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“The species that survive are not the strongest, nor the most intelligent, but the ones that adapt best to change.” wrote Charles Darwin, father of the theory of evolution. But if the changes are too rapid, the adaptation fails, as illustrated by the end of the dinosaurs and which we invite you to follow in these pages the very long reign on the Globe which lasted nearly 200 million years. The question of the direction of evolution on the other hand – does it always point in the same direction? – remains put, as the philosopher Philippe Huneman explains to us. One thing is certain, however: the main and most rapid change driving evolution today is due to humans.

Exponential growth means not wasting time

During a recent seminar, astrophysicist Aurélien Crida made a rather striking presentation of what exponential growth means and its limits.

. Thus, world economic growth, which has continued since the beginning of the industrial era, is conditioned by the contribution of resources, particularly energy. The additional energy need to support this growth is estimated at around 2% per year, which corresponds to a doubling every 35 years. Assuming this pace continues, what energy resources would be needed in the future? In less than 500 years, we would need nearly 10,000 times more energy than today, which is all the energy received on Earth from the Sun!

1100 years later, it would be necessary to be able to recover all the energy emitted by the Sun in all directions; then in 3,000 years, we would need the energy of all the stars in the Milky Way, or about 200 billion stars. The conclusion – obvious to a physicist – is that there is no such thing as sustainable growth! Of course, we can change the parameters, choose 1% growth rather than 2%, but that only shifts things a few years. Another lesson of this reasoning: an exponential growth imposes not to waste time, because the delay between the causes and the effects is deleterious. We saw it during this Covid pandemic: taking data from all countries, it appears that the number of deaths doubles every 2.6 days when SARS-CoV-2 is allowed to spread freely (growth exponential). By imposing confinement, this number stagnates, but with a delay of about 16 days corresponding to the incubation time of the disease. Time lapse during which the number of deaths is multiplied by 80, exponential growth obliges …

Will we be able to adapt to these rapid changes?Let us also take the example of the CO content 2 of the atmosphere, which has been growing exponentially since 1850. As a result, the average temperature of the Globe has increased… but only since the 1950s, due to the delay between cause and effect. However, it is precisely this inertia that alters the perception of danger.“We judge the danger by its consequences, but when we do, it’s too late because the cause has already developed exponentially. Reduce our CO emissions 2 is therefore urgent “

warns Aurélien Crida. Will we be able to adapt to these rapid changes?

Lecturer at the University of Côte d’Azur, Aurélien Crida made this presentation on June 8, 2021 during the days of the French Society of Astronomy and Astrophysics during a workshop “Environmental transition: what role for the astronomical community? “.

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