00:00Have you ever wondered what our planet would look like if it were divided into two equal parts, the earth and the water?
00:07I mean, 50% earth and 50% ocean, like a cosmic pizza whose two fillings would also be distributed.
00:15First of all, we all know that water is essential to life.
00:19This is why scientists are looking for water on other planets in order to find potential forms of life.
00:25On our planet, water covers about 71% of the surface, most of it in the oceans.
00:31What would happen if we removed almost a quarter of this water to replace it with earth?
00:37If we balanced the water-earth ratio, we would see some pretty radical changes.
00:43Because of the decrease in sea level, the regions around the poles north and south would completely dry up.
00:50At the same time, all the continents of the planet would expand to reveal a huge amount of new territory.
00:57This would equate to the current surface of Asia, Europe, Africa and North America combined.
01:04Imagine all the new holiday destinations you could explore.
01:10However, this modification of the relationship between earth and water would not be without consequences.
01:15With much less water on the surface, the ocean currents would be disturbed, which would lead to a destabilization of the climate.
01:23This would result in colder temperatures around the poles and even hotter temperatures in the already burning equatorial regions.
01:31The level of precipitation would decrease, leading to dangerous droughts and the appearance of new deserts in many interior regions.
01:40Let's not forget the creatures living on earth.
01:42Plants, animals and human beings will all have to adapt to be less dependent on water.
01:48Some animals could even become smaller or go into a strictly carnivorous diet due to this new shortage.
01:57Unfortunately, many forms of life in our oceans would have trouble surviving, which would be a shame for all fish lovers.
02:06Let's now try to imagine a totally different scenario for our planet.
02:11In 1884, the press talked about an astronomer who claimed to have discovered a cubic planet beyond Neptune.
02:19We have traveled a long way since then.
02:23We now know that in our universe, it is impossible to find square planets, at least according to the information we have today.
02:32Let's go back in time to 4 or 5 billion years ago, when our planet was just a cloud of gas and dust.
02:40When this chaotic cloud collapsed, a warm star formed and began to attract all the surrounding matter by its gravitational force.
02:49Finally, a rotating disk formed around the star and the collisions between the particles led to the formation of massive bodies, the planets.
03:00And as gravity pulls equally from all sides to the center, the planets naturally take a spherical shape.
03:07But what would happen if we spiced up all this a bit and modified the distribution of gravity?
03:13If you feel like an adventurer and you want to live an extraordinary life, welcome to the cubic earth.
03:20We would now have 6 faces, but do not rejoice too quickly.
03:24None of them would be very pleasant.
03:26Wherever you went, you would constantly have the impression of climbing a steep slope.
03:31Indeed, it is at the center of each face that gravity would be the strongest.
03:35The further away you would be from the center, the more you would be attracted.
03:39Staying straight would be impossible.
03:42If you were on the edges of our cubic earth, you would not find beautiful, luxurious landscapes.
03:50All the water would accumulate in the center of each face and the edges would be rocky and sterile.
03:56Even breathing would become difficult.
03:58The atmosphere along the edges and corners would be too thin, even non-existent, to allow life.
04:05But we will come back to this later.
04:08The climate on the cubic earth would depend on the way it would rotate.
04:12If the rotation was on an axis with two faces, the climate would be similar to the one we currently know, but more extreme.
04:20The upper and lower faces would be polar, while the other four would benefit from an equatorial climate.
04:27On the other hand, if the rotation was made by the corners, the temperatures and the rainfall would be more moderate on each face.
04:35No extreme weather conditions, but no equatorial paradise either.
04:42On the other hand, you could probably walk in space.
04:47Given that the atmosphere is maintained by gravity, and that gravity would now be exercised towards the center of each face,
04:55the atmosphere would be thicker in this place and thinner towards the edges.
04:59If the cubic earth had the same volume as our round world today,
05:05these high angles would exceed our atmosphere, creating unprotected and uninhabitable areas.
05:11But who said that you could not rent a space suit and find yourself both at the top of the world and outside of it,
05:19enough to give a new dimension to your holidays?
05:23What if our planet was entirely covered in water?
05:27It turns out that in reality, it used to be exactly what we had, a water world.
05:33According to some researchers, about 3 billion years ago, our planet was largely covered in oceans,
05:39with only a few scattered islands appearing here and there.
05:44Scientists who made this discovery studied samples of rocks from Western Australia.
05:51By analyzing these rocks, they were able to determine that they had formed in a hydrothermal wind system at the bottom of the sea more than 3 billion years ago.
06:01This information could have major implications on how we understand the origin and evolution of life.
06:08Indeed, scientists are still asking a lot of questions about the origin and date of the appearance of water on our planet.
06:15But by studying these ancient rocks, they hope to get some answers.
06:21They do this by examining the oxygen present in the rocks.
06:26Indeed, water containing different oxygen values can teach us a lot about the environment in which it was formed.
06:34Researchers have discovered that the rocks dating back 3 billion years had a higher oxygen content than those of our modern oceans.
06:42This suggests that at that time, solid earth had not yet appeared, which means that the earth was mainly covered in water.
06:52This may seem trivial, but it could help us understand how life appeared on earth.
06:58If our planet was entirely covered in water when the first unicellular organisms were born, it is very likely that they did not form on solid earth.
07:08If this is the case, it could mean that on aquatic planets, the conditions are ideal for the development of life.
07:16Our planet may never be entirely covered in water again.
07:20But we could end up losing part, if not all, of this precious liquid.
07:26The problem is this.
07:28The sun will become warmer over the next few hundred million years.
07:32This has nothing to do with man and his manigans.
07:35This is a natural phenomenon that occurs with all stars.
07:40The bad news is that as the sun warms up, our planet warms up too.
07:45And if the temperatures rise, our oceans will inevitably begin to evaporate.
07:50Of course, we have plenty of time to go to the beach before that happens.
07:55Experts have worked hard on a very sophisticated computer model to predict exactly when all this will happen.
08:03According to them, we have about a billion years left before things get out of hand.
08:09You may be wondering how they got to this number.
08:13It turns out that when the sun warms up, the atmosphere warms up too.
08:18And the warmer the atmosphere, the more water evaporates in the oceans.
08:22But there is a catch.
08:24Water vapor is actually a greenhouse gas, which means it retains heat and makes things even warmer on the surface.
08:32With evaporation, we enter a cycle, a kind of vicious circle,
08:37whose outcome is the total disappearance of all the oceans on the planet.
08:41But researchers are not only studying the Earth.
08:44Their work could help us find other planets with liquid water.
08:48By determining the type of conditions necessary for the maintenance of water on a planet,
08:53we could be able to identify other hospitable worlds.
08:56And who knows, maybe in a billion years, we will finally be able to colonize one of these planets.
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