Simple, everyday science

[Bozo Erectus]

Ok heres a test for your massive noggins.

Remember Counterclockwise Lake? The other day it presented me with a new puzzle, which I was able to figure out. Lets see how long it takes you guys:

Its been very cold around here, and the lake froze over. Naturally, kids have delighted in throwing heavy objects onto the lake in hopes of breaking the ice. I started noticing that its easy to see where things have been thrown, because a 'crater' remains. Wherever the ice has been broken, even though the water has frozen over again, theres an almost perfectly circular upraised ridge of ice. It hasnt been so cold that the water freezes in mid air as it splashes, so my question is: how did these ridges form?

No running to Von Steidleheims "Theory of Ice Ridges: Volume 35", the answer is all you this time

 

[thetrooper]

Surface tension?

 

[skadistic]

its the same reason why my ice cubes are taller then the void i filled to the top.

 

[Renata]

I need a picture. I can't visualize what you're saying.

 

[Broccoli Man]

I'm thinking this is really simple to catch us out so is it just it freezes back but the other bits continue to freeze so end up getting thicker as the hole freezes back it isn't as thick as the other ice. The ice freeze from surface of the water and leaves ridges because it doesn't reach as thick as the rest of it. I don't think I explained that well.

 

[betazed]

Not sure I understand the scenario but here is a guess anway.

The stone hits. Ice breaks, create a tiny lake. ice floats in the lake with a small piece sticking up (it is lighter than water). The lake freezes. So now you have a small ice hump sticking out of a perfectly flat ice.

Am i Close?

 

[El_Machinae]

I think it's because the lake laps up and down, and lays a surface of ice on top of the ice. As well, due to surface tension, water 'crawls' up the ice and then freezes higher up then you'd expect.

 

[Bozo Erectus]

I need a picture. I can't visualize what you're saying.

I should stop being such a tightwad and go get a digital camera. Let me try to explain better: a big, uniform sheet of ice. Somebody comes along and plonks something onto the ice. It breaks through, and for a time theres a hole in the ice, liquid water is in the hole. I come along hours later. The ice has reformed in the hole created by the heavy object. But now, theres an upraised ring or ridge of ice around the edges of where the former hole was. Hope that helps

skadistic and trooper: nope and nope

 

[nonconformist]

Miniscus?

Or where water has lapped onto thew edges of the ice?

 

[Aphex_Twin]

You mean like this:

It's like a pendulum. The water displaced by the rock flows back into the void the rock created, and due to inertia, a small ridge is formed in the middle. If the water wouldn't freese, that ridge would subside and push the outer edges of the crater a little upwards; and the crater edges would again subside into another smaller dip in the middle (until all energy is exhausted).

 

[Bozo Erectus]

I think it's because the lake laps up and down, and lays a surface of ice on top of the ice.

Bingo! The liquid water laps up and down, depositing water around the edges of the hole, which then freezes. More water splashes over the new higher edge, freezes, and so on.

At least thats the conclusion that I came to.

@Aphex, I think the mechanics of it would work differently (like you describe) under low gravity and the kind of cold temperatures youd find on a non terrestrial body.

 

[Che Guava]

Dang, too late!

Got any more?

 

[El_Machinae]

BozE: would posting other 'simple' questions be within the spirit of the thread?

 

[Bozo Erectus]

El, absolutely! I was desperately trying to come up with a new one in answer to Che, but Im stumped. Go for it

Only one rule though: any new ideas should be things that you need to figure out with common sense, not stuff you can easily look up in a book.

 

[El_Machinae]

Okay!

We're told to turn down the heat in our houses to save energy. Why?

I have my house set at 11 C, and the furnace kicks in every once in awhile to heat it back up to 11 C, and then turns off - "tops up the heat", so to speak. I could have it set at 19 C, and then the furnace would kick on when it went below and would "top up" the heat again. Why shouldn't I live in a warmer house?

Except for the initial investment (which is only about 3 hours of heating), where's the difference?

 

[nonconformist]

Because the rate of cooling, if it's the same temp outside, would be greater for 19 C than it would for 11C.

 

[Bozo Erectus]

Initially, youd need more energy to raise it to 19. Also, it requires more energy to maintain that volume of space at 19. If the volume of space was smaller it would require the same amount of energy to keep it at 19 as it does to keep it at 11, when its larger.

?

 

[betazed]

Because the rate of cooling, if it's the same temp outside, would be greater for 19 C than it would for 11C.

correct. IIRC, it is directly proportional to the fourth power of the difference in temperatures.

 

[El_Machinae]

Actually, yeah, he's correct. Cooling follows an acceleration graph, not a velocity graph - kinda.

It stumped me for awhile, because I thought "if my house only loses a million calories an hour, why should I care what the temp is at?"

Think of it like a balloon with a hole in it. If you put just a little bit of water in the balloon, it will leak out slowly. If you increase the water (akin to adding heat pressure), the water will stream out more quickly.

 

[Bozo Erectus]

Hmmm, I dont mean to be a spoil sport, but I dont think mine is incorrect. To heat a large space to a certain temperature requires more energy than it takes to heat a smaller space to the same temperature.