Ever bathed in sea-water below 0°C?

I have. And most coastal ppl in Northern Europe are aware, you cool out much quicker in water than if you' simply cover yourself in Ice or snow. Cooling a solid object quicker, already saves time. But water's also a better insulator than Ice.

Ice melts at >0°C. Saltwater doesn't. So no endothermic reaction like in Ice neither. Best way to cool drinks quickly isn't Ice, but cold water. How do you keep below-zero water from forming ice? Salt!

tl;dr - Pretty common knowledge where I'm from (Ger/DK).

1- Your pure ice is not at -10 to -20 C, this is impossible

2- Yes adding salt does cool it

The water in equilibrium with ice will be 0 degrees. The ice could be -20.

The brine mixture can indeed be colder, and the water is the bit that's in contact with the fish, so that's important.

It may be that the very cold ice on top of the water loses more heat to the environment more quickly than an even temperatured slurry. There might be a higher temperature gradient between that ice and outside than between the brine slurry and outside, which may mean slower warming overall for the slurry.

Lmaooo this reminds me of that girl in Hell's Kitchen that started a boil with cold water because "I thought cold water was supposed to boil faster" (since more heat transfer).

It doesn't matter that the colder-than-0 mixture absorbs more heat. It will eventually heat until 0c and at that point it'll be at the same starting point as pure 0c water... Except for it also had the extra time before 0c, thus it took longer to heat up. Same reason why starting a boil with hot water will obviously be faster than cold water...

Hot water can hold more salt ions than cold water, as you can observe when crystals fall out of a saturated solution while it cools down.

This implies that it takes energy to dissolve the salt crystals.

So, when you add salt to water, it will cool down as it dissolves the salt, making the claim that the system stays cool for longer plausible.

According to one recent paper the Earth's core might have stopped moving relative to the surface, which is to say it's still rotating as fast as the surface is. From an outside perspective, essentially the core is going from rotating slightly faster than the surface to slightly slower. Per the paper, this happens pretty regularly and won't do much.

[removed]

You're correct, significant kinetic energy is present in the liquid form and lost during the transition, some of that is converted to potential energy by way of the 9% decrease in the density of the ice compared to liquid water.

Because water is really weird! It's unusual for a compound to expand in volume as it goes from liquid to solid. Water freezing is an exothermic process: heat must be given off. While there is net loss, the amount of kinetic energy that water needed in it's liquid, kinetic form is still less than the energy needed that was converted into potential energy with the raising of the ice.

[removed]

Salt lowers the freezing point of water. This causes some of the ice to melt. The melting requires heat energy and this makes the solution drop in temperature.

Take two bowls and put an ice cube in each. Add salt to one. Watch.

Edit cure to cube

It’s been too long since I sat in a physics (or thermodynamics) class to say with certainty, but my guess is that the answer has to do with “types” of energy and sounds something like “some of the thermal potential energy translated to gravitational potential energy”. They alluded to this in the above comments too with the notes on the energy required to move the ball - if the ball wasn’t there, then additional (thermal kinetic?) energy would have been released into the environment.

To say it another way - the gravitational potential energy isn’t the only energy in the system. The total energy of the system after freezing will still be less then before despite the increase in gravitational potential energy due to the decrease in thermal energy.

The rate of change will be faster, but will the total time to “warm” be faster? Since the colder one has a larger way to go to “warm”?

[removed]

[removed]

The rate at which the sun's luminosity will change will vary at different parts of the process, but it would never really be as stable as it is now. The habitable zone has some "width" so some of the outer planets might remain in it for something like hundreds of millions of years (depending on how exactly you define it), but nothing like the billions Earth has had.

It's largely down to heat capacity, mostly that of water. Water requires a good bit of energy to heat up by a given amount, and it has to lose that same energy to cool down; so even though the amount of solar heating is lowest in December, the oceans and other bodies of water are still holding onto heat from summer, and will continue to cool until the rate of solar heating surpasses the rate of cooling at some point in spring.

Heat is distributed pretty widely in the atmosphere, the poles are a fair bit warmer than they would be without an atmosphere and oceans, but the transport still isn't perfect so there is a gradient (compare to somewhere like Venus, which has a thicker atmosphere of mostly greenhouse gasses and so very little temperature variation on the surface, other than that caused by altitude).

I honestly haven't seen an answer here that addresses the real question:

How can you remove energy from a system (lowering it's temperature) and yet end up with more potential energy on the ball?

I don't have the answer but I realize that while the entire system will have less energy overall, some of the energy will get rearranged by the freezing process and the ball will end up with a bigger percentage of the total energy in the system after freezing. I just don't know exactly how it happens.

>No one ever said anything about that.

That's not quite correct. AUniquePerspective, who EmeraldHawk is responding to, introduced that above.

[removed]

This is the correct answer. It's why magnesium chloride is applied to roads in the winter, to prevent water from freezing by utilizing the same principal. Interesting to note that since mag chloride has an additional chloride atom, it can lower the freezing point by more degrees than rock salt.

Unless it was a recent edit, they asked about the moons of the gas giants.

[removed]

Maybe not the Sun itself, any source of energy would work (some chemical reaction such as fire, nuclear, even mechanical energy from stirring the water would convert to some thermal energy), but yes. It was already in the water when the ball was floating.

I have just come back from a kitchen experiment.

I added water to an insulated cup of ice, stirred it, waited a minute and took the temperature. 0.5°C, about 33 in those antique numbers.

I added a big whack of salt, stirred again vigorously to dissolve some and measured -2.6°C. I don’t care what that is in non-science units. If you like I can however convert it to Kelvin.

I’m sure I can go colder by using a proper salt solution (heat it to dissolve as much salt as I can) and crushed ice, not cubes, to increase the surface area. I’m guessing I can possibly get to -17° if I try hard enough. Just a hunch.