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The Deepest Hole in the World And What Weve Learned From It
Deep in western Russia, the frigid desertcontains the remnants of one of the most ambitious scientific experiments ever performed. It'sa ruin now, a wasteland of jagged metal and crumbling concrete. If you search around long enough, you willfind a rusted disc, bolted to the earth. So unassuming that you might even try to pickit up. But you won't be able to. It's the weldedshut cap of a borehole thatplummets more than twelve kilometers into the earth, deeper than the deepest depthsof the ocean. It's the deepest hole on earth. It's called the Kola Superdeep Borehole, andits existence has nothing to do with petroleum
exploration. Rather, when drilling began in1970, Soviet scientists hoped to eventually drill down to fifteen thousand meters in orderto gain a better understanding of the nature of the Earth's crust. Because the truth is,we know less about what's under our feet than what's on the other side of the solar system. They drilled on and off for twentyfour years,and though they didn't quite reach their goal when work came to a halt in 1994, the engineershad reached a record depth: 12,262 meters, a record that still stands today. Two decades later, the Kola Borehole remainsa remarkable technological and scientific
acheivement. To drill it, engineers deviseda new method by which only the drill bit at the end of the shaft was rotated, the lubricant,in this case, pressurized drilling mud, was pumped down through a custom drill bit, allowingit to spin. Instruments had to be invented to take measurements at the bottom of thehole. What did we learn by drilling a third of theway through the Baltic continental crusté For one, there's water down there, at depthsscientists didn't believe water could be found. They suspect that the water formed from hydrogenand oxygen that were squeezed out of rock crystals due to crazy high levels of pressurethat far down.
Unlike groundwater, this water originatedfrom the rock minerals themselves. Never before had this been observed. Also surpising, howabout microscopic fossils discovered by Russians at depths of up to 6.7 kilometersé Researchers catalogued twentyfour speciesof singlecell plankton microfossils over the course of the project, and they weren'tfound in the kinds of deposits we're used to finding them, like limestone and silica. These were covered by organic carbon and nitrogencompounds, preserved thanks to those high pressures and high temperatures so far belowthe surface. As for those temperatures, by
the time the engineers broke through the twelvekilometer mark, where rock samples were dated at 2.7 billion years old, the heat becamea major issue. Researchers thought the temperature of therocks would be about 100 degrees Celsius. What they found were temperatures in excessof 180 degrees. It was this heat that caused the drilling to come to a stop. Engineersdescribed the rocks at 12 kilometers as acting more like plastic than rock. Of course, as astonishing as this projectwas, the Kola Superdeep Borehole only made it through a tiny fraction of the Earth'slayers. 12 kilometers is three times as deep
as humans have ever gone, but the eath's mantledesn't even begin until about 35 kilometers below the surface. The mantle then continues for another twentyeighthundred kilometers; the center of the inner core: more than sixtythree hundred kilometersbelow the surface. Put another way, this borehole which took24 years to drill, made it roughly 0.002 percent of the way to the middle of the Earth. It'sa big planet, you guys. Thank you for watching this SciShow Dose,especially to our Subbable subscribers. To learn how you can support us, just go to subbable to learn more. And be sure to check out our
What if the Earth were Hollow
Flying in a 747 from one side of the earthto the exact opposite side would take about 22 hoursâ€¦ and while I know there's a bitof rock in the way, that's really going the long way round. So what if we did dig a hole all the way throughthe earth, through the center, and jumped iné Well, Michael, you probably would't make itvery far that's because of the Coriolis effect (which is why a ball curves weirdlywhen you toss it while riding a merry go round and why hurricanes always spin counterclockwisein the northern hemisphere). At the equator,
the earth (and you on it) is rotating eastwardsat 1670 kmhr. As you go deeper, the bits of earth around you are still spinning aroundonce per day, but they don't have as far to travel so they're going at slower and slowerspeeds. If you jumped into a vertical shaft, you'd soon be traveling east faster than therock around you so that after falling only a few kilometers, you'd crash into the easternwall. It might not be a disaster, but some miners near Lake Superior tried to test thisby dropping cannon balls down a milelong shaft and the balls never reached the bottom. OK, so what if the tunnel went from pole topole, so the Coriolis effect didn't apply,
and let's also assume that there's no airresistance, or friction Ok. Since the earth's mass is more concentratedclose to the middle, gravity would pull you down with roughly the same amount of forcefor the first 3000 km, or halfway to the center of the earth this familiar, constant forcewould accelerate you until you were falling 8km every second, and the trip halfway tothe middle of the earth would only take 13 minutes. Soon after, you'd reach the earth'souter core, and this is the point in your journey where the pull of gravity would bestrongest but only slightly stronger than the force we're used to on the surface.
As you continued to fall closer to the center,so much of the earth's mass would now be above you that it would begin to seriously cancelout the attraction of the mass below, and the pull would weaken until you reached thecenter. Here, you'd experience no gravitational pull at all or rather, the earth would bepulling on you the same amount in all directions, so you could float freely around with no senseof quot;upquot; or quot;downquot;. Except, remember, that you'd be speeding past at 22,000 miles perhour, or 6 miles a second. Once you passed the center, the whole processwould reverse and you'd gradually slow, pulled down (or is it upé) weakly at first and thenmore strongly, until when you got to the other
side, you'd stop moving and could step outon the surface, a mere 37 minutes, or one dryer cycle, later. Of course, the deepest we've ever been ableto dig is the Kola Superdeep borehole in Russia. But it only went down 12km, which is onlytwo thirds the length of Manhattan. They had to stop because it got too hot: 180Â°C. Andthis is sort of the problem with digging a hole through earth earth is hot, and moltenin the middle. You can't just dig a hole through it with shovels. But here's a question: wasn'tthe middle of earth wasn't all quot;liquidyquot;, what if earth was hollow, but weighed thesameé
Well, with its entire mass concentrated ina thin shell right under our feet, the earth wouldn't have a magnetic field any more, becausethat comes from the molten iron core. So we'd be totally vulnerable to radiation from thesolar wind and storms, and this means we'd see the aurora EVERYWHERE. Look! The NorthernSouthernEasternlights! And if you jumped inside the hollow earthto escape the solar stormé Well, gravity from the different parts of the spherical earthshellwould perfectly cancel out and you'd float freely about inside as if the earth weren'tthere at all! Of course, you'd better bring a space suit, because there's not nearly enoughair ON earth to fill up the entire INSIDE