AUniquePerspective

AUniquePerspective t1_j7ccxje wrote

I don't know if it is the same for cities in Rheinland-Pfalz but I believe Berlin abandoned Local Mean Time in 1893 in favor of CET (Central European Time UTC +1). Currently Rheinland-Pfalz uses CET in winter and CEST (Central European Summer Time UTC +2) in summer.

LMT Local mean time differs from apparent solar time as can be observed with a sundial in that time is constant with LMT but the speed of time varies with a sundial.

This is all confusing without examples so...

At Mainz on this year's summer solstice, the sun will rise at 5:17 CEST, reach solar noon at 13:28, and set at 21:39 CEST.

And on this year's winter solstice, the sun will rise at 8:22 CET, reach solar noon at 12:25, and set at 16:27 CET.

There are (by subtraction) 8 hours ten minutes between noon and sunset midsummer and 4 hours between noon and sunset midwinter. This explains the timing of the candle law.

Edit: But it's also important to recall that sunset isn't the time it gets too dark. There are 3 phases of twilight. During Civil Twilight it is generally possible to do outdoor activities though the sun is below the horizon. During nautical twilight, if the sky is clear, the brighter stars are visible and so is the horizon. During astronomical twilight, some stars that would otherwise be visible are obscured by sunlight.

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AUniquePerspective t1_j6vreni wrote

The point of my explanation is to point out that freezing the fish quickly and solidly is the motivating reason behind using salt. OP's question is ignored here because it's not relevant and because OP came right out and said they didn't understand.

But I'll repeat the parts you seem to have missed too: The goal is to rapidly transfer a great deal of heat away from the fish. Not just quickly but also to a lower temperature.

In this system, you want to declare the marginal difference of having an internal layer of air immediately adjacent to an insulating material as a defect... but it's simultaneously an advantage with respect to the fish which is not insulated. There's a minor trade off here at best.

The heat debt from the phase change if done using sufficient quantities of ice and salt is overwhelmingly sufficient to fully freeze the fish and keep it frozen for the period of transportation. The marginal loss of heat through the insulated walls of the cooler is small enough to be considered irrelevant.

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AUniquePerspective t1_j6vcqpa wrote

It's the transfer of heat that's important.

The goal is to transfer heat away from the fish.

In the cooler, the fish is part of "the environment" that the melting ice will transfer heat from.

The materials that the cooler is made of aren't good for transferring heat and there's not much else in the cooler except for a bit of air. So most of the heat must come from the fish. If the cooler were a hypothetically perfect insulator and a vacuum, then all the heat would come from the fish.

If the cooler were a hypothetically perfect insulator and a vacuum, then the ice would not have anything to get heat from and it could stay the same coldness forever.

It's really intuitive for us to think of mixing temperatures: half a glass of cold water plus half a glass of hot water equals half a glass of warm water. But that's not the concept we're dealing with so try to put it out of your mind.

Don't think of the ice like a bit of a mooch. If it were a mooch, it would take a little bit of of the fish's heat in a similar to the way the two glasses share their heat and both come out warm... or like a friend who goes out for pizza with you but doesn't pay their share but still eats a normal amount of pizza.

Instead, you need to remember that phase change from solid to liquid is really very expensive in terms of the amount of heat it takes. So think of the ice as water that is heavily indebted to it's environment. On its own, water will pay off its big loan slowly as it gradually gathers heat.

And then think of salt as the loan shark who shows up at water's door with a baseball bat and says "Look at you walking around dressed as a solid! You're paying off all that debt now!" Salt forces ice to pay back the solid debt suddenly. So water looks around and there's not much heat in the cooler except for fish.

And fish says, "How much do you owe anyway? I'll give you what I've got since there's no other option." But the amount is way more than the fish expected. But the fish has good credit and pays off the loan in full anyway. But this puts the fish in debt. It now has even less heat than the water. The fish will be colder than freezing. It will be in deep heat debt.

The fish will cool more suddenly and will freeze more deeply with this method (and as a result of the fish cooling more deeply, it will stay cold longer.

It's all counterintuitive unless you get your head around the idea of phase change forcing outsized debt on the fish.

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AUniquePerspective t1_iwcdo4a wrote

u/eduo is getting downvoted because while they may have something to add they've done it poorly.

If the phrase "heats things up" was some strictly defined scientific terminology they could perhaps argue I'd used the term too loosely. But I used loose terminology on purpose the same way I would with comparison between any of the methods that make food hot. Because to me the point is that the food gets hot. You don't have to understand how a microwave works to use it. The same is true of a kettle, an oven or an induction stove top.

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AUniquePerspective t1_iwb1l3p wrote

I made a traditional fondue savoyarde in my microwave and triggered most of r/france but a microwave just heats things up. Admittedly it can be tricky to get the settings just right for whatever kind of heating you want to do but that's also true of other heating methods that people just generally have more practice with.

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