# Retrocausality (Reverse Causality): Today Effects the Past

## Quantum Mechanics Issues: retrocausality

## Retrocausality, Time Travel, and Quantum Physics

**Birth, Live, Die = Here and Now - Past, Present and Future = Now **

The notion of causality has long been associated with the concept of an arrow of time: the effect of an event can only be felt after the event, that is, a cause precedes its effect. In a retrorocket situation, the effects of an event are felt before the event.

The implication hinges upon the idea of “retro-causality,” also called “backward causation” or “backward causality.” Advanced physics experiments might suggest that observations made in the present exist in a kind of causal loop with the past. That is, how we look at things at Time **B** has an effect on a previous Time **A**, which then flows back into Time **B**.

Such are the perils of retrocausality, the idea that the present can affect the past, and the future can affect the present. Strange as it sounds, retrocausality is perfectly permissible within the known laws of nature. It has been debated for decades, mostly in the realm of philosophy and quantum physics.

**Quantum Physics: No Obvious Common-Sense**

Richard Feynman, famously noted that a positron behaves exactly like an electron traveling backwards in time. Others have expanded on his observation with very interesting results. Perhaps these particles even go back in time all the way to the big bang, to affect the fundamental nature of our universe.

In quantum mechanics, an advanced wave, which propagates backward in time, has been usually ignored, as they were considered to be unphysical. Nevertheless, in the sciences of life, advanced waves may permit to answer some of the major mysteries and paradoxes.

Retrocausality has also been proposed as a mechanism to explain purported (pseudoscientific?) effects. Most notably, parapsychologist Helmut Schmidt presented quantum mechanical justifications for retrocausality, eventually claiming that experiments had demonstrated the ability to manipulate radioactive decay through retrocausal psychokinesis.

Open topics in physics, especially involving the reconciliation of gravity with quantum physics, suggest that retrocausality may be possible under certain circumstances. Closed timelike curves, in which the world line of an object returns to its origin, arise from some exact solutions to the Einstein field equation. Although closed timelike curves do not appear to exist under normal conditions, extreme environments of space-time, such as a traversable wormhole or the region near certain cosmic strings, may allow their formation, implying a theoretical possibility of retrocausality. (see above geometric shape that curves in on itself)

**Quantum Mechanics Explains the Membranes Holding Universe Together**

· Macro Cosmology (Quantum Mechanic Laws)

· Standard Model (Newton Laws) - Suspect Quantum Mechanics here too…

· Nano (Quantum Physics Laws)

The exotic matter or topological defects required for the creation of those environments have not been observed. In addition to the conventional interpretation of quantum mechanics in terms of states that evolve forwards in time in accord with strong, or strict, causality, the formalism of quantum mechanics also permits an interpretation in terms of retro-evolving states. The formula for calculating probabilities of measurement outcomes in the latter interpretation is mathematically equivalent to that used in the conventional interpretation. Consequently the retro-evolving state interpretation does not change any of the results of experiments predicted by the conventional interpretation, even though the associated retrocausality violates some of the notions of strong causality.

**Related Science Topics of Interest:**

__http://hubpages.com/hub/Microwave-Hyper-Quanta-Faster-Than-Light__

__http://hubpages.com/hub/Macroverse-VS-Microverse__

__http://hubpages.com/hub/The-Concept-of-the-Mind-Directing-Energy-in-Physics-Zero-Point-Energy-Field__

__http://hubpages.com/hub/What-are-Fractals-Why-Important__

**http://hubpages.com/hub/Retrocausality-Reverse-Causality-Today-Effects-the-Past**

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## Comments 43 comments

I almost got it, but then I became confused again! It really seems to me that researchers of quantum just don’t manage to hit the target. It is like trying to put the tail of the pig where it should be while blindfolded. There is a pig, and there is a place for its tail, but – forgive me if I’m wrong – they just don’t manage to get the tail where it belongs. Thanks for another interesting hub about this subject. I know I will get it... someday.

I love that you looked up and read Feynman...

Within this universe, time is an unknown...and yet the theory of Einstein as it applies here is measured only with the speed of light as a basis..

What if there is something that moves faster than the speed of light?

We cannot reverse the linearity of time in this universe...each moment of consciousness being a stamp of time that we can go back to and erase at will.

We have quantum physics, quantum mechanics now because it is what our minds can at least accept...relate to.

A provocative hub.

You might want to look at Alex's last hub. He has a link for a paper..

I like this kind of highly intelligent conversation, it gets my motor going, but I can only say, thank you. :0)

I don't believe it... this reverse causality that is. Sure Feynman used it to great effect to simplify QED, and you can use it to reason about very real things like tunnel diodes, and single-photon double-slit experiments... but I don't think that the logical conclusion that a photon or any massless particle is everywhere at once hold credibility. It's a useful tool mathematically for sure.

If you consider more than 3 dimensions of space, then there are alternative ways to speculate about these results rather than invoking time-loops.

You see, to make a time-loop, you need to cross infinity which is nonsense. Here is the logic behind that:

The energy in a system is given by E = ymc^2 where gamma (y) is 1/(sqrt(1-(v^2)/(c^2))

v is the velocity of an object under study. c is the cosmic speed limit. Any object with intrinsic mass travels at v, where v is less than c and may be accelerated towards c. However, as v approaches c, gamma tends to infinity. This is an asymptomatic approach and there is no way to cross that asymptote. If you did, then it would be like crossing infinity. In the case of a massless particle, c=v and gamma is essentially in an undefined state. This is not equivalent to saying that it is everywhere at once.

Massless particles are assigned energy from their momentum multiplied by c. The only speed a massless particle can travel is c, otherwise it has to be totally absorbed and then re-emitted as one or multiple particles at different energies that sum to the energy of the absorbed photon.

Using extra dimensions, you can postulate that something like a photon (or a small mass like an electron) pops in and out of our world like you would repeatedly thrust a skewer into a loaf of bread. Each time, your aim would be a little off, but each time is has a definite position and the total stabbing escapade would cluster around your desired target. If you were a bread-dwelling being with no knowledge of the outside, and an inability to discriminate individual stabbing entries in space and time (just as HUP states for us), then these stabbings would appear to do weird things. The stabbings could do particle-like stuff, but also be spread over time. Some experiments the bread-dwelling people could do might conclude similar backwards-time results that we toy with in QM.

In the case of the tunnel diode in our world, one treatment of it suggests that an electron leaves before it enters. But a proper QM wave treatment shows that what really happens is the leading edge of the wave (the first few stabbings) bunch up and appear on the other side of an energy barrier before the peak of the arriving wave hits the barrier. This does not require time-loops.

I would love to know about massless particles.

Paradox of Massless Particles. This is truly a spoiler for my Pet Theory. I've contacted Manna to help me learn about it.

My higher education is not science related.

I have a giant imagination and see in my minds-eye particles. I meditate on quantum problems and find answers.

So, these type of topics are only a hobby for me.

The energy of a photon is directly proportional to it's frequency via the formula E=hf where h is planck's constant, E is the energy, and f is the frequency. So if you travel alongside (but slower than) a photon, it appears (to you) to have a lower frequency, and hence a lower energy. If instead you elect to travel at speed ( even have a head on collision), then its frequency is higher (because you meet more peaks per second). When this head-on collision happens, you would smack the photon's frequency to zero - thus absorb its energy and feel a tiny impact like being hit by a tiny bullet. Rest-mass is not in these equations. What I described is relativistic mass, and hinted at the wave-particle duality of a photon. The frequency of that photon is entirely dependent on the observer's frame of reference something like the Doppler effect of a train.

Silly question: If everything was made up of photons would there be any mass?

"In relativity phenomena, gravity, and nuclear dynamics develop naturally in a universe comprised only of light."

My Pet Theory of Everything does not include spacetime, space, or time. That there is no, as it's called, "Fabric of Space."

In fact, light does bend but not because of space-warp. Light (photons) travel in a curvature trajectory, i.e. a single photon has a duality force that result in a photon-wobble. These are not in scientific terms, I know, but this is the ways my imagination sees it. One long-shot at an example is how the particles curve away when protons are collided.

By the way, my appreciation is enormous for your your comments

"Super Relativity Theory" is what's known as pseudoscience. See http://en.wikipedia.org/wiki/Pseudoscience

"In many circumstances, a photon acts as a classical particle (like in a camera). In other circumstances, a photon acts like a wave when passing through the optics in a camera."

Yes yes yes. That is the duality I refer to in my Pet ToV. Those forces or vibrations or energies are all incapsulated within the photon. We are surrounded by photons but we only see with our human eyes those photons that have wobbles that make them visable to us.

Perry, particles that curve away after a collision do so because they have an electric charge and are embedded in a magnetic field. Photons have no electric charge and therefore do not curve like this in a magnetic field.

You right that light does not bend --- but that's if you are working in the coordinate system provided by general relativity. This means, effectively that light travels in a straight line through curved space just as you could travel in a straight line across the globe and pass through both poles. From our viewpoint it looks like the light is bent. Look up gravitational lens to find experimental evidence of this.

Manna, thanks for the help.

Well, my Pseudoscientific-Pop-Sci-Fy Pet ToV. Must seem cartoonish to the knowledgable.

No electric charge in photons. I thought they do have energy.

You stated above, "You right that light does not bend --- but that's if you are working in the coordinate system provided by general relativity. This means, effectively that light travels in a straight line through curved space just as you could travel in a straight line across the globe and pass through both poles. From our viewpoint it looks like the light is bent. Look up gravitational lens to find experimental evidence of this."

Instead, I said, "In fact, light does bend but not because of space-warp. Light (photons) travel in a curvature trajectory,"

Manna , I just keep on learning.

"Perry, particles that curve away after a collision do so because they have an electric charge and are embedded in a magnetic field. Photons have no electric charge and therefore do not curve like this in a magnetic field."

I hope that curve and electrical charge have been measured, tested and retested. I'm sure the magnetic field they are embedded in, is exactly the same or measured for variances. With that information I could begin some calculations to start working through my psuedopopsyfypetToV. If you know who, where, how I could obtain that data I would be very appreciatetive.

I am only guessing in my assessment of collisions that many viewable particles vary in their degrees of trajectory, velocity, color, electrical charge and influenceability to magnetic fields. I've only. I have only viewed several collisions and if my memory serves me right they seem to vary in appearance. Also, I'm confused about the fact that some of particles curve and become invisible.

I know I am confused. Have any scientific theories been tested and proved and maybe become laws that have been proved to be not exactly correct?

Is it possible that the energy in photons might give off an electrical charge? Is it impossible that photon itself has properties within and about itself that would cause its trajectory just a tiny bit off straight?

Just asking and trying to understand.

Via E=mc^2 energy and mass are interchangeable. Photons have energy equal to E=hf and it has nothing to do with electric charge and everything to do with the frequency that the photons are vibrating at. Because they are massless, if you add energy to a photon it cannot speed up. Instead, it has to jiggle faster. If a photon looses energy, then again, because they are massless, they have to jiggle slower. (h is Planck's constant, while f is frequency). By just combining the two formula, hf=mc^2 we get f=(mc^2)/h and since h and c are constants, as f changes, the mass m has to change accordingly. Confused? Isn't this a massless particle? Yes, but the m in this equation is not simply rest mass. It is the combination of rest mass and relativistic mass where the full formula is E^2 = (m_0)^2 c^4 + p^2 c^2 and p in this formula is momentum. A photon has momentum p, but no m_0 (rest mass) so its energy is E=pc. Now we could equate pc=hf and therefore p=hf/c which shows clearly that the momentum p is proportional to the frequency f with a conversion factor of h/c. The units of h/c is m Kg and the units of f is 1/t so the right hand side is mKg/s which reduces to speed times mass and that is indeed the units of momentum.

Intuitively we know that things with momentum impart energy when you smash them into something. Hence a photon has momentum, and this is the reason for the photo-electric effect. (For which Einstein received the Nobel Prize). Photons can knock electrons from one energy level to another even though they have no rest mass. So you can see they do have energy (and of course momentum).

The 4D space of GR is called Minkowski spacetime (should you wish to look it up.) In this 4D space, light travels in a straight line. But to us, perceiving in only 3D, we view it as if it bends around a large gravitational body.

To further confuse everyone... the maths behind quantum chromodynamics relies on the idea that photons "seek out" the most direct path by considering and using all possible paths from A to B both forward and backward in time but aggregating via statistical combination of the probability functions. This is the result that Richard Feynman got and it's perhaps the most accurate theory in all of physics but unifying this with general relativity has remained illusive. Mr Feynman's lectures are available for free on the Internet. It would be a good move to seek them out.

"Is it possible that the energy in photons might give off an electrical charge?"

Nope. "charged particles interact through the EXCHANGE of photons." This is what is meant by "The photon is the force-carrier for the electro magnetic force."

You probably need to get clear what is the difference between a field and a particle. There is one kind of field for every species of elementary particle.

Furthermore, it might be that particles are epiphenomena of fields. But that's cutting-edge stuff.

Perry, I might have confused you by leaving out a detail. You asked

"I hope that curve and electrical charge have been measured, tested and retested. I'm sure the magnetic field they are embedded in, is exactly the same or measured for variances."

The magnetic field is that which is applied by the experimenter at the detector in order to DETECT charge particles BECAUSE of the resulting curved trajectory. Actually the proof of antimatter was detected by a curve exactly in the opposite direction to it's normal particle -- e.g. positrons like we use in medical equipment. If you look up the construction of a particle accelerator, then the use of the magnetic field will become clear.

Those that "vanish" of which you spoke might be then further decaying into other particles as many particles that are produced in a high energy collision are not stable.

Swoosh, the sound of information flying over my head. Some is soaking in. Manna I thank you for that.

I already have two degrees, not science-related, but my to-do list is much too full for another stretch in formal education.

I do have fun with this quantum stuff and I keep learning things here. So, this will have to do for now.

Questions:

Infinity exists?

Nothingness is nonexistent?

Mass would become infinite at c?

Space and time become zero at c?

Is void actually possible?

Is vaccum actually empty?

"Infinity exists?"

Most likely and if so, then every current theory inexorably leads to the concept of a multiverse in some fashion. That in itself is a mind-bender.

"Nothingness is nonexistent?"

We are deep into philosophy here and I have no idea how to respond.

"Mass would become infinite at c?"

A misinterpretation of the equations. Faulty question because anything with mass cannot reach c. Rest mass will not change, but relativistic mass increases with speed but of course that depends on the frame of reference.

"Space and time become zero at c?"

As above. A non-question since the concept is simply undefined.

"Is void actually possible?"

You don't give up do you! :-)

"Is vaccum actually empty?"

Provably not. Look up Casimir effect / quantum foam / zero point energy...

The Casimir Effect shows that a vaccum has wave activity. I do not buy the two-infinity explanation and I'm confused again with the masses plates used in the experiment.

I will read up on quantum foam and zero point energy.

Thus far my ToV has been overhauled by terms and other theories that fall in place with my imagination.

""Nothingness is nonexistent?"

We are deep into philosophy here and I have no idea how to respond."

Philosophy of Science: Infinity is a given. From the most tiny to biggest of big. Universes of all sizes, in/on bubbles, strings, etc...

Nothingness would imply that something exists other than infinity.

"The Casimir Effect shows that a vaccum has wave activity. I do not buy the two-infinity explanation "

You will have to explain what "two-infinity" means or give me a reference.

The Casimir Effect describes infinite variations of waves between two massesless-plates in a vaccume. Outside the plates in the vaccume are another infinite but bigger infinite number of waves. The bigger infinity of waves cancel-out the smaller infinity of waves and the massless plates press together.

I do not buy into the two-sized infinities nor the massless plates, but I like fact that it seems to prove a vaccume is not empty.

That's not a good description of the experiment or the theory. So you are right to reject the conclusions/method. Try this explanation: http://www.scientificamerican.com/article.cfm?id=w...

... I trust Baez : http://math.ucr.edu/home/baez/physics/Quantum/casi...

I like those explanations better than the one I studied.

An empty vaccume would upset my ToV. References virtual particles and virtual waves just say to me that there is stuff in the vaccume, that kinda know their properties but not exactly.

One of the big puzzles is not so much that there is a cosmic speed-limit, but to ask "why is it a certain value". You can calculate the speed in any medium from two other fundamental constants. 1/( (e u)^1/2) where e - is the electrical permittivity of the material u - is the magnetic permeability of the material. In free space (vacuum) the permittivity is 8.85418782 × 10^-12 and the permeability of free space is 1.25663706 × 10^-6 so you can do that calculation and compute the speed of light in a vacuum. (In any physical medium like glass or air the value is less than c.)

The reason that permittivity and permeability have any values at all is a very strong indication that a vacuum is not empty. WHY do they have THOSE values? To find out is one goal of a TOE... assuming that those values are not anthropic which they would likely be if we live in an infinite sea of universes where each universe is a permutation. In that case then a TOE would be reduced to explaining that certain (or all) fundamental constants have the values we measure because we can only (or do) live in a universe where they are those values not something else.

Getting right on topic now, if there is such a thing as retrocausality then it is not going to be seen in our familiar 4D Minkowski spacetime. I think we would have to invoke new dimensions to convey FLT signalling.

It will take me years to understand the equations. I know I need to know to make any significant progress on my ToV.

I have made some progress by learning some necessary terms but still a long ways to go.

Back to the topic here. Retrocausality fits nicely into the ToV I have imagined. Also, the future effects the now. Can I measure it, test it or prove it? Not yet, and perhaps never.

I imagined a particle burst 35-years ago. It looked like the pictures of particles colloliding like we see now, only much more crowded.

How does one prove or test a theory that includes infinity and nonexistent nothingness?

That would propose that there is some kind of substance everywhere.

Firstly, you can only test theories, not prove them.. Proving is for pure mathematical theorems. Secondly, the various fields that we talk about in physics were initially invented as mathematical tools to explain experimental evidence, but as time went on, it has been shown that many fields are real. They are really 'out there' as a physical manifestation, and the theory says 'everywhere' but you need to be careful to put this in proportion because the field strength that you measure falls rapidly as you move away from the source. For example, gravity falls with the square of distance, and magnetic dipole field strength is more like an inverse cube law. So if you are billions of light years away from, say, an electrically charged cat, then the electric field strength at such distance would be mind bogglingly tiny. In practice, this means that your calculations for local electric field strength experiments can very safely ignore the effect of the cat that is billions of light years away. This assumption relies in part on the equivalence principle and also on linearity. These are easy things to state, but somewhat more difficult to fully appreciate.

The way the maths works for things like this is:

* assume that the experiment you do will yield identical results no matter where it is conducted.

* show that linear properties of your theory and practical measurements allow you to break the problem into units, do the calculations, then combine the results so that the result is correct and accurate. (This is how QED works).

That second step often involves mathematical tools that "sum things from 0 to infinity" or integrate a function from 0 to infinity or -infinity to+infinity and so on. When you sum from zero to infinity and get a finite answer, then it show you a special property about the theory and when you integrate from zero to infinity and get finite answers, it also shows something important about a theory (so would a sum of infinity but often that can mean a broken theory). You could likely do the same calculations between, for example, the definite integral from 1cm and 500 light years and get the same numerical answer to a very high degree of precision, but that kind of calculation would be much harder. When equations have symbols involving zero and infinity in them, then often, significant simplifications follow. What I'm trying to get across here is that talk of infinity etc in these theories is often a direct consequence of formulating the theory to be computable or analytic and still make it agree with experiment.

A really classic example is the assumption that fundamental particles are point-particles. We don't really know this. We just let them be point-particles to simplify the maths and then check the results with experiment. It works; it works spectacularly well for a wide range of applications, and fails under some conditions. Those failures are indications that there are limitations in the theory and they are not a surprise to researchers. String theory for example can get rid of a lot of these limitations by throwing away the assumption of a point-particle and replacing it with tiny strings and loops living in a 10 dimensional backdrop + one of time. The maths is difficult, it may not even be testable, and the results unfortunately give way too many answers... and by "way too many", I mean a stupidly large number of solutions. But progress is gradually being made to try and focus in on a subset of solutions and in some cases there might be some testable results from some string theories.

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