The age of the universe has racked the minds of theologians, philosophers and astronomers for a long time. According to the contemporary orthodox Jews, the world was created in 3761 before the birth of Christ. Bishop James Ussher, Anglican archbishop of Armagh in Ireland, based his estimation on a detailed interpretation of the Bible and concluded in 1650 that the creation occurred in the beginning of the night preceding the Monday 23 October 4000 before Christ. In those early days, the earth was considered by many to be the center of the Universe. Twenty years later, Spinoza pointed out that the Bible was a human achievement of great nobility but rich in errors, contradictions and absurdities. This superb mind currently read Hebraic, Portuguese, Dutch, Latin and Greek, and had good notions of other current languages but apparently ignored Arabic and unfortunately did not criticize the Koran. But Moslems would not listen, no more than contemporary conservative Christians. His critic was no inducement to evaluate correctly the age of the universe for the next 200 years: Spinosa was immediately excommunicated by the Hebraic community of Amsterdam and ostracized by the Calvinists. The other Christian communities (Anglicans and Roman Catholics) also despised him.
I have mentioned the opinion of Einstein and all other cosmologists who thought that the universe was static, neither expanding nor collapsing. The Universe, according to them, always was. At the beginning of the 19th century, the immense majority of the scientists thought that the earth was of unlimited age. Lord Kelvin disputed this in 1844. He evaluated the volume of the earth and its inner temperature, evaluated the thickness of the cold crust that had formed on its surface and concluded that the formation of the cold crust took 200 million years, which was the age of the earth. In 1860, he had a better knowledge of the geothermal gradient and obtained for the earth an age of 24 million years. His former assistant, John Perry, recognized the error committed by Kelvin in the evaluation of the geothermal parameter and assured him that the earth was about 3 billion years old, but he was preaching in the desert: neither Kelvin nor the other scientists paid any heed to his claims for the next 70 years. I discuss this phenomenon of rejection more at length in chapter 12, §6 and relate in detail my own experience of ostracism in “La France malade de sa médecine”. Ed. de Paris, 2005.
In the 1930′s, geologists determined that the age of the Earth was about 4,500,000,000 years (4.5 x 109 years, i.e. 4.5 billion years) while the cosmological age was thought by Hubble to be 2,000,000,000 years (2 x 109 years). In the 1980′s, estimates of the cosmological age based on the age of stars stood in the range of 15-18 billion years. In the 1990′s, the estimate of the cosmological age has been revised down to about 13.5 billion years.
Measuring two parameters can derive the expansion age: the Hubble constant, i.e. a measure of the expansion rate of the Universe, and the deceleration parameter, which is determined by the mean mass density in the Universe. The value of the Hubble constant (H0) is determined by measuring the red shift of a galaxy and determining its absolute distance. Its determination has ranged between 50 kilometers per second per Megaparsec (about 17 kilometers per second per million light years) and 100 kilometers/s/Mpc. How much matter is there in the universe? A critical density of about 10 protons per cubic meter provides the gravitational pull needed to slow down the universal expansion and bring it to a halt. A value above the critical density means programmed contraction into a universal Black Hole; a value below it means unending expansion into a gigantic freezer. The density of the Universe is measured by measuring the density of deuterium or lithium. After the Big Bang, there was produced 1 atom of lithium for 1010 atoms of hydrogen, which allows a deduction of the density of matter. These different techniques reveal that the universe has only about 25% of the critical density. Thus, the universe will expand forever. In a low density universe, H0 = 50 implies an age of 20 billion years, and H0 = 100 implies an age of 10 billion years. The best estimate seems to be 60 km/s/Mpc and this brings the age of an open universe to 13.5 billion years.
At the moment of the Big Bang, all the matter and energy of the whole Universe was in a very condensed form described as a "Black Hole". It is a mass of such a tremendous density and gravitational force that not even light is able to escape from it. This makes a Black Hole invisible since even photons of light will fall back on it. In such a Black Hole, we are likely to find a space-time singularity where the gravitational forces are so infinitely strong that they deform and squeeze matter and photons out of existence. The assumption here made of the existence of a space-time singularity is heretical: we started from a Newtonian theory of attraction and end up postulating a situation where the theory, by definition of universal vocation, does no longer hold.
Suddenly, however, perhaps due to the gravitational beam emitted by the space-time singularity, the process changed 13.5 billion years ago. A gigantic explosion dispersed matter, antimatter and photons into space. This voyage of matter into space will proceed until a gravitational contraction reassembles again all the substance of the Universe into a Black Hole. By definition, such a Black Hole can indeed only increase in size, never decrease, unless by an explosion. This is the theory. Recently, however, massive jets emanating from super massive black holes have been observed. These plumes of gas and dust that extend for thousands of light-years from the center of some galaxies require considerable reserves of firepower, yet the black hole seems to blaze away without a recognizable fuel supply, which leaves theorists at a loss to explain the phenomenon.
The Universe may thus be visualized as an expanding and contracting flow of energy and matter. We are now in an expanding moment, with galaxies moving away from each other. We have no way to know what happened before. For the present expanding movement, the initial annihilation of matter and antimatter with production of photons, and the size of the universe are of such a magnitude that they have effectively protected us from the catastrophe of the universal black hole, i.e. a "closed" universe. Some estimates assume that 60% of the universal matter is condensed into Black Holes at the present time. The mass of the biggest Black Hole yet recorded equates 17 billion suns. The evoked catastrophe of the "closed" universe is thus not unrealistic. If the density of matter, now about ten protons per cubic meter, had been only 10 times greater, the Universal Collapse would have already occurred 2 billion years ago. The initial annihilation of matter and antimatter and the extravagant extent of the universal expansion now reached are thus enormously increasing the time granted to Life to reach high evolutive forms.
Cosmologists can calculate how much matter the universe must contain to make it appear the way we see it. The ordinary matter that astronomers can observe and the dark matter that they infer from the pull of the universal gravity provide just a third of the energy required for the universe as we see it. There is a two-third deficit in matter, which the cosmologists call dark energy. Whereas ordinary energy pulls on other matter, dark energy has the strange property to be repulsive, so that it pushes away everything and makes the universe accelerate faster and faster. It seems almost certain that the Universe is either flat, meaning therewith that the expansion will at some time in the future come to a halt, or else "open" and will continue to expand indefinitely. In doing this, it cools down. We are in an immense freezer at -270°C. If expansion continues, the temperature will drop further and we will die of absolute cold. Yet, in a hotter Universe, one essential reaction of condensation of matter in nebulas destined to form stars is prohibited, so that life would not have eclosed unless the temperature had dropped drastically.