00:00Here you are, while you take a seat on board your submarine, apprehension wins you.
00:06You are about to dive several hundred meters to explore the abysses.
00:10But so many things could go wrong.
00:12Technical failure, crushing pressure, terrifying marine creatures, and strange noises.
00:17Indeed, an enigmatic rumbling emanates from the depths.
00:21Even more disturbing, it seems to manifest only at dawn and dusk.
00:26This sound could play a role similar to that of a bell announcing the time of the meal.
00:31Because it seems to be linked to the movement of large numbers of marine creatures in search of food.
00:36But this is still a hypothesis.
00:39Thanks to extremely sensitive underwater microphones,
00:43researchers have captured a low-frequency rumbling between 200 and 1000 meters deep.
00:48This sound, although perceptible, only exceeded 3 to 6 decibels, the usual background noise of the ocean.
00:55For comparison, a whisper in the calm of a library reached about 30 decibels.
01:01This acoustic phenomenon was distinguished by a tonality oscillating between rumbling and rumbling.
01:06The most intriguing?
01:08Despite their efforts, scientists have not been able to identify with certainty the species at the origin of this sound.
01:14The origin of this sound is located at a depth known as the twilight zone.
01:20This space, plunged into darkness, is poor in nutrients and devoid of essential solar light for photosynthesis.
01:27The fauna that thrives there depends on suspended organic particles and dead organisms falling from the upper layers.
01:34Despite this apparent austerity, the twilight zone is far from desert.
01:39A 2015 study suggests that up to 90% of the fish on the planet could reside there,
01:45among which many species still unknown.
01:49Let's go back to this enigmatic noise.
01:51Researchers estimate that it could be linked to the vertical migration of small marine creatures such as fish, shrimp and squid.
01:58These animals go up to the twilight surface to feed on plankton, taking advantage of the darkness to escape predators.
02:06At dawn, they dive back into the depths to hide.
02:10This phenomenon, one of the largest animal displacements on Earth, mobilizes billions of organisms every day.
02:17Scientists assume that this hustle and bustle accompanies this migration,
02:21perhaps serving as a means of communication or coordination.
02:25They could also signal to the group the right time to go back to feed.
02:29If this hypothesis is confirmed, it would make it possible to better understand life in the abyssal depths.
02:35For a long time considered as the kingdom of silence,
02:37the twilight zone could actually be home to social interactions and much more elaborate behaviors than we imagined.
02:46But the ocean is not the only one to produce strange sounds.
02:49The Earth itself emits an incessant rumbling.
02:52This phenomenon, inaudible to the human ear, has nothing to do with earthquakes.
02:57It results from tiny vibrations and continues within the earth's crust,
03:02so weak that they can only be detected with specialized equipment.
03:07Known as free oscillation, this resonance, observed for a long time by scientists, could be recorded.
03:15Earthquakes, on the other hand, are the most perceptible ground movements.
03:20According to the Institute for Geological Studies of the United States, the Earth undergoes about 5 million earthquakes each year.
03:26Among them, only 100,000 are powerful enough to be felt, and a hundred cause significant damage.
03:34Even during the calms between two earthquakes, the Earth vibrates constantly under the effect of imperceptible movements.
03:40Contrary to the brutal shaking of earthquakes, this rumbling is constant and regular, resulting in micro-seismic activity.
03:48Seismometers, instruments measuring the vibrations of the ground, are able to capture this phenomenon everywhere on Earth.
03:55For years, the origin of this rumbling has been debated among researchers.
03:59Some attributed it to waves deeply penetrating the seabed, others to the collision between surface waves.
04:06In 2015, it was confirmed that these two mechanisms contributed to the permanent vibration of the planet.
04:12If this phenomenon had already been recorded on Earth, the underwater data is now much more precise and detailed.
04:20To study it, scientists deployed seismometers at the bottom of the Indian Ocean, near an island east of Madagascar.
04:27Between September 2012 and November 2013, 57 autonomous seismometers were distributed over an area of 2,000 square kilometers.
04:36Designed to reach the ocean floor, these devices record the most subtle vibrations.
04:42During these 11 months of study, researchers filtered the interferences linked to waves and sea currents.
04:48They were able to isolate clear and constant signals of the Earth's rumbling, with peaks of frequencies between 2.9 and 4.5 millihertz,
04:57well below the threshold of human perception, set at 20 hertz.
05:01The detection of the Earth's rumbling from the abysses goes beyond the scope of simple scientific curiosity.
05:07It offers researchers a new approach to analyze the propagation of energy through crust and the Earth's mantle.
05:15The world around us is full of enigmatic sounds, some of which remain unexplained.
05:20Among them, the bloop remains one of the most fascinating.
05:24Recorded in 1997 by the American Oceanic and Atmospheric Observation Agency, NOAA,
05:30this powerful underwater sound of a minute began with a deaf rumble before seeing its frequency intensify.
05:36With an intensity such that it was captured over 4.8 million kilometers,
05:40the bloop first fueled speculations about the existence of a gigantic marine creature still unknown.
05:46However, NOAA later established that it probably came from the village of Iceberg,
05:51when huge blocks of Antarctic ice detached before collapsing into the ocean.
05:56Other marine sounds remain just as enigmatic.
06:00Julia, a strange murmur, could be linked to the rattle of an iceberg on the ocean floor.
06:06Another, named Train, evokes the rolling on a railway and seems to come from the Ross Sea in Antarctica.
06:14As for Loopsweep, a strident seasonal sound recorded in the Pacific since 1991,
06:20its exact origin remains undetermined despite years of research.
06:25The underwater world also reveals singular sounds similar to fish hearts.
06:30Off the coast of Port Headland, in Western Australia,
06:34scientists have discovered that some marine species sing in synchronization with dawn and dusk, like birds.
06:41Over a period of 18 months, researchers have recorded a multitude of sounds,
06:46including the deaf and deep calls of the cichlids, comparable to mist horns,
06:51as well as the rhythmic ba-ba-ba sequences of the platax.
06:55These songs, characterized by repetitive patterns overlapping within vast groups,
07:00play an essential role in the reproduction, feeding and territorial dynamics.
07:07The abysses also hold their share of acoustic mysteries.
07:11NOAA researchers have explored the sounds emanating from the Challenger Deep,
07:15the deepest point of the Marian Basin.
07:18Thanks to a microphone encapsulated in titanium,
07:21able to withstand a pressure exceeding 1,000 times that of the atmosphere at the surface level,
07:26they have recorded, for 23 days, a myriad of sounds,
07:30ranging from the whistling song of whales to the distant rumbling of earthquakes.
07:34If the depths of the ocean are full of enigmatic sounds, the mainland is no exception.
07:39One of the most confusing phenomena is HUM,
07:42a serious rumbling heard in specific regions,
07:45such as Taos, New Mexico, or Bristol, England.
07:50Described as a slight rumbling evoking the rumbling of an engine,
07:54this noise remains an enigma.
07:56Some researchers advance the hypothesis of a psychological phenomenon,
07:59where the attention of individuals would be focused on sounds of background usually ignored.
08:04To date, no definitive explanation has been found.
08:09Even rock formations are able to sing.
08:12The Rainbow Bridge, a 90-meter-high ridge located in Utah,
08:17vibrates like a guitar string under the effect of sound waves,
08:21distant earthquakes, or waves from Lake Powell.
08:24Scientists analyze these frequencies to assess their impact on the stability of the structure over time.
08:30Intriguing fact, some visitors claim to hear slight rumbling as they approach the site.
08:36The sky, too, reserves its own strange harmonies.
08:40For centuries, the populations of the polar regions have been hearing rumblings,
08:45whistling, and clacking accompanied by the auroras of Boreal.
08:49A Finnish researcher made the first recordings of these sounds
08:53and identified their origin, electrical discharges in the low atmosphere,
08:57about 70 meters from the ground.
09:00Powered by magnetic storms,
09:02these charges produce perceptible low sounds during clear and calm nights.
09:07Other natural phenomena generate sounds as powerful as intriguing.
09:12The rubbing of icebergs on the seabed and underwater volcanic activity
09:17generate rumblings, creaking and creaking
09:20that scientists analyze to better understand the glacial and geological dynamics.
09:25As for me, I also produce my share of strange noises,
09:29but that's a subject for another video.
09:31Or maybe for my next medical report.
Comments