Alone in the universe

With billions of galaxies in the universe, billions of stars in each galaxy, and often a handful of planets per star, it’s easy to imagine that there is life out there, even in the form of a single bacterium. Yet nothing. Earth is, to date, the only planet in the universe to harbor life behind its fragile atmospheric barrier. Are we alone in the universe?

It is this vast question, at the crossroads of philosophy and science, that astrophysicist Jean-Pierre Bibring is tackling. Focusing first on the universe, the author returns to the search for planets “Earth twins”. If planets of diamond, molten lava, or ice have been found, none is Earth. Because even the most similar planet that we could detect would lack a key element: the living as we know it.

The second part of the book, focusing on chemistry, questions this concept: what is living matter? Would life elsewhere be identical to life on Earth? Unlikely. “The Earth and the living things it shelters have been intimately shaped by the succession of stages that have marked its history. In that sense, they are truly unique,” says the astrophysicist.

So would it be different? Would it even be “life”? Scientific, the work prefers to speak « forms of evolution of organic chemistry »different carbon organizations. “The living would then be terrestrial in essence. » A solitary world in the universe and a unique living thing to protect on this « pale blue dot », as Carl Sagan called it. This is an even more dizzying challenge than the search for extraterrestrial life.