I figured it was shocking considering that the Bering Straight is in the Northern Hemisphere, and the Southern Cross is rather prominently reproduced on the Australian flag because the Southern Cross is a constellation of the Southern Hemisphere.
Oh, that makes sense. It did not occur to me that it would not be visible from northern latitudes.
It is a dumb idea, but isn’t the earth slightly wider at the equator? I don’t know what that means for sea level, although presumably it wouldn’t have an effect.
All I can think of is the horrors awaiting those who photocopy their butts…
IIRC, sea level is higher at the equator because of centrifugal force offsetting a portion of Earth’s gravity. That’s kind of irrelevant, though, because the equator isn’t south of everything.
Thanks. Yeah, but it’s south of “the South.” I don’t think aruvqan’s manager was talking about Patagonia.
The name “Southern Cross” subtly hints at this fact.
Manduck, stick a thermometer in some ice water. Wait for its reading to bottom out. It will get to zero Celsius if there’s more ice than water. Drain the zero Celsius water from the zero Celsius ice. Add room temperature salt. Watch the temperature plummet.
Yes, the ice cream can be colder than the ice before salt is added.
But this effect is offset (partially or wholly?) by the fact that the earth itself is higher (farther from the earth’s center) at the equators, because of centrifugal force.
What I don’t know is… Are the mean ocean depths, calculated along lines of latitude, greater at equatorial latitudes? Are equatorial oceans deeper than tropical oceans? I think that there is no strong correlation, because great ocean depths are caused by tectonic forces. When one plate subducts another (is that even the right way to phrase it? Does one plate subduct under another?) then trenches can form, producing the deepest depths. Those can happen at any latitude.
(The Arctic Ocean is fairly shallow…but is that a necessary fact of earth’s composition, or just happenstance?)
No. The system of ice + liquid water will come to an equilibrium of 0 C because the water will keep it from getting any colder. When you add salt to the water, you drive down the freezing point to lower than 0 C, and the ice and salt water then come to equilibrium at a lower temperature.
Ice from your freezer is not at 0 C. For most Americans, their freezers will maintain temp around 0 F, which is -18ish C. The ice and water will come to equilibrium at 0 C as it melts, and then slowly to equilibrium with the ambient temperature. Adding the salt simply lowers the equilibrium temperature. The ice + salt water mixture can never be colder than the temperature at which the ice started without additional external cooling.
You contradict yourself, Bambi. You say “The system of ice + liquid water will come to an equilibrium of 0 C because the water will keep it from getting any colder. When you add salt to the water, you drive down the freezing point to lower than 0 C, and the ice and salt water then come to equilibrium at a lower temperature.” Thus, ice and water at the freezing/melting point gets colder with added salt. (bolding mine)
Then you say “The ice + salt water mixture can never be colder than the temperature at which the ice started without additional external cooling” which contradicts what you just said.
Besides, I have experimentally seen the temperature of 32 degree Fahrenheit ice’s temperature go down as adding salt, well, does what you say it does-
“the ice and salt water then come to equilibrium at a lower temperature.”
The water is at 0 Celsius, but the ice is colder than that. That’s why it’s ice. The ice water is liquid, which is why it’s at 0C. When you add salt, you create a solution that has a lower freezing point, so it allows some of the ice to melt even though it’s below 0. The ice was always below 0, the salt just allows it to melt at that temperature.
It is entirely possible for ice to exist at 0 C. Once one gram of ice has reached 0 C, it takes an additional 540 calories of heat to melt it, with the resulting water being also at 0 C. I contend that a cooler full of ice water that had been in my lab all day and had mostly melted (say, 5 gallons water to 1 gallon floating ice) had plenty of ice at 0 C. If the ice were colder, it wouldn’t be melting. I could scoop out some of that 0 C ice, add salt, and watch the temperature drop. And make ice cream in ziplock baggies with the science club I sponsored, which I did.
Here’s a link to a phase change graph for water-
Ice at 0 C coexists with liquid water at region 2 on the graph.
Not related to the temperature discussion:
I’m shocked when I realize that some people think that black people should be taken care of by white people, because black people would benefit from the benevolent tyranny of slavery.
It’s only a contradiction if you think the ice in your freezer is at 0 C / 32 F. Go out to your kitchen and stick a thermometer on the ice in your freezer and tell me what temperature it is.
Ice + water out of the freezer will come to equilibrium at 0 C on its eventual way to room temperature. Add salt and the equilibrium temperature will be lower. But it will never be lower than the temperature the ice started at.
If you suggest it can happen, then tell me the mechanism by which it occurs. How would ice at 0 C cool a saltwater mixture to lower than 0 C? What is the mechanism for that process?
It can, will, and does. The salt lowers the melting point of the ice, and when it melts, the latent heat of crystallization is absorbed from the brine, since the brine has lowered the melting point, the ice continues to melt and cool the mixture down to about -18C or 0F (not a coincidence, because this is exactly how Fahrenheit established the zero point for his temperature scale.)
Your assessment makes sense if only the specific heat of the ice or water is considered, ignoring the latent heat.
Another way to say the same thing: Mass X of ice at 0 Celsius has a certain amount of heat energy, all of which (since it is solid) is what is keeping its temperature at 0 Celsius; if it had less heat energy, its temperature would be lower. Add salt, and the resulting brine still has the same amount of heat energy (we’ll neglect the small amount added with the salt itself) but that is now divided between:
[list=a]that which is causing the brine to be liquid and not solid (latent heat of fusion)
[li] that which is causing the temperature to be T degrees Celsius.[/li][/list]
Since some of the energy has gone into item a, there is less in b; hence, the temperature T must be lower than zero.
This is why you can spray your frozen car windshield with de-icer, the ice outside will melt, and the windshield becomes cold enough to freeze your breath on the inside really quickly.
So why do I add rock salt to my ice cream maker? What would happen if I didn’t?
This very morning, CNN has a clip showing how many of the “Miss USA” contestants couldn’t name the current vice-president (VPOTUS).
Are you saying the ice somehow “remembers” how cold it was in the freezer? What is the mechanism for that process?