Genesis by Guido Tonelli

Author:Guido Tonelli
Language: eng
Format: epub
Publisher: Farrar, Straus and Giroux

Day Four: And Then, at Last, There Was Light

The first minutes having passed, there is a brutal and totally unexpected change of rhythm. The sequence of spasmodic transformations that the universe has gone through abruptly stops, and everything slows down to such an extent that it is almost lost altogether, entering a process of such laboured slowness as to appear potentially exhausting. We have barely recovered from the crescendo in prestissimo with which the symphony began, and are waiting for a passage of a more regular and reassuring tempo, when everything plummets into a larghissimo that seems to lead nowhere.

The processes have now become infinitely slower, and eras disproportionately prolonged. Waiting for the most significant developments will require a great deal of patience. After the formation of the nuclei of the lighter elements, nothing major will happen for hundreds of thousands of years. Except, that is, that everything continues to be subject to expansion and cooling.

For a period that seems endless, the universe is filled with a dark fog. This is an opaque world, made up of elementary particles and nuclei, all intermingled and immersed in a sea of photons and electrons. Unknown particles of dark matter clandestinely contribute to this apparently perpetual sarabande. There is no structure, no hierarchy, no organisation. Absolutely nothing.

Not a single ray of light manages to penetrate this dark and disturbing plasma. Electrons and photons race after each other, playing a game of tag. Continuously absorbed and then immediately emitted by the dense gas of electrons that infiltrates everything, the photons cannot escape from this suffocating embrace.

This opaque kingdom will last for hundreds of thousands of years. There is no other reign of darkness to compare with it: not even the most imaginative science fiction can rival the hostile atmosphere of this boundlessly dark and dispiriting environment.

The key to its transformation comes, as usual, from a change in temperature. The temperature has been falling, gradually and irrevocably, as the universe continues to expand. Everything changes as it approaches 3,000 degrees. This is approximately half the temperature that is measured on the surface of the Sun – and at this point the opaque fog begins to disperse. With the falling temperature, the kinetic energy of electrons diminishes, and they can no longer break the electromagnetic attraction that binds them to protons. Electromagnetic attraction prevails: a myriad of feral electrons wandering freely now become domesticated by the electromagnetic field. They will no longer enjoy their freedom to roam, but be obliged instead to orbit in a stable fashion around a charged nucleus.

The first atoms are formed, above all those made up of hydrogen and helium. They emerge everywhere, the plasma breaking down into an immense quantity of gas that implacably absorbs all the nuclei and the entire population of electrons. Matter begins to assume a neutral and stable form. In a breakthrough moment, the atoms make it possible to build ever more complex structures that will lead in turn to further transformations.

While electrons become resigned to the

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