00:00You are a person among more than 8 billion individuals living on Earth.
00:04To put this into perspective, our planet is one of the 8 planets of our solar system.
00:09In our galaxy, our stellar neighborhood is one of the almost 4000 known.
00:14And according to our current knowledge, there are billions of galaxies in the entire universe,
00:19which could itself be expanding.
00:21It is therefore very unlikely that we are the only living creatures in the universe.
00:25There must certainly be other habitable planets.
00:29This is where Fermi's paradox comes in.
00:31This idea is called Enrico Fermi.
00:34In the 1950s, he underlined that if other forms of life existed
00:39and possessed the technology necessary to travel in space,
00:43they should have already visited us.
00:45Today, thanks to better telescopes,
00:48scientists have discovered more than 5000 planets outside our solar system.
00:53However, no sign of life has yet been discovered.
00:57Over the years, many solutions have been proposed to solve Fermi's paradox.
01:02These beings from another world are perhaps simply too far away
01:06for us to be able to communicate with them.
01:09We have all seen it in the movies,
01:11where spaceships filter between the stars as easily as cars on a highway.
01:16In reality, traveling in space is a slow and laborious process.
01:21Even our fastest rockets would take thousands of years to reach a nearby star.
01:26By considering the immensity of the cosmos,
01:29it's like trying to find a living needle in the biggest cosmic haystack imaginable.
01:35We could just as well be the very first civilization to emerge in the universe.
01:39It's a very lonely thought, and it also puts a lot of pressure on our shoulders.
01:44If we are alone, we have the duty to preserve life on our planet,
01:48not only for our own survival,
01:50but also because if we disappeared,
01:53any form of life would disappear with us.
01:55The universe has existed for billions of years,
01:58but an intelligent life like ours has only existed for a small part of that period.
02:04Maybe we are just precursors, waiting for other consciousnesses to emerge.
02:10To test this theory, a study carried out in 2015 with the Hubble Space Telescope
02:15has shown that among all the worlds likely to support life,
02:19only 8% were as old as the Earth.
02:23The others are too young and have not yet reached this stage of their evolution where life can prosper.
02:29It is also possible that our galactic parents are watching us from afar.
02:34A scientist from another planet could study us right now,
02:38like primitive life forms.
02:40It is possible that they do not want to disturb us yet,
02:43just as we observe ants in an anthill during science classes.
02:48They could also just wait for the ideal moment to get in touch with us.
02:53They would thus deliberately maintain radio silence.
02:57And they could be right.
02:58Why rush when we have all eternity ahead of us?
03:02It is also possible that our planet and we, humans,
03:06are not yet interesting enough for them to dare to interact with us.
03:11And we may not be,
03:12as long as we have not evolved enough to be admitted to the upper class of the galactic high school.
03:19Or maybe life is more fragile than we thought.
03:22A 2016 study suggests that it is in the early years of a planet that life has the greatest chance of developing.
03:28It is at that moment that it is cold enough for water to form.
03:33But these conditions may not last long due to the greenhouse effect.
03:37Thus, even if life has existed from time to time in the universe,
03:41it may never have evolved to the point of being able to contact us.
03:46What if the ultimate test came much later?
03:49Several intellectuals believe that civilizations tend to self-destruct
03:53past a certain stage of their technological development.
03:57This could also be our future, we just have not yet reached it.
04:02Maybe we will create a technology so advanced and so powerful
04:05that it will submerge us all, leading to our loss.
04:09If this can happen to us, who can say that it has not already happened to other species on other planets?
04:15Among all these theories, there is a serious and serious possibility.
04:20We could indeed be alone in the universe, and forever.
04:25Maybe the conditions necessary for life are so rare
04:28that the Earth is the only oasis in a vast desert of cosmic emptiness.
04:33The most disturbing answer to Fermi's paradox is known as the dark forest theory,
04:39which appeared for the first time in the 1980s.
04:42According to this theory, the universe would be comparable to a huge haunted forest
04:46where various creatures are hidden, playing a deadly hide-and-seek game.
04:52It is an extension of the survival of the fittest.
04:55History on Earth shows that the least technologically advanced groups
04:59are most often disadvantaged when they meet with more advanced groups.
05:05These huge technological gaps often lead me to a situation
05:09where attacking first seems to be the best option.
05:13If there is even a tiny possibility that our cosmic neighbors can harm us,
05:17destroying them first could be our only hope.
05:22Thus, if the galaxy is full of advanced species,
05:25it would be wise of us to remain discreet and avoid any contact.
05:29Other civilizations would surely reach the same conclusion.
05:33Even the most peaceful could feel forced to attack to survive.
05:38This is why some scientists criticize the idea of sending messages into space
05:43and think that searching for them could be futile.
05:47This idea is not new.
05:48A news from the 1940s, entitled First Contact,
05:52describes the meeting of humans with another intelligent species for the first time.
05:56The two groups make friends,
05:58but cannot take the risk of revealing the location of their home planet.
06:03They prefer to destroy each other rather than risk their safety.
06:08Another story, The Forge of God,
06:11evokes the danger that our signs of hostile species represent.
06:15It compares the emissions of the Earth to the cries of a baby attracting wolves,
06:19suggesting that our naivety could put us at risk.
06:23The dark forest theory has also been explored in a radio play entitled
06:29Calls from Far Away.
06:31It shows how the discovery of extraterrestrial life on Pluto affects public opinion.
06:36Some claim that the news is false,
06:38while others try to accept reality,
06:41namely that we are not alone.
06:43But it also suggests that we should perhaps focus on our own problems
06:47before aiming for the stars.
06:50If this does not seem scary to you, here it will be.
06:54We have been sending signals of our existence into space for decades.
06:59Currently, any civilization located hundreds of light years from us
07:03could receive these signals.
07:05And if they are advanced enough,
07:08they will know exactly where to find us.
07:11If we would do better to stay hidden,
07:13it is already too late.
07:16Beyond our potential galactic cousins,
07:18we must continue to search for habitable planets
07:22for a more urgent reason.
07:24Our comfortable Earth will not be there forever.
07:27When our star goes out,
07:29all life in the solar system will disappear with it.
07:33Current estimates indicate
07:35that we have about 1.3 billion years
07:39before our planet becomes uninhabitable.
07:43It will be too hot for water to exist.
07:46And without water, there is no life as we know it.
07:51This raises an intriguing question.
07:53What if other forms of life did not need water to exist?
07:57Our biological model needs water
08:00because it acts as a solvent,
08:01an environment where various chemical substances
08:04can interact to create something alive.
08:07Some new research suggests
08:09that there could be a substitute for water in the universe,
08:12carbon dioxide.
08:15At certain temperatures and under a certain pressure,
08:18carbon dioxide can react in a similar way to water,
08:22allowing the chemical compounds to mix.
08:26If this is proven,
08:27our list of potentially inhabited planets
08:30would increase considerably.
08:32Of course, humans could probably never survive on their surface,
08:36but other types of creatures could have evolved to do so.
08:41A planet that could present its strange living conditions
08:45is closer than we think.
08:47Venus.
08:48Its atmosphere is made up of 97% carbon dioxide.
08:53It is also very hot
08:54and has enough pressure to support this theoretical model.
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