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The universe is vast, as Carl Sagan has already pointed out. "If it's only we, seems to be a waste of space."
Drake's equation fills up gradually, and that sounds good for the existence of life, the rise of intelligence and the likely number of civilizations elsewhere in the universe.
There is even reason to hope that some high-energy technological civilizations will successfully cross the energy-environment bottleneck into which our own global civilization is now entering. But few people manage to get through the bottleneck without suffering major losses, and many just collapse.
Drake's equation was written by American radio astronomer Frank Drake in 1961 to estimate the number of high-tech civilizations in the galaxy. There were seven factors, but they were all empty.
The first three factors, all uncertain in 1961, were: What is the average rate of star formation in our galaxy; how many of these stars have planets? and what proportion of these planets can potentially support life? We know the answers now, and they are quite encouraging.
There is about one new star a year, most stars have planets, and about one in five stars hosts one or more planets with liquid water on the surface. This means that there are probably a hundred billion planets in this one galaxy that can support life, but this is just the beginning.
As Douglas Adams has pointed out in The Galactic Traveler's Guide"The space is big. Really big. You simply will not believe how huge, huge, bewildering it is.
The Hubble telescope has revealed a hundred billion galaxies in the universe. Total number of potentially vital planets? About 10 billion billion dollars.
The remaining Drake factors are still unknown quantities. The only two important points for Adam Frank – because all he wants to know is how many non-human civilizations have ever existed anywhere in the universe – what fraction of life-saving planets actually develop the life; and what proportion of these planets develop an intelligent life.
What Adam Frank did in his recent book Starlight: Extraterrestrial Worlds and the Fate of the Earth, is to emphasize that there must therefore be many exo-civilizations. Make assumptions about the first life and intelligence on any planet, as pessimistic as you want, and there will be many more.
Maybe not billions, not even millions, but even if you assume that one billion-dollar vital planet has already supported a civilization, there would have been ten thousand. It's big enough for a statistical sample, and what Frank really wants to do is hijack the numbers and understand how many of these civilizations could have overcome the bottleneck.
He does not need to know anything specific about these unknown exo-civilizations. It suffices for him to know that all civilizations use large amounts of energy and that there is a strictly limited number of means by which a technologically "young" civilization such as ours can access energy.
There are fossil fuels, if your planet had a Carboniferous era, or just biomaterials if it did not. There is hydroelectricity, wind and tides. There is solar, geothermal and nuclear. That's all. The use of energy still produces waste, but some of these modes produce much less heat, carbon dioxide and toxic chemicals than others.
So put different original mixtures of these sources of energy in your experimental models, also put different planetary conditions (some planets closer to their suns, others more distant) and run a few thousand of these models on your computer .
It turns out that most models are seeing rapid population growth, followed by increasing pressure on the global environment, which is lowering "demographic load capacity".
At some point, the alarmed population is switching to low-impact energy sources. There is still a sharp decline of the population (up to 70%), but a stable state then appears and civilization survives.
In other models, the inhabitants of the planet (creatures? Be?) Delay too long to change their source of energy. They all change at the end, but latecomers still do not. The population starts to fall, then seems to stabilize for a moment, then rushes to extinction. No one has seen that coming, but that's what the models tell us.
There is still a lot of research to be done in this new area, but it is time to ask where is our own global civilization in this range of possible behaviors.
I do not know, but it is only that. Oil production is a record 100 million barrels a day and the Organization of the Petroleum Exporting Countries expects to reach 112 million barrels over the next 20 years. It's the wrong direction.
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