humans have done a pretty good job of exploringthe earth thus far, climbing mountains and crossing continents and planting our flagsall over the place in the name of science. but one part of the world that has remained prettymysterious to us also happens to cover more than 70% of its surface: the ocean. yes , weâ€™ve sailed across it plenty of times.and drilled for oil in it. and managed to create reality shows about fishing in it. but, from glowing oceans to massive deep-seacreatures, and underwater ecosystems with thousands of undiscovered, basically-alienspecies -- we still have a lot to learn about it. probably more than any place on earth, theocean is full of fascinating stuff that we
just donâ€™t know. not yet. [music playing] number one: whatâ€™s the ocean floor like? fact is, we still donâ€™t know exactly whatthe ocean floor looks like in most places. the national oceanic and atmospheric administrationsays that 95% of the ocean's bottom remains unseen by humans. as a result, we have a way better picture of the surfaces of other planets than we do of most of the seafloor.
in 2014, a team of scientists created a mapof the seafloor using data from satellites equipped with special sensors called radaraltimeters. these instruments could precisely measure the distance from the satellite to the surface of the ocean below. essentially, any large mountains or canyonson the ocean floor have a slight gravitational effect on the ocean surface, creating bumps and dips, respectively. these variations are of course too subtle to be detected by human eyes, but they can be measured by these ultra-precise satellite altimeters-- and, after adjusting for the effect of waves and tides, tell scientists whatâ€™son the seafloor.
this map spans the entire ocean floor, which is awesome, and weâ€™re all glad that it exists, but it only has a resolution of about 5 kilometers, which is pretty low. by comparison, most of the surface of mars, venus, and the moon have been mapped to resolutions of 100 meters or less. so, if we want to know whatâ€™s going on down there and really explore the ocean, detecting life, specific mineral formations, or wrecks, weâ€™re gonna need a better map. number two: whatâ€™s under the seafloor? ok, probably thinking that you know whatâ€™sdown there: rock. yes. but not just rock.
in 2015, scientists reported that they haddrilled down about 2 and a half kilometers below the seafloor off the coast of japan,and discovered living microbes. there were only about 10 to 10,000 microorganismsin a cubic centimeter of sediment that they studied, compared to like billions that youâ€™dfind in the same amount of dirt from your garden. but still: there's life down there, evenin the intense heat and pressure many kilometers below where the ocean stops. and the genomes of these under-sea microbesshowed that they were actually more similar to the kind youâ€™d find in forest soil, ratherthan the ones in seafloor sediments.
so itâ€™s possible that these microbes aredescendants of terrestrial ones from 20 million years ago, that just adapted when their habitatbegan to get buried way beneath the ocean. so, who knows what other kinds of life couldexist in deep marine sediments, or what they could tell us about what life on earth used to be like? number three: brine pools. weâ€™ve all seen lakes and rivers on land,but what about lakes that are â€¦ underwater? sounds a little bit unreal, like maybe itâ€™s from a sponge bob episode but these features actually exist -- pockets of seawater that have a differentcomposition than the surrounding ocean: because theyâ€™re super salty.
theyâ€™re known as brine pools, and they seemto have formed when layers of salt from evaporated oceans millions of years ago got buried underlayers of sediment. seawater can reach these deposits and mixwith the salt, forming a dense brine that flows out of the seafloor, sometimes filledwith oils or methane gas. some brine pools, like those found deep inthe gulf of mexico, are four times as salty as the ocean water around it. and the brine is so dense that submersiblescan even â€œfloatâ€ on top of it, like a boat on a lake. all of this salt makes brine pools lethalto larger animals.
but colonies of halophilic -- or salt-loving-- microorganisms can flourish there, usually in much higher concentrations than the nearbynormal seawater. some pools are even lined with mussels thathave symbiotic bacteria in their gills, which use the methane in the brine to make energyfor the mussels. but thereâ€™s a ton that we donâ€™t know aboutthese weird underwater salt lakes -- like how brine pools can be so different from eachother -- and why some have mussels and others donâ€™t -- and even how many there are! number four: milky seas. also known as mareel, this is aphenomenon in which thousands of square kilometers
of the oceanâ€™s surface glow a brilliantwhitish-blue. it lasts for such a short time, and therehave been so few recorded sightings, that these glowing seas were thought to be a mythmade up by crazy sailorsâ€¦ â€¦ until 2005 -- when a group of researcherswas studying satellite pictures of a swath of the indian ocean from 1995. these pictures showed an area of about 15,000 kilometers-square, around the size of connecticut, glowing for 3 nights. it was the first scientific evidence of thephenomenon, but the glowing waters are still not very well understood.
some have suggested that the glow is caused by a mass of tiny dinoflagellates called noctiluca scintillans known as â€œsea sparklesâ€ for the way they glow when disturbed. these protists are what cause the picturesqueglittering waves along coastlines in some parts of the world. but the 2005 study found that it was â€œunlikely,if not impossibleâ€ that the short-lived glowing of dinoflagellates was what scientists had been seeing from space. the prevailing theory these days is that milkyseas are caused by massive colonies of bioluminescent bacteria that are growing on top of an algalbloom.
but weâ€™re still not sure how or why theseephemeral masses of bacteria gather, glow, and disappear. number five: the 52 hertz whale. youâ€™d think we would know a lot about whales. i mean, theyâ€™re big, and we have their skeletons,and we can observe their migratory patterns. but one thing we still have a lot more to learn about is their songs -- from why some whales make them, to how an animal without vocalcords â€¦ or lips â€¦ manages to make song-like sounds. and then thereâ€™s this question -- what whaleis producing the 52 hertz song, and why? this whale song was first noted by a technicianon december 7th, 1992 in the northeast pacific ocean. it sounded like a blue whale, but blue whalecries usually are somewhere between 15 and
20 hertz in pitch. so, blue whales in the pacific typically soundlike this: [blue whale cry playing] but this whale song, played at the same speed,sounded like this: [52 hertz song playing] this high-pitch noise seemed to be uniqueto one animal -- a whale that became known as 52 blue. this raises a lot of questions, and we haveto know more about whales to be able to answer some of them, like, why does this one whale sound different? and can others even hear it?
and if they can hear it, do they understand? some people latched onto to the idea that52 blue is a lonely whale crying out to others that might not hear it or wouldnâ€™t callback. but several scientists have rejected thislonely narrative, and think that other whales may be able to understand its call, even ifthey canâ€™t make that call themselves. also, 52 blue seems to migrate independentlyfrom any other whales. but its migratory patterns do look kindof like those of blue whales -- scientists have been tracking it up and down the northpacific from alaska to mexico for years now. so some researchers think it might have somemalformation that has changed how it sings,
or maybe itâ€™s even a hybrid between a bluewhale and another species. whether or not itâ€™s a lonely whale, 52 blueis an oddity that people seem to love. number six: upsweep. now, ocean sounds are practically their ownfield of study, noaa has been monitoring acoustics in the ocean for decades now. instead of microphones, which are used tocollect sound in air, noaa uses hydrophones to record underwater sounds. mostly, these hydrophones are used to listento the ambient sound of the ocean, to see how humans might interfere with it, and to listen for things like earthquakes and whale calls.
and sometimes, they record things that arehard to explain, at least for a while. in 1997, for example, there was what was knownas the bloop, an extremely loud, low-frequency sound heard by hydrophones some 5,000 kilometersapart. oceanographers recently determined that itwas the result of an icequake -- the cracking and collapse of glaciers into the ocean, inthis case on the coast of antarctica. but thereâ€™s another mystery sound from theocean, known as upsweep. recorded in august 1991, it sounds like arepeating â€œboopâ€ that picks up at the end -- sweeping up -- kind of like the â€œredalertâ€ sound effect you hear on spaceships in sci-fi movies.
but instead of trying to describe it, i could just play it for you. [boop playing] since 1991, this sound has been heard regularlyin the pacific ocean, and it seems to be seasonal, usually becoming more common in spring andfall. researchers have tracked the sound to a partof the pacific that has lots of volcanic and seismic activity, which seem to be importantclues. but according to noaa, â€œthe origin of thesound is unresolved.â€ number seven: why are deep-sea creatures sohuge? from the kraken to sea dragons, all of ourfavorite mythical sea monsters are gigantic.
and the fact is, in real life, many deep-seacreatures are unusually huge. this phenomenon is called deep-sea gigantism. but what drives it is â€¦ you guessed it!â€¦ unknown! in the deep sea, and especially near the polaroceans, some animals seem to get really huge -- like colossal squids, giant isopods, andjapanese spider crabs. scientists arenâ€™t sure why, but they do have some guesses. thereâ€™s bergmannâ€™s rule, for example,which suggests that temperature may influence gigantism. this might be because larger animals haveless surface area relative to volume, so they
radiate less heat based on their mass andstay warmer in colder climates. and then thereâ€™s klieberâ€™s law,which states that more massive animals generally have lower metabolic rates -- and thereforeneed less high-quality food --- to survive. still other theories suggest that gigantismmay help organisms resist increased pressure of the deep sea. but we donâ€™t really have conclusive biologicalreasons why these giant creatures exist. so, the ocean is just full oâ€™ mysteries,maybe because itâ€™s so huge and dark and deep. but just so you know that weâ€™re not hypingyou -- weâ€™re not saying that these 7 topics are things that science canâ€™t explain.
instead, you should just think of them as reminders of how much we still have to learn about the ocean. as our technology improves, and our accessto the ocean takes us to new depths, weâ€™ll be able to see and hear and sample more stuff than we ever have before. so in time, these puzzles will be solved,and new creatures will be discovered, and our understanding of our planet, and the lifeon it, will be that much â€¦ deeper. thank you for watching this scishow list show, and thanks especially to all of our patrons on patreon who make this show possible. if you want to help us keep making shows like this, you can go to patreon.com/scishowâ. anddonâ€™t forget to go to youtube.com/scishow and subscribe!