You cannot ”release the cold”. Cold is not a thing. There is only heat. Heat flows along temperature gradients. So you can add heat or lose heat and that’s it. Ice has heat, as does everything in the universe that is not at absolute zero.

Planetary Sci: In what way does the length of the magma ocean era of a planet scale with mass?

\1. No, we know the the green revolution happened and there was lots more stable food, so population grew.

Climate change is due to increased use of fossil fuels. There are parts of the world that have low density population / high fuel use, such as the United States. Opposite, there are parts of the world with high population density / low fuel use, such as any poor country you can name. Overall: statement is both incorrect and too simple.

Why did the green revolution happen? Going deeper, higher population means local areas start to run out of available renewable fuels (e.g. you chop down your forest faster than it can grow.) The industrial revolution was mostly a search for more fuels. Then someone works out how to turn natural gas into fertilizer and all of a sudden anyone can grow more crops in a given area. More people = more fuel = more food = more people.

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Due to this happening inside a cooler, it will end up being colder longer as well

In principle, yes. In practice that mirror would need absurd dimensions, and a black hole doesn't get sufficient light back to even see the Sun.

There is no "outside the universe" by definition.

Time dilation applies to everything, doesn't matter if you use an atomic clock or a pregnancy to measure x months.

As seen by the ship nothing changes because the ship is at rest relative to the ship and only relative velocities matter.

Which model do you mean?

Orbital parameters in our Solar System change by more than 1 millimeter all the time and it doesn't matter at all. You could move any planet by thousands of kilometers and no one would care (besides the confusion how the thing suddenly went to a different place).

If you can make microscopic black holes then you can extract some energy (but nowhere close to a star). Otherwise the radiation is completely negligible. A black hole with 2 times the mass of the Sun (around the smallest black holes we know to exist) has a power of just 2*10^(-29) W.

To get a power of 1 MW you need a black hole with a mass of just ~10^10 tonnes (emissions would be gamma rays and electrons and positrons). These still live longer than the age of the universe so they might exist as primordial black holes but we have never found one.

A black hole with a luminosity similar to the Sun would evaporate in around a microsecond.

You can feed the black hole with matter and extract energy from the radiation emitted by the accretion disk. This is a very efficient process, better than fission or fusion, and you can use random waste as fuel.

This is a great explanation that ignores the OP's question.

I will bet anyone that does this experiment 5 bucks that adding the salt actually makes the coldness last less time, because liquid water conducts heat into the walls of the cooler faster than solid ice does. The energy absorbed by the phase change and the fish are distractions from the actual question, which is what lasts longer. And the only thing that matters for this calculation is how fast the heat gets through the walls of the cooler. And the still air around the unmelted chunks of ice is a better insulator than the liquid water.

I completely agree that the salt is better, since cooling the fish down quickly will make the fish stay fresher longer. Again though, this is not what OP asked.

Gas giants with a breathable atmosphere would look different from our current gas giants, but you can wear an oxygen mask. Wind would be a concern. Radiation is okay if you get sufficient shielding from the atmosphere. Temperature is a problem unless you are pretty deep in the atmosphere or have a good suit. Saturn's "surface" gravity is just a few percent larger than Earth's, that should be fine. On Jupiter you have 2.5 g however, that is a big problem.

To reach a speed faster than light relativity needs to be wrong. Asking what relativity predicts in situations where it doesn't apply is meaningless. You could ask the question in a completely different framework, e.g. in Newtonian physics (where motion faster than light is possible), but then you don't have black holes any more so you run into the same problem of the question having no answer.

Obviously nonsense.

I thought that was "watching photons slow down". It's actually the beta radiation doing it? How cool.

Thank you.

> If QED says light travels in the path that minimizes the time of travel

It doesn't say that. Classical optics says that if diffraction is negligible.

> shouldn't all the light from an object become part of the mirage image in situations involving mirages?

No. Why would it?

> (I.e., why would there be a "real" image as well since that light takes longer to arrive at the observer.)

The direct image will take less time, but it's on a completely different path so that comparison doesn't matter. The shortest path statement only applies to adjacent paths.

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I feel like there's a lot of silly answers in here. A simple Google search reveals that yes, salt lowers the tempature of ice by melting it. Melting is an endothremic process, and it makes the mixture colder. Which basically means that it releases the cold of the ice into the environment faster.

But! Because the cold is released faster, it means it will warm faster. Because the difference in tempature between the cooler and outside is greater.

So they are half right. It does make it colder, but not for longer.

The more measurable effect is if you have a closed column of water with a piston at the top and freeze it, the increased pressure can do work by moving the piston up. Conversely if you increase the pressure on the piston it will melt the ice.

This is how freeze-thaw erosion works when water enters cracks in rocks, freezes and breaks the rock as it freezes.

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The ball will raise the water level in the container, which increases the average pressure, so the freezing point decreases by an extremely tiny amount.

We are talking about really small effects here. Freezing one liter of water releases 334,000 J. Raising a 10 gram ball by a centimeter needs 0.001 J.

Yes, this most famously happens in nuclear reactors where emitted electrons move through the water at speeds greater than light does. This creates the blue glow you might be familiar with through cherenkov radiation, a phenomenon analogous to a sonic boom.

when i was a kid we got an ice cream maker one year for the 4th. it was a drum filled with salt and ice, and then a second container was put inside the first with the ice and salt surrounding it. and that container you put the milk, cream, sugar etc. and then it mixed the contents until it was ice cream.

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Thanks, this is the first answer I got that explains what is actually happening on a particle level.