Someone posted a video of one of those a few years ago. I have trouble believing they are natural. The wiki entry says they were first noted in the February 1895 edition of Scientific American. I just checked it out. There is no mention of ice circles, nor the Mianus river. All other references in wiki are post 2000.
The 2000 reference is interesting: Rickard, B Unexplained Phenomena Rough Guides, 2000.
as the first link you get when googling is the following: http://en.wikipedia.org/wiki/Teleportation (aka: Crackpot!)
And Mr. Rickard appears to be a very prolific and imaginative author.
IMHO, they are internet inspired ice versions of crop circles. i.e., anyone with an ice saw and piece of string could make one.
Though they are interesting to watch. I'll have to make one some day.
I couldn't find any reference to one in the Feb. 1895 Scientific American either. It could be the wrong month or wrong year, or wrong magazine, was cited by the author, or the citation could be completely invented. I think someone should contact the author about that, if they know how.
As for hoaxing, I think it would be extremely dangerous to stand on that disk, especially near the edges. That's the largest one I've read about, and smaller ones would be even more dangerous to stand on. A 6 foot diameter ones would certainly not support a person.
You don't have to stand on the ice to cut it, just use some large, soft floaters.
Not that I suspect they are artificial.
These things are pretty common here:
I've seen small ones several times on rivers.
"The massive pancake-shaped ice pans often turn up on flowing rivers in cold climates. Video and photos posted online show similar disks discovered in Canada, England and Sweden during winter.
Theories abound to explain their formation. National Weather Service forecasters told the Associated Press that the Sheyenne giant likely appeared because cold, dense air slowly froze the river surface in bits and pieces. The floating ice chunks were trapped in a river eddy, creating the rotating circle discovered by Loegering. In 1993, MIT researchers who sought to explain smaller ice swirls on Boston's Charles River also suggested current-driven eddies."
"Pancake ice" forms in the salt water of the polar regions. It's normal in the Antarctic as it forms in rough seas, but is new to the Arctic. It apparently can also form in the moving water of fresh water streams.
i suppose they can form wherever there's an eddy upstream of a fragile block of ice…
if the sideways pressure is enough to break off a piece of ice on the upstream side of a larger piece, then it won't be able to get past, and the eddy that broke it off will make it rotate
then it'll be like grinding a lens … the edges of both the broken piece and the original piece will (very gradually) be ground down into matching circles
A person could lie on their belly on an inflatable pool raft, yes. This would spread their weight out over a much larger area than their foot prints. Still, the cut disk would have to be thick and strong enough not to break under their weight. Personally, I wouldn't want to mess with river ice, which is going to be much less predictably uniform than pond or lake ice.
In the original link it was suggested that a bunch of ice debris gets caught in an eddy current with an edge of ice around it. The debris would gradually freeze together while being ground against the edge ice, eventually forming a very nice circle.
In any event, the circularity of the disk is the most explainable aspect: the rotation of the mass only prevents freezing at the circumference. All other cracks and irregularities would soon freeze over.
Like a remotely controlled small vehicle?
I can imagine that they can form naturally. But I can also imagine a pot of water atoms jumping out of a pot, all at the same time........
Bamm! Found it! (Ok. That was about 7 hours ago. It was a slow day at work. Please don't tell my boss I was doing science. Please......)
Though in Dave's post's, he never posted a reference to the "lab experiment" that recreated this phenomena.
i reckon it was a bloke called occam, with a razor!
The lab experiment was linked to in an earlier post of his:
Discovery Channel has since taken the video down. Dave, however, explains the process of how they form step by step in that post #27.
I think you have missed the point. If the floater is large enough (imagine you are in the pontoon on the ice) you don't care whether the ice breaks or melts. You will be still floating after that.
But as I said earlier, I can easily image such a disk being created by a natural phenomena, first it is just a rotating piece of ice, then it grinds itself into a perfect circle. You probably need a not too turbulent water flow and correct air temperature for that, but the mechanism seems to be obvious.
Edit: I see I just repeated what Dave posted in the past. It just shows how obvious it is
If the ice breaks, you don't have a nice circle.
But you don't have to start with an ideal circle, all you need is a rotating sheet of ice. Once it rotates, it will grind itself into a circle.
If you believe that, you believe they could also form naturally. I already know you believe they could form naturally.
My point is to explain how many obstacles are in the way of trying to hoax one, for the benefit of people who don't think there's any way they could form naturally, people who think the ice circles are too perfect to be anything but man made. Those people don't think the ice can naturally be ground into a nice circle. The nice circle, in their minds, has to have been cut by people with tools.
A basic crop circle can be made with a board and some rope, yes. I believe cutting a basic ice circle in thin river ice actually presents many more obstacles than that.
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