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.
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