Why are scientists so sure that the light barrier is impenetrable?

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Offline latebind

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If history has taught me anything, it's this : Whenever human kind is faced with a barrier we eventually break through.

There are so many examples, including the sound barrier which no-one thought could be broken either.

As the kinetic energy and speed of an object increase, then so does its mass (E=mc2).
This suggests that to go the speed of light would require infinite energy...

This does not make sense when you think about the fact that the universe expanded faster than the speed of light at the beginning of the big bang, so its been done before.

Also , if you could have an accelerating spaceship orbiting the solar system with frequent fuel topups, then why would it not go faster than light? and why would its thrusters stop producing enough energy to propell it a little faster each minute?


To me, personally, this just looks like another barrier that human kind is going to eventually break one day. And I don't mean bypass with wormholes, I mean we will take an object past the speed of light one day...

BTW cool theory here :: http://www.space.com/businesstechnology/080813-tw-warp-speed.html

 
Late

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Offline graham.d

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In my opinion scientists are not "sure" of anything. To be sure would be a matter of faith, not science. We all use abbreviated language so it is more convenient to state something as a fact rather than preface every statement with, "according to our latest understanding (which may be wrong)...".

So, according to our current understanding on which much of our knowledge and understanding is based, nothing can travel faster than light. Maybe this is wrong, but it would certainly be a matter of faith to say so. It would be ignoring the knowledge we have. If we do not base our assertions on our scientific understanding, we could make any assertion we like without any need for evidence and could ignore contradiction with observations wherever we choose.

I don't remember seeing any theory invoking of faster than light expansion of the universe, but there may be one.

The faster than light spaceship idea is not a correct understanding of special relativity. The spaceship will get asymptotically closer to the speed of light but would never get there. To the people on the spaceship the universe would be contracting in the direction of motion. There would be (given a supply of fuel) no reason why they could not travel considerable distances (as measured by a stationary observer) in a reasonable timespan (to them). But this would not be what the stationary observer would see. He would see them limited to below lightspeed. Time dilation would make space travel rather problematic.

I would like to think we could find a way around this too but it is unscientific to just take this as a matter of faith because we would like it to be so.

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Offline LeeE

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I think latebind is referring to the Inflationary Epoch phase of the Big Bang, where it's believed that the universe expanded faster than 'c'.  However, although the universe may have been expanding faster than 'c' this is not the same as saying that the objects (particles) that existed within the universe were moving through the universe faster than 'c', just in the same way that the receding galaxies are not moving through space but it is that the volume of space that they are within that is moving (due to expansion).

An analogy would be to think of people sitting inside an airliner whilst it's flying along at around ~600mph.  The people are stationary relative to the body of air inside the airliner but that body of air is traveling along at ~600 mph relative to the air outside, with the people inside the airliner moving along with it.
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Offline graham.d

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You are probably right, Lee. Also, the universe model today is based on comoving observers where the comoving distances divided by the age of the universe would have objects moving faster than light. It is possible (and accepted) that the universe could be much larger than the observable universe but that these objects are "cosmically censored" from being observable. That this does not violate Relativity theory is not so easy to explain. It is really that it is the whole universe that is expanding and there is no reason why parts of this universe cannot be receding from us faster than c but that this has no impact on the laws of physics in either of our local frames of reference.

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Offline doppler1

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One thing is for sure and that is that scientists can not be certain of very much. I know that one light year is a measure of distance travelling at the speed of light but how is that affected in a contracting universe? Could we say that if the destination point was 1000000 light years away when we left but is moving closer to the departure point thanks to the contraction of the universe....could we not say that we travelled faster than light, just for the hell of it, because we would have reached our destination in a shorter time than calculated...albeit in a pretty decrepit state and the distance has been reduced.....Just kidding....but really :)

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Offline graham.d

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Actually Doppler you could do exactly that given a suitable supply of energy. You could travel considerble distances (as measured from the rest frame before you start) and the time you would take to get there (as measured by you) would be the classical time as if relativity had no effect. However, if you returned in similar fashion you would find the earth you left would be much aged with maybe your grandchildren older than you, for example. There is no reason why you would be decrepit.

This is a special relativity view. I'm not sure how this gets adjusted by, for example, a constant acceleration which would need to take into account a General Relativity view. I think the principle is the same but the maths may work out slightly differently.

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Offline doppler1

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Sheesh, thanks a mil graham.d......as Neilep would say...ewe people are very smart on this forum. I will be sure to look into special relativity because this fascinates me. I am way out of my depth though but will try and find something I can understand in the theory. Thanks again.

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Offline yor_on

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Doesn't the speed of light, and its covariance for all frames possible, define the theory of relativity? Wouldn't we have to build a new physics platform without that fact? That fact that light always will be measured at 'c' from whatever frame you measure it I mean, and whatever you measure it against too, moving or not. I think 'c' will stand for our universe. If we ever find a way to 'surpass it' it won't be through getting there faster. It will have to be something else, like 'tunneling' perhaps?
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Offline Shadec

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ecause if you factor the speed of light into the equations:
1. for observed time:
tv= t0/√(1-(v2/c2))

2. for observed mass:
mv= m0/√(1-(v2/c2))

if you subbed v (the speed of the object) into the equation as c (ie it's traveling at the speed of light c, ~3x108) , you'll get 1/1 = 1, then you'll have √(1-1) = √0 (and that doesn't go down too well with physicists and mathematicians) but is generally accepted as being zero, so you would be dividing by zero, which is a big no-no. NEVER, EVER divide by zero!

so you get an undefined answer for both mass and time

Oh, and then there's length:

lv = l0 x √(1-(v2⁄c2))

which would end up as l0 x 0 = 0
length of zero, undefined mass and time...
not fun!


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Offline Ron Hughes

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Since the required force to reach C (with respect to an observer) for any mass is infinite then M = ~/C^2. As you can see that is an awful lot of mass.
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Offline krytie75

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Personaly I think the consideration of cross-universe travel by means of faster than light motion is fools errand.  Even if we subsequently (somehow) discovered that faster than light speed travel was possible, there's still the huge factor of time dilation, where any space traveller employing this method would arrive at their destination in the far future of earth or wherever they left from.  All we can hope for really is the discovery of some 'wormhole' technology that would allow us to cross vast distances in a negligable amount of time.

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Offline Shadec

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There was something else I forgot to mention, if you went faster that the speed of light, for the same equations:

tv= t0/√(1-(v2/c2))
if you had say
tv= t0/√(1-((c+1)2/c2))
(which is only 1m/s faster than c, not very much faster!)
√1- (c2+2c +1)/c2
which I work out to be √-0.000000007
 Then you would end up as √-ve. And square rooting a -ve number is a massive no-no. Those are two of the most important rules, never divide by zero, and never square root a -ve number!! (unless you want to go into imaginary numbers and 'i', which still wont make you go at 3x108m/s)

And of course, the same goes for the other equations, as they all have √(1-x), with x being the speed division.

I would be inclined to agree with Krytie, there are far more useful things to be doing with our time than trying to travel faster than light. Though not necessarily spending it making wormholes!
« Last Edit: 15/04/2010 05:22:06 by Shadec »

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Offline JP

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Then you would end up as √-ve. And square rooting a -ve number is a massive no-no. Those are two of the most important rules, never divide by zero, and never square root a -ve number!! (unless you want to go into imaginary numbers and 'i', which still wont make you go at 3x108m/s)

That brings up a good point (though one that's more science fiction than science).  It's theoretically possible to have imaginary-mass particles called tachyons.  Tachyons are always moving faster than the speed of light.  The more energy you put into them the slower they go (approaching the speed of light) and the more energy you take out the faster they go.  Of course, no one has seen them and there would be a lot of problems for causality if they suddenly showed up since you'd have time travel.

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Offline yor_on

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So how about the quantum eraser experiment and the delayed choice quantum eraser. In where you have a possibility, according to some views, for the photons to 'communicate' pass the time barrier, our arrow of time that is. It seems to me as if you also could see this as some sort of 'ftl' if we by speed mean a measurement of distance in time :) After all they are not at the same place, are they, ah, inside our 'four dimensional' reality I mean. :)

The real question is if there is any 'information' exchanged of course, but if there are?
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Offline Good Elf

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Hi All,

There have been some excellent comments made. You "can" travel "faster than the speed of light" as determined from your "rest frame" within a rocket as commented on previously by graham.d and yor_on and others learned people here. The problem is time dilation... On the one hand relativity "gives" by allowing a spaceship to travel any distance it want within any predetermined finite amount of time provided we have some way of protecting the travelers from radiation and acceleration and an also an unlimited source of propulsive energy. Unfortunately time dilation also means that the travelers are "projected" along a near null geodesic into the distant future as reckoned by an external observer from earth. This reconciles the fact that observers viewing this phenomenon from the rest frame of our galaxy or our solar system see this traveler moving near the speed of light (effectively indistinguishable from a beam of light). From this external observer point of view the travelers proper time is progressing very slowly to the point that it is almost "entirely arrested". At the same time it has "relatively" undergone nearly infinite length contraction which "appears" like a rotation of nearly 90 degrees away from the axis of travel placing the traveler and his spaceship very close to the lightcone wall as a "nearly flat object".

This can be put another way... time always "seems" to progress normally to the traveler as he views it from within his spaceship though peering outside he sees the complementary effect in the universe around him. the surrounding universe (which appears to him to be the object in motion) has compressed into the forward direction as a flat object and rotated almost 90 degrees on to the lightcone wall. The problem is "inertia". Acceleration produces dilation of local clocks relative to "homebound" clocks. The accelerated clocks "run slow" relative to unaccelerated clocks.

The "problem" seems hopeless since any hope of traveling faster than the actual velocity of light depends on moving through the exact velocity of light. That is a point at which all temporal processes as observed by external observers cease entirely and the spaceship and it's occupants move exactly like light. Forget the "mass" becoming infinite... there are "other interpretations"... see Lev B. Okun's papers on the matter (.. such as "Mass versus relativistic and rest masses" - 03 Dec 2008)... just one amongst many papers.

Unfortunately how is any object going to accelerate through that "node".... at the speed of light (as reckoned by any external observer) since it requires some temporal acceleration from within that frame... that will not occur? Energy exchange is required for acceleration and that is not about to happen from within that system in which time "appears arrested".

So another way must be found... you cannot move "through" the velocity of light but "around it" in some way. The way to do this is to do what Dr. Who does... invent a TARDIS (Time And Relative Dimension In Space)... Accelerate through space and time together maintaining some control over both. You can do this by "first" nulling the mass of the spaceship. This is what is holding the spaceship back and limiting the amount of acceleration (it also provides you with achievable sources of energy to accelerate your spaceship and also solves that difficult problem of "time dilation" which is "pushing" you rapidly into the future). The next thing is to accelerate in a controlled way ... and any force will cause an infinite acceleration on a zero mass but be sure to adjust the passage of time appropriately otherwise you will end up on the wall of the lightcone (as before) and be eternally "stuck" there. You can do this trick using certain quantum techniques which undoes the quantum exchanges occurring due to the natural passage of time.

Some additional reading material...
The Quantum Zeno Effect
Delayed Choice Quantum Eraser Experiment
A quantum solution to the arrow-of-time dilemma - Lorenzo Maccone 25 Aug 2009
Uncollapsing the wavefunction - Andrew N. Jordan
Uncollapsing of a quantum state in a superconducting phase qubit - Nadav Katz etal
Exerting better control over matter waves

Next trick after reading and absorbing all this is you then need to research this thoroughly and build the TARDIS. Next point is to drop by and pick me up so we can both go for a "spin around the universe".  [;)]


« Last Edit: 16/04/2010 12:59:28 by Good Elf »
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Offline JP

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The "problem" seems hopeless since any hope of traveling faster than the actual velocity of light depends on moving through the exact velocity of light. That is a point at which all temporal processes as observed by external observers cease entirely and the spaceship and it's occupants move exactly like light. Forget the "mass" becoming infinite... there are "other interpretations"... see Lev B. Okun's papers on the matter (.. such as "Mass versus relativistic and rest masses" - 03 Dec 2008)... just one amongst many papers.

Unfortunately how is any object going to accelerate through that "node".... at the speed of light (as reckoned by any external observer) since it requires some temporal acceleration from within that frame... that will not occur? Energy exchange is required for acceleration and that is not about to happen from within that system in which time "appears arrested".

So another way must be found... you cannot move "through" the velocity of light but "around it" in some way. The way to do this is to do what Dr. Who does... invent a TARDIS (Time And Relative Dimension In Space)... Accelerate through space and time together maintaining some control over both. You can do this by "first" nulling the mass of the spaceship. This is what is holding the spaceship back and limiting the amount of acceleration (it also provides you with achievable sources of energy to accelerate your spaceship and also solves that difficult problem of "time dilation" which is "pushing" you rapidly into the future). The next thing is to accelerate in a controlled way ... and any force will cause an infinite acceleration on a zero mass but be sure to adjust the passage of time appropriately otherwise you will end up on the wall of the lightcone (as before) and be eternally "stuck" there. You can do this trick using certain quantum techniques which undoes the quantum exchanges occurring due to the natural passage of time.

Yeah invariant mass is the way to go when describing relativity phenomena.  But if you set your invariant mass to zero you have to instantly be going at the speed of light.  It's not a matter of accelerating to the speed of light.  Although it's probably a moot point unless there's a plausible physical process that lets you set your invariant mass to zero.

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Offline JP

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So how about the quantum eraser experiment and the delayed choice quantum eraser. In where you have a possibility, according to some views, for the photons to 'communicate' pass the time barrier, our arrow of time that is. It seems to me as if you also could see this as some sort of 'ftl' if we by speed mean a measurement of distance in time :) After all they are not at the same place, are they, ah, inside our 'four dimensional' reality I mean. :)

The real question is if there is any 'information' exchanged of course, but if there are?

Yeah--there are plenty of ways for quantum "stuff" to move at FTL speeds.  But actually using any of that stuff as information always seems to require opening up a classical information channel which is limited by light speed...

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Offline Good Elf

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Hi JP, yor_on and all,

That quote you made above "Quote from: yor_on on 15/04/2010 11:53:16" was from my post  [;D]...
Quote from: JP
But if you set your invariant mass to zero you have to instantly be going at the speed of light.
Note... setting invariant mass to zero does not necessarily mean setting momentum to zero too... the exception is the photon.
Quote from: JP
Although it's probably a moot point unless there's a plausible physical process that lets you set your invariant mass to zero.
Um... I can think of one... of course it relies on what you mean by "physical". If you set a system into a superposition of states and the system wavefunction remains uncollapsed... the property of mass along with all other properties will remain "undefined" until it collapses as a unique classical "measurement". That measurement might be "forced" some distance away from the original systems location prior to being set into that quantum state.

Cheers
"Aa' menle nauva calen ar' ta hwesta e' ale'quenle"

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Offline JP

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Quote from: JP
Although it's probably a moot point unless there's a plausible physical process that lets you set your invariant mass to zero.
Um... I can think of one... of course it relies on what you mean by "physical". If you set a system into a superposition of states and the system wavefunction remains uncollapsed... the property of mass along with all other properties will remain "undefined" until it collapses as a unique classical "measurement". That measurement might be "forced" some distance away from the original systems location prior to being set into that quantum state.

Zero mass is perfectly well defined.  And even if it's in a superposition of states, each one evolves according to physical laws as if it's state was well-defined, so you shouldn't have zero mass, no matter what your definition of mass is.  This isn't the same as setting the invariant mass to zero so that you can go at the speed of light.

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Offline Good Elf

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Hi JP,

Quote from: JP
Zero mass is perfectly well defined.  And even if it's in a superposition of states, each one evolves according to physical laws as if it's state was well-defined, so you shouldn't have zero mass, no matter what your definition of mass is.  This isn't the same as setting the invariant mass to zero so that you can go at the speed of light.
Regarding Quantum Electrodynamics... Just pointing out what is obvious... There are no "classical paths" to evolve along for quantum events so mass "falling" along a geodesic while in a quantum state is not able to be determined... only probability outcomes for events. If sufficient material has dephased completely into a "classical particle" it will be possible to track this particle along a path.... however it will no longer "diffract" as a quantum event. These probabilities may be calculated but the calculations cannot be used to choose a path along which an event might evolve... an example is the Double Slit Experiment (which also works for "slow moving" quantum matter particles) in which all "ways" must be summed in order to calculate these statistical outcomes.

Still this wave equation calculation (describing the wave-function) does not in any way constitute a "measurement". An actual measurement will define one state to be valid and all other states to be invalid. The "chance" of that single event happening out from all events possible is usually individually "insignificant". That is the difference between a measurement and this simple statistical calculation. The wave-function describes a global quantum state as probability while the measurement itself tells us the outcome of a "classical measurement" where the quantum particle has already become "dephased". This "measurement" entangles the measuring instrument with the event being measured. Statistics cannot be 'misused" to define paths. We also know that a formal measurements can only occur where there is a suitable measuring apparatus installed.

Nothing is "perfectly well defined" unless it is measured. While in a superposition of states (while a quantum) it cannot be measured. It may be possible to define a partial or protective measurement in the vein of Yakir Aharonov, though this will not usually provide definitive information about a specific event simply because that would collapse the state. It is a measurement problem and provided it is quantum mechanically isolated from the rest of the system will have no classical value... yet. A "full on" measurement will collapse that state. The next most important point is where you make that measurement since all "classical measurements" are local. That means that a particle might be able to tunnel across a barrier unlimited by classical considerations... this is not that "impossible" and the speed of that tunneling has no upper bound on velocity within the evanescent field.
« Last Edit: 20/04/2010 03:33:00 by Good Elf »
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Offline JP

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I could argue with a lot of what you're saying here, but to keep things on point, you haven't addressed my post.  You claimed you could set your invariant mass to zero somehow, which would let you travel at the speed of light.  I said you can't do this.  How does your above post addresses this?

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Offline Good Elf

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Hi JP,

Quote from: JP
You claimed you could set your invariant mass to zero somehow, which would let you travel at the speed of light.  I said you can't do this.  How does your above post addresses this?
No I didn't say anything about travel "at" the speed of light... I meant instantaneous connections through the well known phenomenon of quantum tunneling... that is a lot faster than light. I am not actually claiming anything other than there are well known principles you might like to apply to this general problem... read above.

If a particle is in a quantum superposition state you cannot determine any property and the particle remains unmeasured. It is literally an unknowable... not only for you (the observer) but also to the rest of the universe provided it is decoupled quantum mechanically. While in that state it is "protected" from observations.

This should be seen in the same vein as entangled down converted BBO photons... the properties of the individual photons are not determined until one of the pair "dephases" and is read as an observation. Before this event... it is experimentally known that the states are not defined. At that point of dephasing no matter how far the entangled particles are apart there is an instantaneous connection that determines their orthogonal properties. This this has been experimentally determined and is entrenched in the Bell Inequality. There is an even stronger relationship if the particles are both within the evanescent field... such as in wave mechanical (quantum) tunneling. Until the classical property of mass is "collapsed" out in a measurement, it's final position and value will be determined through a measurement/observation when it dephases from the wave state and quantum entangles with the detector transferring it's qubit. The position of the detector determines where the particle has "traveled" to but it does not determine any specific path. Just apply Quantum Electrodynamic Principles to the particle and you then understand what I mean.
"Aa' menle nauva calen ar' ta hwesta e' ale'quenle"

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Offline JP

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Hi JP,

Quote from: JP
You claimed you could set your invariant mass to zero somehow, which would let you travel at the speed of light.  I said you can't do this.  How does your above post addresses this?
No I didn't say anything about travel "at" the speed of light... I meant instantaneous connections through the well known phenomenon of quantum tunneling... that is a lot faster than light. I am not actually claiming anything other than there are well known principles you might like to apply to this general problem... read above.

This is what you said:
Quote from: Good Elf
You can do this by "first" nulling  the mass of the spaceship. This is what is holding the spaceship back and limiting the amount of acceleration (it also provides you with achievable sources of energy to accelerate your spaceship and also solves that difficult problem of "time dilation" which is "pushing" you rapidly into the future). The next thing is to accelerate in a controlled way ... and any force will cause an infinite acceleration on a zero mass but be sure to adjust the passage of time appropriately otherwise you will end up on the wall of the lightcone (as before) and be eternally "stuck" there. You can do this trick using certain quantum techniques which undoes the quantum exchanges occurring due to the natural passage of time.
My concern is with setting the mass to zero, which isn't achievable. 

Quote
If a particle is in a quantum superposition state you cannot determine any property and the particle remains unmeasured. It is literally an unknowable... not only for you (the observer) but also to the rest of the universe provided it is decoupled quantum mechanically. While in that state it is "protected" from observations.
That isn't true.  You can know plenty about the particle.  The thing you don't know is determined by how the system is set up.  If you entangle electrons with respect to spin, you can know properties other than their spin.  You know their masses, their charges, you can know their position and momentum (up to the uncertainty principle) and their energy. 

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Offline Good Elf

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Hi JP,

Quote from: JP
Quote from: Good Elf
If a particle is in a quantum superposition state you cannot determine any property and the particle remains unmeasured. It is literally an unknowable... not only for you (the observer) but also to the rest of the universe provided it is decoupled quantum mechanically. While in that state it is "protected" from observations.
That isn't true.  You can know plenty about the particle.  The thing you don't know is determined by how the system is set up.  If you entangle electrons with respect to spin, you can know properties other than their spin.  You know their masses, their charges, you can know their position and momentum (up to the uncertainty principle) and their energy.
I am not sure if you are quite "getting this"... Properties such as spin, charge, optical polarization and mass are classical measurements. You can't know any of those things without collapsing the quantum state. You can entangle electrons ... etc... but you cannot know anything about these isolated quantum states until you actually measure them. Obviously it is very important to properly isolate the states and that may be hard... no denying that.

Before you actually measure the properties of these quantum states they do not have these properties... the properties actually come from the measurement and are interrelated. Check out the experimental details of Alain Aspect's Bell Inequality and also Yoon-Ho Kim, R. Yu, S.P. Kulik, Y.H. Shih, and Marlan O. Scully's Delayed Choice Quantum Eraser Experiment which is based on John Wheeler's original concept. The properties are determined at the time of reading of one of the entangled states. Setting up a "classical system" tells you nothing of the quantum state or where it is "evolving" to. After you measure the system it has become "classical" and the original quantum state has been "screwed up".

We obviously have a difference of opinion but I think I have said all I am prepared to say at this point... nice talking to you JP

Cheers
"Aa' menle nauva calen ar' ta hwesta e' ale'quenle"

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Offline diverjohn

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Another thought about exceeding the speed of light: if it were possible, how would we worry about the acceleration to and from such velocities?
 

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Offline Good Elf

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Hi diverjohn and JP,

It is nice seeing interest in these matters... diverjohn is new to this thread so I will make a short comment here...
Quote
Another thought about exceeding the speed of light: if it were possible, how would we worry about the acceleration to and from such velocities?
Quantum physics (more specifically... Quantum Electrodynamics) is concerned with events when the wavefunction collapses. The property of velocity is concerned with classical "paths". Acceleration is a classical phenomenon where a particle (with undeniable classical properties) under continuous observation is observed undergoing instantaneous changes in velocity. This incremental "classical" process of acceleration could never enable one to reach or exceed the speed of light. Some other way must be found to achieve any particle relocation in space.

If quantum physics was in anyway a description of "path"... electrons in atoms would "spiral" into the nucleus radiating energy as it goes... this just does not happen. However quantum wavefunctions do not deal with "paths" and is an entirely different physics dealing with "stationary states" of matter waves so it does not specifically need to worry about "speed" or "velocity"... they involve "quantum jumps".
"Aa' menle nauva calen ar' ta hwesta e' ale'quenle"

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Offline JP

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Good Elf,

You may be finished debating quantum mechanics with me, but if you're going to consistently misrepresent it to others, I'm going to reply.  I understand and agree that there is a distinction between quantum properties and classical properties, but your claims that quantum systems are completely undetermined until you measure them is misleading. 

An example of this is what is called an eigenstate in quantum mechanics.  This is just a fancy word saying that the wave function describing the particle has a definite value of some observable.  For example, if an electron is in an energy eigenstate, then it has a definite energy value.

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Offline Good Elf

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Hi JP, diverjohn, yor_on and all,

Quote from: JP
You may be finished debating quantum mechanics with me, but if you're going to consistently misrepresent it to others, I'm going to reply.
Fine... but please do your research and get your facts as correct as it is known and not just out of elementary texts and their simplified interpretations. I am willing to debate the issue with you but you really must do more work instead of making interpretations based on simplified theories of mechanics because I do not want to repeat myself endlessly if I am not getting across. You got to know to change the way you deal with these issues when speaking about the quantum state.

Quote from: JP
An example of this is what is called an eigenstate in quantum mechanics.  This is just a fancy word saying that the wave function describing the particle has a definite value of some observable.  For example, if an electron is in an energy eigenstate, then it has a definite energy value.
No it does not... wavefunctions are not used to define observables... they describe probability densities. You are sort of suggesting that we have some kind of "probability meter" whereby we are able to "measure" probability... sorry to disappoint... no such device exists.

Regarding atoms and the electron "shells"... There "may" be a definite value for the energy of certain stationary states but what we measure are only the transitions when atoms change state and either emit or absorb photons or electrons. The eigenstates are calculations of the wavefunction and there are no satisfactory explanations of these as classical measurements, they certainly do not satisfactorily address the theoretical problems with simplified models like the "Bohr Atom" for instance. I do not deny that it is possible to determine many things using classical methods of measurement or even calculation but that approach does not address the issues at the base of quantum behavior. Please accept that you need to have a "paradigm shift" to gain a more mature insight into quantum processes. Issues regarding the nature of this stationary state are still unresolved and are still currently satisfied by postulates assuming this "fact"... "a priori". Quantum processes are something that occurs all through all phenomena at this fundamental level and should not be thought of as only a function of atomic transitions. It is also more generally about light and it interactions with matter through electrons. The best way to understand this phenomenon is to read Richard Feynman's Book on Quantum Electrodynamics... "QED - The strange theory of light and matter".. In it all phenomenon at the level of electrons and photons are explained pretty clearly at a simple level... This is still the most accurate theory to describe mostly all known phenomenon. The behavior of atoms is described "loosely" in chapter 3. His approach is pretty casual so you should not expect too much. As a primer to the more general application of these ideas at a elementary level have a look at this short paper...
"Teaching Feynman's Sum Over Paths Quantum Theory" Edwin F. Taylor, Stamatis Vokos, John M. O'Meara, and Nora S. Thornber Computers in Physics, Vol 12, No. 2, Mar/Apr 1998, pages 190 thru 199

The energy of any system is subject to arbitrary baselines which are defined relative to known repeatable baselines such as the 1S0 lowest energy state for the first bound electron. This is not zero energy.  Between transitions when the electron is in a stable eigenstates there is absolutely nothing to be actually measured. There are no direct measurements of this "level" but only it's relative position in relation to the other levels. "Presumably" electrons and the photons are in superposition with all the other eigenstates possible in the system. At room temperature atoms are mostly "classical" objects forming molecules and allowing us to understand the properties of the outer shells through their chemistry but what makes them very interesting to me is their quantum behavior not this overt "classical behavior".

I would also point out that the theory of atomic orbitals is not entirely soluble being a many body problem. Perturbation Theory does not lead to the "stationary states" but the same old problems classical theory has always been prone to in trying to describe this behavior. All that exists are classical approximations for the systems with multiple electrons simply because this is not the accurate way to solve this problem. The idea that electrons simply "whiz" around the nucleus along spiral paths cannot be maintained.

Cheers
"Aa' menle nauva calen ar' ta hwesta e' ale'quenle"

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Offline JP

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Hi JP, diverjohn, yor_on and all,

Quote from: JP
You may be finished debating quantum mechanics with me, but if you're going to consistently misrepresent it to others, I'm going to reply.
Fine... but please do your research and get your facts as correct as it is known and not just out of elementary texts and their simplified interpretations. I am willing to debate the issue with you but you really must do more work instead of making interpretations based on simplified theories of mechanics because I do not want to repeat myself endlessly if I am not getting across. You got to know to change the way you deal with these issues when speaking about the quantum state.

You're getting your point across.  It's just that the points you're making aren't representative of the mainstream theory of quantum mechanics.  Maybe it's a misunderstanding of language.  Just because physicists say that something is undetermined until they measure it in quantum mechanics doesn't mean that they have zero information about the quantum state before measurement. 

As for textbooks, here are two that I've used that come to mind: Principles of quantum mechanics and Advanced quantum mechanics

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Offline Good Elf

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Hi JP,

Your books are 1994 vintage. I do not accept that a blanket quote from a large literary work of 650 pages is any form of scholarship. Quite a bit has happened over the intervening years regarding the interpretation of QM. Some bits will still be good but others may become very dated nowadays. I quote papers which are more or less current theory. Try this, along with the other references I have supplied, for a more modern approach to the interpretation...
Heisenberg, Matrix Mechanics, and the Uncertainty Principle - S. Lakshmibala Check out the section on Matrix Mechanics...
Quote from: S. Lakshmibala
We now face an interesting situation. Recall that, by performing an appropriate measurement on the system, we know the state of the system just after the measurement. Was this the state of the system before the measurement? Not necessarily! For, prior to the measurement, the system could have been in a linear superposition of different eigenstates, with unknown (and unguessable) coefficients. It is like saying that in a coin toss experiment whose outcome is a “head”, the coin could have been in a state which was a combination of head and tail before it was tossed! Of course, this would never be the case for actual coins, governed as they are by the laws of classical physics. But then, what was the precise state of the quantum system before the measurement? The answer is: we cannot know. The Copenhagen interpretation is concerned only with outcomes of experiments. Deep philosophical questions, peculiar to quantum mechanics, now arise (Box 4).
My inference is if we as an observer "cannot know" then this same information is also withheld from the universe at large because information at this level is quantized and is not "duplicated" elsewhere. Ultimately this information is transferred to a de facto measuring system while dephasing acting with quantized action and energy transfers...then read Box 4.
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Box 4. Is quantum mechanics complete?
If we can never know the pre-measurement state of a system, is not the theory inadequate, or at least incomplete? For, after all, the system surely has an existence of its own, independent of the act of measurement! (This question is also applicable to wave mechanics, for it too cannot predict the pre-measurement state.) Numerous proposals, including a variety of so-called hidden variable theories, have been made to overcome this inadequacy, but none of these is fully satisfactory. The last word has probably not been said yet in this regard.
The next experimental point to address is the recent experiments which test the validity of Hardy's Paradox (check out the 5th reference for a recent definitive experiment revealing the problem). The Copenhagen Interpretation of this experiment is clearly not correct and leads to "counter-factual results". The meaning of this is in how probability evolves in quantum states... It is possible to have negative values of probability. Negative values of probability are discussed in part here. This appears to be a couple of ways in which this paradox may be resolved (not including a strict Copenhagen Interpretation). A paper that addresses this conundrum can be found here...
Hardy's Setup and Elements of Reality - Louis Marchildon (Submitted on 17 Feb 2009 (v1), last revised 23 Jul 2009 (this version, v2))
The actual measurement "chooses" the output state. The physical existence before the final measurement is undefined and cannot be resolved using local hidden variables but may be resolved with non-local hidden variables but what this means is not defined (perhaps to do with global values in the external Universe as a whole... perhaps referring to remote entanglement connections as would be the case with Cramer's (Wheeler-Feynman) QM Interpretation. This means no "real valued" local measurables. If some "real" value existed before this state collapse measurement was made it should have had a real positive probability and not a negative value (which is what was found through a partial protective measurement as in the experiment). One conclusion is the "real" value did not exist until the measurement was performed. I take this to mean the "real" value is only determined by the measurement when the wavefunction collapses. Before then the value of a measurable has "no element of reality".
"Aa' menle nauva calen ar' ta hwesta e' ale'quenle"

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Offline JimBob

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I continue to be amazed that a limnologist can take to task a post-doctorate physicist (from one of the most highly regarded schools of physics in the world) for having incorrect ideas in physic when that person is obviously the one who will hold a chair in physics in his old age, while the limnologist, should he survive the waters of Queensland, will still be trying to get grants to count the number of bugs from a canoe. But then, perhaps I have the wrong person and shudder - the actual person is in the field of geology. I am ashamed of my profession if so.

Just who has the training and eduction to most likely have the right answers to the questions being discussed? Did my intro help?

As I tell my students, don't throw a book out. It could be the one that sets the foundation for you future. After all the idiots get through mucking up the subject into an incoherent mess because of the pressure to publish, and publish data that isn't well edited, the roof collapse and that 1994 book that explained in simple literary terms the mystery of quantum mechanics the limnologist so quickly dismissed for pressurr-published quackery will be the source book for a new science based on the ideas it contained. The smart survivor creeps back to seminal 1994 book and start over with the correct assumption. I believe those who threw away William Smith's 1815 Book on The stratification in the canals of England did a bit of backtracking in this manner as newer forces in sciences realized that he had pioneered a completely new field of science. In 1836 William Smith was porclaimed "The Father of English Geology" and was conferred a Doctorate of Laws (LL.D.) from Trinity College, Dublin, for his "Simpleton Work"  Perhaps not as seminal a work as Mr. Smith's, the 1994 book -so recently trashed - can still teach a young non-physicist the value of humility.

The posts of the disaffected dwarf seems an exercise in hubris - the Greeks had this type of behavior well spotted and exceedingly well named. Yet the Greeks were more educated than the a-for-said dwarfed creature of small stature. The Grreks did not find it necessary to vilify, and ascribe habits of ill character to ones verbal sparing partner. The Greeks believed the winner was the one whitch presented the best argument, not the most viscous personal castigations. The winner used his brain, not his power to insult.

I would hope The Good Fairy would re-read the acceptable use policy agreed to when asking for the privilege of posting to the site. Part of that policy prohibits personal attacks.

Any such attack and the elf bites the dust - or is sent to a dwarf as a mining slave. (HEAD THE WORDS OF THE MODERATOR!! ME! The Hornytoaded One) We tolerate fools little here, especially fools that violate the rules. These get hung, drawn, quartered, displayed at the city gates, then banned.

Just so all people know where the rules are - here is the link: http://www.thenakedscientists.com/forum/index.php?topic=8535.0

(I can't speel. Never have been able to. No one hires me a secretary any more!)
« Last Edit: 24/04/2010 17:34:39 by JimBob »
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline JP

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Your books are 1994 vintage. I do not accept that a blanket quote from a large literary work of 650 pages is any form of scholarship. Quite a bit has happened over the intervening years regarding the interpretation of QM.

Quite a bit has happened on the frontiers of quantum field theory and speculative theories like string theory as well as in experimental quantum mechanics.  The postulates of quantum mechanics haven't changed in the past 16 years.  I provided those links to show you that I have actually studied quantum mechanics since rather than debate the science, you seem happier to point out that I haven't done any work to learn the theory.  I have.  But we shouldn't be debating my credentials, we should be talking about the science involved.  

Quote
Try this, along with the other references I have supplied, for a more modern approach to the interpretation...
Heisenberg, Matrix Mechanics, and the Uncertainty Principle - S. Lakshmibala Check out the section on Matrix Mechanics...
I know the matrix formulation of quantum mechanics.  It's used in the sources I cited.  It doesn't support what you're saying.   The paper you cite isn't anything new.  It's a review (for teaching purposes) of existing (vintage 1920s) techniques.  

As for Hardy's paradox, I'm not as familiar with that.  Looking it over briefly, it seems to have nothing to do with the main point of our argument, as it arises from standard quantum mechanics.  Your claims about quantum mechanics are well outside the bounds

Finally, pages 115-118 Principles of quantum mechanics give the basics of eigenstates.