Pete

Would solving that have to show for how the information is transferred?

I don't understand this question. Can you rephrase it for me please? Thanks.

Trying to avoid a word trap, entangled states are responsible for the spooky action at a distance stuff, so I would think to show how this information “traveled” would then mean that particle has that much information in it? Such as using FTL to send a perfect message from controlled point A to controlled point B?

I don't know if entangled states can be used to transmit information FTL if the states are not entangled during a series of measurements. I have the feeling they aren't. But I'm looking into all of this during this fall. Right now I'm waiting for Klaynos to answer my question so I can see the derivation that he's speaking about for myself. Perhaps this weekend I'll create a web page to illustrate what I'm talking about.

As a possible rewording or example, if say a subatomic particle had to occupy space in an atomic shell, would the movement or field or whatever the electron of such then be somewhat like FTL?

No. Because one cannot follow the particle during that kind of motion. In quantum mechanics there are no classical trajectories and the position of a particle cannot be given as a function of time. No information could ever be transmitted this way.

 

Klaynos - You still out there??

 

Pete

But how can we esclude that gravity does not affect time but rather the mechanisms we used to measure its flowing?

Actually gravity is affecting the mechanisms that we are using to measure the "flow" of time. The reason that we say that gravity affects time itself is because gravity affects all mechanisms in the exact same way. Since an operational definition of time is what we measure with a clock and we know that gravity affects clocks then we say that time itself is affected by gravity.

 

Pete

Guys - It has zero relevance to whether or not humans are part of nature, anyway... Which was the original context in which this natural/unnatural power plant issue begain.

You are 100% correct. In retrospect I now see that the Oklo reactor wasn't a very good counter example. Quite interesting, but not relavent to the purpose it was brought up for. Its clear that layman77 was trying to give an example of something that cannot have been assembled without intelligent agent. However I certainly disagree with him in that we are most certainly part of nature. Just because we are intelligent, and in that sense different tha other lifeforms, it doesn't mean that we're not part of nature. As far as animals hitting their young - one might consider how that came to be from an evolutionary standpoint. I got a kick out of one of his responses, i.e.

Well, no, put some covers on the sockets!

This reminds me of when I was a toddler. I was a very curious child. For some reason I was fascinated by those electrical outlets. I ket taking things and sticking them into the sockets. My parents were so worried that I'd get electrocuted that they had all the sockets replaced by ones where you had to stick the plug and and then turn them in order to get them to work right. But I was too clever for that. I learned how to use them. My grandmother on the other hand , who took care of me when my parents were at work, couldn't figure them out for the life of her! She had to have me put to do it.

 

Let me mention one word here folks - moderation. Let us also not forget that parents spank their kids because they have a responsibility of making sure that they don't grow up spoiled. Remember the old saying - Spare the rod and spoil the child

..folks caring more about their Rights rather than their Responsibilities.

That arguement sort of implies that parents are spanking their kids for no good reason. Parents have a specific purpose when they spank their kids. They do it in hopes that the punishment will contribute to the child growing up to be a better adult. Its the responsibility of the parent to make sure their kids grow up well adjusted. That means that they have the responsibility to use spanking with inteligence. That means not to over do it. Never hit a kid to cause them injury. Never hit them too hard either. Use it with responsibility. It also seems that people are automatically jumping to the conclusion that if a parent uses a light slat on the rump when the child does something dangerous that they will carry out this same action, and worse, when the child gets older. Its okay to spank a child for certain things and not for others. Who says what and when? The responsible adult. But we know that all adults aren't responsible! But we also have laws which prohibit parents from beating their child too. Why are people here so ready to forget about that law?

 

Instead of searching for web sites which show the risks of not spanking a child why don't people search for web sites which show what happens when kids gets spoiled and how they get spolied?

 

I guess you could say that when the child gets older' date=' they'll understand that you did it for their own good.

[/quote']

I know that's the case for me.

 

Pete

Layman77 most certainly implied that a natural nuclear power plant is ridiculous and by extension used this to ridicule iNow's argument. This is argument from ridicule. Moreover, the Oklo site doesn't have the manmade plumbing, the signature cooling tower, the turbine generators, and electrical power lines that characterize a manmade nuclear power plant. This stuff doesn't grow on trees; we have to build it.

The idea of referring to Oklo was to cheat. I.e. to refer to an example where the basics of a nuclear power plant exist, i.e. where a a sustained nuclear fission occurs which generates power. Just because the nuclear power plants which exist today which are man-made have plumbing etc. doesn't mean that they are required in order to fit the definition of a nuclear power plant.

 

That a natural nuclear fission plant (sans cooling tower, turbines, and power lines) did exist 1.5 billion years ago just makes this argument from ridicule even more ridiculous.

Then simply ignore it

I'm not sure DH was your intended target with this comment. It was layman77 who inserted that particular non-relevance into the thread.

I mentioned it for two reasons, (1) due to DH's response, i.e.

It is an argument from ridicule in the sense that a "natural" nuclear power plant is patently ridiculous.

and (2) DH's personal information indicates that he's a physics student and this is something a physics student should take to heart. Since layman77 does not indicate it I didn't bother pointing this out. In anycase anyone can read my response. But since you mentioned it -

When was the last time you heard of a "natural" nuclear power plant.

Quite recently. You never heard of one?

 

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

 

Pete

Man, you get some style points on that one, Mr. Skeptic. I had no idea.

 

http://www.ocrwm.doe.gov/factsheets/doeymp0010.shtml

That is a very common example if one knows their nuclear physics. I was refreshing my memory on nuclear physics a few years ago when I came across this natural reactor.

 

DH - Let this example serve as a reminder in the future of when not to assume something can't exist just because you couldn't think of how it could in the first place.

 

Here's another example: From http://arxiv.org/pdf/0808.3283v1 - Physicists have recently observed that the nuclear decay rate of certain isotopes has a seasonal variation. Nothing in physics would even hint at something this odd. So it goes to show how totally unexpected things can be. Its not known exactly why this happens. It could be errors in the raw data or an interaction of the nucleus with the solar neutrino flux (which shouldn't make a difference anyway!?!?!?).

 

Pete

Can't one just re-measure the particles? I mean, then you should get the same result as the previous. If the results are the same, the particles are no longer entangled, or they never were entangled.

Of course you can measure the results. But being entangled means that there is a relationship between the two which exists even when the quantum state is not in a particular eigenstate. Just because two particles have opposite spin doesn't mean that they are entangled. One could create such a system quite easily but that doesn't mean that the particles would be entangled.

 

I have the feeling that the particles aren't entangled after the first measurement but am unsure. One of the physics professors who has an interest in this subject confirmed this for me but I'm not happy until I see it proven. In the present case I'm trying to figure out how to show that after the second measurement (i.e. a subsequent measurement of the z-component of spin) the state would have the following representation

 

|Psi> = a|+,-> + b|-,+> + c|+,+> + d|-,->

 

where [math]|a|^2 = |b|^2 = |c|^2 = |d|^2[/math]. If the particles were still entangled after this second measurement then the state would have the following superposition

 

|Psi> = a|+,-> + b|-,+>

 

If this is the case then the particles would still be entangled. This is a measureable result. If they are still entangled then it would be possible to send information FTL, i.e. it could be used to send information faster than the speed of light.

 

Pete

I think we were hoping the rest of you would change to our system, the way you did with English. Even the UK bowed to our mighty will on that.

We didn't change to English. The Pilgrims came from England and thus were already speaking English.

 

Pete

ajb: It seems that the observation of distant starlight deflected by the sun in 1919 proved Einstein's GR to be correct.

No. That observation confirmed the prediction made by general relativity. Confirm of a prediction does not logically prove that a theory is correct. When many predictions are confirmed then scientists have more confidence in the theory.

 

Pete

Then do the math yourself taking v-->c, or read about it.

I'm very well versed in relativity, thank you. take on the value which it approaches. The notation v-->c means "Let v become closer and closer and closer to the value of c." In this case the ratio of the times recorded on two clocks becomes infinite where one clock is moving with speed c while the other is at rest. For any finite value of c this is possible. But not for the limit since one would have to have a clock moving at the speed of light for this to be true and that is impossible.

 

Note: There is a mathematical distinction between lim(x->a) f(x) and f(a). I.e. it is not always true that lim(x->a) f(x) = f(a). It is also not always true that what is true for all finite x is also true for lim(x->a) f(x)

 

 

In the mean time I recommend that you "read about" what limits mean in more detail. For example: Suppose S_n is a partial sum which, for any finite value of n, is an integer. This does not mean that lim(n->infinity) S_n is also an integer. If could be a real number, like pi for example. What is true for arbitrary values of a quantity does not mean that its true for the limit of that quantity.

Surely we can take limits, or we can limit our discussion to physics without calculus

The answer is yes, I know how to take a limit. However I do question you're understanding of the limit process. What reason do you have to believe that I'm not well educated in mathematics and/or relativity? Is it because I disagreed with your interpretation of the facts?

 

booker - What's with the attitude?

 

Pete

I don't think that spanking and beating are necessarily clear and distinct separate entities. If you were to hire a babysitter and informed her that she could use “spanking” but not beating, could you be sure that you were both on the same page?

Well I'm not a parent so I can't say for sure what I'd do. But I imagine that I wouldn't allow anybody except me and the mother to spank the child.

There could be an awful lot of slapping, smacking, belts, spoons and what not that can come into play under the umbrella of “spanking”. Clearly the issues of severity, context, and frequency need to be addressed to determine whether a particular form of spanking behavior is harmful or not.

If you said it was okay to spank the child if there are extreme situations which require it and they hit the kid with wooden dowel then to me its the same thing as the babysitter abusing the child. Misunderstandings are not acceptable excuses in my book. That's one reason I wouldn't let anyone except me and mom span them. Perhaps even I would be naughty and mommy would have to spank me too! Yikes!! See what you people got me thinking!!

I can understand how it may be considered appropriate to instinctively swat at a child in response to a dangerous situation.

Me too.

Proponents of spanking define it as one or two swats with an open hand on a childs bottom. Is that the scope of what we are talking about in terms of severity?

I don't think I could answer that not having ever had kids and it being a long time since I was one myself. I would hazard to guess that the older the child the more immune they are to a light open hand pat and would thus require more pressure etc.

 

Thank God I don't have kids. I'll never have to be in a position to put my money where my mouth is.

 

Pete

Welcome Reilly! I'm very happy to see that you're posting here!

 

Let's use the example of two spin-1/2 particles, with zero total spin. Particles are entangled if measurement in any particular basis yields the answer of one particle being spin up and the other spin down. This is true for every measurement.

That is certainly sufficient, but it isn't necessary. Two particles are said to be in an entangled state if and only if there is an EPR-correlation between them. There is more than one way to do this. One way is to use the example I provided, i.e. to do just as you said. This is Bohm's method of getting two particles to be EPR correlated. Another way is to do what Einstein, Podolsky and Rosen used did, i.e. use measurements of x and p_x. One could do that using particles with no spin.

 

In Sakurai's QM text the author refers to the following decay process as a source of particles in entangled states. The following decay process creates two particles which are born in a spin-singlet state

 

[math]\eta \rightarrow \mu^{-} + \mu^{+}[/math]

 

The initial value of the total spin of the system is zero. Choose coordinates such that the total orbital angular momentum is zero, i.e. L = 0. Therefore the total angular momentum will equal the total spin angular momentum, i.e. J = S which is zero. When [math]\eta[/math] decays into [math]\mu^{-}[/math] and [math]\mu^{+}[/math]. This means that the spins must add up to zero, i.e. the spins of each of the two particles mut be equal and opposite. The particles are then in an entangled state.

 

I will assume that Klaynos and Reilly are correct and the particles will not be entangled after the first measurement. But I'm also assuming that this is not a postulate (I misunderstood that professor I met yesterday regarding this) . and as such it can be derived. It is that derivation that I'm seeking. Klaynos mentioned above The drivations are quite long,.. . To me that tells me that he knows of a place where teh derivation can be found because Klaynos told me that its in Rae's text. I'm now waiting for Klaynos to tell me what pages the derivation is located on. Calling Klaynos!!!

 

Let me get something straight folks. I am not saying that Klaynos and Reilly are wrong. I never did in fact. I don't understand why you seem to keep assuming that is the case. Please stop making that assumption? Please go back and read the question I asked more closely, okay? Here. I'll make it easy for you. I asked

Does anyone know how to prove whether or not ....

I.e. all I asked was how to prove what the final state of entanglement was. Are we now clear on that? So merely repeating that the particles are no longer entangled is of no interest to me in this thread.

 

Pete

I'm well aware of the ridiculous cost of textbooks nowadays. But when I saw the cost of this particular text I hadda cringe. This one is really pathetic. See

 

Electromagnetic Fields - 2nd Ed., by Ronald K. Wangsness

 

http://www.scribblygumbooks.com.au/9780471811862.html

 

This particular book costs $253.95!!! Is that horrible or what? I saw this at the universities book store new for $123.10. Talk about your markup!

 

I'm having trouble locating this book for a decent price. Does anybody have any suggestions on where I can get a copy for a decent price?

 

Pete

A limit can have a value. [math]\lim_{x \to 8} x = 8[/math]

 

Sorry. I meant to say that infinity is not a number.

Photons are timeless.

 

This is quite easy to show:

 

[math]\Delta t_0 = \gamma \Delta t_s[/math]

 

Where:

[math]\Delta t_0[/math] is the time interval in external observer's frame.

[math]\Delta t_s[/math] is the time interval in co-moving frame.

 

But v=c so:

 

[math]\gamma = \infty [/math]

 

Thus any finite interval [math]\Delta t_s[/math] in the reference frame of the massless particle will be perceived to be infinite.

 

So when massless particles (which must be travelling at c, I can show that as well if you like) are not interacting with massive particles time is effectively stopped, we describe this as being timeless. Because of this photons do not change in flight, and another result is that as neutrinos do change in flight they must not be travelling at c, and therefore can't be massless...

For your derivation to have any physical meaning it requires that a clock be moving at the speed of light and that's impossible. What you've shown is a limit and a limit is not an actually number, its a concept.

 

Pete

The result does not change depending on the measurement, but particle after the measurement will change depending on the measurement method used, an example of this is given above with the polarisation example.

 

The creation method will change what about the two particles is entangled.

Do you know the page number in Alastair I M Rae's text? I'm at the library now and need the page numbers so I can copy them. I'm hoping it will be easy to find but if not please post the page numbers,,

 

Too late: I've been on campus all morning and have to leave now so I can't wait anymore for your reply.

 

Klaynos - In the future can you do me a favor? In the future, if you choose to respond to a post/question of mine, such as the one I asked last night, i.e.

I can make a copy of the derivation myself when I go there tommorrow. Can you tell me where in the book I need to start copying?

Please read it carefully and then, if I ask for a page number, then please either you say that you don't know where in the text you are referring to or post the page numbers of the derivation that you intented to point me to. Now I have to go home empty handed.

 

But don't worry about it though, I'll get over it .

 

I'll be back here next wednesday anyway for my first class. I can try to get it then. In the meantime please post exactly where in the text you claim that this derivation is. I ooked inside the text and saw nothing resembling what you were saying is in there.

 

Thank you

 

Pete

From the perspective of a photon, no. If you could somehow experience time from a photon's perspective, you would be everywhere all at once.

That is a misconception. For that to be true one would have to have a clock moving with the photon so as to confirm that all the events occured at the same time. In any case a photon moves on a geodesic and there is no way to construct a geodesic which could fill the entire universe. The idea of a photon having a perspective is nonsense.

 

Pete

While I appreciate your point, and am pretty sure we agree, it's important to also recognize that there is a line that shouldn't be crossed. Responsible parenting sometimes includes the exertion of ones physical dominance. However, far too many parents cross into that (subjective area I will call the) extreme zone where the hitting is not responsible and is instead more of an expression of personal frustration and feelings of failure as a parent.

I agree. That's kinda why I posted that message the other day asking people to please distinguish between beating and spanking.

 

Pete

The drivations are quite long, and I've not had enough sleep over the last few days due to 18hour days doing volunteer work.

I'm going to a university tommorrow so if you can quote a source then I can merely look it up in their library.

Any advanced undergraduate level text book should explain how to do what I described, and doing so will show you that my first statement is true.

I have two graduate level texts and an advanced undergraduate text and none of them even touch this topic.

My personal preference for text book is Quantum Mechanics my Alastair I M Rae, Institute of Physics, London, 2002 (4th edition). But I don't know whether that's easily avaliable in the US.

I just checked the university online catalog and see that they have it. I can make a copy of the derivation myself when I go there tommorrow. Can you tell me where in the book I need to start copying?

I apologise that I've not gone into the derivations but I know you're not stupid, and I'm really tired so I'd rather point you in the right direction.

No probelmo my good man. I understand perfectly. I was merely looking for a reference anyway since I know I can hit a library and look it up

Oh and spin-singlet state of a spin 1/2-system is still quite general, how was the state created, how was the entanglement created, are the particles in any kind of potential, how are the measurements preformed...

What difference does it make how it was created since the math should be the same? The state vectors should be identical. If it matters how the measurements are performed then thats a problem since quantum mechanics does not make such a distinguishment. If the particle was in a potential then I would have stated it since that's another problem all together. In fact the paper I have on EPR-correlations and superluminal signals describes juust what I've described to you. There was nothing in the paper about how the spin is measured etc.

 

I'm cuious as to why you think that the results of a measurement depend on how the measurement takes place.

That's part of entanglement it only lasts until the first interaction.

Once again all you have done is to make an assertion with no derivation to demonstrate that what you say is true. You didn't provide a derivation which proved that what you claim is true is really the case. When I start a thread whose sole purpose is to find a proof of something then its of absolutely no use to me to simply sau that "It can be shown." Claiming it can be shown does not help me when I'm actually looking for the step by step derivation. And it cannot be deduced from anything posted in this thread so far.

 

In any case I spend most of my day at the university where I'll be starting graduate school again. I start taking classes next week. Yay!!!

 

I met and spoke with one of the professors who teaches quantum mechanics and I told him about my interest in this subject. What a coincidence!! It turned out that he has a strong interest in EPR-correlations. This very subject is one of his areas of interest. The professor explained this to me that (if he's correct that is) there is no such derivation, i.e. it can't be proven. It is something which given as a postulate. This may turn out to be wrong but at least I found a kindred spirit who is also interested in superluminal communication.

 

Klaynos - Your outline does not provide a route to any sort of derivation that I can see. And "Good" QM texts don't address this exact situation, i.e. series of measurements. Texts almost always talk exclusively about single measurements.

Well it depends on the situation you're dealing with' date=' you'd need to write out the wavefunctions for the particles.

[/quote']

I see no need to write out the wave function. All one needs here is the spin degree of freedom.

And then work out the operator that is applied to them (the measurement).

What operator are you referring to? The situation here is not to take one measurement. In this case one is taking a series of measurements. In what sense are you speaking about "Work out the operator"?

And then apply that operator to the wavefunctions.

Do you mean apply the operator to the spinor since the wave function is of no use in this problem.

You can't really do it for general situations.

Ummmmm ... nobody mentioned "general situations". I know that I sure I didn't. I stated something very specific' date=' i.e. a [i']spin-singlet state of a spin 1/2-system[/i]. That is something very specific.

 

I appreciate your efforts.

 

swansont - Glad to see you posting on this topic. Much appreciated.

This is true for every measurement.

What do you mean "for every measurement"? Which measurements are you refering to? Are you referring to the first measurement of the spin of each pair of particles?

Only if the individual states aren't known can they be entangled.

I was hoping that I'd be clear by now that I don't accept statements like this on faith. Either this is something that is derived or it is something postulated. Which are you saying it is?

I think you may be mis-understanding him a little being fair here

Nah. I was just being a wisenheimer. I didn't get any sleep last night so I'm cranky.

only number 2, there`s no need whatsoever to "Tap" your child.

I have 3 year old daughter and have never lifted a finger against her ever, in fact I rarely tell her off.

my Wife will tell her off regularly and also give her a smack.

the result is that when it`s just her and I she`s as good as gold and doesn`t play up at all, when my wife is around she does play up, and what`s more she doesn`t listen to her either.

but when I say something to her she does it immediately and happily without a problem, and on the rare occasion that I do have to be firm with her (such as in your example), a single word and a look from me and she`s in tears!

no need at all for physical force to be used.

Are you assuming that since it works with your daughter then that implies it would work with all children? Is there a need to put your child to tears?

I don't think you folks are giving kids enough credit. Children are pretty resiliant little buggers. They get bumped and bruised all the time on the playground. Eventually most kids will run into a bully or get into a fight and get smacked around somewhat. Getting the rare spanking at home isn't much compared to the crap kids have to take from their piers. I recall getting dropkicked in the eye by a kid who was wearing steel toed boots which followed getting the wind knocked out of me when he socked me in the stomach first. I remember those times infinitely more than the occasional smack on the rump with Grandmother's fly swatter.

 

My point? The appropriate use of spanking won't hurt a kid psychologically. Sending him to the school playground will do much more damage from the school yard bully.

 

So what is it that you pacifist "Don't lay a finger on the precious children!" parents do in order to prevent those bullies from ever letting them lay their filthy hand on your kid? Suppose your kid comes home and tells you that the school bully is out to get him and he's scared? What do you plan on doing when that happens? Keep in mind that the school bully is going to cause much worse emotional scars then a mere spanking could ever do. Those scars can last a lifetime.

 

Pete

I don't know about the rest of you but I'm real tired of the way seasons run nowadays. It used to be that a season started in September and ran until spring. Not its like you have to wait an entire year for the season to start, then they run two new shows, then run repeats, then a new show, then a repeat, then three more shows and then the season finale two months later. Very frustrating!!! And the number of commercials!! Yikes! Its like they have 10-12, very terrible, commercials between 5 minuts of TV. And the commercials are so bad that 15 seconds after the commercial is over you can't recall what the heck it was that they were trying to sell you!

 

Pete

Hi CalleighMay

 

Welcome to the forum. I'm glad to see young adults such as yourself work so hard at things like this. Its refreshing!

 

One of my majors as an undergraduate was mathematics. I was also a tutor in my college's math lab for several years. Please feel to PM me anytime with any question that you have. I'd be glad to help in anyway I can. That applies to everyone on this forum too.

 

I like to see students work so hard as you are and trying to impress their teachers. That's what I did in college.

 

Good luck

 

Pete