will dissolve gives rise in the reader to the disconcerting impression that the gigantic cosmic transformations predicted for the far-off future, woefully, are relatively imminent.

The winner of the 2006 Balzan Prize begins with an inescapable observation: with respect to the total mass of the universe, our planet represents less than the tiniest grain of sand on which the replication of life forms is ultimately subordinate to the stability of the temperature, derived from an energetic balance between the solar radiation that the Earth absorbs and the energy that it reflects. This balance is suspected to be somewhat unstable given the fact that even the smallest quantities of gas that allow heat to enter the atmosphere but prevent reflected heat from leaving — such as carbon dioxide, methane, and the other gases at the heart of the 1997 Kyoto Protocols — could noticeably and quickly alter thermal stability. But what is given less consideration is the fact that, even if the greenhouse effect were thwarted, the earth’s temperature is destined to rise inexorably when, in roughly a billion years, the sun produces ten percent more than its current output of heat and this transforms our planet into a boiling sauna.

This scenario could occur a great deal earlier if, as predicted by physicist Aleksandr Michajlovič Ljapunov (1857- 1917), the entire solar system becomes chaotic within only 50 million years. A physical system is said to be chaotic when a small variation in its initial state leads to an enormous alteration in its dynamic development; a characteristic example of a chaotic system is the well- known “Butterfly Effect”, pioneered by meteorologist Edward Norton Lorenz (1917-2008) to explain the difficulty of meteorological predictions, since the flapping of the wings of a butterfly in the Pacific can give rise to a cascade of events that lead to the formation of a hurricane in the Gulf of Mexico.

Thus, there would be relatively little time remaining for terrestrial life forms to emigrate to a so-called exoplanet with the characteristics to sustain life in its known forms. Until now, fewer than 10 extrasolar planets or natural satellites with an index of sufficient adaptability have been identified, but many more could orbit one of the at least 200 billion stars of the Milky Way. Nevertheless, as the Lincei scholar de Bernardis would point out, even if terrestrial life is not extinguished during a journey that could last decades, if not hundreds of millions of years at the speed permitted by current technology, our galaxy, being in a rotational motion itself, in approximately six billion years, could collide with its gigantic cousin Andromeda, in a clash with unforeseeable consequences.

Hoping against the occurrence of such a cataclysm, Hubble’s law would not in any case, allow an escape. The American astrophysicist Edwin P. Hubble (1889-1953), who lent his name to the largest telescope ever put in orbit, observed that the farther galaxies were from our vantage point, the more rapidly they were moving away. His investigation was based on the Doppler Effect — first described by Austrian physicist Christian A. Doppler (1803-1853) — which everyone knows: when you hear an ambulance pass, you note that the siren’s frequency increases as the emergency vehicle approaches and decreases as it moves away. Since light in space behaves like a wave and therefore like the sound produced by an ambulance, the movement toward red, known as ‘redshift’ — the frequency of red light is lower than that of violet, which represents the other extreme of the visible spectrum — observed in the light arriving from stars, implies that the universe, after originating from the explosion of an extremely dense, incredibly hot nucleus, is constantly expanding, becoming profoundly emptier and glacially colder in an irreversible process which, over billions and billions of years, will lead to its extinction in a plausible thermal death.

Thus it would be the triumph of the second principle of thermal dynamics which provides that the entropy (the degree of disorder) of a system inevitably increases when it is transformed. It should not be too shocking that one of the mythical fathers of thermodynamics, Ludwig E. Boltzmann (1844-1906), conscious, perhaps more than anyone, of the inevitability of the victory of chaos, committed suicide by hanging while on holiday in the picturesque town of Duino near Trieste, Italy, and that the tombstone at his grave in Vienna’s Central Cemetery bears only the inscription of the laconically merciless formula he discovered: S=kb log Ω (entropy, S, is the product of the logarithm of a system’s possible configurations, log Ω , multiplied by the Boltzmann constant kb.

But it should be rather surprising that the man who formulated the theory of an explosive beginning of the universe which thrust it into an irreversible expansion was a priest from the Wallonian region of Belgium: Georges H.J.E. Lemaître (1894-1966). After completing his studies at the Massachusetts Institute of Technology, the engineer from the city of Charleroi published this hypothesis in the journal “Nature” in 1931, entitled Hypothesis of the Primeval Atom.

Being sarcastically labeled the Big Bang Theory by atheist British astrophysicist Sir Fred Hoyle (1915-2001) increased the reputation of its originator, who would become first a member (1936) and later President (i960) of the Pontifical Academy of Sciences. The life and work of the professor of the Catholic University of Leuven — who confided in 1933 to “New York Times Magazine” that he had found two ways to the truth (faith and science) and followed both — were proof of the soundness of the 1893 Encyclical Providentissimus Deus: “Nulla quidem theologum inter et physicum vera dis- sensio intercesserit” [“There can never, indeed, be any real discrepancy between the theologian and the physicist”].

Maria Rosati Buffetti — in La Specola Vaticana. Racconto fotografico d’una straordinaria avventura scientifica [The 'Specola Vaticana’: A Photographic Account of an Extraordinary Scientific Adventure] (Rome, Gangemi Editore, 2016) — recalls that it was Leo XIII who relaunched the work of the well known observatory, following the recommendations of Francesco Denza (1834-1894), the Barnabite priest whose Jesuit mentor, the brilliant astrophysicist Angelo Secchi (1818-1878), had the harbinger idea of classifying stars according to the spectral analysis of their light, thereby opening the door to observation of the so-called red-shift. All these priests, enthusiasts of the observation of celestial bodies, perfectly embody the words of Pierre Teilhard de Chardin (1881- 1955) in the fifth chapter on the Christian perfection of human strength in the first part dedicated to the divination of human activities, in Le Milieu Divin. Essai de spiritualité [The Divine Milieu: Essays on Spirituality]: “By virtue of creation and, even more so, of the incarnation, nothing is profane, here on the Earth, to those who know how to see”. The stars, one would be tempted to add.

L'Osservatore Romano
Weekly Edition in English
11-18 August 2017, page 11

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