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Maine's giant spinning ice disc looks like it's reforming

theguardian.com

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Re: Maine's giant spinning ice disc looks like it's reforming

#51

Post by Someone »

_nalply wrote: post #29
k_sze wrote: post #22

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 min…

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?)

Re: Maine's giant spinning ice disc looks like it's reforming

#52

Post by bnegreve »

bnegreve wrote: post #24
spritecranberry wrote: post #8

Earlier quoted context omitted.

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.

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

Re: Maine's giant spinning ice disc looks like it's reforming

#54

Post by dTal »

dTal wrote: post #44
k_sze wrote: post #22

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...

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).

Re: Maine's giant spinning ice disc looks like it's reforming

#55

Post by JoBrad »

lmilcin wrote: post #45
k_sze wrote: post #22

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...

In absence of gravity there would be no atmosphere, no pressure, no liquid water and especially no flowing liquid water.

I wonder if water ice in space forms large geometric patterns if it is sufficiently dense.

Re: Maine's giant spinning ice disc looks like it's reforming

#57

Post by yardshop »

I walk home most work nights and cross the Presumpscot River on my way. It adds about 20 minutes to go up to that end of town and see it. I did that a couple times last year, and will be doing so this coming Tuesday (since Monday is MLK day). Thankfully the weather will be mostly below freezing until then, although it will go up to 37 today.

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!

Re: Maine's giant spinning ice disc looks like it's reforming

#59

Post by lmilcin »

wongarsu wrote: post #49
lmilcin wrote: post #45

Earlier quoted context omitted.

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.

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.

Re: Maine's giant spinning ice disc looks like it's reforming

#60

Post by jsjohnst »

dTal wrote: post #54
dTal wrote: post #44

Earlier quoted context omitted.

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.
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