# The "double slit" phenomenon.

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In the classic experiment, particles sent through a single slit behave as if they've been sent through a single slit, while even if sent one at a time in a direction with two slits, they display an interference pattern after enough have been sent to make a pattern show up.

That still dosn't explain really how each individual particle KNOWS it has a choice of two slits... right?

How is this mathmatical change distributed through the path of the experiment? It must happen instantly, therefore the effect travels faster than light - but no force can travel faster than light - as it needs carriers of that force to interact with.

What if the very act of creating an extra choice in the path of/for the particle makes some kind of inherent "pattern" within the fabric space/time for the particle to travel through?

This "pattern" is what directs the particle to exhibit it's wave-like properties or interference. No force involved, just math.

(While writing this I just struck upon the idea that gravity could also be faster than light? If the sun suddenly wasn't there - would we still orbit where it was for the next 8 mins or not?)

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"Spooky" action resulting from quantum entanglement does occur faster than light, however it cannot be used to send information. (or rather, it can, but it will always require something else travelling at the speed of light or slower) However, fire two entangled photons in opposite directions, and have a double slit for one to pass through a kilometer, an AU, a light year, or a parsec away... if you try to garner 'which path' information from the entangled photon, it will destroy the interference pattern for the other photon instantaneously. Such behavior is said to be non-local and thus not subject to the limitations of the speed of light (which is a limitation of movement over a distance)

Quantum physics would say the interference pattern demonstrated by one-particle-at-a-time double slit experiments is the result of the interference between the probability waves for the two slits.

Einstein predicts that gravity waves (or any gravitational effects) are also bound by the speed of light. If you could somehow magically teleport the sun away to the other side of the universe, we wouldn't know or care until 8 minutes, when we would notice the sun blipping out of the sky and its gravitational effects vanishing.

At least one experiment has claimed to have verified this intrinsic limit:

http://www.newscientist.com/article.ns?id=dn3232

However several subsequent papers have called their result into question. All we can really claim is that GR predicts the effects of gravity propagate at the speed of light, but this is still lacking proper experimental verification.

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What you refer to as a particle has wave properties. The wave passes through both slits, and the particle interferes with itself. Unless you can determine that it can only go through one slit (aka a "which-path" experiment), in which case there will be no interference pattern.

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Some people believe this little phenomenon to be physical evidence for parallel universes.

Also, my physics teacher says that if the sun was to spontaneously disappear we would feel the effects immediatly, however, I would not trust her word as undoubtably correct.

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Some people believe this little phenomenon to be physical evidence for parallel universes.

Also' date=' my physics teacher says that if the sun was to spontaneously disappear we would feel the effects immediatly, however, I would not trust her word as undoubtably correct.[/quote']

8 minutes later... not instantly

Regards

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Some people believe this little phenomenon to be physical evidence for parallel universes.

Not so much parallel universes as extra dimensions. String theory speculates that the interference comes from extradimensional particles entangled as part of the same p-brane.

Also, my physics teacher says that if the sun was to spontaneously disappear we would feel the effects immediatly, however, I would not trust her word as undoubtably correct.

Good, because she's wrong. Gravity propagates at the speed of light, at least according to GR and the best experimental evidence to date. Otherwise you would have a means of sending information (albeit in an EXTREMELY difficult impractical/improbable process) faster than the speed of light, which is a big no no according to GR.

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However, fire two entangled photons in opposite directions, and have a double slit for one to pass through a kilometer, an AU, a light year, or a parsec away... if you try to garner 'which path' information from the entangled photon, it will destroy the interference pattern for the other photon instantaneously. Such behavior is said to be non-local and thus not subject to the limitations of the speed of light (which is a limitation of movement over a distance)

I don't understand how this could be right. It looks like a perfect setup for FTL communication:

Fire two entangled photons in opposite directions, one at a manned station 1 AU away, and the other at a manned station 1 AU away. Have double slits for them to pass through at each station. But at one of the stations, garner which path information from the entangled photon if you want to say hello to the other station 2 AU away. This will destroy the interference pattern for the other photon instantaneously.

The other station could easily read it as:

Interference pattern = no hello

No Interference pattern = hello

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I don't understand how this could be right. It looks like a perfect setup for FTL communication:

Fire two entangled photons in opposite directions' date=' one at a manned station 1 AU away, and the other at a manned station 1 AU away. Have double slits for them to pass through at each station. But at one of the stations, garner which path information from the entangled photon if you want to say hello to the other station 2 AU away. This will destroy the interference pattern for the other photon instantaneously.

The other station could easily read it as:

Interference pattern = no hello

No Interference pattern = hello[/quote']

I don't think you can garner that information from the entangled photon. The other photon would still be "facing" 2 slits and 2 choices. So that "portion" of the photon's wave function could not be collapsed in this way.

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You can't deduce an interference pattern from a single photon. You need several over a period of time in order to begin to notice it.

Also, in order for photons to be entangled they have to start at the same place. So communication is still bounded by the speed of the photon, namely the speed of light.

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You can't deduce an interference pattern from a single photon. You need several over a period of time in order to begin to notice it.

Also' date=' in order for photons to be entangled they have to start at the same place. So communication is still bounded by the speed of the photon, namely the speed of light[/b'].

The idea though is if you could do what losfomot suggests then you could communicate faster than light. If we set up a few (I think you need 3 but with more we could be closer, and at least keep it in our solar system) communications "corridors" with steady streams of these photons then I could tell you tommorrows race results or stock market results.

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Gravity is faster than light if you consider black holes where light/photons doesn't even escape. Contrary to popular believe gravity is the fastest thing in our universe, not light. An inference from the experiment is that causality is not universally true, and a good arguement for free will.

"we see the world as we assume it exists" ...Bohr

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Gravity is faster than light if you consider black holes where light/photons doesn't even escape. Contrary to popular believe gravity is the fastest thing in our universe' date=' not light. An inference from the experiment is that causality is not universally true, and a good arguement for free will.

"we see the world as we assume it exists" ...Bohr[/quote']

Hmm... otherwise gravity, and the light affected by it would move at the same speed. Therefore an "escape velocity" for light in black holes wouldn't be relevant.

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Hmm... otherwise gravity, and the light affected by it would move at the same speed. Therefore an "escape velocity" for light in black holes wouldn't be relevant.

But the gravity causes curvature, and that curvature is already in place. I think it might be more appropriate to think of it as changes in gravity propagating at c.

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Since the resultant force between light and gravity in black holes act in direction of gravity it is reasonable to assume gravity is faster, and not necessarily at C. As in all curvature the deciding force follows after its crest, which will go in favour of gravity.

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Since the resultant force between light and gravity in black holes act in direction of gravity it is reasonable to assume gravity is faster, and not necessarily at C. As in all curvature the deciding force follows after its crest, which will go in favour of gravity.

Since GR predicts that gravity propagates at c, and there is data to support the notion, I don't see how that is reasonable at all.

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Since GR predicts that gravity propagates at c, and there is data to support the notion, I don't see how that is reasonable at all.

That gravity isn't faster than light? Anyway I am not entirely sure what GR is trying to say, I only gathered my own reference. I think he is trying to say gravity is constant, at least in proportion to photons, which is not entirely true depending on the system of the suspension. Gravity on earth is 9.8, but this value is not universal for all forces of similar nature. On a Quantum level for instance, gravitational pulls between classic electrons are of variable speed depending on the charge, state, excitation, and atomic structure.

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That gravity isn't faster than light?

Changes in the curvature of space (i.e. gravity waves) propagate at c

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Can someone please explain space/time curvature at the speed of light. From my little inference I think it means gravity(curveture) spreads at the speed of light. If this is true then why can't light escape the gravitational force of black holes?But what do I know? Help.

http://www.metaresearch.org/cosmology/speed_of_gravity.asp

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Can someone please explain space/time curvature at the speed of light. From my little inference I think it means gravity(curveture) spreads at the speed of light. If this is true then why can't light escape the gravitational force of black holes?But what do I know? Help.

http://www.metaresearch.org/cosmology/speed_of_gravity.asp

But once the curvature is there' date=' you don't need anything to propagate - it's static. Changes in the curvature will also propagate, and do so at c.

Van Flandern's site just goes to show that Sturgeon's Law is valid.

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What you refer to as a particle has wave properties. The wave passes through both slits, and the particle interferes with itself. Unless you can determine that it can only go through one slit (aka a "which-path" experiment), in which case there will be no interference pattern.

Swansont - the model QM presents here makes no sense . Electrons do not glibly separate into two halves and then make an orderly reformation and produce th interference pattern. The "wave aprticle duality": is a *stop-gap " term conveniencing the experimentors that want to move along and away from the two slit experiment. The electron has never been measured other than a near point particle.

QM is on an analogous trrack , but frightfully as long a way from the correct description as one theory can get. What is occuring is the + and - spin states of the electron are oscillating in time so the electrons are demonstrating +-+-+-+-+-+- for the spin state history of the prepolarized electron.

. When one hole is open only, the polarized electron (and the polarized observed state either (+ or -) ) must take one of the holes. When two holes are open the nonobserved state transitions through the extra hole to merely providuing navigation input for the electron that is rapidly adjusting its intrinsic vibration motion to an equilibrium state.

The unobserved element location in a parallel trajectory has a broader range of adjustment input to the electron, as opposed to trailing the electron down one hole only. The electron is evolving from a massive chaotic vibration mode to the ordered complex mode as demonstrated by the scinitillation pattern.

The electron provides its own STern-gerlach transition environmjent by creating an inhomogeneous magnetic field when the electron charge distribution reflects off the surface containing the hole in the screen, Yess the electron picks its own hole. Look at the physics: the electron is predeeded to the hole by its own varying geometry distribution charge distribution and the recoil of the electron as it compresses the charge distribution tend to push the electrion back in the direction of its origin, but hallelujahjah!!, the electron senses a potential well in the volume over the hole where there is no reflected charge distribution to impede the electron motion. When the space where the charge distribution did not reflect from the wall of he screen. Where there is no repuslive force there is a natural hole that the electron enters long before it arrives at the screen. As the charge distribution is changing in time from reflection and the ever closer to the screen of fthe eklectron.proividing ean impulse through one of the allowed trajectory routes from hole exit to the screen. Th electron is doing it to itself in the hole during transition; after the electron leaves the hole the electron is polarized and all internal adjusments have been completed. (defined by the pattern on the screen) .

Likewise, the spin state of the electron is intrinsic to the electron which provides the on/off attributes of the spin states. on/nonlocal -l/nonlolocal + nonlocal - nonlocal + nonlocal None of the sdtates get turned off like a wall light switch, Thje spen states come and go as observed or and unobserved where the + and - states have observed status with eqalitarian perfection.and fairness..

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It's a shame that they were banned. I liked discussing the Sagnac effect with them. Until they came along, id never even heard of it.

Their posts yesterday left much to be desired, but the individual obviously spent a lot of time learning physics... to be ignored so easily.

Anyways, i think its a loss rather than a gain to the forum. It's not like that many people in the world are interested in physics to the point where they are familiarized with the Stern-Gerlach experiment.

Well anyways thats my two cents.

I don't think permanent bans should be come to so hastily. People should get warnings, and then temporary bans, and then if they continue, make them permanent. but to be so quick about it, is a bit well...

Regards

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But once the curvature is there' date=' you don't need anything to propagate - it's static. Changes in the curvature will also propagate, and do so at c.

Van Flandern's site just goes to show that Sturgeon's Law is valid.

If a local "curvature" changes, what would the need be to radiate the change? As the masses in a solar system are constantly changing their respective positions and relative gravity attractions throughout the solar syatem, it would seem that any one solar system would be a very visible, and noisy, radiator of "curvature". But, Einstein told us the forces of gravity gave way to a spatial curvature, so there doesn't seem like there is anything to radiate.

What is the signature of the signal in radiated curvature? How is the signal in a radiated curvature detected as an erstwhile gravity pulse?

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If a local "curvature" changes' date=' what would the need be to radiate the change? As the masses in a solar system are constantly changing their respective positions and relative gravity attractions throughout the solar syatem, it would seem that any one solar system would be a very visible, and noisy, radiator of "curvature". But, Einstein told us the forces of gravity gave way to a spatial curvature, so there doesn't seem like there is anything to radiate.

What is the signature of the signal in radiated curvature? How is the signal in a radiated curvature detected as an erstwhile gravity pulse?

[/indent']

As I understand it the curvature changes only if there is an acceleration. So for a single mass, moving at a constant v, there is no radiation. It looks completely static in its own frame. A binary system (or bigger) will radiate, but if one mass is large compared to the others, the acceleration is very small. Since the scaling factor is related to G you need really large accelerations to give off appreciable radiation.

This is why binary pulsars are one target of investigation. The binary stars will accelerate a lot (e.g. center of mass outside the star) and the fact that they are pulsars gives an easy thing to measure. Solar systems such as ours would be a much weaker source.

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Gravity is faster than light if you consider black holes where light/photons doesn't even escape. Contrary to popular believe gravity is the fastest thing in our universe' date=' not light. An inference from the experiment is that causality is not universally true, and a good arguement for free will.

"we see the world as we assume it exists" ...Bohr[/quote']

good point - remember, the universe is NOT a perfect vacuum, therefore c will be lower than the defined physical value - I cannot say how that impacts on the propagation of gravity.

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Stuff for first page:

Richard Feynman's "Sum of histories" is a good way to explain single particle travel in the double slit experment. The particle can travel either left or right, and therefore, the histories of ALL the paths it can take through the left and ALL the paths in can take through the right need to be taken into account. If you graphed these possibilities, you'd have a pretty good image of a pair of probability waves. Then you could combine them into a single wave. Fuzzy...

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