Ces phénomènes montrent que la nature passe en plein bug

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Transcript

00:00:00Wow! A gigantic storm cloud is heading towards you.

00:00:04It is completely black and contrasts strongly with the bright blue sky

00:00:09which is just above and behind you.

00:00:12You see a blinding flash and a few seconds later

00:00:15you hear the deafening noise of a thunderbolt.

00:00:18And then the rain starts to fall from the sky.

00:00:21The wind rises, you see the tops of the trees bending towards the ground

00:00:25and the storm is approaching at high speed.

00:00:28You freeze on the spot, realizing that you will not be able to escape.

00:00:32But when the rain curtain almost reaches you,

00:00:35its movement suddenly stops.

00:00:37A few meters in front of you, there is a real flood,

00:00:41but where you are, it is dry and even sunny.

00:00:44And shortly after, the storm cloud in fury

00:00:47pours its last drops and dissipates.

00:00:50Seeing the limit of the rain is a rare but not impossible thing.

00:00:54The rain must be really powerful

00:00:56so that the wind cannot deflect the drops from their vertical trajectory.

00:01:00If the rain is light, you will only be able to see its edges from afar.

00:01:03It will look like a gray, wavy curtain that goes from the sky to the ground.

00:01:08Now the rain has passed, but the wind is still blowing and stronger and stronger.

00:01:12You see leaves fluttering and you realize that a tornado is about to form.

00:01:17You run as fast and as far as you can.

00:01:20You climb to the top of a hill, then you stop and you turn around.

00:01:24No tornado yet, but the cloud that is suspended up there looks threatening.

00:01:29Another lightning and a crack.

00:01:31The lightning struck an isolated tree near where you were a moment ago.

00:01:36It caught fire and a column of flames rises to the sky.

00:01:40Still no rain and the column becomes bigger and bigger.

00:01:43You have already heard of such a thing, but you have never seen it.

00:01:47A fire tornado.

00:01:49This phenomenon occurs when the wind is caught in a whirlwind close to the ground

00:01:53because of the difference in atmospheric pressure.

00:01:56Such mini-tornadoes are generally easy to notice.

00:01:59Small debris, dust, sand and leaves rise in the air and begin to fly in a fast circle.

00:02:06But if there is a source of fire nearby, the funnel can catch it and blow it harder.

00:02:12The flames will then turn in a circle, rising higher and higher,

00:02:15and eventually creating a flaming whirlwind.

00:02:18Fortunately, fire tornadoes are short-lived and generally do not cause much damage.

00:02:23And as if that were not enough, you feel a rumble coming from below.

00:02:27No, it's not your belly, it's serious and bad omen.

00:02:31You look up and you see strange lights suspended above the ground.

00:02:36They look like balls of flickering light floating in the sky.

00:02:40Your throat dries up and you hardly swallow your saliva.

00:02:44This is what we call seismic lights.

00:02:47This phenomenon is misunderstood, but witnesses claim to have seen it in different shapes and sizes.

00:02:52It can be light balls, lightning in the form of leaves,

00:02:56serpentines or constant glare in the sky.

00:02:59Shortly after, a strong earthquake follows.

00:03:02Scientists fail to explain why these lights appear, and this is not always the case.

00:03:08Some believe that it is a reaction of underground gases released in the atmosphere.

00:03:13This time, an earthquake happens, but you are lucky, it is not as strong as you thought.

00:03:19The ground shakes, but you manage to keep your balance.

00:03:22It stops as abruptly as it started and you go home.

00:03:26Later at night, you look out the window and see something incredible, a rainbow.

00:03:32But it is already night and the moon shines in the clear sky.

00:03:36So it must be a lunar rainbow.

00:03:39This event happens extremely rarely.

00:03:42It is very similar to an ordinary rainbow,

00:03:45except that it appears by a clear night after a downpour.

00:03:48Happy to have been able to attend this show, you fall asleep peacefully.

00:03:52The next morning, you look out the window again,

00:03:55and suddenly the sun is almost hidden and it seems to be night again.

00:03:59You hear a noise in the distance and a kind of rumbling.

00:04:03Perplexed, you raise your head and you do not believe your eyes.

00:04:06There are thousands and thousands of birds in the sky,

00:04:10so many that they block all the sunlight.

00:04:13This is what is called a black sun, or black sun in Danish, very appropriate.

00:04:18Normally, this only happens in Denmark, hence the name,

00:04:21where many migratory birds fly at the same time to look for a place to spend the winter.

00:04:27They are so numerous that they literally obscure the sky for a few moments.

00:04:32So what are they doing where you are? That's a good question.

00:04:36You are now teleported as if by magic to Antarctica.

00:04:39We are in an imaginary universe, so anything can happen.

00:04:43Of course, you wear warm and comfortable clothes.

00:04:46You look around you with perplexity,

00:04:48and you realize that you have been transported on the slopes of Mount Erebus,

00:04:52one of the many volcanoes of the frozen continent.

00:04:55At the moment, it is slowly melting, gas escapes from its summit and cracks on its flanks.

00:05:01But what attracts your attention are the snowy pillars that surround you.

00:05:05They are called snow chimneys.

00:05:07They are formed because of the boiling magma below.

00:05:11From time to time, they release hot gases towards the surface,

00:05:14but the outside cold stops the hot substance.

00:05:17This results in the formation of fume rolls.

00:05:19The hot gas freezes as soon as it touches the air, thus creating these particular ice statues.

00:05:25It lets out thin strings of smoke, almost constantly,

00:05:28and develops when the gas tries to escape from the depths.

00:05:32Well, that's enough with the cold and the volcanoes.

00:05:35It's time to go to softer climates.

00:05:37And hop, you find yourself in Los Angeles.

00:05:39Open your eyes.

00:05:41Just above you, there is a beautiful rainbow-shaped cloud cap.

00:05:46This is called a fire rainbow, or circumhorizontal arc.

00:05:51Once again, it is a rare thing,

00:05:53but here in Los Angeles, it is much more likely than, say, in London.

00:05:58Fire rainbows only appear when certain conditions are met.

00:06:02Near the equator, in clear weather, with feather-shaped clouds in the sky,

00:06:07and when the sun is over 58° above the horizon.

00:06:11These clouds are made of ice crystals,

00:06:14and when the sun's rays cross them,

00:06:16the particles refract the light and create a magnificent rainbow.

00:06:20Hop, let's teleport to a new place.

00:06:23This time, you find yourself in Indonesia, overlooking another volcano.

00:06:27It's called the Kawah Ijen, and it's the most beautiful mountain of fire in the world.

00:06:32You see it slowly erupt,

00:06:34but the lava that pours out of its mouth is not red, it is blue.

00:06:39Inside the Kawah Ijen, there is much more sulfuric gas than in any other volcano.

00:06:45When the mountain erupts, the gas escapes under extreme pressure.

00:06:50As soon as it reaches free air, it triggers a chemical reaction that turns the fire blue.

00:06:55Have you ever seen a burning gas cooker?

00:06:57The basic principle is basically the same.

00:07:00And hop, you're back in the Arctic's ice cold this time.

00:07:04But as soon as you see the frozen ocean, you forget the cold.

00:07:07Fungal flowers bloom on its surface.

00:07:10Wonderful fragile ice crystals seem to grow from the thin layer of the frozen sea.

00:07:15Such flowers only appear near the shores or on lakes,

00:07:19when the temperature difference between the surface and the shore is significant.

00:07:23It takes at least 15 degrees Celsius more.

00:07:26When the warmer ice on the surface meets the colder air above,

00:07:30water vapor appears and freezes quickly.

00:07:33This creates fragile but beautiful structures on the surface,

00:07:37which can even grow over time.

00:07:39Your next destination is not much warmer.

00:07:42Still the Arctic Circle, but Siberia now.

00:07:45Strangely, at first you see nothing but an endless green valley

00:07:50and a small hill nearby.

00:07:52But then you notice that the ground is shaking.

00:07:55Another earthquake?

00:07:57No, you see the hill shaking as if it were going to burst.

00:08:00And then it really bursts.

00:08:03A powerful boom pierces your eardrums and makes you deaf for a few seconds.

00:08:08And you see huge rocks flying in all directions like meteorites.

00:08:12When you look at the ground again, there are no more hills in front of you.

00:08:16Instead, there is a huge crater, wide and deep.

00:08:20You have just witnessed an explosion of permafrost,

00:08:23a new and little-known phenomenon.

00:08:26The main theory is that small clumps sometimes form in the frozen plains of Siberia,

00:08:31pushed up by the expansion of natural gas hidden below.

00:08:35At some point, this gas can explode,

00:08:38causing a powerful explosion and the clump bursts like a bubble.

00:08:42Watch out, a rock is flying straight at you.

00:08:45Phew, you've been teleported just in time.

00:08:47And you're back home.

00:08:49The storm has passed and...

00:08:51Wow, what are these clouds?

00:08:53They look extremely sinister.

00:08:56Don't worry, they are called mammoths and they are safe.

00:09:00They tend to appear before or after a strong storm or a hurricane.

00:09:05Normally, clouds are formed because of the rising hot air,

00:09:08but they are formed because of the falling cold air.

00:09:11This creates pockets made of ice and water that descend into the abyss.

00:09:17But they don't last long,

00:09:1915 minutes at most and then they disappear.

00:09:22You admire the view, shake your head and go home.

00:09:25A little too much emotion for just one day.

00:09:29The Baltic Sea Anomaly

00:09:31In 2011, a diving team went all the way down to the north of the Baltic Sea.

00:09:37They went treasure hunting,

00:09:39but they discovered a rather strange object.

00:09:42They took pictures that they then shared

00:09:45and some people thought it was the spaceship of an unknown civilization.

00:09:50Others thought that a natural phenomenon had formed this object.

00:09:54But the metals inside the structure could not have been formed naturally.

00:09:59Today, some scientists think it is an object dating from the Ice Age.

00:10:04Maybe even a meteorite that found itself caught in the ice at that time.

00:10:09A maelstrom is a whirlwind,

00:10:11a kind of powerful rotating current that forms when two currents meet,

00:10:16creating a circular vortex.

00:10:19Even the intrepid Vikings were afraid of maelstroms.

00:10:22Their power was such that they could make very large ships sink.

00:10:26These whirlwinds are still dangerous today.

00:10:29But fortunately, the great modern ships are no longer afraid of anything.

00:10:33They are now able to resist this power.

00:10:37However, a ship that crosses the path of a maelstrom

00:10:40will generally be exposed to such massive waves that it will be violently shaken.

00:10:46The strength of some maelstroms is so formidable

00:10:49that they are sometimes compared to black holes.

00:10:52And no, black holes do not only belong to the interstellar space.

00:10:56They are found right here, on our planet, in the form of oceanic whirlwinds.

00:11:01What brings them closer to these celestial monsters

00:11:03is the fact that nothing they capture can escape them.

00:11:08These underwater black holes can reach up to 150 km in diameter.

00:11:12If you were caught in one of them, you would probably not even realize it.

00:11:16Their influence extends far beyond what can be detected.

00:11:20Because of their size, they even escape the most modern equipment.

00:11:25Here is something more relaxing.

00:11:27The next time you go to the beach,

00:11:29open your eyes wide and you may see this optical phenomenon called the green flash.

00:11:34You can see it a little after sunset or just before getting up.

00:11:38It occurs when the sun is almost completely below the horizon,

00:11:42but its upper edge is still visible.

00:11:46For one or two seconds, the solar crown will seem green to you.

00:11:50Because in reality, you will observe the sun

00:11:53through the thickest parts of the atmosphere, at the bottom of the sky.

00:11:57As it descends below the horizon, its light refracts into the atmosphere,

00:12:01where it curves and disperses.

00:12:04Choose a clear day, without clouds or mist on the horizon,

00:12:07and you will be able to observe this phenomenon.

00:12:11You were impatient to swim, but when you arrive at the beach,

00:12:14you see that the ocean is red.

00:12:16It is better to avoid making a storm.

00:12:18Florida is famous for its red tides.

00:12:21This occurs when the concentration of the Karenia brevis algae is higher than normal.

00:12:27Most of the algae in the sea, rivers and lakes

00:12:30are safe for animals and humans.

00:12:33They even help us.

00:12:34They are indeed a great source of oxygen.

00:12:37But some, like the one that gives this red tint to the ocean,

00:12:40can be extremely dangerous for aquatic fauna,

00:12:43sea turtles, fish and marine birds.

00:12:47This type of algae can develop uncontrollably

00:12:50and produce very harmful neurotoxins for humans,

00:12:53especially for those who have respiratory problems.

00:12:56These people must avoid areas of red tides at all costs,

00:12:59especially when strong winds push the algae to the shore.

00:13:04Volcanoes can emit toxic gases, ashes and a reddish lava.

00:13:08These dangers have been well known to humans for centuries.

00:13:13But underwater volcanoes can also be dangerous.

00:13:16Sometimes, those located in shallow waters

00:13:19reveal their presence by projecting debris of rocks and steam

00:13:23very high above the surface.

00:13:26Because of the presence of water,

00:13:28their effects will be different from those found on land.

00:13:31When they erupt,

00:13:33sea water can penetrate their events.

00:13:37The lava can spread on the ocean floor,

00:13:40sometimes even pour from terrestrial volcanoes.

00:13:44When it enters the water, it cools down so quickly

00:13:47that it can become a gravel of sand.

00:13:50There is a lot of volcanic debris in these areas.

00:13:53Have you ever seen these strange beaches of black sand in Hawaii?

00:13:56They are the result of this activity.

00:13:59Lava and powerful eruptions represent an obvious danger.

00:14:02But underwater volcanoes, in deep waters,

00:14:05are just as dangerous,

00:14:07even when they do not erupt.

00:14:09They produce air pockets.

00:14:12These bubbles reduce the density of the surrounding waters,

00:14:15which can even cause shipwrecks.

00:14:18The worst is that when you look at the surface of the ocean,

00:14:21you will not know that a danger is waiting for you.

00:14:23You will not see these air pockets,

00:14:25which can even unbalance very large ships.

00:14:28And without warning.

00:14:31The cross-sea is a rare phenomenon,

00:14:33beautiful to observe, but also very dangerous.

00:14:37It is when we see square waves.

00:14:39They are quite common in the shallow areas of the ocean.

00:14:42You can observe this phenomenon near the island of Re,

00:14:45or from the beaches of Tel Aviv,

00:14:47but also in many other areas of the world.

00:14:51This happens when two waves,

00:14:53propagating in two different directions,

00:14:55come across each other.

00:14:57They then form a pattern.

00:14:59This usually happens after the passage of an atmospheric front.

00:15:03And this state of the sea is structured

00:15:05in a large number of directional flows.

00:15:07These waves can be dangerous

00:15:09for swimmers and amateurs.

00:15:12The waves produced by strong ocean currents

00:15:14can be unpredictable

00:15:16and measured up to 3 meters high.

00:15:19They are sometimes called white walls.

00:15:22Their power is such that they can

00:15:24make large boats sink.

00:15:28If you fill a glass with seawater

00:15:30and look carefully,

00:15:32you will see quantities of very small particles.

00:15:35The seawater contains dissolved salts,

00:15:37fats, algae, proteins,

00:15:39and other artificial and organic matter debris.

00:15:44If you shake this glass,

00:15:46tiny bubbles will appear on the surface.

00:15:48This is how seawater forms,

00:15:50when the waves and winds shake the ocean.

00:15:53When seawater is thick,

00:15:55it can be due to a large concentration of algae.

00:15:57When the algae disintegrate in the sea,

00:16:00their matter often drifts to the shores.

00:16:04In general, seawater is not dangerous for humans.

00:16:08But when it contains decomposed algae,

00:16:10it can be harmful to our environment.

00:16:14It can happen that air pockets burst

00:16:16and release toxins they contain.

00:16:19This can cause irritation to the eyes

00:16:21and other health problems.

00:16:24Square masses occur in the mouth

00:16:26and the lower part of some streams.

00:16:30A strong tide meets the current

00:16:32and pushes the river back.

00:16:35Square masses are part of the hydraulic spring category,

00:16:38a sudden change in the water level.

00:16:40This is a positive push,

00:16:42which means that the wave pushes the river back,

00:16:44making its mass much larger.

00:16:47A negative tide is when the water level

00:16:49suddenly becomes shallow.

00:16:52You won't see square masses everywhere.

00:16:54The river must be shallow

00:16:56and its mouth must be narrow.

00:16:58The area where the sea meets the river

00:17:00must be flat and wide.

00:17:02In addition, the area between low tide and high tide

00:17:05must be at least 6 meters wide.

00:17:08Of course, there are some exceptions,

00:17:10like for the Amazon,

00:17:12the largest river in the world.

00:17:14The mouth of the Amazon is not narrow,

00:17:16but it still produces square masses.

00:17:19This is because its mouth is shallow

00:17:21and has many sandbanks and other low islands.

00:17:24This square mass is the reason

00:17:26why the Amazon does not have real deltas.

00:17:29The Atlantic Ocean quickly takes these sediments,

00:17:32preventing such a formation.

00:17:35Square masses are often unpredictable

00:17:37and can be extremely violent.

00:17:40Sometimes, the water of the river

00:17:42changes from a greenish or blueish color

00:17:44to a brownish color.

00:17:46They can damage the vegetation

00:17:48and even tear down trees.

00:17:50Thus, leisure sports such as kayaking and surfing

00:17:53can be dangerous in these areas.

00:17:55But if you just want to observe

00:17:57a square mass a little closer,

00:17:59be careful.

00:18:01It could literally tear the ground

00:18:03under your feet and take you

00:18:05into these agitated waters.

00:18:07How beautiful!

00:18:08Imagine you are walking with your friend

00:18:10and you look at the sky.

00:18:12The sun seems a little different today,

00:18:14as if it had a kind of ring around it,

00:18:16a bit like a rainbow.

00:18:18Hey, look at that!

00:18:20Your friend raises his head from his phone.

00:18:22You shouldn't look at it directly.

00:18:24Stop it, he says abruptly.

00:18:26It's a solar halo.

00:18:28You have to find shelter right away,

00:18:30unless you have the biggest umbrella

00:18:32in the world on you.

00:18:34A solar halo is a sign of nature

00:18:36that consists of billions of small ice crystals

00:18:38floating at an altitude of 6,000 meters.

00:18:40The sunlight passes through these crystals

00:18:42so that they divide and refract,

00:18:44as in the case of a rainbow.

00:18:46Don't look directly at the solar halo.

00:18:48It's certainly very tempting,

00:18:50because it's not a phenomenon

00:18:52that you can observe every day.

00:18:54And besides, it's really beautiful,

00:18:56but ultraviolets can burn the tissues

00:18:58exposed to your retina

00:19:00and cause serious eye injuries.

00:19:02So it's not worth it.

00:19:04If you have sunglasses,

00:19:06it shouldn't be a problem.

00:19:08This phenomenon lasts about 40 minutes.

00:19:10These clouds are the same as those

00:19:12that can sometimes cause the appearance

00:19:14of a ring around the moon at night.

00:19:16In reality, nature sends

00:19:18precursor signs of disasters

00:19:20in many different ways.

00:19:22J-shaped trees can mean

00:19:24that a landslide is preparing.

00:19:26As the ground moves slowly,

00:19:28trees take this very photogenic shape.

00:19:30Try to find a flat area

00:19:32where you can get closer to the trees,

00:19:34except if you have superhuman strength.

00:19:36You're taking a nice walk on the beach.

00:19:38Sand, sun,

00:19:40not a cloud in the sky.

00:19:42Then, all of a sudden,

00:19:44you see the water move away from the shore.

00:19:46Suddenly, you can even see pieces of coral,

00:19:48small fish and other small marine animals.

00:19:50It's a sign that you have to move

00:19:52as fast as possible from the shore.

00:19:54There could be a tsunami

00:19:56in preparation.

00:19:58Such a phenomenon occurs

00:20:00under water, and can occur

00:20:02on the coast at 800 km per hour.

00:20:04It occurs mainly in the Pacific Ocean,

00:20:06but why take the risk?

00:20:08If you see a channel of agitated water

00:20:10near the coast, stay away.

00:20:12There could be a current of return

00:20:14under the surface, which can be

00:20:16extremely dangerous.

00:20:18Sometimes, the waves hit the shore

00:20:20in a strange way, forming currents of return.

00:20:22You may see a strange void

00:20:24in the waves, where you will notice

00:20:26pieces of algae going in all directions.

00:20:28If you ever find yourself caught

00:20:30in a current of return,

00:20:32try to stay afloat

00:20:34and don't waste your energy

00:20:36swimming against the current.

00:20:38Shout for help and try to swim

00:20:40parallel to the beach.

00:20:42Once you're out of the channel,

00:20:44swim diagonally to the shore.

00:20:46If you find yourself in the ocean

00:20:48and you see a group of sharks

00:20:50swimming, don't panic.

00:20:52The good news is that they

00:20:54don't necessarily come to bite you.

00:20:56Sharks can sense these things,

00:20:58so when nature gets angry,

00:21:00they regroup and swim

00:21:02deeply under the surface

00:21:04to be safe.

00:21:06You probably shouldn't follow them.

00:21:08However, the golden rule

00:21:10since ancient times is

00:21:12follow the animals.

00:21:14Insects, rats and snakes

00:21:16leave their terriers a few days

00:21:18before the big earthquakes.

00:21:20Scientists can't really explain

00:21:22how they know what's going to happen.

00:21:24It seems that animals can sense

00:21:26the earthquakes in advance,

00:21:28maybe because they can sense

00:21:30these small initial shock waves

00:21:32that we don't even notice.

00:21:34And if you see animals running towards you,

00:21:36it could mean that you're about to be devoured

00:21:38or that there's a forest fire behind them.

00:21:40Amphibians like frogs,

00:21:42toads and salamanders

00:21:44try to protect themselves by

00:21:46plunging into the ground.

00:21:48The others just run.

00:21:50Before running to their side,

00:21:52you can smell the smoke.

00:21:54You wouldn't want to run for nothing.

00:21:56There are not only animals.

00:21:58You can also spot other signs

00:22:00of an imminent disaster.

00:22:02For example, if you notice that

00:22:04your hair is suddenly standing on your head

00:22:06and that your jewelry is starting to wrinkle,

00:22:08put yourself right away under cover.

00:22:10The lightning may be about to strike

00:22:12somewhere nearby.

00:22:14If you're outside and you can't

00:22:16take refuge inside,

00:22:18make sure you don't make the following mistakes.

00:22:201. Stay close to high structures

00:22:222. Lie flat on the ground

00:22:243. Stay close to a stretch of water

00:22:264. Take shelter under an isolated tree

00:22:285. Stay in an open space

00:22:30And it's certainly not a good idea

00:22:32to climb to the top of the Empire State Building.

00:22:34This building is lightning-fast

00:22:36hundreds of times a year.

00:22:38Do you like skiing?

00:22:40It's a very fun activity

00:22:42until you can only see white.

00:22:44Avalanches can move up to 130 km per hour.

00:22:46So be careful of the signs before you run.

00:22:48Do you feel a hollow when you move on the snow?

00:22:50Are there cracks around your feet?

00:22:52Can you see a huge avalanche coming?

00:22:54It's time to go.

00:22:56Sometimes a storm mixes its blue light

00:22:58with the red light of the sun

00:23:00and you get a pretty impressive green.

00:23:02Take advantage of a safe distance,

00:23:04preferably inside.

00:23:06This stormy cloud stretching very high

00:23:08in the sky usually means

00:23:10that you are about to be hammered

00:23:12by the hail or worse,

00:23:14that a tornado is preparing.

00:23:16Find a shelter somewhere

00:23:18like an underground parking lot or a cave.

00:23:20OK, we know that volcanoes can be dangerous

00:23:22but what about lakes nearby?

00:23:24Aren't they dangerous too?

00:23:26Lakes near something very hot

00:23:28that never cools down

00:23:30like volcanoes

00:23:32are like soda cans

00:23:34shaken wildly waiting to explode.

00:23:36The magma underground

00:23:38actually pushes carbon dioxide

00:23:40to the bottom of the lake

00:23:42and this gas stays there to wait.

00:23:44Then, even something banal

00:23:46like rain can disturb

00:23:48the lake a little too much

00:23:50and bam or boom,

00:23:52you see the picture.

00:23:54Diving, swimming, snorkeling,

00:23:56the sea can be fascinating

00:23:58but it is quite unpredictable.

00:24:00When two currents of waves meet,

00:24:02they can create a cross sea.

00:24:04It looks pretty nice from a distance

00:24:06but it can be really dangerous

00:24:08for swimmers, surfers or even boats.

00:24:10This means that a strong current

00:24:12can get in your way.

00:24:14If you walk on the beach,

00:24:16it looks like all good things start like this

00:24:18and all of a sudden,

00:24:20oh, a cave!

00:24:22Great, isn't it?

00:24:24You should probably go in,

00:24:26explore a bit and...

00:24:28No!

00:24:30If it's the full moon,

00:24:32you may not be able to get out of this cave.

00:24:34The full moon affects the tide

00:24:36and makes it lower than usual.

00:24:38This cave may be more accessible

00:24:40than the next full moon.

00:24:42So don't forget your supplies

00:24:44if you really want to go in.

00:24:46A wall cloud is one of those things

00:24:48that you will be excited and scared to see.

00:24:50Scared because you don't know what it is.

00:24:52Excited because...

00:24:54Well, how many times have you seen

00:24:56something like this in your life?

00:24:58But whatever your emotion,

00:25:00tell your legs to start running.

00:25:02During a storm,

00:25:04these wall clouds are lower than everything else

00:25:06and can be up to 8 km wide

00:25:08You know what that means.

00:25:10We are in 2009 in Italy.

00:25:12A man is in his kitchen.

00:25:14He sees flickering lights.

00:25:16He knows exactly what to do.

00:25:18He puts his family in safety.

00:25:20A few seconds later,

00:25:22a huge earthquake hits the whole region.

00:25:24His family survived

00:25:26thanks to his quick reaction.

00:25:28He knew that these flickering lights

00:25:30were the sign of an imminent earthquake.

00:25:32People see these mysterious lights

00:25:34from chandeliers.

00:25:36It was a kind of sign from space.

00:25:38Scientists never took them seriously,

00:25:40but after the invention of photography,

00:25:42more and more evidence

00:25:44of these strange lights appeared.

00:25:46Soon, they understood the link.

00:25:48The lights appeared

00:25:50and very quickly,

00:25:52the earthquake occurred.

00:25:54After digging a little,

00:25:56they actually found traces

00:25:58of these earthquake lights

00:26:00hundreds of years ago.

00:26:02There were blue flames

00:26:04but let's go back to the beach

00:26:06one last time.

00:26:08If you see that the ocean

00:26:10has a brown-red hue,

00:26:12it does not go into the water

00:26:14or even near the water.

00:26:16This red tide is caused

00:26:18by toxic algae

00:26:20and it is a phenomenon

00:26:22that you can find

00:26:24everywhere in the world.

00:26:26These toxic algae can be there

00:26:28even if the ocean

00:26:30is a normal color.

00:26:32In 2018,

00:26:34the largest active

00:26:36underwater eruption ever occurred,

00:26:38at least the one

00:26:40we were able to officially record.

00:26:42Scientists followed the earthquakes

00:26:44that hit an area

00:26:46in the Western Indian Ocean

00:26:48off the coast of Madagascar.

00:26:50Between 2018 and 2021,

00:26:52more than 11,000 earthquakes

00:26:54hit the small island of Mayotte

00:26:56between Madagascar and Mozambique.

00:26:58The strongest of them

00:27:00were 5.9.

00:27:02Until then, this region

00:27:04had been quite peaceful.

00:27:06There had only been two earthquakes

00:27:08recorded in 50 years.

00:27:10In addition to regular earthquakes,

00:27:12there were also unusual seismic

00:27:14earthquakes, such as

00:27:16earthquakes at fairly low frequencies

00:27:18that formed deeply underground.

00:27:20People could not feel

00:27:22these earthquakes on the surface,

00:27:24but researchers from all over the world

00:27:26discovered them and realized

00:27:28that something strange had happened.

00:27:30This underwater eruption created

00:27:32a giant volcano the size of a skyscraper.

00:27:34This new underwater volcano

00:27:36was about 1.5 times

00:27:38the height of the

00:27:40One World Trade Center in New York

00:27:42and almost 10 times more

00:27:44than the Statue of Liberty.

00:27:46The area where it appeared

00:27:48had been explored in 2014,

00:27:50but it was almost flat,

00:27:52peaceful and empty at the time.

00:27:54Now there is a real volcano

00:27:56about 2,600 meters

00:27:58below sea level.

00:28:00The volcano draws its magma

00:28:02from a very deep reservoir

00:28:04located 55 km underground.

00:28:06It is the deepest

00:28:08volcanic magma reservoir we knew.

00:28:10The earth has layers

00:28:12and the middle one is quite thick.

00:28:14It looks a lot like the peanut

00:28:16caramel filling found

00:28:18in many chocolate bars.

00:28:20Research shows that there are

00:28:22probably pieces of oceanic crust

00:28:24in the liquid mantle of the earth.

00:28:26They are stuck there, creating

00:28:28big lumps in what was supposed

00:28:30to be a smooth layer.

00:28:32Our planet has a rigid outer layer.

00:28:34It includes a hot upper mantle

00:28:36and a cracked crust.

00:28:38The mantle moves constantly,

00:28:40which moves the crust

00:28:42to the surface as well.

00:28:44Thus, the oceanic crust

00:28:46plunges into the depths

00:28:48and brings up huge amounts of magma

00:28:50to the surface of the planet.

00:28:52This is an ancient piece

00:28:54of the Pacific Ocean,

00:28:56hundreds of kilometers below China.

00:28:58These are the ancient remains

00:29:00of the Pacific's seabed

00:29:02from a long time ago.

00:29:04They were pulled down

00:29:06under the surface of the earth

00:29:08in the transition zone of the mantle.

00:29:10This rocky slab

00:29:12at the bottom of the ocean

00:29:14is composed of the crust

00:29:16and some solid parts

00:29:18of the upper mantle.

00:29:20About 70%

00:29:22of all volcanic activity

00:29:24occurs in the oceans

00:29:26and mainly in the Pacific South,

00:29:28with more than 1,100 volcanoes

00:29:30concentrated in this area.

00:29:32Coastal cliffs, mountain ranges,

00:29:34soils and sediments

00:29:36bordering the valleys

00:29:38are just a small part

00:29:40of our planet's rocks.

00:29:42The oceans hide much more

00:29:44in the depths of the earth's surface.

00:29:46Between the earth's surface

00:29:48and the mantle,

00:29:50a thick and hot layer of rocks

00:29:52constantly moves and flows.

00:29:54A few hundred kilometers below,

00:29:56there is an area where diamonds are created.

00:29:58When they form,

00:30:00they go through high temperatures

00:30:02and pressures and then freeze.

00:30:04When they reach the surface,

00:30:06scientists can explore their structures,

00:30:08discover how they formed

00:30:10and better understand what happens

00:30:12in the depths of our planet.

00:30:14Thanks to diamonds,

00:30:16the mantle was very humid

00:30:18and contained perhaps much more water

00:30:20than all the oceans of the earth.

00:30:22Our planet is eating

00:30:24its own oceans.

00:30:26When tectonic plates move,

00:30:28plunge and pass under each other,

00:30:30they draw huge amounts of water

00:30:32into the earth.

00:30:34The water under our planet

00:30:36can help develop magma

00:30:38and lubricate the cracks,

00:30:40making earthquakes more likely.

00:30:42The water is stored in the minerals.

00:30:44It is incorporated into the crust

00:30:46of the planet when new oceanic plates

00:30:48are formed.

00:30:50They undergo a process of bending

00:30:52and cracking, passing under other plates,

00:30:54and huge amounts of water

00:30:56then sink into the crust and the mantle.

00:30:58Scientists have done research

00:31:00on an area 29 kilometers

00:31:02below the surface.

00:31:04They realized that such areas

00:31:06draw 3 billion teragrams,

00:31:08which represents 3 billion tons.

00:31:10Every ocean is like a new world.

00:31:12There are incredible landscapes

00:31:14under the surface,

00:31:16magnificent waterfalls, lakes,

00:31:18and rivers.

00:31:20There are thick layers of salt

00:31:22under the ocean floor,

00:31:24and rivers and lakes are formed

00:31:26because the sea water

00:31:28crosses these layers and dissolves them,

00:31:30creating something like a pool.

00:31:32The dissolved salt makes the surrounding water

00:31:34denser.

00:31:36This water is then deposited

00:31:38in this place,

00:31:40creating canyons.

00:31:42In the Bering Sea,

00:31:44there is a canyon

00:31:46more than 2,600 meters deep.

00:31:48It makes the Grand Canyon

00:31:50look much smaller than it is,

00:31:52because the underwater canyon

00:31:54is nearly 800 meters deeper.

00:31:56The deep parts of the ocean

00:31:58are very cold.

00:32:00The water temperature can be

00:32:02around 4 degrees Celsius,

00:32:04but deep down,

00:32:06the water can become boiling.

00:32:08These are hot springs

00:32:10located on the edges of tectonic plates.

00:32:12The water they release

00:32:14can reach a temperature

00:32:16of 400 degrees Celsius.

00:32:18But the pressure at such a depth

00:32:20is very intense,

00:32:22so intense that no human being

00:32:24can withstand it.

00:32:26Yet it is the pressure

00:32:28that prevents the water from boiling.

00:32:30The depth of the oceans

00:32:32is on average 3.7 kilometers.

00:32:34Light waves can still penetrate

00:32:36even if it is in very small quantities.

00:32:38So that all the mysteries

00:32:40hidden below this point

00:32:42remain in total darkness.

00:32:44The really lit part of the ocean

00:32:46goes up to 180 meters.

00:32:48Even if the sun gives us light,

00:32:50most of our planet is dark

00:32:52all the time.

00:32:54This is because the oceans

00:32:56cover more than 70% of our planet.

00:32:58The loudest sound coming from an ocean

00:33:00and one of the loudest sounds

00:33:02ever recorded came from

00:33:04the Antarctic Ice Cap.

00:33:06It was so loud that researchers

00:33:08recorded it with sensors

00:33:10located more than 4,800 kilometers away.

00:33:12Seismic activity

00:33:14caused the frozen ground to collapse.

00:33:16The Antarctic Ice Cap

00:33:18is larger than the continental part

00:33:20of the United States and Mexico combined.

00:33:22A large Antarctic iceberg

00:33:24contains more than 75 billion liters of water,

00:33:26which could make up

00:33:28a water supply of 5 years

00:33:30for a million people.

00:33:32This means we won't be able

00:33:34to drink seawater.

00:33:36As time goes by

00:33:38and the ice ages,

00:33:40the ice crystals

00:33:42are trapped in the ice wall.

00:33:44In this way,

00:33:46the ice becomes soft enough

00:33:48to be drunk.

00:33:50If all the ice caps

00:33:52and glaciers we have on Earth

00:33:54melted at the same time,

00:33:56the sea level would rise

00:33:58to 80 meters,

00:34:00which would make

00:34:02the ice caps

00:34:04more solid.

00:34:06These ice caps

00:34:08can live more than 500 years.

00:34:10To know the age of a tree,

00:34:12you can use the cerns of its trunk.

00:34:14And to know the age of an ice cap,

00:34:16you can examine the cerns

00:34:18inside its shell.

00:34:20This is also how scientists

00:34:22get information about the ocean,

00:34:24the climate and other elements.

00:34:26Ice caps can help you

00:34:28understand the ocean.

00:34:30The Australian Ocean

00:34:32was officially recognized

00:34:34only a few months ago.

00:34:36It borders the Atlantic,

00:34:38Pacific and Indian Oceans.

00:34:40Scientists couldn't agree

00:34:42whether it was a new ocean

00:34:44or just one of the colder regions.

00:34:46We don't just divide the oceans

00:34:48on maps.

00:34:50Each of them has different conditions

00:34:52for unique marine species.

00:34:54For example,

00:34:56there are orcas,

00:34:58mangroves and other animals

00:35:00that live in cold and icy seas.

00:35:02There are also krill,

00:35:04small creatures that look like

00:35:06shrimp and serve as food

00:35:08for many larger animals.

00:35:10Life on our planet began

00:35:12about 3.5 billion years ago.

00:35:14The question of how and when

00:35:16it appeared remains a mystery.

00:35:18But some theories say

00:35:20that life may have emerged

00:35:22for the first time

00:35:24a few hundred years ago.

00:35:26Scientists discovered tubes

00:35:28and microscopic filaments

00:35:30in rocks formed about

00:35:324 billion years ago.

00:35:34These rocks are fragments

00:35:36of an ancient ocean crust.

00:35:38These tiny tubes and filaments

00:35:40are similar to microbes

00:35:42found on hydrothermal chimneys

00:35:44in the deep parts of the ocean.

00:35:46The idea is that these living cells

00:35:48found the conditions to survive

00:35:50in tiny rocky ports

00:35:52on the surface of the ocean.

00:35:56Welcome, dear guests,

00:35:58and welcome to SympAquarium.

00:36:00Here you will be able to admire

00:36:02the most dangerous marine

00:36:04and oceanic creatures,

00:36:06but don't be fooled

00:36:08by what I said.

00:36:10It is highly possible

00:36:12that you will come across

00:36:14one of these creatures

00:36:16during a simple walk

00:36:18on the beach.

00:36:20What you are looking at

00:36:22is commonly called the stone fish

00:36:24or, as it is known,

00:36:26for the intimate.

00:36:28If you like diving

00:36:30and observing the seabed,

00:36:32you may have already come across

00:36:34one without even noticing it.

00:36:36Its appearance makes it

00:36:38almost impossible to distinguish

00:36:40it from any other stone

00:36:42because of its gray color

00:36:44and sharp appearance.

00:36:46Especially if your diving glasses

00:36:48don't allow you to see it.

00:36:50Stone fish are among

00:36:52the most venomous.

00:36:54Although some types

00:36:56of stone fish are known

00:36:58to live in rivers,

00:37:00most of them live

00:37:02in coral reefs

00:37:04near the tropics

00:37:06of the Pacific and Indian Oceans.

00:37:08The spines of their dorsal fins

00:37:10in the shape of needles

00:37:12stand up when they feel

00:37:14disturbed or threatened

00:37:16and can be found in the water

00:37:18to be stung.

00:37:20As they can survive

00:37:22out of the water up to 24 hours,

00:37:24you should also be careful

00:37:26where you walk

00:37:28when you go to the beach.

00:37:30People who have been stung

00:37:32by stone fish

00:37:34describe it as an extremely painful

00:37:36experience.

00:37:38This venom can cause infections

00:37:40and in some cases

00:37:42it is known to have resulted

00:37:44in death.

00:37:46When the fish is cooked,

00:37:48its venom decomposes

00:37:50and if its dorsal fins,

00:37:52which are the main source

00:37:54of its venom, are removed,

00:37:56the stone fish can also

00:37:58be served as sashimi.

00:38:00This creature may seem

00:38:02from a science fiction movie,

00:38:04but it is real.

00:38:06Say hello to the blue-winged

00:38:08octopus.

00:38:10Don't be fooled by its small size

00:38:12it can eat up to 26 people

00:38:14in a few minutes.

00:38:16Like stone fish,

00:38:18blue-winged octopuses

00:38:20are found in the Pacific and Indian

00:38:22oceans, from Japan to Australia.

00:38:24They generally live in the coral

00:38:26reefs and rocky areas

00:38:28at the bottom of the seas.

00:38:30They can also be found

00:38:32in residual marshes,

00:38:34marine herbivores and lidalgae.

00:38:36Blue-winged octopuses are not

00:38:38aggressive by nature.

00:38:40They often hide in marine reefs,

00:38:42seashells or crevasses.

00:38:44It is only if they are provoked,

00:38:46stung or caught in the act

00:38:48that they become dangerous to humans.

00:38:50When they are threatened,

00:38:52they take a bright yellow color

00:38:54and iridescent blue rings

00:38:56appear all over their body

00:38:58as a warning to their potential predators.

00:39:00Their sting usually goes unnoticed,

00:39:02so you can't realize you've been

00:39:04stung before it's too late.

00:39:06The venom of a blue-winged octopus

00:39:08can cause you to lose your senses

00:39:10and motor skills,

00:39:12and eventually paralyze you.

00:39:14So it's better to keep your hands

00:39:16to yourself and slow down

00:39:18if you see one.

00:39:20No, it's not a bouquet of flowers,

00:39:22so don't try to pick and feel

00:39:24one of these pink cubes.

00:39:26What you see is a marine animal

00:39:28called the flower bear.

00:39:30It may look beautiful,

00:39:32but don't be fooled by its appearance.

00:39:34It was named the most dangerous

00:39:36in 2014.

00:39:38Flower bears live in tropical areas

00:39:40of the Indo-Pacific basin

00:39:42and generally live in coral reefs,

00:39:44rocks, sand and marine grasslands

00:39:46from 0 to 90 meters deep.

00:39:50Their most remarkable feature

00:39:52is their pedicels,

00:39:54which are defensive organs

00:39:56in the shape of claws,

00:39:58also found in starfish.

00:40:00What sets them apart from other bears

00:40:02is the fact that their pedicels

00:40:04are made of flowers,

00:40:06and generally of pinkish-white

00:40:08to yellowish-white,

00:40:10with a central violet point.

00:40:12Hidden under these flowers,

00:40:14they also have short,

00:40:16foamy spines.

00:40:18Although many bears

00:40:20deliver their venom

00:40:22through these spines,

00:40:24flower bears do it

00:40:26through their pedicels,

00:40:28or flowers.

00:40:30If they are not disturbed,

00:40:32their surface has tiny sensors

00:40:34with which they can detect danger.

00:40:36And when they come in contact

00:40:38with such threats,

00:40:40these flowers close up immediately

00:40:42and start injecting their venom.

00:40:44What is curious is that

00:40:46the small fangs of these flowers

00:40:48can sometimes detach from their spines,

00:40:50cling to the point in contact

00:40:52and continue to inject venom

00:40:54for hours, no matter who touches them.

00:40:56It looks like a giant ice flake

00:40:58with a melted raspberry, doesn't it?

00:41:00You'd love to,

00:41:02but it's a lion's mane jellyfish,

00:41:04also called capillary cyanide.

00:41:08They are known

00:41:10to prefer cold waters,

00:41:12which is why they are found

00:41:14mainly in the Arctic Ocean,

00:41:16North Atlantic and North Pacific.

00:41:18But it is also possible

00:41:20to see them around the British Isles

00:41:22and in the Scandinavian waters.

00:41:24The lion's mane jellyfish

00:41:26is one of the largest species

00:41:28in the world.

00:41:30They are called long tentacles,

00:41:32similar to hair,

00:41:34and can reach a length of 3 m.

00:41:36Although the average diameter

00:41:38of a lion's mane jellyfish

00:41:40is about 50 cm,

00:41:42it can sometimes reach a diameter

00:41:44of more than 2 m.

00:41:46The largest never-seen lion's mane jellyfish

00:41:48was seen in 1865

00:41:50off the coast of Massachusetts.

00:41:52It was estimated to have tentacles

00:41:54about 36 m long

00:41:56and a diameter of more than 2 m.

00:41:58To give you an idea of its size,

00:42:00it was longer than a blue whale.

00:42:02Lion's mane jellyfish

00:42:04hunt by spreading their tentacles

00:42:06all around them,

00:42:08creating a trap

00:42:10to catch their food.

00:42:12As it has about 1,200

00:42:14stinging tentacles,

00:42:16it would take an extremely lucky

00:42:18fish to hope to escape them.

00:42:20The sting of a lion's mane jellyfish

00:42:22generally does not present

00:42:24its tentacles,

00:42:26as it can be very painful for humans.

00:42:28And if you see one on the beach,

00:42:30it is better not to touch it

00:42:32as it can sting you for a long time

00:42:34after being thrown on the shore.

00:42:36Fun fact, the lion's mane jellyfish

00:42:38appears in the story of Sherlock Holmes

00:42:40The Lion's Mane as a suspect.

00:42:42But don't worry,

00:42:44we won't give any spoilers.

00:42:46The last marine animal you see

00:42:48is a sea snake.

00:42:50Yes, they are different from eels.

00:42:52There are 69 identified species

00:42:54of sea snakes.

00:42:56Most of them are found in tropical

00:42:58and subtropical waters of the Indian

00:43:00and Pacific Oceans.

00:43:02And they have existed for millions of years.

00:43:04To make things easier,

00:43:06scientists have separated all

00:43:08the different species of sea snakes

00:43:10into two categories.

00:43:12The real sea snakes

00:43:14and striped tricots.

00:43:16While the real sea snakes

00:43:18spend almost all their time at sea,

00:43:20the striped tricots are not so active.

00:43:22If you see a snake on the beach,

00:43:24you can determine if it is

00:43:26a land snake or a sea snake

00:43:28by looking at its tail.

00:43:30If it looks like a striped tricot,

00:43:32then it is a sea snake you have there.

00:43:34But make sure to keep your distance

00:43:36in both cases.

00:43:38All sea snakes must surface regularly

00:43:40to breathe because they have no branches.

00:43:42That's why you could run into one

00:43:44while you're swimming.

00:43:46If that happens,

00:43:48the striped tricot must be

00:43:50as active as a cobra

00:43:52or an average crotal.

00:43:54However, since they only attack

00:43:56if they are provoked,

00:43:58bites are quite rare.

00:44:00Another trivial fact about sea snakes,

00:44:02they are the only reptiles

00:44:04to give birth in the oceans.

00:44:06The majority of sea snakes

00:44:08keep their eggs in their eggs

00:44:10and give birth to small snakes

00:44:12that are almost already formed

00:44:14while they are still alive.

00:44:16That's right,

00:44:18that's the food chain.

00:44:46A solar halo is a sign of nature

00:44:48indicating that a snowstorm

00:44:50or rain is coming.

00:44:52It is caused by the clouds

00:44:54made up of billions of small ice crystals.

00:44:56The sunlight

00:44:58crosses these crystals

00:45:00so that they divide and refract,

00:45:02like when there is a rainbow.

00:45:04Don't look directly at the solar halo.

00:45:06It's tempting

00:45:08because it's not something you see every day.

00:45:10And it's really beautiful.

00:45:12But ultraviolet rays

00:45:14can burn the tissues

00:45:16exposed to your retina

00:45:18and cause serious damage to your eyes.

00:45:20So it's not worth it.

00:45:22Or put on sunglasses.

00:45:24This phenomenon lasts about 40 minutes.

00:45:26These clouds are the same

00:45:28as those that can sometimes

00:45:30cause a frightening ring

00:45:32around the moon at night.

00:45:34In June 2020,

00:45:36people saw a cloud in the clouds,

00:45:38a rare storm formation in the sky.

00:45:40Formed when strong air currents

00:45:42push water vapor upwards,

00:45:44the air expands and expands

00:45:46when it reaches the bottom of the stratosphere.

00:45:48It pushes the dense cloud

00:45:50giving it an anvil shape

00:45:52and sometimes it even becomes a mushroom.

00:45:54Anvil-shaped clouds

00:45:56produce some of the most dangerous

00:45:58lightning of all storms.

00:46:00These lightnings seem to come out

00:46:02as if by magic from the blue sky

00:46:04when the storm is several kilometers away.

00:46:06This type of lightning

00:46:08comes from the top of the anvil

00:46:10and can be 10 times more powerful

00:46:12than a standard lightning strike.

00:46:14People were so scared

00:46:16by the giant cloud

00:46:18that they thought something terrible

00:46:20had happened.

00:46:22They posted pictures of the monster

00:46:24on social media

00:46:26before the authorities

00:46:28could explain what was happening.

00:46:30Experts managed to calm everyone's fears

00:46:32by explaining that it was

00:46:34nothing more than a natural phenomenon.

00:46:36Before dissipating,

00:46:38the storm was always in the same area

00:46:40no matter how strong the wind was.

00:46:42If you go to the west coast of France,

00:46:44you will find the island of Ré.

00:46:46Thanks to its beautiful blue waters,

00:46:48its clean sand beaches

00:46:50and its amazing lights,

00:46:52this place is a very popular holiday destination.

00:46:54But what is perhaps the most amazing

00:46:56on the island of Ré

00:46:58is what is just on the edge of the shore.

00:47:00Square waves.

00:47:02This strange wave pattern

00:47:04looks like a giant chessboard on the ocean.

00:47:06Many visitors to the island

00:47:08are captivated by these waves

00:47:10and go to high places

00:47:12like the nearby lighthouse

00:47:14to take pictures of this natural phenomenon.

00:47:16They say that when you see

00:47:18these square patterns in the water,

00:47:20it is almost as if there was

00:47:22a kind of metallic grid underneath.

00:47:24But even if these wave patterns are fascinating,

00:47:26it is better to admire them from afar

00:47:28and stay out of the water.

00:47:30To understand how these square waves are formed,

00:47:32it is important to know

00:47:34that in general,

00:47:36waves can travel several kilometers

00:47:38at the surface of the water

00:47:40depending on the wind and the weather.

00:47:42And even on days when the weather seems rather calm,

00:47:44storms located in the distance

00:47:46can send waves

00:47:48that affect the calm waters of the shore.

00:47:50When the waves move

00:47:52to the shores of distant lands,

00:47:54this is called a swell,

00:47:56which is different from a wave

00:47:58that occurs because of a local wind.

00:48:00When two different swells

00:48:02meet, this is called

00:48:04a cross sea.

00:48:06This is what generates these square waves

00:48:08that we observe near the island of Ré.

00:48:10Although these waves are one of the reasons

00:48:12why people flock to the island,

00:48:14they can still expect to enjoy

00:48:16calm and relaxing waters most of the time.

00:48:18The cross sea only occurs

00:48:20at certain times of the year,

00:48:22in specific weather conditions.

00:48:24In addition, everyone knows

00:48:26that it is necessary to avoid the ocean

00:48:28when these square waves appear,

00:48:30but it is not so common to hear

00:48:32about victims who have been trapped.

00:48:34And since many people on the island

00:48:36are tourists, there are many signs

00:48:38to warn them to get out of the water

00:48:40during this period.

00:48:42However, not everyone

00:48:44necessarily receives the information.

00:48:46There have been some cases

00:48:48where people were caught in the cross sea,

00:48:50but luckily they managed to get out.

00:48:52These square waves have become

00:48:54relatively famous over time,

00:48:56as no other place in the world

00:48:58has a cross sea like this.

00:49:00In fact, no one has ever spotted

00:49:02square waves elsewhere

00:49:04than off the island of Ré.

00:49:06However, there are swells

00:49:08in all the oceans of the world,

00:49:10and a cross sea can take place anywhere.

00:49:12But if the angle with which

00:49:14they approach each other is lower,

00:49:16the wave can give the impression

00:49:18of coming from the same direction,

00:49:20even if it is not the case.

00:49:22Not to mention that the swells

00:49:24can slowly lose their momentum

00:49:26so that their crest,

00:49:28or the top of the wave,

00:49:30seems rounder and less defined.

00:49:32The wind and weather regimes

00:49:34specific to the island of Ré

00:49:36create the perfect conditions

00:49:38to create a cross sea

00:49:40that people can clearly recognize.

00:49:42We are in 2009 in Italy.

00:49:44From his kitchen,

00:49:46a man sees flickering lights.

00:49:48He knows exactly what to do.

00:49:50He takes his family to a safe place.

00:49:52A few seconds later,

00:49:54a huge earthquake hits the region.

00:49:56His family survived

00:49:58thanks to his quick reaction.

00:50:00They knew that these flickering lights

00:50:02were the sign of an imminent earthquake.

00:50:04People have seen these mysterious lights

00:50:06since chandeliers,

00:50:08and some thought it was a kind of sign

00:50:10coming from space.

00:50:12Scientists did not take them seriously,

00:50:14but after the invention of photography,

00:50:16more and more evidence

00:50:18of these strange lights appeared.

00:50:20Soon they understood the link.

00:50:22The lights appear,

00:50:24and very quickly, the earthquake strikes.

00:50:26After digging a little,

00:50:28they actually found very old

00:50:30testimonies of these earthquake lights.

00:50:32It is said that blue flames

00:50:34came out of the ground

00:50:36just before an earthquake.

00:50:38The crabs of Christmas Island

00:50:40participate in a surprising phenomenon

00:50:42once a year.

00:50:44Their migration period

00:50:46is determined by the phase of the Moon

00:50:48and the first rains between October and February,

00:50:50although the exact date

00:50:52cannot be predicted.

00:50:54Once the crabs have received the signal,

00:50:56they leave their habitat in the forest

00:50:58and migrate in massive hordes

00:51:00to the sea.

00:51:02Counting by millions,

00:51:04we can observe a sea of red crabs

00:51:06blocking the roads as they cross the island,

00:51:08making their way to the ocean.

00:51:10There, they lay their eggs,

00:51:12then take their way in the opposite direction,

00:51:14returning to the forest

00:51:16until the following year.

00:51:18In the Indian state of Meghalaya,

00:51:20there are bridges

00:51:22that are entirely made of living tree roots.

00:51:24The bridges are made of

00:51:26these thick and arched roots

00:51:28which are strong enough

00:51:30to support the weight

00:51:32of more than 50 people at a time.

00:51:34The Kazi and Jaintya tribes

00:51:36have become masters

00:51:38in the art of growing these insensitive bridges.

00:51:40They need them to more easily cross

00:51:42the streams that flow down.

00:51:44Some of these root bridges

00:51:46are more than 80 years old.

00:51:48To make them,

00:51:50the members of the tribes

00:51:52take care of the roots

00:51:54until they are long enough

00:51:56to reach the opposite bank.

00:51:58It can take up to 10 or 15 years

00:52:00to grow a bridge.

00:52:02During the process,

00:52:04the roots intertwine

00:52:06closely with each other

00:52:08and that's how the bridges

00:52:10become so strong.

00:52:12Once a bridge is completely formed,

00:52:14it continues to grow.

00:52:16That's why these unusual natural structures

00:52:18last so long.

00:52:20The luminous columns

00:52:22are colored light beams

00:52:24that shine from the earth to the sky

00:52:26or that shine from the clouds.

00:52:28Usually, they only occur in cold weather

00:52:30because they form when the sun's light

00:52:32is reflected on ice crystals

00:52:34floating in the air.

00:52:36The higher the crystals are in the air,

00:52:38the larger these luminous

00:52:40and colored columns become.

00:52:42In the whole world,

00:52:44there are hidden caves

00:52:46that are filled with phosphorescent light.

00:52:48This light comes from hundreds

00:52:50of luminous worms

00:52:52that have settled comfortably

00:52:54in these caves.

00:52:56Some of these caves

00:52:58are more than 30 million years old

00:53:00and most of them are in New Zealand

00:53:02and Australia.

00:53:04The worms themselves don't really shine,

00:53:06but the green babies,

00:53:08called larvae,

00:53:10form nets

00:53:12and these nets can illuminate

00:53:14the whole cave.

00:53:16Their goal is to attract flies

00:53:18and other tasty insects

00:53:20that the worms enjoy.

00:53:22Rainbow trees do exist.

00:53:24They originate from the Philippines

00:53:26and Indonesia.

00:53:28These colorful wonders are called

00:53:30rainbow eucalyptus.

00:53:32The colors are created by the contrast

00:53:34between the old and the new bark.

00:53:36When the thin layers of the bark

00:53:38are removed,

00:53:40they reveal new barks

00:53:42with brighter colors.

00:53:44The most recent bark is green,

00:53:46then purple,

00:53:48then red,

00:53:50and finally brown.

00:53:52It is because these trees

00:53:54contain a substance called chlorophyll

00:53:56that makes the bark green.

00:53:58As each strip of bark ages,

00:54:00it loses chlorophyll

00:54:02and slowly changes color.

00:54:04Some nights,

00:54:06there are elves,

00:54:08gnomes, sylphs,

00:54:10or blue geese.

00:54:12Blue geese don't belong

00:54:14in this list, you say?

00:54:16In fact, I'm not talking

00:54:18about fairy tales,

00:54:20but about different types

00:54:22of lights visible

00:54:24very high above

00:54:26thunderstorms.

00:54:28Let's take the red sylphs.

00:54:30These flashes of light

00:54:32appear in the clouds

00:54:34and are caused

00:54:36by a specific type of lightning.

00:54:38Positive lightning

00:54:40cloud the ground.

00:54:42A positive charge is transferred

00:54:44from a thunderstorm

00:54:46to the ground

00:54:48when lightning strikes.

00:54:50This type of lightning

00:54:52represents only 10%

00:54:54of all lightning.

00:54:56For more than a century,

00:54:58people have believed

00:55:00that these lightnings

00:55:02are the most powerful.

00:55:04In short, even if we had the chance

00:55:06to see one,

00:55:08it was impossible

00:55:10to call a second person

00:55:12to witness the phenomenon

00:55:14and confirm it.

00:55:16Even when respectable

00:55:18scientists or pilots

00:55:20talked about it,

00:55:22the scientific community

00:55:24ignored them.

00:55:26In 1989,

00:55:28something strange happened.

00:55:30People started sharing

00:55:32videos and photos of red sylphs.

00:55:36Red sylphs can appear

00:55:38in the form of balls

00:55:40of a hundred meters of ionized air.

00:55:42These balls descend

00:55:44from a height of about 80 km

00:55:46at 10% of the speed of light.

00:55:48Researchers have studied

00:55:50not only the lightnings

00:55:52that fall from the clouds in a fury,

00:55:54but also these colored flashes

00:55:56that rise into space.

00:55:58Thus, electricity rises

00:56:00up to the ionosphere,

00:56:02but at the same time,

00:56:04it descends to Earth.

00:56:06Red sylphs appear

00:56:08in different forms.

00:56:10For example, in the form of jellyfish,

00:56:12which can have a surface

00:56:14of 77 km².

00:56:16There are carrot-shaped

00:56:18and column-shaped sylphs.

00:56:20They are similar,

00:56:22but the carrots have long fangs.

00:56:24The lower part of the fangs

00:56:26is blue and the upper part

00:56:28is red.

00:56:30On August 22, 2022,

00:56:32we took some stunning pictures

00:56:34of red drifts

00:56:36in the desert sky of Atacama,

00:56:38Chile.

00:56:40They were surrounded

00:56:42by another more important

00:56:44light, greenish.

00:56:46This is called the light of the night sky,

00:56:48which is poorly distinguished

00:56:50when the light pollution

00:56:52is important.

00:56:54In particular, to observe the stars and other objects that we could normally see in a clear sky.

00:57:00This glare of the air is due to the atoms of nitrogen and oxygen present in the atmosphere.

00:57:06The light of the sun erases their electrons during the day.

00:57:10They then recombine slowly and this process makes them shine.

00:57:17How can we see a red sylph?

00:57:20First of all, we have to find a big storm.

00:57:22They are more frequent in summer and spring, for example in June.

00:57:26Of course, the sylphs can appear at any time if there is a powerful storm, with lightning at ground level.

00:57:35The sky must be clear and very dark, ideally without moonlight.

00:57:40The storm must be at a distance between 160 and 320 km.

00:57:44Thus, the clouds will not obstruct the sky and the visibility will be better.

00:57:49In the ideal scenario, the storm will move along a distant horizon, so that it will be possible to see above the clouds.

00:57:57We can follow a storm using a meteorological radar.

00:58:00Your eyes need some time to adapt to the darkness around you.

00:58:04Give them a little time, about 20 to 30 minutes.

00:58:10Keep your eyes above the clouds and try not to look at them directly.

00:58:14Ignore the lightning.

00:58:17A sylph may appear once every two light scenes.

00:58:21Don't expect to capture all this with your camera.

00:58:24It's not easy, but the show will be worth the wait.

00:58:28We call this phenomenon, and other similar ones, TLEs, the English acronym for Transitional Light Phenomena.

00:58:37Light blue also deserves our attention.

00:58:39These are weak blue lights that rise very quickly above powerful thunderstorms.

00:58:46They are also very rare and, in most cases, it is only possible to see them on board an airplane.

00:58:54And now, let's talk a little about these fairy tale creatures.

00:58:57The elves in the world of lightning are short discs of light that can be seen at about 100 km in altitude in the atmosphere.

00:59:05This is just an acronym.

00:59:06Their full name is,

00:59:14Yes, we can continue to use the word elf.

00:59:18And there are the trolls.

00:59:20These are red spots that appear near the top of the clouds after the lightning of a very powerful red sylph.

00:59:27The gnomes are the smallest and fastest lightning.

00:59:31These are tiny points of white light that spring from the top of a large cloud of thunderstorms.

00:59:38The cloud is an elongated cloud that we see at the top of a thunderstorm.

00:59:43It spreads in the direction of the wind at an altitude.

00:59:46Gnomes only last a microsecond.

00:59:51And look at that, the ball lightning presents itself in the form of flaming orbs that can be as big as a golf ball and even reach the size of a big beach ball.

01:00:00They can be yellow, red, white, orange, green or purple.

01:00:05They can be visible for a few seconds, or even a few minutes.

01:00:10Over the centuries, many people have said they have witnessed this phenomenon, sometimes even seeing the balls floating all the way to their house.

01:00:19But such events are really unpredictable and rarely occur.

01:00:24Scientists have managed to recreate this lightning in a laboratory, or at least something very similar.

01:00:31They have realized that it appears after a lightning strikes the ground and results in the vaporization of various mineral particles.

01:00:41Here is something spectacular, volcanic lightning.

01:00:45It is born in the panache of an eruption.

01:00:49Like any storm, volcanic lightning is formed when static electricity accumulates in the earth's atmosphere.

01:00:56It is then released in the form of lightning.

01:01:00Scientists do not yet understand the whole process, but they think it is linked to a powerful charge.

01:01:07For example, the ice charge is at the origin of the formation of storms.

01:01:11It also plays a role in the production of lightning during volcanic eruptions.

01:01:16This phenomenon occurs when the air heated by an eruption rises in the sky and meets cold air.

01:01:22The water from the eruption turns into ice particles and, when these particles collide with each other, some electrons leave in all directions.

01:01:33The ice particles, which now have a positive charge, move higher in the sky and gather.

01:01:39It can also be a frictional charge, another event that leads to volcanic lightning.

01:01:44The phenomenon is similar to that of the ice charge.

01:01:46Except that here it is ashes and pieces of rock that collide and create an electric charge.

01:01:52There are also the gamma-ray flashes.

01:01:55More than ten years ago, researchers discovered that storms could generate short but very strong gamma-ray bursts, the most energetic form of light.

01:02:05These rays are so bright that they can blind the sensors of satellites, even when they are hundreds of kilometers away.

01:02:12They can also create antimatter.

01:02:14Antimatter is a type of matter composed of charged particles opposite to that of normal matter.

01:02:21Imagine that you are two boxes filled with blocks.

01:02:24Some blocks are red and others are blue.

01:02:27When these blocks touch each other, they disappear, or annihilate, and transform into energy.

01:02:33This is what happens when particles of matter and antimatter meet.

01:02:38And these flashes could be the result of gamma rays, because they emit a light that is not really visible.

01:02:44Ordinary lightning involves slow electrons.

01:02:47In gamma-ray flashes, electrons are very energetic.

01:02:51They crash into air molecules and produce this strange phenomenon.

01:02:56In 1991, somewhere in the luxurious jungles of central Vietnam,

01:03:02a local lumberjack found a mysterious hole among the leaves and bushes.

01:03:07He took a look at it and felt a strong wind blowing on his face.

01:03:11Then he heard a strange sound coming from the depths of the cave, and realized that it was the sound of a river.

01:03:18The lumberjack did not examine the cave, but decided to return later with a flashlight and a rope.

01:03:24But when he returned, he did not find the cave.

01:03:27He spent several years looking for it.

01:03:29Finally, in the 2000s, he managed to locate it again.

01:03:33In 2009, he brought scientists to this place.

01:03:36They discovered that the cave, called Son Dang, is the largest in the world.

01:03:41There is so much space here that you will hear a long echo if you scream.

01:03:45The main passage of Son Dang reaches 200 meters in height in some places,

01:03:50which is more than half the height of the Empire State Building.

01:03:54The surface of the cave is so huge,

01:03:56that a whole house of New York City with 40-story skyscrapers could hold it.

01:04:02Under the Vietnamese jungle, a deep underground labyrinth hides three of the largest caves in the world.

01:04:07And Son Dang is number one on this list.

01:04:10The vast interior space is filled with varied plants, unique microclimates and different landscapes.

01:04:16It is a real jungle that grows underground.

01:04:19This has been made possible by the collapse of the ceiling in some places.

01:04:23It lets the sunlight penetrate from above.

01:04:26There are huge stalactites 76 meters high on the ceilings and walls,

01:04:31which is more than the length of a Boeing.

01:04:34They have been there for hundreds of thousands and millions of years.

01:04:38Some limestone deposits are more than 450 million years old.

01:04:43This means that they have existed since much earlier times than dinosaurs.

01:04:47In addition to the jungle, there are also many rivers in the cave.

01:04:51They formed because of the rainwater that came down from the holes in the ceiling.

01:04:55These rivers are smooth and fast, like slides in an aquatic park.

01:04:59But the horseshoe is not the best idea,

01:05:02because they can drag you into one of these long labyrinths whose cave is filled.

01:05:06And we still don't know where they go.

01:05:09You can find yourself in another unknown part of the cave.

01:05:12This is what happened in 2018.

01:05:15Three divers accidentally discovered new areas in Sundang.

01:05:19The cave turned out to be much larger than everyone thought.

01:05:23They dived into one of the lakes of the cave and reached a depth of 78 meters.

01:05:28At the bottom, they found an independent tunnel.

01:05:30The divers set up a fishing line with lead

01:05:34and discovered that this place reached a depth of 120 meters

01:05:38and that the tunnel was more than a kilometer long.

01:05:41Even today, the exact size of the tunnel is not known.

01:05:45Sundang is also connected to another huge cave.

01:05:48There are many other things you can see in Sundang in addition to labyrinths and underground rivers.

01:05:54You can find large rooms with lakes

01:05:57and you can walk for hours along the dark corridors of the mountain.

01:06:00This place is breathtakingly beautiful but also dangerous.

01:06:04But yes, the coolest thing is that you can walk there.

01:06:07Since 2013, the Sundang cave has been open to tourists.

01:06:11But it's not just a little walk to take selfies.

01:06:15The expedition in the cave lasts several days.

01:06:18During the first day and a half, you will explore the third largest cave in the world.

01:06:23And only after that, you will reach Sundang.

01:06:25The path will take you through rivers, dense forests, mountains and rocks.

01:06:31You will be able to meet many exotic birds, monkeys and other animals.

01:06:35And according to many people, the path to the cave is even more impressive than the cave itself.

01:06:41Once at your destination, you will spend the next few days exploring Sundang.

01:06:46With other tourists, professional guides and porters,

01:06:50you will sleep every day in tents in different parts of the cave.

01:06:53You will see breathtaking landscapes and, get ready,

01:06:57majestic fossils 400 million years old.

01:07:01There are also dark rooms with lakes in which you can swim.

01:07:05These adventurous expeditions become more and more popular every year.

01:07:09People who have visited the cave say that it is the most amazing place they have ever seen.

01:07:15Another incredible cave is located in Indonesia, on the island of Flores.

01:07:19It is quite small, but contains surprising things.

01:07:23In 2003, a group of scientists discovered ancient artifacts here,

01:07:28including primitive tool fossils, such as carved stones.

01:07:32Scientists realized that hundreds of thousands of years ago,

01:07:36this place was home to our distant ancestors.

01:07:39Then, they found a very unusual female skeleton.

01:07:43This woman was only one meter tall.

01:07:46This is the height of the chest of an average adult.

01:07:50However, this woman had no problem with her spine or with the development of her bones.

01:07:55This skeleton and others found in the cave belonged to unknown human ancestors.

01:08:00Scientists have called this species Homo florensiensis, or simply Hobbit.

01:08:06The weight of the woman was between 16 and 35 kilograms.

01:08:10The analysis of the skull and bones showed that she was about 30 years old.

01:08:13The Hobbits probably lived on Earth between 190,000 and 50,000 years ago.

01:08:19It is likely that they met the ancestors of today's humans.

01:08:23The next cave is located in Turkey.

01:08:26Imagine that you live in an old house and that you decide to make some repairs.

01:08:30You throw away all the old parts of the rooms.

01:08:33The last place to sort is your basement.

01:08:36You have practically never visited it and you have no idea what is hidden there.

01:08:40But as it is quite spacious, you decide to make a room out of it.

01:08:43You destroy a wall and you discover the entrance to the cave.

01:08:47It is a tunnel that leads underground.

01:08:50You cross the cave and you see a real underground city.

01:08:53This happened in Turkey in 1963.

01:08:57A resident discovered a secret passage to a lost city in his cellar.

01:09:01About 20,000 people could live there.

01:09:04There was enough space for cattle and food reserves.

01:09:08It is not just a tunnel maze.

01:09:10There is a chapel, a school, squirrels, kitchens, walls and other signs of civilization.

01:09:18The city was built in the Byzantine era, in the 780-1180s.

01:09:23It is not the only one and is connected to many tunnels and underground cities that extend for several kilometers.

01:09:29Let's finish our journey in the strangest and scariest cave.

01:09:33We go to the southeast of Romania, near the Black Sea.

01:09:37Here, on a large desolate plain, you can find a hole.

01:09:41It is a tunnel that leads deep underground.

01:09:44The air inside the cave has high levels of hydrogen sulfide and carbon dioxide.

01:09:49Under normal conditions, the air we breathe contains about 20% oxygen.

01:09:54But there is only 10% here.

01:09:57You will not be able to breathe freely without an oxygen bottle.

01:10:00Water and air here are poisoned.

01:10:02Almost no animal is able to live in these conditions.

01:10:06At least those we know.

01:10:08And this cave is filled with 48 species of living organisms,

01:10:12of which 33 are new unknown species.

01:10:15The creepy things that live here can frighten you, especially if you are afraid of insects.

01:10:20Strange blue snails and white spiders crawl along the walls.

01:10:25An unknown species of translucent and transparent shrimp swims in the water.

01:10:29Thousand white legs with huge mustaches crawl on the ground.

01:10:34Here, you can also meet an unknown species of scorpion with a transparent white body,

01:10:39which looks like no other species of scorpion.

01:10:42Nothing here looks like normal animals.

01:10:45All the creatures of the cave are white or transparent.

01:10:48They have no eyes, but they have long legs and antennas,

01:10:52mustaches that help them move in space.

01:10:55Plants cannot live here without sunlight and clean air.

01:10:59This means that the production of oxygen is zero in this place.

01:11:03So how did these creatures manage to survive?

01:11:06The answer is in the water.

01:11:08The surface of the lake and puddles of water here are covered with a foam that moves strangely.

01:11:12This substance is a living organism.

01:11:15It is made up of a billion bacteria called autotrophs.

01:11:19Ordinary plants absorb carbon dioxide and use photosynthesis to produce oxygen.

01:11:25This cave is filled with carbon dioxide.

01:11:27The autotrophs absorb it and create tiny particles of food.

01:11:32Bacteria feed on these particles.

01:11:35Larger organisms then feed on these bacteria.

01:11:38And so on.

01:11:40In the end, there is enough food for everyone.

01:11:42This process is called chemosynthesis.

01:11:45It's like photosynthesis, but water is used instead of sunlight in chemical reactions.

01:11:50In this cave, evolution has created a completely unique biological system,

01:11:54distinct from the rest of the world.

01:11:57Something interesting happened recently in the South Dakota.

01:12:02It was everywhere on the Internet, so maybe you've heard of it.

01:12:06In July 2022, the sky in this state suddenly turned green.

01:12:11What happened exactly?

01:12:14Was it caused by humans or nature?

01:12:17Let's find out.

01:12:19Tuesday, July 5, 2022.

01:12:22Shortly after a strong storm, the sky in the South Dakota was still covered.

01:12:27Residents ended up leaving their homes and saw that the sky had turned an intense dark green.

01:12:34They had never seen anything like it before.

01:12:37They said they felt like they were in a science fiction movie.

01:12:43Unsurprisingly, residents immediately started spreading the news on all social networks.

01:12:49They shared their beautiful but strange photos on Twitter.

01:12:53They showed the sky above Sioux Falls and a few other cities.

01:12:59Even if it may look like something supernatural, it's not a terrifying phenomenon at all.

01:13:05It's a simple game between light and atmosphere.

01:13:09But such a phenomenon happens quite rarely and generally means that very bad weather is approaching.

01:13:16And that was the case in the South Dakota.

01:13:19Just before people started sharing their photos, a storm swept through the city of Sioux Falls.

01:13:25This was confirmed by the American Meteorological Service.

01:13:28This hurricane was terrible.

01:13:30The wind speed was about 160 km per hour.

01:13:34According to the Beaufort scale, measuring the wind speed, it is the fastest and most destructive storm.

01:13:40There are only 12 levels on this scale.

01:13:43And if the wind speed exceeds 117 km per hour, it is that we have reached the maximum level.

01:13:48Why didn't it make the news?

01:13:51Because it is quite common in this region.

01:13:54Storms occur very often in the United States, especially during the hottest months.

01:14:00And a storm out of 10 can become something more serious like a tornado.

01:14:05This one was no exception.

01:14:07It was the famous derecho.

01:14:11The derecho is very widespread and long-lasting.

01:14:14It is in fact the combination of a group of violent storms moving quickly and rain.

01:14:21People often say that a derecho is as strong as a tornado.

01:14:25However, there is a difference between the two.

01:14:28A tornado is a vortex, a column of air in rotation.

01:14:32Its diameter is about 150 m, although it can reach up to 4 km.

01:14:37And in this case, it is better to be far away.

01:14:40But the main point is that the tornadoes rotate.

01:14:42The wind moves very quickly and in a circular way around an invisible center.

01:14:50A derecho is a strong storm or a system of strong storms with winds in a straight line.

01:14:57In other words, it does not rotate.

01:15:00Instead, the derecho chooses a point somewhere and simply runs there.

01:15:05Like a very motivated marathon runner.

01:15:08If we compare a derecho to an ordinary tornado,

01:15:12the latter has 6 levels of force, from 65 to 600 km per hour.

01:15:18While a derecho is a bit like a small tornado of average level 1 or 2.

01:15:24Usually, its speed is between 115 and 180 km per hour.

01:15:30And in both cases, they can be accompanied by violent storms, lightning and rain.

01:15:35But they are still different phenomena.

01:15:39A storm becomes a derecho if the damage it leaves exceeds 385 km away

01:15:46and if the wind speed is at least 95 km per hour.

01:15:51It is quite difficult to predict.

01:15:54It can form even in clear weather when meteorologists do not predict storms.

01:15:59And then the winds appear suddenly.

01:16:02It is so surprising that they can even seem explosive.

01:16:06But the National Meteorological Service tries to warn the inhabitants at least half an hour or an hour

01:16:12before it happens so that they have time to prepare and shelter.

01:16:17It was no different this time.

01:16:19The storm swept almost the entire South Dakota as well as the neighboring states of Minnesota and Iowa.

01:16:25The consequences were quite serious.

01:16:28More than 30,000 people were left without electricity.

01:16:32Fortunately, no one was injured, especially because the inhabitants are rather used to hot air.

01:16:40However, the green sky is something different.

01:16:43It has become a very unusual spectacle for the inhabitants.

01:16:46Everyone wondered why this was happening.

01:16:49Was it a bad omen or a normal meteorological phenomenon?

01:16:53To be completely honest, scientists have no exact explanation.

01:16:58But although there are only hypotheses, they seem rather convincing.

01:17:04A green sky is a very rare phenomenon.

01:17:07Most scientists think it happens when a powerful storm approaches the region

01:17:12before sunset or sunrise.

01:17:15The sky then turns green in the area.

01:17:18NBC meteorologist Bill Karins, who himself was confronted with a similar event,

01:17:23suggests that the green sky appeared because of the huge hail that preceded the storm.

01:17:30First of all, let's talk about the reason why the sky is generally blue.

01:17:35Or any other nuance, depending on one's mood.

01:17:38The sun simultaneously carries all the rays of the spectrum of colors.

01:17:42It may seem white to us, but it actually has all the colors at the same time.

01:17:46However, these color waves all have different lengths.

01:17:53For example, the blue rays are shorter than the others.

01:17:57They pass through the air molecules better than the red waves,

01:18:00so that they reach us faster.

01:18:03This is why, in bright weather, the sky seems blue.

01:18:08Conversely, the red and orange waves are very long and move more slowly.

01:18:15They are generally left behind.

01:18:17But when the sun passes under the horizon or rises,

01:18:20the direction of the rays changes and these waves reach us better.

01:18:26All this means that even if the sunrises and sunsets seem red and orange to us,

01:18:31there are actually always blue and green waves.

01:18:35But they have to bounce on something to reach us faster

01:18:38and become stronger than the red rays.

01:18:42You know where we're going with this.

01:18:46This is where the water comes into play.

01:18:49Clouds are made up of droplets of water.

01:18:52When they become big enough but don't fall yet,

01:18:55for example because of strong winds,

01:18:57they affect the behavior of light in the sky.

01:19:01Violent storms are mainly composed of water and hail.

01:19:05However, it is water that best reflects blue and green rays.

01:19:09This is also why the water of rivers and lakes seems blue-green to us,

01:19:14when in reality it is transparent.

01:19:17So there are a few key factors that make the sky green.

01:19:22First of all, the sun must be at horizon level.

01:19:26Another factor is that even if storm clouds approach,

01:19:29they must not completely cover the sky.

01:19:32There must still be some space for the sun's rays.

01:19:35Then, barely perceptible blue rays head towards storm clouds,

01:19:40but they are repulsed by droplets of water and hail.

01:19:42By mixing with the red sunset,

01:19:45they turn into a bright green light,

01:19:48and this green light spreads throughout the sky.

01:19:52This is why in most cases, when the sky becomes green,

01:19:56people can only see it in the evening.

01:19:59This can possibly happen in the middle of the day,

01:20:02but it is very rare,

01:20:04given that the conditions are very specific.

01:20:08Anyway, if you see a green sky,

01:20:10if you see a green sky,

01:20:12don't panic.

01:20:14This does not necessarily mean that a terrible storm is approaching.

01:20:18The probability is high,

01:20:20but it is not an absolute rule.

01:20:22It can simply be a heavy rain,

01:20:24or a heavy hail.

01:20:26In other words,

01:20:28if you see a green sky,

01:20:30it would be better to take shelter,

01:20:32and to put your car under protection.

01:20:34But if you are lucky enough to be able to admire a magnificent green sky

01:20:37from the comfort of your home,

01:20:39you will have the chance to experience something very rare.

01:20:43Some people have said that it was the most incredible thing they have ever seen.

01:20:48The Moon.

01:20:50Our faithful friend.

01:20:52Our only companion in this large dark and cold space.

01:20:55It is not surprising that all the events associated with it,

01:20:58such as solar or lunar eclipses,

01:21:00fascinate us.

01:21:02But what about the black moon?

01:21:04The blue moon?

01:21:06The super moon?

01:21:08Well, let me tell you everything,

01:21:10and explain to you how you can observe them.

01:21:12Prepare your calendars.

01:21:14The distance between the Earth and the Moon is 384,472 km.

01:21:18Yes, I measured it.

01:21:20It doesn't seem that far, does it?

01:21:22But believe me, most people greatly underestimate this distance.

01:21:25Did you know that all the planets in the solar system,

01:21:27including Jupiter and Saturn,

01:21:29could stand between the Moon and us?

01:21:31I couldn't believe it myself.

01:21:33The Moon is linked to the Earth by its position.

01:21:35That's why it is always facing us, with only one side.

01:21:38There are several phases in a lunar cycle.

01:21:41The new moon is the first phase.

01:21:43The sun illuminates the hidden phase of our satellite,

01:21:46so we can't see the Moon.

01:21:48It is almost invisible in the sky.

01:21:50The crescent moon is the light part that gradually grows.

01:21:54The full moon is the phase during which the sun completely illuminates the visible phase.

01:21:58The descending moon is a progressive decline of the luminous part.

01:22:02And finally, another new moon arrives.

01:22:05And the entire cycle starts again.

01:22:08There are 29.5 days in a lunar cycle,

01:22:11so it takes about a month if we subtract the month of February.

01:22:14But why am I telling you all this?

01:22:17So that you can better understand the black moon.

01:22:20A rare astronomical event that occurs once every 29 months,

01:22:24that is, two and a half years.

01:22:26This term does not exist in astronomy.

01:22:28It was invented by astrologers.

01:22:30It is not official and has several meanings.

01:22:32The black moon can mean the second new moon in a month.

01:22:36Usually, there is only one new moon per month,

01:22:39having two is therefore a rare phenomenon.

01:22:41This is due to a slight offset between the lunar cycle and the annual cycle of the Earth.

01:22:45A bit like the bisextile years.

01:22:47The black moon can also mean something else.

01:22:50For example, usually there are only three new moons per season.

01:22:54Basically, a new moon every 30 days.

01:22:57However, if there are four, the black moon means the third.

01:23:00There are also less popular meanings.

01:23:03For example, this is how people call the month of February

01:23:06when there are no new moons or full moons.

01:23:08This happens about once every 19 years.

01:23:11But what makes it so special?

01:23:13The satellite is entirely hidden in the sky during a normal new moon.

01:23:17But during a black moon, you can see its dark silhouette.

01:23:21You will have to choose a good place without light from the city.

01:23:24If you live in a big city, you will have trouble seeing it without a telescope.

01:23:27In addition, as the sky turns black during this phenomenon,

01:23:30you will be able to see different constellations that were hidden before,

01:23:34as well as Jupiter and Venus.

01:23:36The last time this phenomenon occurred was April 30, 2022.

01:23:40You could see it in most regions of the United States,

01:23:43except for the areas of the Pacific Ocean, Alaska or Hawaii.

01:23:47Aloha!

01:23:49Yes, unfortunately, if this is the first time you hear about the black moon,

01:23:53you have already missed it.

01:23:54You will now have to wait another two and a half years.

01:23:57The next black moon will take place in September 2024,

01:24:00according to the standard method,

01:24:02and on May 19, 2023, according to the seasonal method.

01:24:06But don't worry,

01:24:08you will always be able to see another astronomical event.

01:24:11There was once a blue moon.

01:24:13I'm not kidding, I'm serious.

01:24:16You can still see the blue moon.

01:24:18Well, not literally, of course.

01:24:20The moon doesn't turn blue.

01:24:21It's just what astrologers call the second full moon in a month.

01:24:24The black and blue moons are similar by definition,

01:24:27but they are actually opposite.

01:24:29If the black moon is a second new rare moon in a month,

01:24:32the blue moon is a second rare full moon.

01:24:35They also occur both every 29 months.

01:24:38Not so rare, is it?

01:24:40It is quite ironic that this event is called the blue moon.

01:24:43Folklorist Philip Hiscock

01:24:45assumes that the term blue moon in his calligraphic version

01:24:48was invented by the farmers of Maine in 1937.

01:24:51Another interesting astronomical event is called the supermoon.

01:24:55Fill up your telescope and look for hills,

01:24:58because you will see an exceptionally bright and large moon,

01:25:01like the one we only see in the movies.

01:25:04What exactly does a supermoon mean?

01:25:07You see, the moon does not revolve around the Earth in a circular orbit.

01:25:10Its orbit is elliptical,

01:25:12and the place where it is located is called the supermoon.

01:25:14A supermoon is a phenomenon that occurs

01:25:17when the full moon coincides with the supermoon.

01:25:20For this reason, it seems particularly large and bright to us.

01:25:23Its diameter is 14% larger,

01:25:26and it is 30% brighter than usual.

01:25:29In this regard, this phenomenon is often confused with the lunar illusion.

01:25:33During the lunar illusion,

01:25:36the moon is low above the horizon,

01:25:39and the moon is high above the horizon.

01:25:41During the lunar illusion,

01:25:44the moon is low above the horizon and appears to be visually larger.

01:25:47Of the 12 or 13 full moons annually,

01:25:503 or 4 are supermoons.

01:25:53But most of them are not very significant.

01:25:56You will probably not see any difference at all.

01:25:59The most interesting are the large and rare supermoons.

01:26:02During this one, the moon becomes really large.

01:26:05The last large supermoon occurred in 2016.

01:26:08Unfortunately, large supermoons are rare

01:26:11and only occur once every 18 years.

01:26:14The next one will occur only in 2034.

01:26:17But we can observe smaller supermoons quite frequently.

01:26:20In 2022, they will take place on June 14 and July 16.

01:26:24There is also an opposite phenomenon

01:26:27called micro-moon.

01:26:30You have probably already guessed what that means.

01:26:33It occurs when the full moon is at its farthest point from the Earth.

01:26:36This point is called apogee.

01:26:38The last supermoon, in 2022, took place on June 29.

01:26:41In 2023, we can observe it on January 7,

01:26:44February 5 and August 16.

01:26:47Of course, you don't have to follow each of these events.

01:26:50Most people are more interested in lunar and solar eclipses.

01:26:53By the way, are you one of the people who confuse these two events?

01:26:56Do the test.

01:26:59Pause this video.

01:27:02Describe what these two eclipses mean.

01:27:05Compare your answer with the correct definition.

01:27:08OK.

01:27:11So, a solar eclipse is a phenomenon

01:27:14where the Moon partially or entirely covers the Sun.

01:27:17A solar eclipse is possible only during the new moon,

01:27:20when the Moon itself is not visible.

01:27:23Many people think that this event is incredibly rare,

01:27:26but it is not entirely true.

01:27:29A lunar eclipse is a phenomenon

01:27:32during which the Moon is completely or partially in the shadow projected by the Earth.

01:27:35The lunar eclipse can only occur during the full moon,

01:27:38if you guessed right, bravo!

01:27:41Otherwise, don't worry, many people confuse them.

01:27:44In 2022, a partial solar eclipse will take place on October 25.

01:27:47It will be visible in Europe,

01:27:50South and West Asia, North and East Africa,

01:27:53and in the Atlantic.

01:27:56As I mentioned, a total solar eclipse is not as rare as many people think.

01:27:59But the problem is that it is not always visible from any part of the planet.

01:28:02So if you want to see this event,

01:28:05make sure to check the calendar

01:28:08to be able to see it.

01:28:11And don't forget special glasses!

01:28:14However, lunar eclipses are much more frequent.

01:28:17Partial lunar eclipses occur almost every month.

01:28:20But a total lunar eclipse will take place in 2022,

01:28:23on the night of the 7th to the 8th of November.

01:28:26You will be able to see it in almost all regions of the world,

01:28:29except in Africa.

01:28:32I heard that zebras were downright disgusted.

01:28:35The Moon is a really fascinating satellite.

01:28:38There are so many interesting events related to it.

01:28:41What rare lunar events have you seen or want to see in your life?

01:28:45Have you observed rare and fascinating astronomical events?

01:28:48Do not hesitate to share them in the comments.

01:28:51When a lightning strikes the sky,

01:28:54it releases some 300 million volts,

01:28:57the equivalent of the combined voltage of 25 million car batteries.

01:29:01Some say that you are more likely to be struck by lightning

01:29:04during your life than to win the lottery.

01:29:06And statistics seem to prove this adage.

01:29:09Because every year, about 28 inhabitants of the United States

01:29:12are indeed electrocuted by the sky.

01:29:17Our infrastructures can also be affected by lightning.

01:29:20This is because they are generally focused

01:29:23on the tallest structures around.

01:29:26But in some conditions, they can also fall in the middle of the field.

01:29:29Scientists have therefore come together

01:29:32to imagine a kind of laser skyrocket that could remedy it.

01:29:34This unique invention could make electric storms

01:29:37a little more bearable because it is able to protect

01:29:40an area much larger than an ordinary skyrocket.

01:29:43And it is very flexible.

01:29:46Classic skyrockets work like magnets

01:29:49for this powerful electric charge.

01:29:52They are high metallic devices,

01:29:55generally placed at the top of buildings.

01:29:58When a storm approaches,

01:30:01this rod offers an easy path to follow for lightning,

01:30:04allowing the electric current to discharge safely into the ground.

01:30:07This device protects the building

01:30:10and all the people who are there,

01:30:13by redirecting the electric energy elsewhere.

01:30:16We have only been using skyrockets for the last 300 years,

01:30:19following the experience of Benjamin Franklin.

01:30:22But they are not indestructible.

01:30:25When it comes to protecting vast spaces,

01:30:28like airports, they remain insufficient.

01:30:31It is because they can only cover an area proportional to their height.

01:30:34Here is how this new improved skyrocket

01:30:37could be useful to us.

01:30:40When the laser hits the sky,

01:30:43it leaves behind an overheated air stream called plasma.

01:30:46In the same way that a sculptor traces cracks in clay,

01:30:49the laser creates channels in the air.

01:30:52These channels then become the new route privileged by lightning,

01:30:55guiding it to the ground.

01:30:58This new method was tested in the Swiss Alps in 2021

01:31:01and the results seemed at least promising.

01:31:04However, they have their own drawbacks.

01:31:07They are not always available and require some preparation.

01:31:10This is because they must be activated before the lightning strikes.

01:31:13If you take a second too late, it is a failure.

01:31:16In addition, once the laser has stopped,

01:31:19the air quickly loses its conductivity.

01:31:22This means that this skyrocket could not have enough power

01:31:25to guide the lightning safely.

01:31:28A solution could be to measure the electric fields

01:31:31around a certain area,

01:31:34but these new skyrockets still need to be tested

01:31:37and generously financed.

01:31:42The European Space Agency has discovered

01:31:45another way to use laser technology.

01:31:48To transform lunar dust into roads.

01:31:51We could considerably facilitate our future lunar exploration missions

01:31:54if a laser beam could accomplish these difficult tasks,

01:31:57allowing astronauts to drive around the Moon.

01:32:00This discovery could also help solve another problem.

01:32:02The lunar dust that sticks to everything it touches.

01:32:05These lunar roads may seem an insurmountable challenge for the moment,

01:32:08since we have not visited our satellite since 1972.

01:32:11But when future astronauts light up again,

01:32:14they do not just plan to walk for short distances.

01:32:17It will then be useful to allow them to be motorized.

01:32:20This way, they will be able to explore larger areas.

01:32:23The problem is that this cursed lunar dust

01:32:26is extremely thin, abrasive and sticky.

01:32:28During the Apollo missions,

01:32:31it obstructed equipment, eroded space suits

01:32:34and even caused a rover to overheat.

01:32:37This is why scientists are trying to bombard

01:32:40lunar dust simulated by laser.

01:32:44This project used a 12 kW laser

01:32:47to melt false lunar dust

01:32:50into a solid and glassy surface.

01:32:53Perfect for lunar roads.

01:32:55The plan is not to send a huge laser to the Moon.

01:32:58This device that we test here on Earth

01:33:01is like a substitute for the Sun,

01:33:04reproducing what the lunar sunlight could accomplish.

01:33:07The idea would be ultimately to concentrate solar light

01:33:10by using a large lens at the very surface of the Moon.

01:33:13Some experiments have been conducted so far

01:33:16with different sizes of lasers,

01:33:19demonstrating that a larger beam

01:33:22made the whole process more homogeneous.

01:33:25We obtained a stable layer of glassy lunar dust

01:33:28on which it is easier to drive.

01:33:31It turned out to be a glassy material,

01:33:34slightly brittle and able to resist downward forces.

01:33:37And even if it cracks, it remains repairable.

01:33:40The laser beam was used to create sections of roads

01:33:43in the shape of triangles that fit like pieces of a puzzle

01:33:46and form solid surfaces on the lunar soil.

01:33:49If everything goes as planned,

01:33:52we will thus obtain lunar roads made up of embedded triangles.

01:33:55We will also be able to offer a solution at the time of the lunar landing.

01:34:00Lasers can also be used to collect information

01:34:03on long-lost civilizations.

01:34:06The discovery of the Mayas city

01:34:09has always been arduous for researchers

01:34:12who explore the Mexican peninsula of Yucatan.

01:34:15For decades, experts have estimated that no ancient civilization

01:34:18could have prospered in this difficult environment.

01:34:21However, technological advances such as telemetry

01:34:23and laser technology show us that

01:34:26CE could not be the only solution.

01:34:29LIDAR technology can help archaeologists,

01:34:32especially in difficult areas of access.

01:34:35It is as if we were equipping our computers with a pair of gods.

01:34:38The entire system works like a flashlight

01:34:41that sends small luminous beams in the form of laser pulsations.

01:34:44These beams bounce on objects

01:34:47such as trees and buildings

01:34:50to finally return to the point of emission.

01:34:53When an autonomous car or a robot

01:34:56wants to know where it is,

01:34:59it uses LIDAR to send these luminous beams.

01:35:02By determining how long they take to return

01:35:05and where they hit,

01:35:08the car or the robot is able to understand

01:35:11what surrounds it,

01:35:14which allows it to move at night or in the fog

01:35:17without hitting anything.

01:35:20And it is thanks to this technique

01:35:23that we are now in the Mayan city of Ocumtun.

01:35:26LIDAR technology has helped researchers

01:35:29map the soil of the jungle,

01:35:32revealing hidden structures.

01:35:35However, someone still had to confirm

01:35:38all these discoveries on foot,

01:35:41but the journey to Ocumtun was not particularly difficult.

01:35:44The region, quite far from the nearest airport,

01:35:47is essentially unexplored

01:35:50and accessible only by old hunting and forestry routes.

01:35:53It is only 50 km away,

01:35:56but the effort has paid off,

01:35:59revealing monumental structures

01:36:02like a large acropolis and intriguing shapes,

01:36:05letting you guess a market or a temple.

01:36:08LIDAR is also embarked on astromobiles

01:36:11that we use to explore other planets.

01:36:14This allows the robots we send there

01:36:17to locate themselves in their environment

01:36:20without human directives.

01:36:24We could also be able to use lasers

01:36:27to predict how a volcano will behave.

01:36:30These structures are filled with magma,

01:36:33the melting rock that infiltrates up

01:36:36from the bowels of the earth.

01:36:39When a volcano erupts, a chemical reaction occurs,

01:36:42transforming the magma into CE, which we call lava.

01:36:45The specialists at the origin of this new use of the laser

01:36:48consider magma as the computer coding of volcanoes.

01:36:50There is no information on how a volcano could erupt.

01:36:53This is because all eruptions do not produce lava,

01:36:56and even if it was CE, there are different types

01:36:59distinguished by their fluidity.

01:37:02Magma is like a mixture of liquid, gas

01:37:05and crystals that agitate inside the volcano.

01:37:08Many elements come into play before a volcanic eruption.

01:37:11It is therefore difficult to study

01:37:14and understand this complex chemistry.

01:37:17To find out a little better,

01:37:20scientists use a laser.

01:37:23Just like those sometimes used in eye surgery.

01:37:26This makes chemical compounds easier to study.

01:37:29This latest laser method was used on samples

01:37:32from an eruption in 2021

01:37:35that lasted 85 days.

01:37:38It covered more than 10 square kilometers,

01:37:41spitting out tons of lava that destroyed more than 1,000 homes

01:37:44and forced more than 7,000 people to evacuate.

01:37:47To prevent such events from occurring again,

01:37:50it is true that earthquakes and landslides

01:37:53help experts predict how a volcano could behave.

01:37:56But learning a little more about its chemistry

01:37:59can prove all the more useful.

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