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The universes expansion accelleration solved.
by Marchimedes
05/14/20 07:25 AM
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#35994 - 09/07/10 06:47 PM Have I caused someone to kill his grandfather ?
Bill S. Offline
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Consider the following scenario, (the “grandfather paradox”). I decide that I will try to build a time machine which will allow me to travel back in time in order to kill my grandfather, and thus prevent my birth. In a single universe this creates a serious paradox, but the multiverse appears to offer us a way out of this by creating a new universe in which I was never born. However, we should look more closely at this situation. My decision to try to build a time machine creates a range of paths through different universes, all of which become “real”. The range must include paths in which I do, and do not actually make this decision.
The paths in which I do make the decision must include paths in which I do, and do not succeed in building the time machine.
The paths in which I build the machine must include paths in which the machine is, and is not successful.
The paths in which the machine is successful must include paths in which I do, and do not travel back to the appropriate point in time.
The paths in which I travel back to the appropriate point in time must include paths in which I do, and do not kill my grandfather.
All these paths are created by my initial choice. They must all become real, whatever my first decision happens to be. Even if I decide not to try to build the time machine, this decision will mean that another version of me, in another universe will decide to build the machine; so all the ramifying possibilities mentioned above, and perhaps lots more, will become “real”. So, if time travel to the past is, or ever will be, possible, and if the multiverse theory is right, and if I even think about building a time machine, then all these possibilities become “realities”, whatever decision I make. The point I seem to have reached here is that I have to accept that whatever choice I make in this, or any other matter, makes absolutely no difference in the context of the multiverse, because any choice I make will be countered by the choices made by other versions of me in other universes.

Does it make any difference if we assume that the universes are not created by the making of choices, but already exist? The answer must be “no”, because even if the universes have always been there, the paths through them, taken by the various versions of me, will be governed by the decisions made by each of those versions of me as we (I?) make our ways through our different worlds. Throughout the multiverse, all possible paths will always be taken, or so we are told. Of course, any decision I make will be of importance to the version of me that I recognise in the universe I experience as real, but the multiverse theory says that the other versions of me are just as real, and just as really “me” as the one I experience. It seems that, in the multiverse, I have no monopoly on “me-ness”. It also seems that if I want to travel back in time, all I have to do is decide not to build a time machine and use it to go back and kill my grandfather, and this will ensure that I will do just that in another universe. Who needs to build time machines?
What have I just done?
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#35996 - 09/07/10 11:01 PM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
redewenur Offline
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Bill: "What have I just done?"

I think you've said that, whether or not certain quantum phenomena can be explained by a multiverse hypothesis makes no difference to our daily lives.
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#36003 - 09/08/10 07:39 PM Re: Have I caused someone to kill his grandfather ? [Re: redewenur]
Bill S. Offline
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My intention was to instigate a discussion about multiple universes, rather than how we might direct our daily lives. I half expected Kallog to pour scorn on the idea of alternative universes and multiple Kallogs!, but I guess he (she?) doesn't like to be predictable.
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#36005 - 09/08/10 10:59 PM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
redewenur Offline
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Ah, excuse me then. Actually, on second thoughts it seemed you might be implying that belief in such a multiverse could provide a rationale for unethical behaviour; or at least, a reason for modifying behaviour in some way. Apparently not.

Personally, I'm not scornful of the various multiverse ideas (there are at least five, as far as I know), but...

While some reputable scientists, including David Deutsch, take the existence of this kind of multiverse to have been demonstrated experimentally by quantum computation - albeit thus far limited to a few qubits of processing power - it seems that others, despite the logic of Deutsch's reasoning, deny that it necessarily demonstrates any such thing, and are disinterested in what they regard as metaphysics.

For all we know, there may be several types of multiverse coexisting. Infinities within infinities within infinities...On the other hand, maybe not.
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#36020 - 09/10/10 12:19 AM Re: Have I caused someone to kill his grandfather ? [Re: redewenur]
Bill S. Offline
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David Deutsch does seem to have a lot of faith in the ability of quantum computing to support his multiverse ideas, but I suppose he knows a lot more about QC than most people. Personally. I was more impressed with his interpretation of the double-slit experiment, but even there, I am more inclined towards the de broglie - Bohm pilot wave theory, than to the idea that interference comes from a multitude of other universes.
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#36021 - 09/10/10 02:10 AM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
redewenur Offline
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Originally Posted By: Bill S.
...but even there, I am more inclined towards the de broglie - Bohm pilot wave theory, than to the idea that interference comes from a multitude of other universes.

Why is that your inclination, Bill?

The reason I ask is summed up in a Physics Forums post by Frame Dragger:

"I am a little disturbed by the number of arguments that center on liking one theory over another for reasons that seem to have less to do with the science and more to do with what is most palatable. I'm not sure why a work in progress (QM) needs an interpretation that makes a series of assumptions for the sake of remaining at least semi-classical."

http://www.physicsforums.com/showpost.ph...mp;postcount=13
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#36024 - 09/10/10 01:39 PM Re: Have I caused someone to kill his grandfather ? [Re: redewenur]
Bill S. Offline
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Originally Posted By: redewenur
Why is that your inclination, Bill?


There is more than one reason for this, but perhaps the simplest is that Ockham's Razor might lead us to prefer one universe over a multiplicity of universes, unless we have good reason to opt for the latter. (Don't ask me why I prefer Ockham to Occam, in spite of the spell checker)
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#36028 - 09/10/10 05:13 PM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
redewenur Offline
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Probably because the man's name was William of Ockham.

BTW, you may well have seen this cartoon. It's my favourite 'lecture' on the double-slit experiment:

http://www.youtube.com/watch?v=wEzRdZGYNvA
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#36038 - 09/11/10 09:06 PM Re: Have I caused someone to kill his grandfather ? [Re: redewenur]
Bill S. Offline
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Thanks. Good "lecture".

Have you come across David Deutsch's idea that when photons go through the double slit set-up singly, it is virtual photons from other universes that do the interfering? I would love to hear someone's opinion on that.
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#36041 - 09/12/10 07:31 AM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
redewenur Offline
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Yes, I have. D.D. is an entertaining guy, and he's not shy of publicly contradicting his famous peers. I could listen to him all day.

A single particle taking all possible routes simultaneously vs. many particles from many universes, each taking a single different route - and either way, the act of observing causing the elimination of all but a single route. Deutsch is a brave man, as was Hugh Everett** half a century ago, but I suspect he's got all the evidence he's going to get; and that's not enough for many.

My opinion? The options are equally incongruous with reality as we otherwise know it, but both are in accord with experimental data.

** Back in the distant days of 12" monochrome TV, I watched a programme(olde worlde English) about the many worlds theory. I reckon that must have been one of the first mass media explanations of Everett's hypothesis.
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#36042 - 09/12/10 03:01 PM Re: Have I caused someone to kill his grandfather ? [Re: redewenur]
abacus9900 Offline
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Some serious cosmologists take the idea of the 'many universes' model seriously nowadays. I think, to enable science to work towards a grand unification of all the known forces, it is necessary to postulate the 'multiverse' since there appears to be little choice when attempting to producing a viable theory.

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#36043 - 09/12/10 03:25 PM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
abacus9900 Offline
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The only rational approach to this is to hypothesise that the photon is able to be in several places at once. Of course, the problem is a photon cannot really be considered an 'object' in the way that ordinary everyday objects are defined.

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#36060 - 09/13/10 02:07 PM Re: Have I caused someone to kill his grandfather ? [Re: abacus9900]
Bill S. Offline
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Originally Posted By: abacus9900
The only rational approach to this is to hypothesise that the photon is able to be in several places at once.


I would be inclined to go further and say that because the photon travelling at "c", it is everywhere within the set-up at the same time, in its own F of R.

With regard to the double slit experiment, we should remember that the major problem involves sending single photons through the setup, and finding that, provided there is no observation made of the passage of each photon, an interference pattern results which, with time, builds up into a pattern that is indistinguishable from that produced by continuous waves of light passing through the same slits. There can be no doubt that something interferes with the single photons as they pass through the slits, but what could it be? The idea that this something could be a “probability wave” leaves the more down-to-earth among us wondering what a probability wave might be, and if, in fact, it is anything more than a semantic convenience. However, its established place in scientific thought demands that it be considered.

Various candidates have been suggested as agents of interference, including:
1. Probability waves.
2. Pilot waves.
3. Photons from other universes.

If any of these is correct, the question still remains as to how observation disrupts the mechanism. How does observation collapse the probability waves, disrupt the pilot waves or exclude the interference from a vast number of other universes?

The simplest answer would seem to be that the time lapse involved in the experiment occurs only in the F of R of the observer. In its own F of R the photon is at every point in the set-up at the same time.

In the photon’s F of R:
1. There are no probability waves, the outcome is always a certainty.
2. The act of observing disturbs the photon and its pilot wave, but because this is part of the infinite existence of the photon, its appearance as part of a sequence of events occurs only in the observer’s F of R.
3. Photons from other universes will also be travelling at “c”, so they too will be at every point in the set-up at the same time, so the above reasoning will apply to them as well.
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#36065 - 09/13/10 03:14 PM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
abacus9900 Offline
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Are any of these waves real or purely mathematical though?

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#36067 - 09/13/10 04:09 PM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
abacus9900 Offline
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Quote:


The simplest answer would seem to be that the time lapse involved in the experiment occurs only in the F of R of the observer. In its own F of R the photon is at every point in the set-up at the same time.




If that is in fact the case, would a reasonable hypothesis be that it is the specific experimental set-up plus the experimenter(s) own awareness, acting in given time-frame, that 'experiences' the concept of a 'photon?' We have to be aware that in something like the double-slit experiment we are forcing nature to yield outcomes we can conceptually deal with, i.e. 'particles' and 'waves.' In other words, this may not really be anything to do with the way nature is but the way 'we' are! If I am right here then the implication is that science is fundamentally subjective inasmuch as it must always have to be 'interpreted' in terms of the 'language' of out native conceptual attributes.

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#36069 - 09/13/10 07:08 PM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
redewenur Offline
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Let's remember that the electron, which does have mass, behaves just like the photon in the double-slit experiment.

http://www.upscale.utoronto.ca/PVB/Harrison/DoubleSlit/DoubleSlit.html
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#36072 - 09/13/10 08:38 PM Re: Have I caused someone to kill his grandfather ? [Re: redewenur]
abacus9900 Offline
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I don't know whether you are familiar with the 'delayed choice quantum eraser experiment', but what happens, basically, is that a photon, say, is sent through a double slit apparatus.


Now, the photon either goes through one or both slits, ok?


So far, this is just like the original double-slit experiment.


Placed right behind the slits, however, is placed a device that converts the photon(s) into two identical 'entangled' photons.


One of the twin photons acts as what they term the 'signal' photon, which is directed to a detector. This detector can be examined later on to see whether an 'interference' pattern has occurred.


The other entangled photon, called the 'idler' photon is directed by a prism that sends it in two separate directions, depending on which slit it came from.


Now, beyond this are placed beam splitters that each have a 50% chance of allowing the idler photon(s) to pass or to be reflected.


The beam splitters are arranged in such a way that allow the idler photon(s) to be detected by several detectors.



If the idler photon is detected at a particular detector then it could only have come from slit B.


On the other hand, if the idler photon is detected by another detector it must have come from slit A.


If the idler photon is detected at other detectors then it might have come from either slit.


All this comes down to the fact that some detectors reveal information, others reveal no information about the path of the photon(s) to the signal photon(s) with which it is entangled.


If the idler is detected at some detectors then the 'which-path' information is erased, so it is impossible to know whether it came from slit A or B.


When a human experimenter looks at the signal photon(s) whose entangled idlers were detected as 'erased which-path' they find an interference pattern (because lack of knowledge).


However, when they look at the signal photon(s) whose entangled idlers *were* detected by the detectors that yielded information about which slit they came from, they found no interference patterns.


This result is similar to that of the double slit experiment, since interference is observed when it is not known which slit the photon went through, while no interference is observed when the path is known.


The astonishing thing with this experiment though, is that the choice of whether to keep or erase the 'which-path' information of the idler photon(s) need not be made until *AFTER* the status of the signal photon has already been measured by its detector, which would have occurred at an earlier point in time than the detection of the idler photon! So, making a conscious decision to either preserve or erase 'which-path' information about the idler photon(s) seems to magically determine whether there will be an interference pattern or no interference pattern shown by the signal photon, which had already been measured!!


Is this rational?

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#36073 - 09/13/10 08:50 PM Re: Have I caused someone to kill his grandfather ? [Re: redewenur]
Bill S. Offline
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Originally Posted By: redewenur
Let's remember that the electron, which does have mass, behaves just like the photon in the double-slit experiment.


If the experiment is conducted in a vacuum, how fast does the electron travel?
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#36081 - 09/14/10 05:09 AM Re: Have I caused someone to kill his grandfather ? [Re: Bill S.]
redewenur Offline
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Bill

An electron can be accelerated close to c, but no amount of energy will enable it to reach c (speed of light in a vacuum).

But as a matter of interest:

http://en.wikipedia.org/wiki/Cherenkov_radiation

"Cherenkov radiation results when a charged particle, most commonly an electron, travels through a dielectric (electrically polarizable) medium with a speed greater than that at which light would otherwise propagate in the same medium."
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#36082 - 09/14/10 06:12 AM Re: Have I caused someone to kill his grandfather ? [Re: abacus9900]
redewenur Offline
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Originally Posted By: abacus9900
So, making a conscious decision to either preserve or erase 'which-path' information about the idler photon(s) seems to magically determine whether there will be an interference pattern or no interference pattern shown by the signal photon, which had already been measured!!


Is this rational?

It's insane! Psychic photons smile

Wheeler got the ball rolling back in 1978 with his delayed choice thought experiment, and in more recent years there have been several experiments similar to the one you describe. Was that the one by Leonard Mandel's team at theUniversity of Rochester?

http://www.fortunecity.com/emachines/e11/86/qphil.html

- haven't had time to read it yet.
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