99 Years Later... We Solved It

look at this okay so here's a trail and the trail goes pop pop pop pop pop over here and then it takes a right angle turn there are rocks in the death valley desert that move across the ground on their own leaving behind bizarrely long tracks and for a century nobody could figure out why so look at the size of that puppy and it turns out no sweat to move every single rock out here we're talking many many bulldozers strength worth of force so what force has been making rocks move for over a hundred years when humans aren't looking the first recorded account of the trails was in 1915 when a prospector named joseph crook who was supposed to be out searching for precious metals found the rock trails crook reportedly showed the rocks to his wife who couldn't believe that the larger rocks would move naturally so she skeptically marked the position of a big rock and of course it eventually moved away from the mark the lake bed came to be known as the racetrack playa and the stones the sailing stones you go to the desert and you see the tracks these giant rocks have left behind some that are parallel where the rocks have moved at the same time and then they've turned the same time and you're like what is going on so i started looking into it and what i found was a heartwarming story about two cousins who solved the mystery together and a clever experiment that had convinced scientists that the correct solution was wrong and then this moment where scientists all over the world were reaching out saying oh i have this other mystery with rocks moving and a young scientist whose life was changed by this mystery so back in 2014 cousins dr richard norris and james norris solved the rock mystery at the racetrack playa and now they're back so i spent 16 hours traveling out to meet them and join in on their latest adventure check your spare tire sharp rocks ahead no triple a ah it's vibrating my butt hey dad hey diana hey i'm diana you're watching physics girl i think it's also worth taking a minute to appreciate how incredible the setting is for these rocks death valley is in the northern mojave desert sitting in the rain shadow of the sierras death valley is one of the driest places on the planet and it is certifiably the hottest so naturally we went there in the winter when we went we camped out for a night in stove pipe wells which is a nice midway point because it has a gas station and a general store that once served 12 pots of coffee in an hour and then we took a four-wheel drive jeep and then trekked the 24 miles down a bumpy dirt road and you sit there clenching and hoping you don't pop a tire all up until you see the playa i couldn't even wait for levi to come film me because i raced out onto the racetrack by myself everything is so uniform and then boom a track that's so cool this is the lowest point over here and uh and if you go up to the grandstand which is the pile of rocks at the far end okay that's that's what the grandstand called the grandstand the lake bed of the racetrack is filled with dried sediment that extends 1 000 feet down into the ground so one of my first thoughts was whether the tracks were caused by an animal but then you see this place we're like what lives in death valley it's called death valley there can't be much well we had a beautiful kangaroo rat in our camp last night oh cute and they are the cutest little thing they're cute but they're not pushing around rocks that way as much as refrigerators richard had heard about the racetrack problem many years prior in school and eventually the itch of the mystery got to him enough well so what happened fundamentally is that jim said i think we could probably solve this little problem so they began coming out to the racetrack and trying out experiments jim had the idea of putting the gps's on the rocks we set out our own rocks of course drilled holes in the rocks to put a gps tracker in the switch would be thrown and the gps would turn on to live mode okay collecting data constantly well you would know the rocks had moved but how would you know what had happened and then connecting that with the weather station meant that we would know what the weather conditions were so the duo set out their trackers in the winter of 2011 and their collaborator ralph lorenz reportedly claimed this would be the most boring experiment ever as they prepared to wait for something to happen knowing that it might take decades but a mere two years later the motion activated gps trackers switched on on a day when they least expected movement before we find out why the gps trackers switched on a quick message i'd like to thank the sponsor of today's video better help is there something interfering with your happiness or preventing you from achieving your goals sometimes i get caught up worrying about conflict with other people for months or years and i wish i just talked it out and frankly just stopped ruminating betterhelp assesses your needs and matches you 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the gps trackers turned on when the cousins hadn't expected it because after reviewing prior experiments here's what they had expected to see there's these two camps you know it's strong powerful winds it's ice and we were both inclined towards the wind idea the sharp and carry experiment sure suggested that ice wasn't the driver that was i have to confess convincing to me the reason richard is confessing is because the experiment he was referencing was so beautifully convincing that it was not ice here's how that experiment went scientists put stakes in the ground surrounding a couple rocks and then one day one rock moved out and the other one stayed in the researchers were convinced if sheets of ice were dragging the rocks then both of the rocks would have moved so at this point james and and richard pretty much rule out ice they're team wind so they head out to the playa expecting a hurricane to blow the rocks around and our expectation was that we would come out here with a four season tent we would stake it down when it was howling outside we'd peek out you know and we'd see the rocks scooting by kind of thing but on a chilly morning with a light breeze a few days after a snow storm had brought enough water to make a three-inch pond on the playa something happened i have an embarrassing thing to say you know we saw it like an hour after it happened okay but we were unfortunately over there about a kilometer away and we saw all the ice that had been part of this big ice panel piling up out there from the other side and it was like hmm jim what's going on and then we walked along the shoreline over there and there was big piles of this clinker ice it kind of goes clink clink clink clink clink all over the shoreline that's you know plate glass thin you know clear beautiful glass with rocks in it giant sheets of ice hundreds of feet across were starting to move across the playa and then we arrived down here we climbed up on the what we call the source hill because that's where almost all the rocks come from and it was like oh my god we missed it you know the biggest the biggest move event in 10 years and we were on the wrong you know kilometer away well and then it was like the scales fall from your eyes that literally that you know then we understood immediately what was going on what they realized was that on rare occasions when the playa fills with water from rain or snow and is deep enough to form floating ice during exceptionally cold nights the pond freezes to form thin sheets of ice the ice then begins to melt in the daytime sun the ice breaks up and as the wind picks up it blows the sheets of ice across the playa and drags the rocks with it and of course the rocks drag trails in the ground as they go the winds are not strong i had to kind of hold my hat off yeah that wind stress over a couple square kilometer area of floating ice of course it causes the ice to move here's why this is all so amazing we do know how thick the ice was and the ice was about an eighth of an inch thick wow isn't that great what richard and james soon realized was that the chorale experiment hadn't disproved the ice theory it had disproved thick ice like yeah move a rock like that with ice that is you know thin enough to tear past those stakes no that doesn't seem reasonable the ice was thinner than anyone thought was possible yeah this is thin sheet of ice that's amazing both start moving and then they move for 16 minutes with the same exact pattern but they're 650 feet apart yeah and you're going that's a single panel of ice so the wind moves the ice and drags the rocks and the rocks make the tracks but here's the thing the pond isn't big enough to fill the entire playa and yet some of the rocks do travel all the way over to the distant shoreline how do we know and you know that they've far traveled because they're this distinctive dolomite okay and the only source of dolomite is from there which is just right there how do they get there when you get a pond the pond forms here it's almost a flat surface the pond goes there it's a classic so what the oceanographer is called a sea chavant event a sish is when strong winds can cause really rapid changes in the height of water in this case it moves the entire pond from one end of the playa to the other the pond essentially rolls uphill and all the rocks just go off they go and then at the end of the day the wind dies down and it moves all the way back so they published a paper describing what was going on in 2014 and what happened next was amazing my favorite part of this whole story is that after you publish your paper there are all these scientists from all over the world that are sending you emails and mailing you photos they're like wait wait i have something we were out here at one point and we met this couple in the parking lot and the wife told us this story about seeing this video uh on tv of of ice bursting through somebody's garage in the great lakes and you can find these on youtube these pictures of of ice that is being blown across the great lakes of course an enormous area big long fetch right and it forms mountains that are like i don't know at least a couple meters high everywhere he went people started telling him about mysterious things that they had found of rocks and ice being moved by unusual forces and then we've observed in in google earth images of great slave lake uh basically house size rocks that apparently have scribed trails in the bottom of the lake but there are also still some other unanswered mysteries and then there's this place in spain uh that is out in the lamanche area man of la mancha you know and they have had documented rock trails on them those folks say that it is not this mechanism and their argument is that they're salt lakes and so the salt it lowers the freezing temperature of water enough that you wouldn't get ice forming on the surface to make the rocks move i don't believe that story that's going to be you know a future adventure to spain so i think i finally understand why it took so long to solve this mystery we could tell that the rocks move for about 15 minutes and then they stopped they're done you you have to be here right at the right time the exact perfect goldilocks it's goldilocks on cocaine yeah that's a whole different children's story that we don't usually tell it's the hottest place on earth but you need it to be freezing at night or it doesn't rain that often i would imagine that's the key it's incredibly windy but you need just gentle winds and you need a source of rocks on this playa that's mostly a thousand feet deep of just straight sediment everything about this problem is just perfect which is one of the things i love about this story but the thing i love the most is this next bit about a little girl from germany so one of the people who contacted us after our paper was published was a 13 year old girl in southern germany her name is ronya spanky and she had been doing experiments to simulate what was going on here at death valley for her science fair project and it turns out like no sweat okay to move every single rock out here we're talking many many bulldozers strength worth of force the whole notion that it had to be like really super slick you know to get the rocks to move this is bold okay and ronya showed that in her little you know after school experiment and it turns out that she won a whole series of science fair projects there's not that many scientific things we go see that there's a lot of people out here coming to visit and check out so this one is pretty spectacular and you can go see the stones if you want it's not easy i know richard and james were really eager to solve the mystery but i don't think they ever expected the impact they were going to have on other people's lives and i can't wait for the answers they uncover next thanks so much for watching and happy physicsing [Music]

Channel: Physics Girl

Views: 5,788,239

Keywords: physics girl, dianna cowern

Id: JFFhD5HeByM

Length: 14min 29sec (869 seconds)

Published: Thu Mar 31 2022

Reddit Comments

[u/Yatta79]

/r/titlegore

[u/Khufuu]

tldw sheets of ice form rarely and wind blows the big sheets of ice which carry rocks with them along the ground

[u/soup_mix]

I disagree with the sentiment that one dude had about how it would take "many many bulldozers strength worth of force" to move those rocks. Most of the ones in the video I could move with my lawn tractor, or at maximum with my Toyota pickup.

[u/goof_schmoofer_2]

9:00 minutes in is where they answer the question....

https://youtu.be/JFFhD5HeByM?t=575

[u/Comrade132]

Post this again with a title written in english

[u/turbodude69]

amazing video, horrible title.

[u/Eoin_McLove]

I remember this being solved when I was a kid. I'm in my 30s now...

[u/aNeonSpecter]

I was totally expecting this to be an April fool's joke for the first half of the video.