Can the future affect the past

[PrestonFM]

In SCIAM, it seems it was the fall of 2010, I read an article where the past was being affected by the future. If I recall correctly, the researchers had measured the spin of an electron (many many times) and then they would randomly decide to do it again in the future. Somehow the act of measuring it in the future was affecting the result that was taken in the past.

I can't remember the details nor can I find the article. I was hoping someone here would remember the details.

 

[Forestman]

There is nothing in GR that prevents time travel, although there might be once a full theory of quantum gravity is developed. Nobody knows yet.

Also in quantum physics there is the delayed choice experiment first thought up by John Wheeler. What you wrote about might be connected to that in some way. I don't know. It has been a long time since I read about the delayed choice experiment, so I don't remember how is works, but I am sure that you could find out on the Internet.

But the answer to your question appears to be yes.

 

[harrylin]

In SCIAM, it seems it was the fall of 2010, I read an article where the past was being affected by the future. If I recall correctly, the researchers had measured the spin of an electron (many many times) and then they would randomly decide to do it again in the future. Somehow the act of measuring it in the future was affecting the result that was taken in the past.

I can't remember the details nor can I find the article. I was hoping someone here would remember the details.

I don't know the details, but I suspect that it's like so-called "quantum erasers" - perhaps you read about an experiment with an electron quantum eraser? Despite suggestions to that effect, there is no need to think that the future can change the past!

 

[Forestman]

Here is a little about the delayed choice experiment.

http://en.wikipedia.org/wiki/Wheeler's_delayed_choice_experiment

 

[Forestman]

Also according to GR if one were to go at close to the speed of light around the ergoshere of a black hole then in theory one could go back in time. This would be the result of frame dragging. Because spacetime would be being dragged along with the rotation of the black hole then it would appear to an outside observer that an object going around the black hole in the direction of the black holes rotation at close to the speed of light would be breaking the light barrier. And when things go faster than light, they also go back in time.

For the object in the ergoshere things would still go slower than light, but again to the outside observer things could appear to go faster than light since the dragging of spacetime would be giving the object extra speed.

 

[PrestonFM]

I read the wiki entry about the delayed choice experiment. I think the concept of that experiment and what was described in the SCIAM article are similar. Thanks for posting that, it was very interesting to ready.

I'd still really like to find that article or something describing the exact experiment they used. I looked at every physics article title for 2010 and didn't see it. I'm sure it was there but the title didn't jump out at me. I really hope this is ringing a bell with someone :)

 

[Forestman]

I found this video on time travel using black holes on You Tube

 

[Forestman]

I found this too about the delayed choice experiment.

http://www.scientificamerican.com/article.cfm?id=quantum-eraser-delayed-choice-experiments

 

[Forestman]

A video on quantum physics, consciousness, and time.

 

[Forestman]

A video on the delayed choice experiment

 

[PrestonFM]

A video on the delayed choice experiment

That was a fairly good video. Thanks.

 

[Forestman]

Your welcome, I am glad it helped.

 

[Phrak]

I read the wiki entry about the delayed choice experiment. I think the concept of that experiment and what was described in the SCIAM article are similar. Thanks for posting that, it was very interesting to ready.

I'd still really like to find that article or something describing the exact experiment they used. I looked at every physics article title for 2010 and didn't see it. I'm sure it was there but the title didn't jump out at me. I really hope this is ringing a bell with someone :)

Was the Sci Am article similar to this one on Time Symmetric Quantim Mechanics in Discovery Magazine?

http://discovermagazine.com/2010/apr/01-back-from-the-future/article_view?b_start:int=1&-C="

One of the tactics used to explore time symmetry in quantum mechanics is through experiments involving weak measurements.

You might also try some of the ArXiv articles by Yakir Aharonov and/or Jeff Tollaksen such as http://arxiv.org/abs/0706.1232"

 

[Dale]

I have been quite interested in the time symmetric formulation of QM for several years, but I don't have a good grasp on it yet.

 

[PrestonFM]

Was the Sci Am article similar to this one on Time Symmetric Quantim Mechanics in Discovery Magazine?

You might be right. I happen to subscribe to both and sometimes I get the articles mixed up. This isn't the specific article I read but it does seem to be referencing (see below) the experiment. The article I read was only a page long (single sided). Thanks for the tip.

"Tollaksen and Aharonov proposed analyzing changes in a quantum property called spin, roughly analogous to the spin of a ball but with some important differences. In the quantum world, a particle can spin only two ways, up or down, with each direction assigned a fixed value (for instance, 1 or –1). First the physicists would measure spin in a set of particles at 2 p.m. and again at 2:30 p.m. Then on another day they would repeat the two tests, but also measure a subset of the particles a third time, at 3 p.m. If the predictions of backward causality were correct, then for this last subset, the spin measurement conducted at 2:30 p.m. (the intermediate time) would be dramatically amplified."

 

[DrChinese]

You may enjoy these articles on Relation Block World.

http://arxiv.org/abs/0908.4348
http://arxiv.org/abs/0903.2642

It would be reasonable to say that a future configuration (context) participates in what happens in the relative past. At least as one interpretation of QM, in which there is a degree of time symmetry.

 

[Meader]

Somehow the act of measuring it in the future was affecting the result that was taken in the past.

Or does it just LOOK that way? I'd love to read that article.

 

[Phrak]

Somehow the act of measuring it in the future was affecting the result that was taken in the past

Or does it just LOOK that way? I'd love to read that article.

Well, for something in the future to effect the past is non sequitur. By definition, a cause proceeds an effect. The authors of these popular articles are interested in hooking readership with a provocative byline.

But ignoring the Pop article hook, what's really going on?: Arharonov and others are proposing that the evolution of a system explained by quantum mechanics can be time reversed and combined with the usual time evolution and correctly predict experimental results.

In fact, it gets even better. If you were to possibly run an experiment backwards, it would also be "predictively correct". I have to put 'predictively' in quotes, or I also hazard a non sequitur. It is really saying that given the results of an experiment we can say what was the cause. Arharonov seems to say, that I can decipher, that this cannot be done with standard quantum mechanics.

Anyway, setting up an experiment to decide this is a difficult thing to arrange in quantum experiments, where usually, the initial state is a pure state, and the measurement is done on very distinguishable groups of resultant outcomes.

To get over this problem, an interim state is weakly measured so it only changes very little. This means that the very coherent state of the preparation at time t0 is changed by a small amount at time t1, then measured again at time t2, so that the state of the system at times t2 and t3 are still nearly coherent. To get more out of this search on "weak measurements" in quantum mechanics.

I think the proposal is exceptionally brilliant, exceptionally clever, and exactly twice as goofy as quantum mechanics itself.

 

[writermalou]

There is nothing in GR that prevents time travel, although there might be once a full theory of quantum gravity is developed. Nobody knows yet.
I just want to tell an experience and then you tell me if you call it time travel...

I'll be brief: A friend needed help to find a guy who robbed his house. He asked me to help. I went to the house and felt energy at the front door. (other things happened but being brief) I stood at the door and reached out to touch the knob. In that instant I went back to the day of robbery. The robber came out, it was so real I jumped out of his way, I described everything about him as I watched him walk up the walkway to the street, I even saw the car he got into... Everything was exactly the way I saw it. Now I ask, is that not time travel?

 

[Meader]

There is nothing in GR that prevents time travel, although there might be once a full theory of quantum gravity is developed. Nobody knows yet.
I just want to tell an experience and then you tell me if you call it time travel...

I'll be brief: A friend needed help to find a guy who robbed his house. He asked me to help. I went to the house and felt energy at the front door. (other things happened but being brief) I stood at the door and reached out to touch the knob. In that instant I went back to the day of robbery. The robber came out, it was so real I jumped out of his way, I described everything about him as I watched him walk up the walkway to the street, I even saw the car he got into... Everything was exactly the way I saw it. Now I ask, is that not time travel?

You have a very active and vivid imagination sir.

 

[Darrell Smith]

In general it is a violation of the first principle of scientific inquiry to observe a new effect and assume you know the cause. That's how some idiot came up with the god concept. Retrograde time travel is a very severe exercise involving technologies that we do not now possesses and my never realize. Whereas it's true that the laws of physics do in preclude such an exercise, it's also true that a level 0 civiization isn't going to accomplish that feat. On the other hand physics phenomenon is real abeit not controllable so far as we know. It can be triggered by a seemingly innoculous event. Yours is extremely detailed and so it's easy to check it for validity. The proof is in the pudding as they say, so in order for your experience to be considered for validation the bad guy needs to be caught and convicted. If for instance you did not get the license plate number than the validity of your experience is highly suspect. If you did get it and the thief is convicted I really want to know as I had one and one only highly detailed psychic experience that I was able to verify.

 

[Demystifier]

Contrary to frequent claims, delayed-choice quantum erasers do not affect the past:
https://www.physicsforums.com/showthread.php?t=402497