Causal loops in quantum theory is a subject pretty close to my heart. That said, I would approach it bottom-up, rather from this cosmological standpoint. The bit I take issue with is:

That reasoning boils down to two propositions: the first is that all events must have causes; the second is that only in closed causal chains do all events have causes.

Out universe as we best understand it can support an infinite regression of causes. If you imagine running the universe in reverse -- a unireverse, you might say -- it looks (and is mathematically described as) something like a humongous black hole.

Just as anything falling into a black hole falls forever from its point of view (ignoring death and spaghettification), anything falling back in time to the big bang could also fall forever.

And since time began at the big bang, there is no need to terminate this outside of that freefalling frame. Causality only applies inside a timeline.

The transactional interpretation of quantum mechanics though does have causal loops, an idea entertained in quantum theory since Feynman's QED. In the latter, the creation and subsequent annihilation of short-lived pairs of particles and antiparticles looks like one particle stuck in a temporal loop forever, emitting energy to change its temporal direction.

In transactional QM, the complex conjugate of a wavefunction is (mathematically validly) interpreted as the wavefunction moving backwards in time. For instance, an electron fired from a cathode arrives at a point on an anode. In the forward part of the loop, the electron wavefunction might have spread to many points on the anode. It is only when part of the anode sends a positron backward in time, essentially saying 'Yes, I have a place for you' that the wavefunction becomes real along the trajectories between the cathode and the receiving point on the anode.

Essentially, information from the anode in the future causes the cathode in the past to send an electron to it. But only because the cathode sent an electron to it: a causal loop!

Speculative or not, still :cool:

There is some Christian female quantum physicist who argues along the line of the Chinese room riddle that an Intelligence must be behind the working of universe. I think matter can have infinite intelligence, so scratch her off the list. A leading nanoscientist said the same at a seminar down the street from me at some church. Again I don't buy it. Who is to say what matter is? Who is to say what it can do. Photographs were once considered impossible.

"Time can't be frozen" they said. Now we have movies lol

"Time can't be frozen" they said. Now we have movies ... — Gregory

I get the joke, but in what way are "movies" time? They aren't even clocks.

Were a medieval who had never seen photos to watch a movie, it would alter his reality forever. We do this now with digital technology and there is no way to determine if there could be a limit to matter and energy (energy being a vibration)

Speculative or not, still :cool: — 180 Proof

Oh yeah, it's not a popular interpretation of QM.

Just as anything falling into a black hole falls forever from its point of view (ignoring death and spaghettification), anything falling back in time to the big bang could also fall forever.

I'm not entirely sure that's true -- I thought that's just a mathematical artifact from relativity which doesn't necessarily apply to reality. Isn't this why relativity and QM cannot be reconciled -- since relativity breaks down at the smallest scales into infinities? I could be wrong, but that's how I understand it.

The transactional interpretation is certainly interesting! Need to read up more on that.

I'm not entirely sure that's true -- I thought that's just a mathematical artifact from relativity which doesn't necessarily apply to reality. — ChrisM

Well, it's a cosmological model. The whole field is a little sketchy. But on the other hand it might be true, and the possibility must be accounted for. The model is certainly reasonable, and the notion that time itself started with the big bang uncontroversial.

Isn't this why relativity and QM cannot be reconciled -- since relativity breaks down at the smallest scales into infinities? — ChrisM

Not for that reason, although you're right that QM can't handle singularities. But the infinities appear generally in quantum field theories of gravity, except string theory. There are other, probably better, approaches, such as generalising existing quantum field theories to curved spacetimes. It's hard math and slow-going, or used to be anyway.

There really is only one conclusion in thinking on infinite causality. In the end, the inception of the universe is a first cause, and has no reason for its being.

Take two options. Finite causality versus infinite causality. Finite causality means there is something in the beginning of it all that does not have a prior cause. In detail, this means it is not necessarily dependent on something prior for its existence. It simply...is. No reason, no rhyme, no limitations as to what it could have been.

If we look at infinite causality, there is still one question of cause left. Why does infinite causality exist over finite causality? There is no causal answer to that question besides the fact that it simply...is.

Meaning the infinite causality versus finite causality question is a false dichotomy (Love that phrase).
The reason for our universe's ultimate existence is the fact that it simply is. And if it simply is, there is no rule or necessitation of how exactly it had to have come about, or continues to exist.

In short, we can conclude absolutely nothing about the necessity or nature of our universe from looking at causality, because we reach a point in which there are no rules of prior necessitation, only the unyielding result of the existence that is there.

I disagree. If it were a loop then those who engineered the loop would've left clues, hints, on how to stabilize the universe in order to prevent having to go back to square one over and over again unless...that's an impossibility.

Did you read the article? That very topic is talked about.

Did you read the article? That very topic is talked about. — ChrisM

If I were part of the team that recycled the universe in the sense managed to reset the entropy level back to a lower level like in a Big Bang singularity, I would've asked for clues to be revealed once intelligence in the universe evolved to a level capable of handling the probably complex science involved in making some headway, some real progress, toward stabilizing the universe to prevent ensuant heat death. Is the 21st century, 13.8 billion years from the Big Bang singularity, the best time to look for cosmic clues to the riddle of entropy? Your guess is as good as mine.

You're assuming that a causeless cause is possible, simply on the basis that anything exists -- this does nothing to refute the claim that all events must have causes, thus that the universe must be a causal loop.

The fact that anything exists still follows a causal loop model, where causal loops as a whole are not create and do not have a first cause - they simply exist. But causality still obeys a logical consistency within the loop (i.e. no event without a cause). So the fact that anything exists cannot necessarily be attributed to a causeless cause as you suggest, and shows that there's still an important distinction to be made between infinite vs finite causality that cannot be waived off as a false dichotomy.

So what you may view as a causeless cause is what I view as the causal loop as a whole -- which is above causality itself.

I would've asked for clues to be revealed once intelligence in the universe evolved to a level capable of handling the probably complex science involved in making some headway — TheMadFool

I totally agree with you, and I also agree that we might not even be far enough along to be able to grasp the clues, if any, that may have been left for us. But its fun to think about and I don't think it rules them out -- maybe we'll come to decipher a code left in our DNA, like the article suggests.

You're assuming that a causeless cause is possible, simply based on the basis that anything exists -- this does nothing to refute the claim that all events must have causes, thus that the universe must be a causal loop.

The fact that anything exists still follows a causal loop model, where causal loops as a whole are not create and do not have a first cause - they simply exist. But causality still obeys a logical consistency within the loop (i.e. no event without a cause) — ChrisM

No, a causeless cause is the only logical conclusion. It is logically impossible for there not to be a causeless cause, even within the idea of a causal loop. That is because there is still the question, "Why is there a causal loop, instead of there not being a causal loop?" The answer cannot be found inside the loop, except for the fact it exists. There is no prior explanation as to why it exists, therefore it is a causeless cause.

Certainly causality is obeyed within the loop itself, or even within finite causality itself, but the only way to find the causality within that loop, is to observe it directly. We can conclude nothing greater about the universe whether there is a loop, or is not a loop.

One aspect I did not point out is that since a first cause has no prior reasoning for its existence (in this case, the infinite loop), it is not necessary that there be an infinite loop, or a finite regress. The only way we could determine it is if we reached that particular end. As we logically cannot tell whether we have an infinitely regressive loop, or we just haven't reached the logical end yet, we can just as easily claim there is an infinite loop as there is a finite end.

But we can logically conclude that there absolutely must be a "first cause" in some aspect. Feel free to propose a counter to this idea.

I totally agree with you, and I also agree that we might not even be far enough along to be able to grasp the clues, if any, that may have been left for us. But its fun to think about and I don't think it rules them out -- maybe we'll come to decipher a code left in our DNA, like the article suggests. — ChrisM

Excellent detective work! Where better to plant the clues than on the detective's own person. The DNA code is quaternary (base four) - the four dimensions of spacetime? I wonder what special/general relativity has to say about the Big Bang singularity? Gravity seems to be the "force" that initiates nuclear fusion in stars, it causes planet formation, it's also behind galaxy formation. To add there are four fundamental forces: 1. Gravity, 2. Strong Interaction, 3. Weak Interaction, and 4. Electromagnetism. I wonder... :chin:

No, a causeless cause is the only logical conclusion. It is logically impossible for there not to be a causeless cause, even within the idea of a causal loop. That is because there is still the question, "Why is there a causal loop, instead of there not being a causal loop?" The answer cannot be found inside the loop, except for the fact it exists. There is no prior explanation as to why it exists, therefore it is a causeless cause. — Philosophim

Sometimes there are just brute facts. Why are you you instead of me? It's just the way it is. In logic, there cannot be complete relativism. There has to be the over arching truth the everything besides the arch, is relative. This doesn't apply to the universe though. Causes can simply go back in time forever with no end.

Causes can simply go back in time forever with no end. — Gregory

So what is the cause for why that is? Why can it go back forever instead of their being a first cause?

Because it simply is. There is no explanation for its being. You cannot escape the fact that there is something that has no cause besides the fact of its existence. Feel free to try.

There could be a beginning, or there could not. Gravity, friction, and other principles govern it. How is not why. I don't care for the "why is there something rather than nothing". The answer could be because 1 is greater than zero, and loving life is better than nonexistent. There is no need to go into divine realms for an answer

There is no need to go into divine realms for an answer — Gregory

I never said anything about divine realms. This is not religious, its simply logic. There is inevitably an uncaused cause. It could be the big bang, a God, or something completely unknown. Because a first cause is bound by no rules, if we do not know what it is, anything could be possible.

But that is the only thing we can conclude. We can conclude the specifics, or some natural law of the universe from it.

The

It's sounds like Schopenhauer, your last post that is. Interesting idea. Does uncaused cause come from nothing. And can nothing be a power?

Does uncaused cause come from nothing. And can nothing be a power? — Gregory

No. An uncaused cause does not "come" or is "caused" by nothing, or anything. It has no prior explanation for its being. It is quite literally, magic that we logically conclude must be real.

It can take time to wrap your head around what that means, it did for me anyway.

Nothingness for me is Yin

Is cosmology vertical or horizontal for you generally

I don't ascribe to taoism or buddhism. Nothing against yourself if you do. =) Whatever you read in an astronomy text book is my view of the universe.

we reach a point in which there are no rules of prior necessitation, only the unyielding result of the existence that is there. — Philosophim

Good conclusion, for there is no alternative to 'what is', such as a lack of anything, and it's doubly shown since there is not only something but also that any supposed 'it' of 'Nothingness' has no productive means (or it would be something and not 'Nothing.)

We can then go on to say that 'what is' is eternal in the sense that it cannot have a beginning or an end, making it to be unbreakable and unmakeable, deathless and ungenerated, etc.

Thus, we can then know that it must be here all at once, partless, continuous, and all the same, plus always only itself, which still goes if there are several such fundamental 'its'.

So, then, we look about us at what's suggested, finding what fully qualifies is:

On What ‘IS’

(Particles as excitations of fields)

An Eternal Basis has to be so,
For a lack of anything cannot sow,
Forcing there to be something permanent,
As partless, from which composites can grow.

There can’t be other directions given,
To that which no start; it is undriven;
So, it is as Everything possible,
Either as linear or exists at once.

Consider quantum fields of waves atop
One another: waves are continuous,
And so qualifiy as Fundamental;
Quantized lumps are particles, then more.

The particles, etc., are temporary;
The Basis is coterminal with stuff,
But is not cosubstantial with the things;
Its information content is the same as Null!

Note that there is no other absolute:
Newton’s fixed space and time got Einstein’s boot;
Particle spigots making fields are mute;
Classic fields have no fundamental loot.

Further

There are no ‘if nots’ for happened events;
That would be a fantasy world but meant
For simulations and playing mind games;
No use entertaining real replacements.

I sometimes consider poetry to be a form of philosophy. Didn't Shiller say there is more wisdom in children books than philosophy books? And I think Freud said psychology is always one step ahead of philosophy. Then there is physics. Is theoretical physics just philosophy because it doesn't deal with experiments directly? All these ideas can be very perplexing

Didn't Shiller say there is more wisdom in children books than philosophy books? — Gregory

Did he say it in a children's book?

Nah. Even if it was the case, what is the origin of the loop? I mean, an loop can't generate itself out of nowhere, even less so an entire universe.