Les écotremblements sont des sons mystérieux et tonitruants qui semblent provenir du ciel, et personne ne sait exactement ce qui les cause. Ces détonations puissantes peuvent être si fortes qu'elles secouent les bâtiments et effraient les gens, mais elles ne laissent aucun signe d'explosion ou de tremblement de terre. Des personnes ont signalé avoir entendu des écotremblements partout dans le monde—dans des lieux tels que les États-Unis, le Japon et même l'Italie. Certains scientifiques pensent que ces bruits pourraient provenir de météores entrant dans l'atmosphère ou de tremblements de terre sous-marins envoyant des ondes de choc dans l'air. D'autres suggèrent qu'ils pourraient être causés par des changements atmosphériques ou même des tests militaires secrets. Quelle que soit la cause, ces détonations étranges sont imprévisibles, donc si vous en entendez une, ne paniquez pas—sachez simplement que vous faites partie d'un mystère mondial! Animation créée par Sympa.
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FunTranscript
00:00The sound of the storm
00:04For hundreds of years, people in the United States reported hearing strange loud noises.
00:10These mysterious sounds are called skyquakes, and yes, it's a reality.
00:15If you've ever heard loud and distant noise that wasn't clearly a storm or the noise of a car engine exploding.
00:22Congratulations, it seems that you have yourself experienced a skyquake.
00:27People report them all over the world, from the United States to India and Japan.
00:32They have different names, and we still don't know exactly why they happen.
00:38Sometimes, these loud noises accompany earthquakes.
00:41People heard them during the earthquakes of New Madrid at the beginning of the 19th century and until January 2020.
00:48Those who have experienced them describe skyquakes as a noise of rustling or rolling.
00:54The famous American writer, James Fenimore Cooper, describes it in a more poetic way,
00:59as the lake speaking to the surrounding hills, which sends back the echo of his voice in a precise response.
01:07Sometimes, these mysterious noises occur in cold weather instead of during earthquakes.
01:13One of the hot spots of skyquakes is near Lake Seneca in New York.
01:18They are called the Seneca Guns.
01:21The detonations can be so loud that they shake windows and doors.
01:25In August 1886, after an earthquake in Charleston, people heard these noises for several weeks,
01:33at the same time as the numerous replicas of the earthquake.
01:38In 2020, scientists from the University of North Carolina examined old press articles,
01:44notably from North Carolina, where people often reported these sounds.
01:49They hoped to match the noises to seismic data, but they found no link between the sounds and earthquakes.
01:56One of the researchers stated that they thought the noises occurred in the air and not underground.
02:01The team studied the infrasounds, which are low-frequency noises that humans cannot hear.
02:07They found signals lasting between one and ten seconds,
02:09which corresponded to the moment when people reported hearing the detonations, but nothing is certain here.
02:16Some people think that solar eclipses, tsunamis, or the collapse of caves under the sea cause skyquakes.
02:23Others believe that the sounds come from planes producing powerful sonic bangs.
02:27However, this does not explain the old skyquake recordings before the invention of airplanes.
02:33Some scientists think that a type of meteor, called bolide, causes these sonic explosions.
02:39These meteors explode when they penetrate the Earth's atmosphere.
02:43If this happened above thick clouds, the sound would become louder and spread far away,
02:49but we would not find anything on the ground.
02:51Another idea is that gas could escape from the bottom of deep lakes, such as Lake Seneca.
02:58If you find the resonances of the strange sky, let me introduce you to foggy sky arches.
03:04They are also known as white sky arches, ghost sky arches, or cloud sky arches.
03:11They are shaped in a similar way to regular colored sky arches, but they are much wider.
03:16Sky arches appear when large raindrops are in the sky,
03:21and you can always spot them on the opposite side of where the sun shines.
03:26Foggy sky arches are created by tiny droplets in the fog, or clouds instead of large raindrops,
03:33and they also appear opposite the sun.
03:36If you want to see a foggy sky arch, you have to look for it in a light fog when the sun is shining.
03:44You could see one when the sun begins to pierce the fog, or if you are near the ocean,
03:50where the fog often forms.
03:52Since the droplets of water in the fog are very small,
03:56foggy sky arches do not have vivid colors like sky arches.
03:59They can even appear all white or have pale colors.
04:04To find one, turn your back to the sun and look at an angle of about 35 to 40 degrees
04:10relative to where your shadow is.
04:13Some foggy sky arches are difficult to see at first because they melt in the fog,
04:18but once you have spotted them, it is easy to recognize them.
04:22The next rare meteorological phenomenon to monitor is thunderstorm.
04:27You guessed right, it's a particular type of storm that occurs during a snowstorm.
04:32Unlike regular storms, which often strike in spring and summer,
04:37thunderstorms are much rarer because they occur during the strongest winter storms,
04:41like big snowstorms, and require hot air at the same time, which is not a frequent combination.
04:47For a snowstorm to occur, you need humidity in the air,
04:51a certain instability and something to lift the air, like rising winds.
04:55Just like in normal storms, lightning can appear when you hear thunder.
05:00Lightning in snowstorms usually moves from cloud to cloud instead of striking the ground.
05:06And the sound of thunder is also different,
05:08more like a deaf rumble rather than a loud noise because the snow softens the sound.
05:12You are less likely to be struck by this one,
05:15but it is always important to stay inside when you hear thunder for your safety.
05:22Fans of Boreal auroras, this one is for you.
05:25Scientists have noticed a new kind of glow in the sky that looked like a purple haze.
05:30They nicknamed it Steve, making fun of it, but then gave it a more scientific name.
05:36Increasing the speed of strong thermal emissions, Steve for short.
05:40Steve is actually a fast stream of overheated gas
05:44that always moves west and appears only shortly before midnight.
05:47They wondered if something like Steve could happen after midnight,
05:52but moving in the opposite direction.
05:54And now, scientists think they have discovered this anti-Steve
05:59by analyzing data from a research station in Norway.
06:02In December 2021, they took a picture of a bright purple band
06:07extending over 998 km in the sky.
06:11And it only appeared after midnight.
06:17The satellites of the European Space Agency
06:20have also measured the conditions in this part of the sky
06:23and found that the ions were moving east.
06:26Steve's nocturnal twin has not yet been officially named,
06:31but it would be nice if he was called Sam, abbreviation of Steve after midnight.
06:36If you have ever seen snow on a sunny day, falling from the sky without a single cloud,
06:42it was probably diamond dust.
06:44It is a type of particular weather phenomenon
06:47where millions of tiny ice crystals form near the ground.
06:51These ice crystals float slowly in the air,
06:54a bit like dust floats in your house.
06:56When the sunlight hits these crystals, they sparkle like diamonds.
07:01Unlike ordinary snow,
07:03diamond dust can fall from a clear sky,
07:06which explains why it is sometimes called
07:09precipitation in clear sky.
07:12This occurs due to an inversion of temperature.
07:15Normally, it is colder when rising from the ground,
07:18but during an inversion of temperature,
07:20the cold air stays near the ground,
07:22and the warmer air is above.
07:24The warm air contains more water vapor,
07:26and when it mixes with the cold air near the ground,
07:29it turns directly into ice crystals,
07:31and the ice powder is formed.
07:34For this to happen, the air near the ground must be extremely, extremely cold,
07:39well below the freezing temperature.
07:42Diamond dust can fall for several days,
07:45but it is so light
07:46that it usually does not accumulate on the ground like ordinary snow.
07:50A viral hole,
07:51also known as a perforated cloud,
07:54is the next on our list.
07:56This large circular or oval space sometimes appears in some clouds.
08:00These types of clouds float high in the sky,
08:03and are often made up of tiny droplets of colder water
08:06than the freezing point,
08:08but which are not yet frozen.
08:10These special water droplets are called oversaturated,
08:13and they need a reason to freeze.
08:16Ice crystals provide them with this reason.
08:21When a plane crosses a cloud,
08:23it can then introduce these ice crystals.
08:26Once the ice crystals are present,
08:28the oversaturated water droplets quickly freeze,
08:31thicken, and begin to fall from the cloud.
08:34This creates a hole in the cloud,
08:36and as other droplets near it freeze,
08:39the hole widens and spreads outwards.
08:42Any tornado is scary,
08:45but a fire tornado brings horror to a whole other level.
08:49These bad boys are swirling towers of flames and ashes
08:53that form when there is extreme heat,
08:56strong winds,
08:57and an irregular ground.
08:59The intense heat of the fire quickly heats the air.
09:02The cooler air on the sides rushes to replace it,
09:05and creates strong winds.
09:07When winds from different directions meet,
09:11it turns the fire into a tornado.
09:14It becomes stronger, and can even create its own climate.
09:18It sucks in flames, ashes, dirt,
09:22and everything that is on its way.
09:25Winds can reach speeds of more than 225 km per hour,
09:29and these fire tornadoes can last more than 20 minutes.