Death Valley National Park: First Observation of Rocks in Motion
plosone.org
plosone.org
[1] http://www.livescience.com/37492-sailing-stones-death-valley...
If you can find a working experimental scientist who has never done that, then they are either absurdly lucky or a charlatan.
It's just in the heavily politicized fields it becomes toxic to say "I was wrong."
Another reason I like to keep politics away from science.
I read about his theory about a year ago, and it described thin sheets of ice then, also.
I heard him on NPR this morning, and he said that the sheets of ice are like tugboats, pushing the rocks instead of carrying them.
From linked article: > Floating ice may sometimes be ineffective at moving rocks since stones with low profile may be over-ridden by floating ice; rocks at the edges of ice panels may fail to sufficiently engage with floating ice to be moved, and rocks may be too massive for the available force (Fig. 8d). > A surprise is the thinness of ice involved in rock movement. Ice sheets 3–6 mm thick are insufficient to float rocks off the playa surface, as proposed in some models [8], [11], and, in any case, we observed that ice melts first around rocks. However, moving sheets of ice tens of meters in extent but only a few millimeters thick are clearly effective at moving rocks in their path. Forces on stones increase when multiple sheets of ice pile on the upstream side of a rock and increase the effective surface area of the rock exposed to stresses of wind and flowing water (Fig. 8a).
Author's 2011 publication (citation #11): > 11. Lorenz RD, Jackson BK, Barnes JW, Spitale J, Keller JM (2011) Ice rafts not sails: Floating the rocks at Racetrack Playa. American Journal of Physics 79: 37–42. doi: 10.1119/1.3490645 Abstract: >> We suggest that the existence of many of the rock-carved trails at Racetrack Playa in Death Valley National Park is predominantly due to the effect of arbitrarily weak winds on rocks that are floated off the soft bed by small rafts of ice, as also occurs in arctic tidal beaches to form boulder barricades. These ice cakes need not have a particularly large surface area if the ice is adequately thick—the ice cakes allow the rocks to move by buoyantly reducing the reaction and friction forces at the bed, not by increasing the wind drag. The parameter space of ice thickness and extent versus rock size for flotation is calculated and found to be reasonable. We demonstrate the effect with a simple experiment.
Perhaps if you were reading something 1yr ago, it was in correlation to this new hypothesis, but this 2014 publication sits contrary to the 2011 publication.
You need to rent a Jeep with reinforced tires, otherwise you could find yourself in the same predicament as some people we met, who got a flat tire on their rented SUV at Racetrack Playa.
As another word of caution, just "renting a Jeep" doesn't mean you should go into all parts of the back country willy-nilly. Buddies and I have been going to Death Valley (and much of the back country) for over 14 years. We've never had a mechanical or other problem, but we are careful and we have had our share of road building (even just 2 years ago), helping out others, etc.
Most people aren't used to this environment, I certainly wasn't. But we rented a Jeep with reinforced wheels and a satellite communicator that we could use to get help at any time. And given how it's mainly tourists that would be going to places within Death Valley, you would get a lot of uneducated people attempting this trip in a normal vehicle, and without any proper way to contact help. Given that temperatures reach 120 F, it's not hard to imagine a scenario where people die because they are completely unprepared for how dangerous it is.
A drive out to the racetrack, assuming no recent storms/floods, in a 2wd drive vehicle is probably sane @25mph or so paying attention to where you are going. A jeep in the same situation, probably 35-40mph. I took my old tacoma 2wd pickup well back into the backcountry, but we were going through contortions to make up for lack of clearance (after 10 years of going, you know the challenges).
My last trip to DV two years back, a buddy and I rented a Jeep from Farrabee's near Furnace Creek (my buddy's 4wd vehicle was out of commission) and typically he rents to people taking the jeep to the racetrack or around the park, which makes total sense and if you are there for a day and want to do such is perfectly reasonable.
We were taking the jeep out for a week on a trip that included having to build up the road in places, a bit of trail blazing in one case, etc. For that adventure, since he hadn't rented the DV jeeps for such (Farrabbe has in his Moab location), we had to make him comfortable with our experience and knowledge.
All that said, it really comes down to being aware of what you are doing, where you are going, what the risks are, and being prepared. Lots of stories of people w/ 4wd vehicles going into the back country, getting lost/stuck (relying on GPS) and in some cases dying. It's not an area to take lightly, even in Fall/Winter.
"The surrounding mountains were still covered with snow, and the playa itself was firm but had a large lake covering about a fifth of its surface, perhaps an inch or two deep at its edges, concentrated at the playa's south end where it's lowest. We ventured out, armed with cameras, shortly before sunrise. The temperature was just above freezing. The wind, from the south, was quite stiff and very cold. When we reached the lake, we found to our great surprise that the entire lake was moving with the wind, at a speed we estimated at about one half of a mile per hour. The sun was on the lake by now and we could see a few very thin ice sheets that were now dissolving back into water. This whole procession was washing past many of the famous rocks. It's easy to imagine that if it were only few degrees colder when we were there — as it probably had been a couple of hours earlier — the whole surface would be great sheets of thin ice. Solid ice, moving with the surface of the lake and with the inertia of a whole surrounding ice sheet, would have no trouble pushing a rock along the slick muddy floor. Certainly a lot more horsepower than wind alone, as has been proposed. The wind was gusty and moved around some, and since the surface is not perfectly flat and with rocks and various obstructions, the water didn't flow straight; rather it swapped around as it moved generally forward. Ice sheets driven by the water would move in the same way, accounting for the turns and curves found in many of the rock trails."
Edit: n/m, it appears the ice sheets are massive and free-of-friction enough to actually push the rocks around. Cool!
Ice is quite strong, especially in compression.
To buckle the ice (i.e. flexure strength) you would need enough force to lift the ice both against gravity and against the air pressure holding it to the water below.
Edit: Nope, not embedded, just pushed.
"Lorenz (one of the co-authors of this piece) has disproven his previous theory--that the rocks were temporarily embedded in a slab of ice which then floated."
Velocity is a vector quantity--it describes a directional rate of change. Speed is the magnitude of the velocity. When they use the term velocity, they mean speed. For example, even in the abstract:
"along trajectories determined by the direction and velocity of the wind"
Velocity has a direction! The use of direction in this sentence is redundant to anyone that has had a college level physics course. This trend of using "velocity" instead of "speed" continues through the entire paper. I find this very upsetting.
Of course, it may seem pedantic, but good science is pedantic.
I'm surprised that it made it through peer-review like this.
That's it. They solved a problem because not knowing the answer bothered them. This is how most science works, it's just rarely this naked.
Why does the fact that people spent time figuring this out bother you so much?
> In 2006, Ralph Lorenz, a NASA scientist investigating weather conditions on other planets, took an interest in Death Valley. Lorenz was particularly keen on comparing the meteorological conditions of Death Valley to those near Ontario Lacus, a vast hydrocarbon lake on Titan, a moon of Saturn. But while investigating Death Valley, he became intrigued by the enigmatic sailing stones of Racetrack Playa.
--begin quote-- Then I had another thought: Physics disgusts me a little bit now, but I used to enjoy doing physics. Why did I enjoy it? I used to play with it. I used to do whatever I felt like doing - it didn't have to do with whether it was important for the development of nuclear physics, but whether it was interesting and amusing for me to play with. When I was in high school, I'd see water running out of a faucet growing narrower, and wonder if I could figure out what determines that curve. I found it was rather easy to do. I didn't have to do it; it wasn't important for the future of science; somebody else had already done it. That didn't make any difference. I'd invent things and play with things for my own entertainment. So I got this new attitude. Now that I am burned out and I'll never accomplish anything, I've got this nice position at the university teaching classes which I rather enjoy, and just like I read the Arabian Nights for pleasure, I'm going to play with physics, whenever I want to, without worrying about any importance whatsoever.
Within a week I was in the cafeteria and some guy, fooling around, throws a plate in the air. As the plate went up in the air I saw it wobble, and I noticed the red medallion of Cornell on the plate going around. It was pretty obvious to me that the medallion went around faster than the wobbling.
I had nothing to do, so I start to figure out the motion of the rotating plate. I discover that when the angle is very slight, the medallion rotates twice as fast as the wobble rate - two to one [Note: Feynman mis-remembers here---the factor of 2 is the other way]. It came out of a complicated equation! Then I thought, ``Is there some way I can see in a more fundamental way, by looking at the forces or the dynamics, why it's two to one?''
I don't remember how I did it, but I ultimately worked out what the motion of the mass particles is, and how all the accelerations balance to make it come out two to one.
I still remember going to Hans Bethe and saying, ``Hey, Hans! I noticed something interesting. Here the plate goes around so, and the reason it's two to one is ...'' and I showed him the accelerations.
He says, ``Feynman, that's pretty interesting, but what's the importance of it? Why are you doing it?''
``Hah!'' I say. ``There's no importance whatsoever. I'm just doing it for the fun of it.'' His reaction didn't discourage me; I had made up my mind I was going to enjoy physics and do whatever I liked.
I went on to work out equations of wobbles. Then I thought about how electron orbits start to move in relativity. Then there's the Dirac Equation in electrodynamics. And then quantum electrodynamics. And before I knew it (it was a very short time) I was ``playing'' - working, really - with the same old problem that I loved so much, that I had stopped working on when I went to Los Alamos: my thesis-type problems; all those old-fashioned, wonderful things.
It was effortless. It was easy to play with these things. It was like uncorking a bottle: Everything flowed out effortlessly. I almost tried to resist it! There was no importance to what I was doing, but ultimately there was. The diagrams and the whole business that I got the Nobel Prize for came from that piddling around with the wobbling plate. --end quote--
The OP research was just measuring exactly how much wind, how much water was required. Not really figuring out anything. And I get it - taking pictures of it is cool - Big rocks! Moving! But that's a youtube video, not something to spend govt research money on.
Your comment was also inaccurate.
> Some wind moved some rocks
Well, no, not quite. The wind moved the ice, and the ice moved the rocks. The wind wasn't enough to move the rocks.
Your other comments mention films. The film of water isn't enough for the rocks to move, even if there are algal films reducing friction.
And it contains a bizarre bit of anti-science sentiment
> Where is this research going?
IvyMike has already given you a good example of where this research might be useful. But, actually, FUCK USEFUL. Science and math do not need to have useful purpose. It is still good that people pursue them.
So ok, these guys are 'the reader' and do the legwork. Where can it go? Its not basic or fundamental research; its applicable only to 'rocks on a flat surface'; there aren't a whole lot of places where this will ever be reproduced.
That was what I was asking about: other than the novel circumstance what's to be gained? Got interpreted as anti-science.
It starts with something completely boring, like learning how peptidoglycan cross-links form. Then it's another long series of research trying to determine what cycloalkanes bind to a DD-transpeptidase enzyme. These two boring pieces of research are combined to create Penicillin.