Maine's giant spinning ice disc looks like it's reforming(theguardian.com)
theguardian.com
Maine's giant spinning ice disc looks like it's reforming
https://www.theguardian.com/us-news/2020/jan/19/maines-giant-spinning-ice-disc-looks-like-its-reforming
75 comments
Off topic, but I like to hear about the experiences of tech people living in Maine. If you’d like to chat, send a message to my username at gmail.
There's surprisingly many of us! The Portland metro area has some decent opportunities for tech work. Not anything on par with Boston, but it's there.
Job opportunities not on par with Boston, but rents fast approaching... I would've loved to stay in ME/NH after graduation, but it just wasn't realistic.
You can also do these yourself. Just some sticks, rope and chainsaw needed. Throw in an outboard motor and you get a nice carousel.
https://www.sitra.fi/en/news/giant-ice-carousel-spinning-fro...
https://www.sitra.fi/en/news/giant-ice-carousel-spinning-fro...
I work nearby and went to check it out some random weekday. There was at least one news crew camped out there. What a time to be alive.
There are others; such as this one in Estonia. commons.wikimedia.org/wiki/File:Vana-vigala_spinning_ice_disk.webm
That one is huge compared to the Maine disc as well.
That one is huge compared to the Maine disc as well.
An interesting phenomenon. Are we interested in it because it seems to be a rare and observable event that seems “magical”? Or is there a deeper search for meaning here?
Looked wikipedia.
"An unusual natural phenomenon, ice disks occur in slowly moving water in cold climates and can vary in size, with circles more than 15 metres (49 ft) in diameter..."
There has been few more of them around the world.
https://en.wikipedia.org/wiki/Ice_circle
There has been few more of them around the world.
https://en.wikipedia.org/wiki/Ice_circle
The near-perfection of the circular shape is what really makes it stand out. It's strange to see such regularity in natural phenomenons.
Not really. Nature is full of beautiful symmetry
Not that large
https://en.m.wikipedia.org/wiki/Saturn's_hexagon
> Saturn's hexagon is a persisting hexagonal cloud pattern around the north pole of the planet Saturn, located at about 78°N.[1][2][3] The sides of the hexagon are about 14,500 km (9,000 mi) long,[4][5][6][7] which is more than the diameter of Earth[8] (about 12,700 km (7,900 mi).
> Saturn's hexagon is a persisting hexagonal cloud pattern around the north pole of the planet Saturn, located at about 78°N.[1][2][3] The sides of the hexagon are about 14,500 km (9,000 mi) long,[4][5][6][7] which is more than the diameter of Earth[8] (about 12,700 km (7,900 mi).
Why do the two photos at the top of that article look so weird? They look like 3D renders almost. Is that what it actually looks like to the eye too, if one looked at Saturn from a spacecraft orbiting around it?
They look like bad 3D renders because there are no walls and no sky in space, so all the light comes directly from the sun and shadows are absolutely black. The image looks different than with the naked eye though, because they filtered certain wavelengths. https://www.nasa.gov/jpl/cassini/pia18274
The question is legitimate though as sometimes we do get 3D renders, e.g. when it comes to this image of the Korolev crater on Mars: https://www.esa.int/var/esa/storage/images/esa_multimedia/im...
They even added the fog (the fog in the picture is white and while there is dust on mars it's rather brown as the planet's surface https://mars.nasa.gov/imgs/mep/weather/PIA22520-600.jpg ).
They even added the fog (the fog in the picture is white and while there is dust on mars it's rather brown as the planet's surface https://mars.nasa.gov/imgs/mep/weather/PIA22520-600.jpg ).
Shadows in space are often very high contrast, as there's no ambient light. Simple 3D renderers don't handle ambient light either, as simulating it can be very computationally expensive (instead of e.g. one light source, pretty much everything in the scene acts as a light source with the light it reflects). These images in particular are also in near-infrared, so they may look a little different to colour images of Saturn you've seen.
Let me go edit that config file...
I don’t know the earth is pretty big :) It is a near perfect circle, as are all the other planets & moons we observe. Maybe the rings of Saturn?
Just kidding around really, but I have to imagine that pockets of circular water currents like this, are more common than we would think.
We just can’t easily observe the dynamics of water flow until something like this happens, where a bunch of ice builds up and makes it obvious.
Just kidding around really, but I have to imagine that pockets of circular water currents like this, are more common than we would think.
We just can’t easily observe the dynamics of water flow until something like this happens, where a bunch of ice builds up and makes it obvious.
A near-perfect sphere? sure! Only looks-like-a-circle from some distant projection.
Vortices in a near-2d-flow like a river will absolutely be circular, vortices need to be coherent in some plane in order to sustain themselves.
The specific circumstances here must be that that the water is on the edge of freezing during downstream flow and there is a naturally-very-long-lived vortex in one region for it to initially form the ice-disc. Must also be followed by some very-gently-bounceing-off-the-edges, and the river never getting too thin for it to get stuck.
Vortices in a near-2d-flow like a river will absolutely be circular, vortices need to be coherent in some plane in order to sustain themselves.
The specific circumstances here must be that that the water is on the edge of freezing during downstream flow and there is a naturally-very-long-lived vortex in one region for it to initially form the ice-disc. Must also be followed by some very-gently-bounceing-off-the-edges, and the river never getting too thin for it to get stuck.
The earth is pretty lumpy, what with mountains and oceans, and the earth is where I learned the term "oblate spheroid".
Less lumpy than a billiard ball. The mountains and trenches only seem significant because the whole thing is so big. Totally not a perfect sphere though, yeah.
> Less lumpy than a billiard ball.
Well, no: https://ourplnt.com/earth-smooth-billiard-ball/
The myth is springs from the fact that if you had a smooth earth with a radius of center to Mariana Trench, and another smooth earth with a radius of center to Mt. Everest, you could shrink both of them by the same factor and fall within allowed billiard ball specifications. That says nothing about smoothness, only about the allowed size of ball.
If you actually shrunk the earth we're living on, the ball would still be rejected as quite too rough.
Well, no: https://ourplnt.com/earth-smooth-billiard-ball/
The myth is springs from the fact that if you had a smooth earth with a radius of center to Mariana Trench, and another smooth earth with a radius of center to Mt. Everest, you could shrink both of them by the same factor and fall within allowed billiard ball specifications. That says nothing about smoothness, only about the allowed size of ball.
If you actually shrunk the earth we're living on, the ball would still be rejected as quite too rough.
If you shrunk the earth down to the size of a billiard ball and the imperfections where only as rough as the bumps in medium sandpaper then that's still pretty darn round even if it wouldn't be acceptable under official billiard ball specifications. I never could get behind the idea that it would be smooth as a billiard ball but to know you could feel the ridges is pretty neat and yet it's very very round.
Earth is a disk?
On the back of 4 elephants, then it's turtles all the way down.
One turtle, and everyone is very worried about the order a second would be added in.
I think what you mean is "not that medium". You can find this sort of shape at the astronomic and the microscopic scales, just not usually at human scale.
Agreed (though circle is pretty common, but,) has anyone ever seen any trace of a mandelbrot-shaped feature anywhere in nature? (I mean the whole set, not just seahorses/etc) I'm on the hunt!
If you aren't looking for Mandelbrot specifically, Romanesco broccoli is the most fractal-y plant I know.
The actual Mandelbrot is a very specific and complex mathematical pattern; I'd be very surprised to see it. But fractals in general are everywhere.
ferns, palms, and sunflowers are good places to start
It's very neat.
I am certain that someone would have noticed this happening before. Maybe it is a symptom of climate change. Instead of ice being dammed up earlier in the river, it moves further down and freezes in the currents.
Ice circles are uncommon, but many people have noticed them before, going back a long time: https://en.wikipedia.org/wiki/Ice_circle
What's different about the modern day is that there are 1. way more people to look, 2. way more cameras to record, 3. the internet to disseminate any unusual thing widely.
What's different about the modern day is that there are 1. way more people to look, 2. way more cameras to record, 3. the internet to disseminate any unusual thing widely.
This sort of speculation harms the argument for climate change more than it helps it. To convince others, it's better to build a case on scientific fact and large-scale issues than one specific interest of a likely-natural oddity.
You're being unfair. Speculation is how you create new hypothesis and it is perfectly ok as long as you don't confuse your hypothesis with a theory. (which GP did not)
This particular hypothesis seems to be invalidated by the fact that the phenomenon was observed before, back in 1895. See the wikipedia link in comment above.
This particular hypothesis seems to be invalidated by the fact that the phenomenon was observed before, back in 1895. See the wikipedia link in comment above.
As a response to whoever thinks ftvy was arming HN community by doing unreasonable speculation (and downvoted both our comments), let me quote the first, most upvoted comment on another thread, currently on the main page.
> I agree in part in that I am skeptical that full self-driving cars will happen in the next few years, but he is completely wrong when it comes to the long term. Not only will the tech get as good as humans, but most forget to account for the fact that the environment will meet the cars part way. [..]
As you can see, speculation is well accepted in the HN community. This is why I think spritecranberry's comment was unfair.
Full thread here: https://news.ycombinator.com/item?id=22085756
> I agree in part in that I am skeptical that full self-driving cars will happen in the next few years, but he is completely wrong when it comes to the long term. Not only will the tech get as good as humans, but most forget to account for the fact that the environment will meet the cars part way. [..]
As you can see, speculation is well accepted in the HN community. This is why I think spritecranberry's comment was unfair.
Full thread here: https://news.ycombinator.com/item?id=22085756
It's an observation, not a statement of fact.
>large-scale issues
Oh, so since this is an isolated phenomenon that it is your preference to ignore this as evidence for your cause because it doesn't meet your criteria. That's not science either.
>This sort of speculation harms the argument for climate change more than it helps it.
What? Do you get mad at people for saying "it looks like rain"?
>large-scale issues
Oh, so since this is an isolated phenomenon that it is your preference to ignore this as evidence for your cause because it doesn't meet your criteria. That's not science either.
>This sort of speculation harms the argument for climate change more than it helps it.
What? Do you get mad at people for saying "it looks like rain"?
this is cursed
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Good, it was getting awfully corrupt
I wonder if, in the absence of gravity (and thus no issue of buoyancy), a spherical ice ball would form in a stream of slow moving cold water...
A disk is rotating its circumference scraping along obstructions such that the growth of ice is steered naturally to a perfect circle. This rotation has a fixed center and axis. A ball however would be scraped towards a cylinder if the same thing happened. To create a ball nature would need the same thing as someone making a wood ball on a belt grinder: vary the rotation axis. However if there are local stability minima, the block of ice would degrade to a preferred rotation configuration. Just thinking aloud here...
On the one hand, pebbles are more like spheres than like cylinders. On the other hand, they’re different in that they can only lose weight, whereas this can also grow.
I guess the end result would depend on the shape of the surrounding cave and on what fraction of its volume the object would eventually fill. I don’t see a tumbling cylinder made of ice inside a hollow sphere filled with icy water remain cylindrical in shape, for example.
On the other hand, inside a relatively tall cylindrical space where the water is below freezing temperature, things could be different (does the production of M&Ms involve tumbling?)
I guess the end result would depend on the shape of the surrounding cave and on what fraction of its volume the object would eventually fill. I don’t see a tumbling cylinder made of ice inside a hollow sphere filled with icy water remain cylindrical in shape, for example.
On the other hand, inside a relatively tall cylindrical space where the water is below freezing temperature, things could be different (does the production of M&Ms involve tumbling?)
In zero gravity, liquid water will form a sphere all by itself thanks to surface tension.
(Of course, pressure and temperature that sustains liquid water is rarely found in zero gravity, outside of human space stations).
Human space stations aren’t zero gravity (it’s actually 0.89g). The apparent weightlessness is due to continually falling and never hitting the ground. You don’t need to be in zero gravity to see the water form a sphere shape either, use an eye dropper and a high speed camera and you’d see similar results.
Getting a little off topic here, but general relativity is based on there being no observable difference between inertial motion and free-fall within a gravitational field. The weightlessness from free-fall isn’t just apparent. It’s identical in every way to the weightlessness experienced if you were sitting in one of the universe’s vast voids.
It is of limited meaning to say the gravity in LEO is 0.89G. That’s an Earth-centric statement, and ignores the gravitational contribution of the sun, the galaxy, the local group, and so on.... At best, you can say “a body initially at rest relative to the Earth at altitude 300km experiences an acceleration of 0.89g towards Earth”. Earth itself is in free fall around the Solar System’s barycenter, which in turn is in free-fall around the galaxy’s center of mass, which in turn is in free-fall around etc... etc...
The only gravitational experiment that could be done on the ISS to determine they were orbiting Earth (vs sitting in empty space far from any other bodies) would be to measure gravitational tidal forces.
When you create a drop of water and let it free-fall, it forms a sphere precisely because, from its frame of reference, there is zero gravity.
It is of limited meaning to say the gravity in LEO is 0.89G. That’s an Earth-centric statement, and ignores the gravitational contribution of the sun, the galaxy, the local group, and so on.... At best, you can say “a body initially at rest relative to the Earth at altitude 300km experiences an acceleration of 0.89g towards Earth”. Earth itself is in free fall around the Solar System’s barycenter, which in turn is in free-fall around the galaxy’s center of mass, which in turn is in free-fall around etc... etc...
The only gravitational experiment that could be done on the ISS to determine they were orbiting Earth (vs sitting in empty space far from any other bodies) would be to measure gravitational tidal forces.
When you create a drop of water and let it free-fall, it forms a sphere precisely because, from its frame of reference, there is zero gravity.
Getting even more off topic, your comment is completely right except for this:
“a body initially at rest relative to the Earth at altitude 300km experiences an acceleration of 0.89g towards Earth”
which is false in the general-relativistic way of looking at things. An accelerometer initially at rest at 300km would show no acceleration as it starts to fall towards earth. If the atmosphere and the earth could be removed without affecting the shape of spacetime the accelerometer would continue speeding up till it reached where the center of the earth was, then slow down, reaching a speed of zero at a point opposite from where it started, at which point it would repeat the motion in reverse. At no point would it register an acceleration. Nor would an accelerometer in orbit register an acceleration. In the general-relativistic framework, free fall means no acceleration, and the motion of a body in free fall is determined solely by the shape of spacetime. So, at best you can say,
“The shape of spacetime at 300km affects a body's motion the same way an acceleration of 0.89g towards Earth would if spacetime were flat.”
By the way, an accelerometer on the surface of the earth, e.g., the one in your smartphone, registers a constant acceleration of 1.0g in the up direction caused by the normal force of whatever the smartphone is resting on. If someone knocks the phone off a table, the acceleration becomes zero till it hits the floor. (Air resistance can also apply an (upward) acceleration to the smartphone, but is negligible at the speeds reached during a fall of only a few feet by an object as heavy and dense as a smart phone.)
“a body initially at rest relative to the Earth at altitude 300km experiences an acceleration of 0.89g towards Earth”
which is false in the general-relativistic way of looking at things. An accelerometer initially at rest at 300km would show no acceleration as it starts to fall towards earth. If the atmosphere and the earth could be removed without affecting the shape of spacetime the accelerometer would continue speeding up till it reached where the center of the earth was, then slow down, reaching a speed of zero at a point opposite from where it started, at which point it would repeat the motion in reverse. At no point would it register an acceleration. Nor would an accelerometer in orbit register an acceleration. In the general-relativistic framework, free fall means no acceleration, and the motion of a body in free fall is determined solely by the shape of spacetime. So, at best you can say,
“The shape of spacetime at 300km affects a body's motion the same way an acceleration of 0.89g towards Earth would if spacetime were flat.”
By the way, an accelerometer on the surface of the earth, e.g., the one in your smartphone, registers a constant acceleration of 1.0g in the up direction caused by the normal force of whatever the smartphone is resting on. If someone knocks the phone off a table, the acceleration becomes zero till it hits the floor. (Air resistance can also apply an (upward) acceleration to the smartphone, but is negligible at the speeds reached during a fall of only a few feet by an object as heavy and dense as a smart phone.)
> The weightlessness from free-fall isn’t just apparent. It’s identical in every way to the weightlessness experienced if you were sitting in one of the universe’s vast voids.
Also agree with this as well (I again just wasn’t as detailed in my response). I used the word apparent because that’s the established convention from all scientific papers on the topic, but you are 100% correct that it’s identical. The VomitComet flights are a great example, but a lesser known example is going downhill on a roller coaster.
Also agree with this as well (I again just wasn’t as detailed in my response). I used the word apparent because that’s the established convention from all scientific papers on the topic, but you are 100% correct that it’s identical. The VomitComet flights are a great example, but a lesser known example is going downhill on a roller coaster.
> When you create a drop of water and let it free-fall, it forms a sphere precisely because, from its frame of reference, there is zero gravity.
Correct, which is what I said (just not as explicit). I now realize that the “you” could be ambiguous though, the intended “you” is the person performing the experiment doesn’t need to be themselves in zero gravity.
Correct, which is what I said (just not as explicit). I now realize that the “you” could be ambiguous though, the intended “you” is the person performing the experiment doesn’t need to be themselves in zero gravity.
In absence of gravity there would be no atmosphere, no pressure, no liquid water and especially no flowing liquid water.
You could imagine a glass donut filled with water, as well as a small rotor to move the water in a circle.
You obviously have to balance the water pressure and temperature to reach slow ice formation, and maybe you need a more interesting container shape than a donut to get interesting results.
You obviously have to balance the water pressure and temperature to reach slow ice formation, and maybe you need a more interesting container shape than a donut to get interesting results.
Well, in space water starts to boil away immediately so you would need a gas tight container which don't typically happen in nature in sizes that would allow internal currents to develop.
Earth is a (reasonably) gas tight container filled with flowing liquid (lava propelled by convection currents). Europa (the moon) is a reasonably gas-tight container filled with water under an ice sheet.
Of course Earth also has appreciable gravity. The real problem isn't that nature produces no gas tight liquid-filled containers, it's that gravity is the primary mechanism by which things are naturally created in space. Asking for a situation without gravity virtually requires artificial construction.
Of course Earth also has appreciable gravity. The real problem isn't that nature produces no gas tight liquid-filled containers, it's that gravity is the primary mechanism by which things are naturally created in space. Asking for a situation without gravity virtually requires artificial construction.
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I wonder if water ice in space forms large geometric patterns if it is sufficiently dense.
I think it wouldn't, unless there was something making it (also) rotate in a different axis than the water flow
What would drive a stream in the absence of gravity?
I assume that can be artificial. Just use a pump.
You can have a directed spray (maybe shot out of a giant fire hose at high pressure and flow), but without gravity, the liquid will disperse over a short distance. I don't see how that's avoidable because of entropy/diffusion. Gravity plus a container (river bed) create a perfect condition for the sorts of liquid flows we're accustomed to: a nearly identical acceleration on all particles, with a bounded displacement.
Just recreate the river bed from a solid material (to prevent dirt from floating away) and add a lid
if you have a laminar flow, wouldn't some equivalent of surface tension keep it together?
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"All right stop,
Collaborate and listen,
Ice is back with a brand new invention..."
<g>
Collaborate and listen,
Ice is back with a brand new invention..."
<g>
I think its the combination of the single digit nights which allow ice to form on the river, and warmer days which let the thin edges break free so it can turn. Then it's the action of grinding against the shoreline ice that creates the round shape, like a block of wood on a lathe under the worker's tools. We got another six inches of snow last night which will help to beef up the solid portion.
It's fascinating that it happened a second time. If I didn't have so much shoveling to do today I would almost be inclined to walk over there and take a look!