BET À DAY
We pretty much know how it all started, some 13.8 billion years ago. The big bang transformed the universe into a cosmic ball of fire, creating stars, galaxies and planets and driving its continued expansion. A rocky planet that was called Earth, “a speck of dust lost in a universe as vast as it is diverse”, was thus formed and developed into what we know today.
But how will it all end? Because our universe does indeed have a programmed end. In some five billion years, our sun will swell and swallow up everything around it. The Earth will be nothing more than a vulgar charred pebble devoid of life. It's not me who says it, but a recognized scientist, Katie Mack, a cosmologist and astrophysicist who studies the Universe in its entirety.
In principle, she says, it should be possible to survive the death of a planet.
“Billions of years from now, it is conceivable that humanity will continue to exist, in perhaps unrecognizable form, venturing into the far reaches of space, finding new homes and building new civilizations. »
Knowing this, what meaning can we give to our life? Obsessed by the very real possibility that in the blink of an eye, the cosmic apocalypse will occur and that our universe could cease to exist, Katie Mack wants to bring her grain of salt here, outside of any religious consideration. The frail humans that we are, she says, are incapable of influencing or bringing about the end of the cosmos, but they can at least understand it. A kind of “intellectual luxury”. She thus offers us five possible scenarios with as many different apocalypses: the Big Crunch, “which will occur if the current course of cosmic expansion is reversed”; the endless expansion of dark energy; or its heartbreak; the appearance of a “deadly quantum bubble that devours the cosmos”; and finally the collision with a parallel universe.
These scenarios are all currently under the magnifying glass – increasingly powerful telescopes – of scientists. Moreover, the author invites us to observe in the sky, on a moonless autumn night, the great W drawn by the constellation Cassiopeia. “If you stare for a few seconds into the space below, if the sky is dark enough, you will see a faint diffuse spot, about the same diameter as the full moon. This is the Andromeda galaxy, a huge spiral disk made up of a trillion stars and a supermassive black hole; this set is charging towards us at the speed of 110 kilometers per second. Four billion years from now, Andromeda and our Milky Way will collide, creating a pretty light show.” Something to send shivers down your spine.
Some astronomers refer to the existence of a vast cosmic energy field “capable of forcing the vacuum of space itself to undergo an intrinsic outward thrust […] which would cause the Universe to expand forever”. Another possible death, faster this time, may come from dark energy – “something that accelerates the expansion of the Universe” – “the aptly named 'Big Rip' or Big Rip >. […] This alarming possibility is not a far-fetched idea, assures us the scientist. In fact, the best cosmological data available to us not only do not exclude it, but they even seem to timidly point in this direction. Our universe would experience a kind of unraveling, an evaporation before entering total darkness. No possible survival. Quite a dismal ending.
New Big Bang?
It could be a depressing book, with no hope of survival. Everything we have built over the centuries will disappear. No inheritance possible. Any trace of our civilization or that which will exist in five billion years will be destroyed, burned, pulverized. It's far, I know, and above all we can't help it. But in the meantime, more than the thermal death of our universe or its disintegration by vacuum, it is our planet Earth that we must worry about.
Slim hope. The author goes so far as to affirm that even after the thermal death of our universe, “nothing prevents a fluctuation from causing a big bang to arise from nothing to make the Universe start again”.
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