What are you, exactly?

[Eonwind]

I understood Eonwind to be saying that a better understanding of why the second law of thermo (entropy always increases) holds could help stitch together QED and general relativity.

There are interesting physics papers out in the past year on the second law of thermo and why it holds, it's a valid scientific inquiry.

Stitching together QED and general relativity?  That's just electromagnetism and gravity - why don't we see if it can unify all the forces, so include strong and weak?  Anyway, I've no idea how that would be done. 

But it would not surprise me if the second law was connected to the arrow of time (always heading to the future, I guess that is another way of stating the second law, not sure about this) which was somehow connected to the structure of spacetime (space and time are not on completely equal footings, there is a minus sign difference), which a better understanding of could point a way towards unifying gravity with the other forces.

Pierre correctly understood what I meant, just a note about time: what I meant time in relativity is just a simple coordinate (sure, with a different sign) but it's otherwise equal to the space coordinates.

I also think the introduction and a better understanding of the second thermodynamic law especially in the relativity theory can make it possible to make the QED theory and relativity come closer to each other, perhaps ending all the silliness about possible time travels in the past.

Mate, sorry, but that just nonsense. Thermodynamics is just statistics, and nothing else. There are no laws on its own, they are a consequence of the underlying theory. If you don't get that, it's best we don't further this argument.

Sure Thermodynamics is just statistics and QM/QED/... are they not???
If you don't get that, it's best you don't further this argument.

Whatever you consider psuedo-science has always been an integral part of physics, interpreting whatever our model means for us. The many world interpretation or the Copenhagen interpretation are just two of those.

Yes correct, whenever physics tries to interpret the meaning of a relativity equation telling us about physical phenomena is in its own right, when pretends to do the same with consciousness (which I say for the n-th time - is not even able to define it) or likely matters is pseudo-science.

My argument is (And perhaps you've heard a little about QFT and can follow) that as you can not say which state you were in precisely, as it is bound to be subject to quantum mechanical uncertainties (Heisenberg uncertainty principle) you must weigh all possible pasts according to their likelihood in order to determine a "physical" past. Only in the now you are truly observing sharply. The past and future are quite muddy.

Speaking about Heisenberg uncertainty principle, you can't take a postulate and stretch it wherever you want. The uncertainty principle is all about measurement and while I think it can be, using common sense, stretched to include "perceptions" as a means to make a measure, you cannot measure now something in the past so it's not even applicable.
The past is past whatever configuration may have been superimposed to the configuration that has become our common past has already collided creating our common past.

I don't see any problems with time travel either, considering I can go around a building and return at the same point in space. Relativity is so much more than just a geometrical theory, it tells us, and to the best of our experimental capacity, that time and space are actually equal parts of spacetime.

Lots of problem and paradox are created by past time travel, possibly including the break of some fundamental physic laws. Many thinks Relativity is a geometrical theory, and the fact that treats time and space in the same exact way (except for a sign) is one for the main reason why it cannot be merged with other theories like QED.
My theory is the always increasing entropy works like an "inflation" mechanism that makes it impossible to move backward in the time coordinate, but it's just my thought. But about time travel there is a great news, we're all traveling through time to the future 

About experiment c) you're going a bit wild with your fantasy, what is possible for a single particle (admitted the experiment is not falsified later) cannot be automatically transferred to a more complex structure or life form. It's science-fiction, full stop.

[Donari Tyndale]

Eonwind, the whole laws of thermodynamics are derived from quantum statistics. Well, they were there before quantum mechanics, but these days one can derive the laws from quantum mechanics and statistics. The second law of thermodynamics is implied by unitarity of the quantum theory, thus whenever you have a unitary theory, the second law of thermodynamics holds.

Thus, assuming the second law holds, we require any quantum theory to be unitary, including one of quantum gravity. This, in my eyes, is a sensible prediction for and possible quantum theory of gravity.

In fact, most theorems and things like Maxwell's equations/Newtonian gravity can be derived from quantum field theory and general relativity, and thus the phenomena we see every day are just large scale limits of these two theories.

Here, my point of view is that as thermodynamics etc. are just generalizations of QFT, the quantum theories are valid to be applied in large scales. We are, in fact, wave functions. Albeit heavily localized decoherent ones, that is why we do not notice quantum phenomena in our every day lives (Well, some).

I agree that extending these to something like consciousness is far from proper science, call it pseudo-science if you wish. But we are here to speculate on one of the biggest mysteries in life, anyway

Perhaps we can agree to the following points?

a) In fact, we CAN measure things in the past. And it has been done experimentally. It is called a quantum eraser.
en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

b) Thermodynamic laws can be derived from quantum mechanics and statistics alone.
en.wikipedia.org/wiki/Quantum_statistical_mechanics

c) If there is such a thing as a quantum gravity theory, then everything should only be quantum mechanics at a large scale.

I fully agree that the concept of time travel is something that would violate a lot of physical expectations. A past subject to quantum uncertainties, however, would allow for time travel, as any paradox appearing would just result in a zero likelihood.

Then, the way time travel would be viewed is: Time and space are one, and you are traveling along a time-like curve on spacetime. You have a clock with you that gives you your "eigentime", i.e. the time you as an observer measure to pass.
However, the world is not just a set of four dimensional points. You, on your timeline, have also something that is an additional variable, i.e. your measurement of the world. Going back into the past (the same point in space time) occurs, according to your measurement, later than when you were there before.
On going back, there however is a different measurement of the world. You are back on the same point in spacetime, yet you measure a different world, namely one where you have travlled back in time.

[Eonwind]

Eonwind, the whole laws of thermodynamics are derived from quantum statistics. Well, they were there before quantum mechanics, but these days one can derive the laws from quantum mechanics and statistics. The second law of thermodynamics is implied by unitarity of the quantum theory, thus whenever you have a unitary theory, the second law of thermodynamics holds.

You're saying one thing and its contrary... the fact the thermodynamic laws can be derived from quantum mechanics, means they are coherent theories. My concern about the 2nd law is that a better understanding especially regarding relativity (and QED don't matter anything) may break the "symmetry" or equality between the space and time coords. I'm just speculating.

a) In fact, we CAN measure things in the past. And it has been done experimentally. It is called a quantum eraser.
en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

excuse me but where does it exactly say the measure are done in the past??

On the contrary here say http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser#Does_delayed_choice_violate_causality.3F causality is not violated, which basically means chances to violate time sequence through quantum means are still science-fiction.
so speaking about this:

Then, the way time travel would be viewed is: Time and space are one, and you are traveling along a time-like curve on spacetime. You have a clock with you that gives you your "eigentime", i.e. the time you as an observer measure to pass.
However, the world is not just a set of four dimensional points. You, on your timeline, have also something that is an additional variable, i.e. your measurement of the world. Going back into the past (the same point in space time) occurs, according to your measurement, later than when you were there before.
On going back, there however is a different measurement of the world. You are back on the same point in spacetime, yet you measure a different world, namely one where you have travlled back in time.

my speculation is nothing of the above is possible without introducing more dimensions, in fact I think there may be more than a single time dimension where quantum phenomenon may exist at the same time in different time dimensions (sort of time "parallel" universe) but going back in your actual "time line" would still be impossible.

So in the end, going back to philosophy: you're doomed to stick to the choices you made in the past and live with it, no matter what you can only change the future and the science can't say this it's wrong; on the contrary all the experimental data from physic, to archeology to geology are coherent in telling us time travel in the past is still unheard of, and unlikely to be possible.

I agree that extending these to something like consciousness is far from proper science, call it pseudo-science if you wish. But we are here to speculate on one of the biggest mysteries in life, anyway

Feel free to speculate, but sorry I have fun when science is kicked in a discussion where it can barely say anything about. I repeat this is the field of philosophy not science, it's very funny (and honestly not very constructive imo) trying to use a tool (because I repeat science is a method, a tool) not fit for the use it's used for.

[Donari Tyndale]

Eonwind, the whole laws of thermodynamics are derived from quantum statistics. Well, they were there before quantum mechanics, but these days one can derive the laws from quantum mechanics and statistics. The second law of thermodynamics is implied by unitarity of the quantum theory, thus whenever you have a unitary theory, the second law of thermodynamics holds.

You're saying one thing and its contrary... the fact the thermodynamic laws can be derived from quantum mechanics, means they are coherent theories. My concern about the 2nd law is that a better understanding especially regarding relativity (and QED don't matter anything) may break the "symmetry" or equality between the space and time coords. I'm just speculating.

A speculation it is. The mainstream view is that relativity can be incorporated into a theory of quantum gravity, though. I tend to adhere to the mainstream in this regard. Also, note that there is relativistic thermodynamics, i.e. you can reproduce thermodynamics of relativistic systems by relativity and quantum mechanics. Thus, relativity and quantum mechanics are consistent.
The symmetry between space and time are broken by the fact that all masses are real and energy is positive. Thus, the particles can only move in their lightcone.

a) In fact, we CAN measure things in the past. And it has been done experimentally. It is called a quantum eraser.
en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

excuse me but where does it exactly say the measure are done in the past??

On the contrary here say http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser#Does_delayed_choice_violate_causality.3F causality is not violated, which basically means chances to violate time sequence through quantum means are still science-fiction.

You do not seem to understand the setup of the experiment and causality. Take a look at the sections above in the article.

The setup is essentially two entangled photons going through a double slit. One is detected at some time, the other one is detected at a later moment. Depending on whether you choose to measure which path the the second photon took or not, you influence the outcome of the detection that has already taken place.

Yet this does not violate causality as the information from the first photon can only be extracted after the second photon has arrived, there is no faster than light or backwards time transfer of information. Which is just what causality states:
Information can only be relayed in a forward light cone, not faster than light, not backwards in time.

my speculation is nothing of the above is possible without introducing more dimensions, in fact I think there may be more than a single time dimension where quantum phenomenon may exist at the same time in different time dimensions (sort of time "parallel" universe) but going back in your actual "time line" would still be impossible.

Agreed, I am myself quite open to the option of multiple time dimensions.

So in the end, going back to philosophy: you're doomed to stick to the choices you made in the past and live with it, no matter what you can only change the future and the science can't say this it's wrong; on the contrary all the experimental data from physic, to archeology to geology are coherent in telling us time travel in the past is still unheard of, and unlikely to be possible.

It just means that the possibilities of violating reality are tiny, just as the possibility of all your atoms simultaneously tunneling through a doorway. That too is something unheard of.

Feel free to speculate, but sorry I have fun when science is kicked in a discussion where it can barely say anything about. I repeat this is the field of philosophy not science, it's very funny (and honestly not very constructive imo) trying to use a tool (because I repeat science is a method, a tool) not fit for the use it's used for.

Philosophy and science go hand in hand. Without philosophy, you're not able to come up with new ideas and principles in science.

[Donari Tyndale]

I think I finally know where we disagree but really talking about two different things. I agree that thermodynamics, the behaviour of an ensemble of quantum objects, has increasing entropy. On very tiny timescales, entropy may decrease, but in average and over timescales relevant to us, the chances of that happening are near zero and utterly negligible.
 
My point was that it is possible that the universe did not exist until just now and you just now observing it, which is pure speculation and just an amusing thought. In observing it, you would have also observed a past that conforms to the rules of quantum mechanics and thus thermodynamics.

However, if quantum field theory, the current standard model, holds, your observation is invariably subject to quantum fluctuations, the past as well. You can not give a time-energy graph of anything, that is just Heisenberg. Just as well as you can't give a position-momentum graph.

[Volki]

[Eonwind]

You do not seem to understand the setup of the experiment and causality. Take a look at the sections above in the article.

The setup is essentially two entangled photons going through a double slit. One is detected at some time, the other one is detected at a later moment. Depending on whether you choose to measure which path the the second photon took or not, you influence the outcome of the detection that has already taken place.

Yet this does not violate causality as the information from the first photon can only be extracted after the second photon has arrived, there is no faster than light or backwards time transfer of information. Which is just what causality states:
Information can only be relayed in a forward light cone, not faster than light, not backwards in time.

The article is still saying nothing about measure done in the past, and for a good reason... I think you're misunderstanding the experiment results. A measure done in the past would be able to backward change an event happened, and it says (and you say) it's not the case. Also note that it would violate causality.

My point was that it is possible that the universe did not exist until just now and you just now observing it, which is pure speculation and just an amusing thought. In observing it, you would have also observed a past that conforms to the rules of quantum mechanics and thus thermodynamics.

And my point is this is just not possible until the violation of causality will be proved to be possible. But right now it's not.

Philosophy and science go hand in hand. Without philosophy, you're not able to come up with new ideas and principles in science.

Can be true but it's not a bi-univocal relationship, philosophy has (by design) a greater domain than science and while some scientific facts can be use to strengthen a philosophic theory, science is useless or harmful when thrown at some concepts like consciousness where it can really say nothing about.

[Donari Tyndale]

The experiment is all about influencing the result of the measurement that already happened. That's why there is an article. It does also state that this is just what happens in the experiment, yet causality is something different. You can only cause the observed phenomena once you have the measurement from both photons, you need to wait for the second result to come in even though the first result is already there. That is why causality is preserved.
You can not change the past, however. The measurement from the first photon stays the same.

[MishkaL1138]

[bilbous]

We are stardust
Billion year old carbon
We are golden
Caught in the devil's bargain
And we've got to get ourselves
Back to the garden
Songwriters: MITCHELL, JONI

[Pierre]

Full stop.    Joni Joni Joni...we are the hexagrams of the heavens, the strings of a guitar...

https://www.youtube.com/watch?v=gcTDoi9JQiY