Quantum idea where the present influences the past gains some theoretical support

Keep in mind these are only philosophical interpretations. As far as science goes right now, there's no way to prove or disprove them. Wave functions never really "collapse", they just become entangled, and once their wave function becomes entangled they manifest a different wave function relative to what they have become entangled with. Meaning the particle would not be where it was before because it is entangled. Keep in mind two particles don't actually have to physically interact for them to become entangled; their wave functions could simply overlap. For example, that double slit experiment, you could alter the outcome probabilities even if you observed a photon that wasn't there (you observed that particular photon of light didn't take that path). And physical interaction doesn't necessarily break entanglement, for example, a photon of light can still be temporarily caught up in the electronic structure of a transparent medium while still maintaining its superposition. (The medium actually slows the light down)

 

Interesting! So the concept of collapse is gone altogether?

The concept of collapse has been around for almost 100 years now!

Yes, I am familiar with some of the experiments to this effect. It just keeps getting stranger and stranger.

I assume another manifestation of this is found in anti-reflective surfaces? The photon passes through and doesn't reflect because in the alternate reflected path, it would interfere destructively with another photon, and energy would not be conserved. I remember a Chinese professor trying to argue this was purely statistical. He didn't like the spooky stuff. But the way I read it, it would apply to even two photons.

 

Yes

Well then the professor would need to explain what causes those statistics. It would still apply to one photon or two.

I've always found that particularly interesting, that even just a single photon by itself would bounce perfectly off a reflective surface, instead of being scattered off in some random direction. It is because the wave nature still applies, even if it's only a single particle. That particle is interacting with itself! Or rather, to be more precise, different parts of that particle's wave function in two different places are having interaction among themselves, ultimately guiding that point-like particle where it should go. The double slit experiment still works with only a single photon, experiments have been done to verify this. It's the same with a photon traversing through a transparent medium. By conventional understandings one might expect it to be scattered (because at different intervals there is transient absorbance by the electronic structure, this is what slows down the speed of light).

But again, the wave function doesn't really carry any mass. It's more like how the particle would have behaved if it had gone in that direction.

 

Yes! A single photon. I should have said that. Fun stuff!

The reason I studied physics instead of engineering was that it never disappoints. About the time the universe seems to make sense, reality comes along and slaps you upside the head.

 

Is any agreement emerging on what causes entanglement for the observer - what is the physical interaction that constitutes an observation? I know for a time there was a popular model that assumed gravitational interactions were responsible. By introducing even minute gravitational forces, say due to a photon, the wave function for that observed, "collapsed".

 

I don't know much about entanglement other than it links the particles, so I can't describe it.

But about the wave function collapse, yes, it appears that gravity, in addition to observations, collapses it. Observation isn't the only thing that collapses it, it's just the most well known and odd thing about it.

 

This is not for me intuitive? If the present can effect the past, and the past can effect the present and the future, then everything all the time will be ants in the pants!

Isn't a magnetic field storage for energy?

 

In physics, a virtual particle is a transient fluctuation that exhibits some of the characteristics of an ordinary particle, but whose existence is limited by the uncertainty principle. The concept of virtual particles arises in perturbation theory of quantum field theory where interactions between ordinary particles are described in terms of exchanges of virtual particles. Any process involving virtual particles admits a schematic representation known as a Feynman diagram, in which virtual particles are represented by internal lines.[1][2]

Virtual particles do not necessarily carry the same mass as the corresponding real particle, although they always conserve energy and momentum. The longer the virtual particle exists, the closer its characteristics come to those of ordinary particles. They are important in the physics of many processes, including particle scattering and Casimir forces. In quantum field theory, even classical forces—such as the electromagnetic repulsion or attraction between two charges—can be thought of as due to the exchange of many virtual photons between the charges.

The term is somewhat loose and vaguely defined, in that it refers to the view that the world is made up of "real particles": it is not; rather, "real particles" are better understood to be excitations of the underlying quantum fields. Virtual particles are also excitations of the underlying fields, but are "temporary" in the sense that they appear in calculations of interactions, but never as asymptotic states or indices to the scattering matrix. The accuracy and use of virtual particles in calculations is firmly established, but as they cannot be detected in experiments, deciding how to precisely describe them is a topic of debate.
https://en.wikipedia.org/wiki/Virtual_particle

Note that while a photon has no rest mass, they do have a mass due to the energy of the photon - E = MC^2 = hv [planks constant times the frequency]. This energy is the electromagnetic energy.

 

You have to throw out your understanding of cause and effect. The past and future are correlated to each other in wierd ways. The order of everything may seem random to us, in any given frame of time, but it is as if everything was ordered so the past would be compatible with events in the future.

So rather than everything being crazy, it's actually another degree of order. Things aren't as random as they seem.

 

Basically entanglement results when the wave functions for the two particles overlap. They could have overlapped in the past, or will overlap in the future. Regardless, the two particles are now entangled.

Entanglement isn't something that is or is not, there are different degrees of entanglement.

"Observation" implies whether any physical information could theoretically be extracted to determine something definite about the particle. We may know it's wave function, but that still does not tell us exactly where or what that particle is doing inside the bounds of its wave function. Basically an observation is made when the particle becomes entangled with the outside world. If you take a closed system, it is as if information will eventually leak out to everything around it.

If hypothetically everything in the universe was simultaneously and completely fully entangled with itself, all particles would behave point-like and manifest no wave-like nature. (This is not the case though)

Entanglement usually is used to refer to the fact that unknown information in one particle is linked to information in another particle. But so far the two particles behave like a closed system and this information is not yet known outside of this system of two particles. It doesn't matter where these two particles are in space and time, they are still entangled. But if the information from one particle "leaks out" of the system, both particles will stop behaving as waves.

This is probably not an "effect" but has to do with the fundamental design of the existence of these particles across time. Predetermination, if you want to use that word.

We talk about "information" and "observation", but on the most basic level it really has nothing to do with that. It's wave mechanics, existing in four dimensions across time. As if the wave-like strings settled in the most comfortable places, and now their courses are fixed. To understand where a particle will be, you have to understand the mathematics of its wave trajectories, all of the potential possibilities.

We don't really know for certain whether there is really quantum randomness, or whether we are just not able to see a detailed enough picture and so things just seem random, with the imprecise information we have. Einstein was reluctant to believe God would "play dice with the universe", but a lot of quantum phenemena seem completely random, with a distinct set of possibilities. Which possibility will manifest is intimately connected to the wave function.

Something very wierd with neutrinos, if they have enough energy they can seem to oscillate between 3 different neutrino varieties. But of course, they never really change in reality. Currently held theory is that the event that led to the neutrino sends out three different wave functions, and then these wave functions interfere with each other along the trajectory of the neutrino. The probability of finding a certain type of neutrino depends on exactly how far along the trajectory you are. In other words, the event that created the neutrino in the first place knew exactly how far it would be until the neutrino would get intercepted in another interaction. Even though that second interaction may be millions of kilometers away.

Wave functions never really "collapse", they just seem to when you become entangled with the particle in question.

I personally suspect it may be possible to observe a particle without collapsing it's wave function, and that it might just be a matter of technological difficulty. The "information" paradigm may not really be correct. What a wave does need is a possibility of doing something, without that possible pathway being interferred with too much. Typically when we "detect" something we stop it, or drastically interfere with its course. It's hard to detect a subatomic particle without substantially bumping it off course or entangling it to a great extent.

 

Maybe I should say that entanglement is when something about one particle is conditional on something else in another particle, but where different "possibilities" of reality exist that haven't been narrowed down yet (such as we would expect if the enclosed system here got entangled with the outside). Once there's a connection to the outside, it's real easy for the "information" to leak out, which will make the possibilities have to conform to a more certain fixed reality outside. Because in the quantum world, even possibilities that don't exist end up "having an effect" on how particles will behave.

If I can use this bizzarre analogy, it would be like 3 open doors in a wall, and everyone who goes through (into the other room) inexplicably, by a bizzarre coincidence of chance, always goes through one of the doors, all of them the same door. But when you close and lock one of the doors, one of the two that people weren't going through, then everyone goes through the other two doors with equal probability.

It's because two of the probabilities interferred with each other, which ends up reinforcing the third possibility.

 

Okay, but something is still required to entangle me with something else. Now I know that everything is entangled with everything else and has been since the big bang. But if I don't make some kind of measurement, how can I become uniquely entangled? The debate about what constitutes an observation in QM has been ongoing for almost a century.

Planck addressed that one. We know the minimum interference possible unless we can figure out something less invasive than a photon.

Humorous note: Have you ever considered that if you walk through a doorway slowly enough at very low temperatures, you will diffract? [Ignoring that you would be frozen solid ]

 

You do realize interference patterns still appear even if both beams are directed with mirrors, right? Do you think that would still work with one photon at a time?
If so, you have a problem, because a slight amount of momentum is imparted on the mirror.

Too small for us to practically measure, but we know it is there, so theoretically the information should be able to be extracted.

Well they did diffraction with bucky balls, so I suppose anything is possible.
http://physicsworld.com/cws/article...-particle-duality-seen-in-carbon-60-molecules

 

Well thanks for this information which has turned my brain to mush. I have read about virtual particles and they don't exist and are more of a tool to allow mathematical calculations about the interactions between particles. And I get this because we only know what we know at this moment and today we require the fabrication of virtual particles to assist in calculations. But I don't see how virtual particles can provide any evidence that the present influences the past? Intuitively if the present can effect the past, and the past effects the present and the future, then we will have constant chaos...I could name it a 'chaos loop'! How could this ever be mathematically calculated...

 

How can we ignore cause and effect? If the present and the past are influencing each other it seems to me a constant state of chaos.

 

Well it depends on your perspective. One main line of thought is that they do exist, but only for a very short span of time because they are temporarily borrowing energy from the vacuum. "Empty space" may not actually be empty at all but could constitute a tremendous amount of energy. This form of energy is very poorly understood, but it constantly keeps swishing around into different forms, which is why sometimes particle and anti-particle pairs will appear out of nowhere.

(A different theory, held by a smaller minority of physicists, holds that the transient appearance of two particles constitutes a loop in time, with the anti-particle being the part of the loop going backwards)

Again, depends on your perspective, doesn't it?

I know it's really hard to think about things from this perspective, but imagine for a moment there is no cause and effect. Everything just exists in time.

Or imagine the present and past both influencing each other but they are doing it in perfect harmony with no conflict. Or maybe you could imagine that they have reached a sort of equilibrium, where the future has an equal effect on the past, and both put pressure on the present. In an equilibrium system, things will adjust until they reach an equilibrium point, until two opposing forces balance.

 

Well it doesn't (not directly anyway). That only got discussed because HereWeGoAgain brought up something else.

Maybe there's no paradox, it's just a loop.
You only assume it would result in a paradox because you think everything that exists right now was only decided by the past and not the future.

Actually these types of things can create some huge calculation problems for theorists trying to accurately model these particle interactions.

You shouldn't feel bad about it, these things can be extremely difficult to understand. Probably many PhDs that try to specialize in the topic do not really have a completely perfect grasp of it either.

I can try to summarize the original article for you as simply as possible. The idea that the present may influence the past is not at all surprising for those already familiar with how things work on the quantum scale. Some extreme ideas are needed in order to explain the results of experiments.

Let me point out again that none of this is "proven". These are only attempts to come up with explanations for the strange things observed in experiments. Basically everyone agrees on the results of the experiments, but there are several different schools of thought on what the interpretation of those observations should be. If you take away all the speculative philosophy, all that's left is mathematical equations.

 

I sense that virtual particles can only exist within the mathematical calculations which depend on them? It's simple to also say 'another line of thought' is that they don't exist.

How can a vacuum provide anything...energy? If a vacuum has something in it (other than a few H-atoms) then how can it be a vacuum? We know about gravity being omnipresent, and we know about magnetic fields, and the energy from the BB, and I suppose either or all could be the stuff in empty space? But now you add virtual particles? Dark energy...dark matter? Maybe it's not energy...it's just glue? It must drive scientists ape-crazy not being able to test a hypothesis!

I can 'imagine' no cause and effect but I know for sure that I can effect the future with my present actions. Therefore my past actions effect my present and future. Regarding 'time', I've thought about someone on a space ship that has exited Earth's reach and another person asks 'what time is it?'. The only 'time' these people understand is Earth time but Earth time no longer exists...so the answer to the question is 'I don't know?'. And, it doesn't make much difference anymore on their travels...it's as if time does not exist. It will exist on the space ship when someone asks 'how long until dinner?' but will be meaningless to everyone else in the Universe. Since all that we know did not happen instantaneously, we 'think' that there's been about 13.7 billion years of 'time', and all of this time originated at the BB and has been traveling in one direction since then. It seems odd to me that in this scenario that the present can effect the past...

 

Regarding the present, my actions in the past created my present. Surely there were external actions that also influenced by present. In order to assume a future exists we must guess what lies beyond this moment? Is there just infinite time in front of us waiting to be filled by our present, or, is there already stuff in the future that can effect our past? If there is 'something' already existing in the future, why would it need to effect our past? Why doesn't the concept of linear one-way time work?

Since Earth is only 4.5 billion years old and the Universe is 13.7 billion years old, obviously there must be about 9.2 billion years of time ahead of us. But what lies beyond 13.7 billion years? If there is no more time, and no future beyond that point, how will the past be effected...

 

It seems to me that someone would first offer proof that the past exists. I have never seen any proof of this. In order for the future to affect the past there has to be a future and a past.

 

I can see how you might think that way, but actually that is kind of irrelevant. We know for a fact that the past "affects" the future (if you want to phrase it like that). That's not in question.
What the article is saying here is that the future affects the present. That experimental results are affected by events yet to take place.
So you see, whether the past exists or not isn't really of any consequence here (at least not directly).

 

May be that I am thick headed. You must also prove that the future exists. Is this not a claim that events travel in time?

 

The equations that describe the experimental observations seem to imply that the future exists. Although I suppose there are other possible explanations.
There are some strange things going on, and you need to accept some strange things to make sense out of what scientists are observing. For example, for a long time most quantum physicists suspected there must be some sort of faster than light speed dispersal of information. That was the only way they could understand how the wave functions of two particles could collapse simultaneously so far away from each other. (You can look up "spooky action at a distance" to learn more information about this perspective) Today most physicists are moving away from that type of understanding.

Basically, in the experiments, here's what they're observing:
Take two particles that arose out of the same process, or have certain characteristic properties that arose out the same process. We don't immediately know what they are, but we know the characteristic properties of the two particles have to balance out. Therefore, if we know something about one particle, we automatically know something about the other particle, even if we haven't measured it. Here's the very strange thing. If they intercept one of these particles, the other particle stops behaving like a wave (or at least stops displaying wave-like characteristics in certain ways) statistically. The particle can be manipulated without giving up its ambiguous properties, but if affected to too great extent (which would cause it to give up its unique characteristic properties) then the other particle that wasn't affected to this greater extent suddenly has a fixed property, and doesn't behave like a wave statistically (when it's manipulated in the less invasive process). So it almost seems as if one particle is "telling" the other particle what to do.

The idea is that when the wave function of one particle "collapses", when it is forced to choose where exactly it has to be, that also causes the collapse of the other particle, no matter how far away that other particle is at the time. Obviously when we measure a particle, we don't directly see it as a wave, we see it as a point-like object. So when we measure a particle, the property we're measuring can't be ambiguous anymore.

In the realm of wave-like nature, different possibilities cancel each other out and interact with each other. When the particle loses its ambiguity, those different possibilities stop existing. The particle will then behave differently when put through certain processes (or to be more exact it will have a different statistical probability of how it will behave).

Here's a list of the type of experiments they have been running:
https://en.wikipedia.org/wiki/Bell_test_experiments

Now it's true that not every quantum physicist accepts the idea of the future affecting the past, but for those that don't, most of them have to accept the faster than light speed transmission of information explanation. When faced with that type of a choice, the first really isn't that unbelievable of a theory.

 

The only thing I am reasonably sure of is the present. I do not, and never have, experienced the past or the future. And even if I could travel to the past or future... it would still be the present. Relative to me.