Why we're immortal

[brimstoneSalad]

I don't know now, my perception is that nearly all physicists agree that it's impossible to determine via experiment which of the mainstream interpretations of quantum mechanics are correct.

Well when they make the same predictions it's not possible. You'd have to find something they disagree on that could be tested.
It's not possible to distinguish Copenhagen from MWI. Hidden variable hypotheses like pilot wave struggle to just explain the same phenomena that have already been observed.

And why exactly would it be impossible for entangled particles to communicate faster than light? I mean, quantum mechanics forbids us from sending information faster than light by interacting with the entangled particles, but that doesn't mean the particles themselves can't communicate faster than light, right? And neither does the theory of relativity, it says that a particle can't accelerate to the speed of light, that doesn't mean the space isn't full of particles that have been going faster than light since the beginning of the universe and that can carry some information, right? Those particles don't even have to be completely impossible to detect by us, neutrinos may be going faster than light, although it's hard to tell.

The variable c isn't necessarily the speed of light, it's the speed of light (or anything massless) in a perfect vacuum; any medium slows actual photons down. It's possible to have particles traveling faster than light in medium, but whatever c is (if it's faster than we have calculated) it's impossible to travel faster than that due to the nature of space-time itself. Propagating actual information faster than c means propagating back in time, and that potentially yields paradoxes.

If quantum collapse is random that carries no information at all -- we know the other particle however many light years away has a certain state, but we can't send information using that. If quantum collapse is controlled by local variables, that means information is being carried faster than the speed of light to the entangled particle (which may be very far away).
If collapse is controlled by a pilot wave that travels faster than light, we could also extract information from that pilot wave with e.g. a double slit experiment where the second slit opened only some time *after* the particle passed through where the pilot wave would travel instantly and cause an interference pattern despite the slit not being open at the time the particle went through.

To give a thought experiment, say we're firing electrons at 10% c from the moon to the Earth (about 1.3 light seconds away), we fire them through a single slit and it takes them 13 seconds to reach the Earth (to create an interference pattern or not), 12.9999 seconds after firing the electrons we could decide whether to open the second slit or not thus transmitting the information about whether we opened it or not to the Earth instantly through the pilot wave which would create or not create an interference pattern. Instantaneous communication on that scale doesn't create a paradox in itself because you're only sending the information back in time a little and far away, but if you then made a relay to transmit that information back to the moon in the same way, and you repeated the cycle you could send the information back in time as far as you wanted (as long as the aparatus was set up). That creates paradoxes.

Obviously you can add on more ad hoc rules to the already ad hoc hypothesis that is the pilot wave hypothesis, but I think we both agree that's bad practice since you can keep any hypothesis alive that way, even Flat-Earth or Ether.

Well we don't exactly know what counts as possible.

And why would a world in which some person gets to live forever be impossible (rather than just highly improbable)?

Big crunch scenarios, perhaps.
If you're talking about living billions of years though, sure, "quantum immortality" on that scale is astronomically improbable but may not be impossible, so perhaps in a small subset of universes you're still alive by some improbable series of events billions of years from now. Not quite immortality proper, but it may not matter once you get up into those numbers.

[teo123]

By the way, @brimstoneSalad I still don't understand, why don't bombs contradict the second law of thermodynamics? The second law of thermodynamics says that a body can't do work from its own internal energy (Croatian "unutarnja energija"), and that no body can convert 100% of the input heat to work. But bombs appear to violate that. They receive very little input heat, they have no external source of energy, yet they are supposed to do a lot of mechanical work. Exploding and destroying everything around the body is a lot of mechanical work, right? Does maybe "internal energy" (Croatian "unutarnja energija") in the 2nd law of thermodynamics mean something different than energy that's directly stored in the body? Does, for some reason, chemical energy not count as "internal energy" (Croatian "unutarnja energija")?
This isn't really meaningful, since obviously all or nearly all experts agree bombs exist, but it's still interesting to know.

[brimstoneSalad]

By the way, @brimstoneSalad I still don't understand, why don't bombs contradict the second law of thermodynamics? The second law of thermodynamics says that a body can't do work from its own internal energy (Croatian "unutarnja energija"), and that no body can convert 100% of the input heat to work.

The translation must be bad, the second law of thermodynamics is about entropy which is a difficult concept to understand. It's not a term that means energy, it means something like "disorder" or "chaos".

When the chemicals in a bomb undergo a chemical reaction (like oxidation) the entropy increases from that. Energy was stored as a potential from the chemical reaction and is released as heat (a more chaotic form of energy). Heat is more entropic than the stored chemical energy. The heat can't just change back into that chemical energy, it's a one-way reaction unless you put a lot more work into the system.

It absolutely CAN do work, but the work is does is less than the entropy increase of the bomb. You could even extract a slight majority of the energy from the explosion as work with a perfect device, but not ever 100%.
Look up "Carnot Efficiency". There's a theoretical maximum conversion into work based on the thermodynamics of the system.

For example, a car engine (which is just a series of explosions) has an efficiency of about 20% in practice, but the maximum theoretical efficiency for a perfect car engine is 37% http://news.mit.edu/2010/explained-carnot-0519
Some real systems can get as high as 51% carnot efficiency if they were designed perfectly, but you're always losing some energy you can never get back to do useful work.

The efficiency depends on the heat difference, so if you made an engine with an internal heat like the core of the sun and a source of cold that was 0.0000001 degrees Kelvin, then you'd get an extremely high efficiency. Like 99.999...% etc. You'd still never hit 100% though. You always lose some. That's the point of the second law.

Of course in practice the maximum temperature is limited by the melting point of the materials you're using, which is going to be pretty low, and the minimum temperature in this universe is going to be 2.73 Kelvin from Cosmic Microwave Background Radiation (anything colder requires energy to create which defeats the purpose).
If you made a perfect tungsten heat engine in space with a very large radiator, you could get an efficiency of over 99%
Plug in the temp of deep space and a degree short of the melting point of Tungsten: https://www.omnicalculator.com/physics/ ... efficiency

Hope that helps explain it better.

Does maybe "internal energy" (Croatian "unutarnja energija") in the 2nd law of thermodynamics mean something different than energy that's directly stored in the body? Does, for some reason, chemical energy not count as "internal energy" (Croatian "unutarnja energija")?

Right, I think it's just a very bad translation.
The is the trouble trying to learn this stuff in languages other than English, and probably German and French where the terms are better established and there's more material.
Always read about physics in English if you can, it will lead to less confusion because there won't be translation errors.

[Red]

Looks like Sunflowers checked out. Too bad as this was one of the most interesting/entertaining threads I've followed in a long time. Intellectual humiliation at its very best.

[brimstoneSalad]

Looks like Sunflowers checked out. Too bad as this was one of the most interesting/entertaining threads I've followed in a long time. Intellectual humiliation at its very best.

I like how it ends with Sunflowers claiming we don't know anything about physics, and then teo and I proceed to discuss advanced physics concepts on our own.

[Red]

Looks like Sunflowers checked out. Too bad as this was one of the most interesting/entertaining threads I've followed in a long time. Intellectual humiliation at its very best.

I like how it ends with Sunflowers claiming we don't know anything about physics, and then teo and I proceed to discuss advanced physics concepts on our own.

Haha yeah. Want to split the thread or keep it to show how wrong Sunflowers is?

@teo123 You're coming into your own, there is hope for you.

[brimstoneSalad]

@Red no it's fine, it doesn't need to be split. It's good that anybody who is interested in why sunflowers is wrong can read those descriptions of how QM works.

[teo123]

The translation must be bad, the second law of thermodynamics is about entropy which is a difficult concept to understand.

And you said elsewhere that it isn't complicated and that me not understanding it is embarrassing.

Right, I think it's just a very bad translation.

When I think about it, maybe what's meant is: "There can be no device which will turn its own temperature into mechanical work, which will cool itself down by doing mechanical work.", maybe "unutarnja energija" somehow means "temperature". Do you think that is equivalent to the second law of thermodynamics? Though that seems a bit counter-intuitive. Can there really be no machine that will do mechanical work by a gas inside that machine expanding and therefore cooling itself down? Also, I can think of countless better ways to phrase that in Croatian.

Always read about physics in English if you can, it will lead to less confusion because there won't be translation errors.

When I read in Croatian, I feel like there can be no language barrier between the expert who wrote that text and me. If I read in English, there obviously can be. I don't know how justified that feeling is.
Besides, don't you think it may be somewhat arrogant of me to think I would be able to explain the second law of thermodynamics in Croatian better than the academic Jakov Labor, who has authored most high-school textbooks currently in use?
Anyway, many atheists respond to "Bible has perhaps been mistranslated." with "Languages shouldn't matter if what you are saying makes sense. I can translate a physics textbook into Greek and it would still make sense.". So, you think that's not a valid argument?

[brimstoneSalad]

The translation must be bad, the second law of thermodynamics is about entropy which is a difficult concept to understand.

And you said elsewhere that it isn't complicated and that me not understanding it is embarrassing.

Now that you have explained how bad the translation is it's more understandable. However I can not read the original Croatian so I'll have to take your word for it.

When I think about it, maybe what's meant is: "There can be no device which will turn its own temperature into mechanical work, which will cool itself down by doing mechanical work."

That's true in an isolated system with no other variables. Only differences can do work, so you have to use the difference in one temperature and another, and in so doing you can extract work but end up equalizing those temperatures so no more work can be extracted.

Can there really be no machine that will do mechanical work by a gas inside that machine expanding and therefore cooling itself down?

You'd have to expand against a differential in pressure. There are other forms of difference that can be used to extract work -- not just temperature, but a pressure difference (with no difference in temperature), difference in potential energy relative to gravity or magnetic field or electric charge attraction, etc.

So a piston with room temperature gas at a high pressure can expand against a room temperature atmosphere at a low pressure. It's the pressure difference there (not the temperature) that's being used. Normally the way to increase pressure is to increase temperature though (that's how it works in most engines).

When I read in Croatian, I feel like there can be no language barrier between the expert who wrote that text and me. If I read in English, there obviously can be. I don't know how justified that feeling is.

Maybe the expert was incompetent, or just bad at writing textbooks. You'd get yourself in less trouble reading it in English, your proficiency is pretty high.

Besides, don't you think it may be somewhat arrogant of me to think I would be able to explain the second law of thermodynamics in Croatian better than the academic Jakov Labor, who has authored most high-school textbooks currently in use?

No, I don't think so. Even English language highschool text books are pretty bad, riddled with inaccuracies.

Anyway, many atheists respond to "Bible has perhaps been mistranslated." with "Languages shouldn't matter if what you are saying makes sense. I can translate a physics textbook into Greek and it would still make sense.". So, you think that's not a valid argument?

The reason language shouldn't matter for a Bible translation is because they claim that God magically makes the translations perfect. Without that no scripture is trustworthy because most of it was oral tradition before it was written down and if God doesn't preserve it then it's about as accurate as any game of telephone.

In the real world translations are often very poor, and there's plenty of evidence of that for Biblical translations if you study it without the assumption that God fixed it.
That said, if you read multiple versions of the Bible you should get a pretty good sense of what it means.

[teo123]

Now that you have explained how bad the translation is it's more understandable.

And there is probably a big difference between saying "I don't see how bombs are compatible with the second law of thermodynamics, can you explain that?" and saying "Vukovar Massacre didn't happen, I can prove that by proving bombs don't exist.", right?

However I can not read the original Croatian so I'll have to take your word for it.

Yeah, it also doesn't appear to be available on the Internet.

Only differences can do work, so you have to use the difference in one temperature and another, and in so doing you can extract work but end up equalizing those temperatures so no more work can be extracted.

That appears to be exactly what enciklopedija.hr has to say about the 2nd law of thermodynamics: "Perpetuum mobile druge vrste bio bi stroj koji bi toplinu iz jednoga spremnika izravno i bez posrednika pretvarao u rad.".
I am not sure I understand the difference between entropy and heat capacity. Does it make sense to say water has higher entropy than most forms of matter just because it has higher heat capacity? How can water be more chaotic than air?
Would heating up some hypothetical body which has the temperature of 0K, and therefore no entropy, take infinite energy to heat up, just like it takes infinite energy to reach absolute zero? It seems to me that the law of conservation of energy would suggest that, but that the 2nd law of thermodynamics would suggest exactly the opposite.

Maybe the expert was incompetent, or just bad at writing textbooks.

Probably. My physics teacher also often commented that the textbooks by Vladimir Paar were better, but that they were probably replaced to punish him because of his political beliefs.

You'd get yourself in less trouble reading it in English, your proficiency is pretty high.

People on the Internet forums, including this one, often tell me they think I don't understand English well.
And you think I correctly understood the basics of quantum physics?