Splitting Space From Time

[thnkrx]

http://www.scientificamerican.com/article.cfm?id=splitting-time-from-space

Apparently, this offers a resolution of sorts to some of the thornier problems in quantum mechanics, and puts forth a solution of sorts to the 'missing mass' (dark matter/dark energy) thing as well.

More specifically, the problem is the way that time is tied up with space in Einstein’s theory of gravity: general relativity. Einstein famously overturned the Newtonian notion that time is absolute—steadily ticking away in the background. Instead he argued that time is another dimension, woven together with space to form a malleable fabric that is distorted by matter. The snag is that in quantum mechanics, time retains its Newtonian aloofness, providing the stage against which matter dances but never being affected by its presence. These two conceptions of time don’t gel.

The solution, Hořava says, is to snip threads that bind time to space at very high energies, such as those found in the early universe where quantum gravity rules. “I’m going back to Newton’s idea that time and space are not equivalent,” Hořava says. At low energies, general relativity emerges from this underlying framework, and the fabric of spacetime restitches, he explains.

This is interesting as well:

Gia Dvali, a quantum gravity expert at CERN, remains cautious. A few years ago he tried a similar trick, breaking apart space and time in an attempt to explain dark energy. But he abandoned his model because it allowed information to be communicated faster than the speed of light.

Whats wrong with having information moving faster than the speed of light?

 

[MeteorWayne]

It violates physics?

 

[thnkrx]

Whats wrong with having information moving faster than the speed of light?

It violates physics?

Or maybe it doesn't...at least not if this theory is actually legit. It does give at least the appearance of valid solutions or approaches to valid solutions in other areas of exotic physics...

 

[SpeedFreek]

Well, the reason that faster than light information violates physics is due to causality. With FTL you end up with some observers calculating that the effect happened before the cause. Someone might work out that information arrived before it left!

 

[andrew_t1000]

Could this be exploited for a "warp drive"?
Somehow getting time and space out of phase so to speak?

Ok Wayne, shoot me down in flames!
But when you say any kind of FTL drive violates the laws of physics, I'm going to have to point out that an FTL drive violates known laws of physics.
We don't know everything, far from it!

Ok, flame me now!

 

[thnkrx]

Well, the reason that faster than light information violates physics is due to causality. With FTL you end up with some observers calculating that the effect happened before the cause. Someone might work out that information arrived before it left!

According to relativistic theory, which closely links space and time. The scheme put forth in the article has space and time being separate in at least some instances, hence faster than light communication might be possible in some circumstances.

 

[Solifugae]

Well, the reason that faster than light information violates physics is due to causality. With FTL you end up with some observers calculating that the effect happened before the cause. Someone might work out that information arrived before it left!

This is only based on carrying on the curve from known experiments of time dilation, right? It's not like we can actually experiment with what will go on beyond light speed, however I wonder why physicists have come to the conclusion that faster than light results in events occurring before their cause.

If lower than light velocities have causes occurring before events, but due to time dilation this asymptotes towards infinity at light speed, it does not logically follow as a necessity that beyond this point, events occur before their causes. There must be a specific mathematical reason this is the case that I'm not aware of.

To simplify: if time before light speed is numbers decreasing towards 0 and at c it is 0, it does not necessitate that beyond c, it will be minus numbers.

 

[darkmatter4brains]

Well, the reason that faster than light information violates physics is due to causality. With FTL you end up with some observers calculating that the effect happened before the cause. Someone might work out that information arrived before it left!

This is only based on carrying on the curve from known experiments of time dilation, right? It's not like we can actually experiment with what will go on beyond light speed, however I wonder why physicists have come to the conclusion that faster than light results in events occurring before their cause.

If lower than light velocities have causes occurring before events, but due to time dilation this asymptotes towards infinity at light speed, it does not logically follow as a necessity that beyond this point, events occur before their causes. There must be a specific mathematical reason this is the case that I'm not aware of.

To simplify: if time before light speed is numbers decreasing towards 0 and at c it is 0, it does not necessitate that beyond c, it will be minus numbers.

Special Relativity does predict the effect preceeding the cause thingy you guys are talking about. Utilizing the Lorentz transformation equations and analyzing different frames you will run into this problem for FTL travel. It doesn't say that this will always happen in every frame, but you can almost always find a frame that will see the effect before the cause. it's simple algebra and frame analysis in special relavitity. If you'd like to see the math, check out Spacetime Phyiscs by Taylor and Wheeler. They have a well written detailed example of how this will come about.

I guess you could argue that if special relativity is incomplete and FTL is somehow possible - although beyond our current understanding of physics - then these mathematical predicitons of SR are just plain wrong, becuase we are using it outside it's domain of vailidity. I doubt it though - FTL just doesn't seem to fit into the structure of the Universe.

 

[andrew_t1000]

Haven't there already been quantum entanglement experiments that have received data faster than it could have been sent by normal means?

 

[emperor_of_localgroup]

To simplify: if time before light speed is numbers decreasing towards 0 and at c it is 0, it does not necessitate that beyond c, it will be minus numbers.

There you go. See another thread in which many here agree with the idea there is no Negative quantities.

If that is the case, time can not be negative but it would be opposite of previous value (most likely opposite direction). In such case can we logically conclude object will reverse its direction of motion? Note, if time is 0, is object's motion virtually stopped?? Then how can it be traveling at c? Does it reach an unknown territory of time? Further increase in c can only reverse object's motion. It sounds very practical to me. If not,then it is an example of failure of our current math which relies too much on imaginary and negatives.

 

[GreyMatters]

Well, the reason that faster than light information violates physics is due to causality. With FTL you end up with some observers calculating that the effect happened before the cause. Someone might work out that information arrived before it left!

Sorry to be a stickler here, but isn't this only with inifite speeds? Einstien stated that the universe had to have a non-infinite speed limit for causality to be logical. The speed of light is thought to travel at this speed, the speed limit Einstien talked about. However, the speed of light is hardly inifinite, or even near infinite.

Please, explain how something traveling faster than the speed of light, but non-inifinite, can create illogical causality. Illogical causality only arises at infinite speeds, if my math memory serves correctly. I guess that you assume that if it is traveling faster than light it is traveling infinitely fast. Inflation theory takes care of this question quite nicely without having illogical causality but having a speed limit larger than the current speed of light.

Next, please explain how the restriction of Mass to being less than the speed of light, the speed limit, is associated to information. To be more specific, what mass has been described by physics, measured, and observed to be transporting the information between quantum entangled pairs? It might have mass, sure, but it might not. It might be something we know nothing about, travels faster than light, but non-infinite, and remains logical to causality.

Finally, you still haven't responded to this puplished, peer reviewed article claiming faster than light information transfer:

http://www.nature.com/nature/journal/v454/n7206/full/nature07121.html



Thanks.

 

[SpeedFreek]

Firstly, I must apologize for missing your post from the beginning of this month in that other thread. All I can say is that I had to clear my cache, cookies etc a couple of weeks ago, and all posts were then marked unread, so that is probably why I missed it.

Okay, this is complicated to explain. Firstly, you are confusing the "spooky action at a distance" - the influence between entangled particles, with the transfer of information in the classical sense. We can know afterwards, once the "wavefunction has collapsed" and we are able to compare the particles final states, that the influence between them was indeed faster than light. But we cannot find a way to use entangled particles as a mechanism to send information at all, which is a whole subject unto itself! But in a nutshell you might think of it like this - you cannot create particle pairs with predetermined spins, you have to measure them to know their spins, and doing so changes their spins... there is no way to "orient" both ends of the communication with those spins.

An example of this "influence" is found with the delayed choice quantum eraser. In fact, with this experiment we find that the "spooky action at a distance" even seems to work backwards in time!

When they send photons through the slits and then down-convert them into two separate streams of entangled pairs, then send one of the pair from each stream to the first detector, they cannot correlate those "signal" photons that hit the first detector screen with their entangled pairs until their pair particles have been detected themselves. Then they have to correlate the data, which can only happen at the speed of light.

So, they have an entangled partner particle, an "idler" photon, for every "signal" photon that hits the main detector. They know which slit each of these "idlers" original photon went through, and if they send them straight to another detector and correlate these hits with those of their "signal partners, after the fact, they find no interference pattern buried in the data for all the hits on the first detector. But if they mix the "idlers" up and so do not know which slit their original photon went through, they do find an interference pattern when they correlate the data from the detector screens.

They can even make the choice as to whether to erase that "which slit" information, or not, after all the signal photons have hit the first detector, and find that if they then choose to mix up the "idlers", their hits on the final detector create an interference pattern with the hits of their partners, which were recorded earlier. So, the spooky action at a distance has an influence that seems to work backwards in time. The reason for this might seem to be that the spooky "influence" moves faster than light does.

So, why does moving faster than light mean something moves backwards in time, violating causality? Because, if it applied to the actual transfer of information, you would know in advance what choice the experimenter made about whether to erase the "which slit" information from the "idler" photon, before they made their decision! :x

It all depends on how you choose to define "now". My "now" and your "now", if we are standing a meter apart. If the speed of light is the fastest that information can be sent at, then the difference between my now and yours is the speed that the information of our "now"s passes between us. If no information can pass between us faster than light (even if the spooky action can), then our information of each others time-frame can only be thought of in terms of c. This means that if I shot you with an FTL bullet, somebody standing closeby would work out, after subtracting light/information-travel time from their calculations, that I died before you shot me!

Now as for inflationary theory, that is just an extreme case of expansion where distances down at the planck length are increasing at c, so everything in the universe is receding from everything else superluminally. But just the same is true today, at a larger scale. Galaxies that are at the edge of our Hubble sphere are receding at the speed of light and the galaxies beyond are receding faster still. But just as the speed of light is c relative to us over here, it is also c relative to those galaxies over there. Nothing is moving through space faster than a photon, except for the spooky quantum action. Inflation does not mean information traveled through the universe faster than light, it means the universe expanded faster than light.

Now that nature paper (I am not a subscriber so I can only read the abstract).

They are talking about the speed of the influence across space-time, as viewed by a hypothetical universal privileged reference frame, and the influence exceeds c. Of course, with relativity Einstein showed us there is no actual privileged universal frame - so, in local frames of reference like our own we cannot consider classical information to travel faster than light without violating causality and we cannot find a way to use quantum entanglement to transfer information, but we understand that the spooky action at a distance works faster than light once we correlate the information about the influence.

But, in the end, the best way I can think of right now to describe the whole shebang is that, relative to space, time moves at the speed of light, but entanglement moves faster than time.

I hope this post goes some way to making up for my previous oversight regarding your earlier question!

 

[weeman]

So Speedfreek, I have a question that came about after your discussion about quantum entanglement.

I was recently watching Dr. Michio Kaku's show on the Science channel about the possibilities of teleportation in the near future. Dr. Kaku talked repeatedly about how quantum entanglement is being studied in laboratories to possibly harness the instantaneous transfer of information. Yet, your explaination describes quantum entanglement as not being able to transfer information (at least now with our present understanding). Was I misunderstanding what he was saying or are these two sides to the same coin?

Where am I getting confused?

 

[thnkrx]

Of course, with relativity Einstein showed us there is no actual privileged universal frame - so, in local frames of reference like our own we cannot consider classical information to travel faster than light without violating causality and we cannot find a way to use quantum entanglement to transfer information, but we understand that the spooky action at a distance works faster than light once we correlate the information about the influence.

That is relativity. The article I linked to and quoted from describes a theory which separates time from space in the above situation - at least if I understood it correctly.

 

[GreyMatters]

Thanks again for the reply speedfreak.

Still very confused by all this. You say entanglement interactions happen at FTL speed, but it can't send information. Ok.

So, why does this article, and many others, discuss using quantum entanglement as a tool for quantum computers? It seems reasonable to assume that if they think a computer can be built using quantum entanglement then quantum entanglement can be used to send information. And, even if we can't "read" the information FTL, the information WOULD be sent FTL in quantum entanglement computing.

Here is the article:

http://plato.stanford.edu/entries/qt-entangle/

 

[SpeedFreek]

I was recently watching Dr. Michio Kaku's show on the Science channel about the possibilities of teleportation in the near future. Dr. Kaku talked repeatedly about how quantum entanglement is being studied in laboratories to possibly harness the instantaneous transfer of information. Yet, your explaination describes quantum entanglement as not being able to transfer information (at least now with our present understanding). Was I misunderstanding what he was saying or are these two sides to the same coin?

Where am I getting confused?

In my opinion you should take whatever Michio Kaku says about FTL transfer of information with a pinch of salt (and the same goes for his multiverse descriptions). He likes to sensationalize the subject for the masses, perhaps with good intent, to raise awareness about science (and perhaps to encourage funding!) but I think he does the real science a disservice with his descriptions.

http://en.wikipedia.org/wiki/Faster-tha ... _mechanics

 

[SpeedFreek]

Of course, with relativity Einstein showed us there is no actual privileged universal frame - so, in local frames of reference like our own we cannot consider classical information to travel faster than light without violating causality and we cannot find a way to use quantum entanglement to transfer information, but we understand that the spooky action at a distance works faster than light once we correlate the information about the influence.

That is relativity. The article I linked to and quoted from describes a theory which separates time from space in the above situation - at least if I understood it correctly.

Remember, the article says that other physicists have looked into this issue but found that whatever they tried they ended up with FTL information (which violates causality).

The key issue though, is the domain of applicability. Quantum physics accurately describes what happens at the quantum scale, whereas relativity accurately describes what happens at the macro scale. But as to what happens in the conditions close to those just after the Big-Bang, we need a theory of quantum gravity, and perhaps there is a chance that Hořava is onto something.. we will have to wait and see.

 

[SpeedFreek]

Thanks again for the reply speedfreak.

Still very confused by all this. You say entanglement interactions happen at FTL speed, but it can't send information. Ok.

So, why does this article, and many others, discuss using quantum entanglement as a tool for quantum computers? It seems reasonable to assume that if they think a computer can be built using quantum entanglement then quantum entanglement can be used to send information. And, even if we can't "read" the information FTL, the information WOULD be sent FTL in quantum entanglement computing.

Here is the article:

http://plato.stanford.edu/entries/qt-entangle/

If you read the section of the article about quantum computing you should see it has nothing to do with "sending" information FTL, it is about using the "superposition" of a quantum "bit" to examine multiple values at the same time, rather than sequentially as is the case with normal computers. The potential is enormous for things like code-breaking and encryption.

I think the confusion here lies with the notion of "classical" information transfer. Whilst quantum entanglement means information passes between particles FTL, we cannot use it as a form of communication. Even with quantum teleportation, we can pass information of a quantum state from one place to another, faster than light, but we cannot define that state before the event. I might be wrong, but I all can see so far is the potential to be able to communicate what is effectively random garbage information faster than light. We might be able to pass information faster than light, but we cannot control what that information is. Remember, you cannot know the quantum state of something until you measure it, and measuring it changes the state.

It seems to me that, in all the cases cited, they find out afterwards what the information was, rather than being able to "code" the information themselves.

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

 

[GreyMatters]

A quote from the article:

5. Quantum Computation
Quantum information can be processed, but the accessibility of this information is limited by the Holevo bound (mentioned in Section 3). David Deutsch (1985) first showed how to exploit quantum entanglement to perform a computational task that is impossible for a classical computer.

Seems the article is very clear that quantum entanglement can be used to do a computational task. Are you saying that in the process of a theorectical "computational task" that no information is being transmitted?

Then there are articles saying QTE interacts with its pair at FTL, but we can't interrupt the "information" of the interaction until the wave collapses. You even said the same in this thread.

Is it this interaction of the QTE pair that is used to perform the "computational task", the same interaction that is FTL, or is it some other property of a QTE pair that is being "exploited"?

Not arguing the slower than light "reading", due the the wait time of the collapsing wave, how could the computer know what order the interactions are happening in, if the interactions are FTL, and happening, as you say, before they happened?

I know, lots of questions. It is just this is very interesting. Thanks for taking the time for your responses.

 

[SpeedFreek]

A quote from the article:

5. Quantum Computation
Quantum information can be processed, but the accessibility of this information is limited by the Holevo bound (mentioned in Section 3). David Deutsch (1985) first showed how to exploit quantum entanglement to perform a computational task that is impossible for a classical computer.

Seems the article is very clear that quantum entanglement can be used to do a computational task. Are you saying that in the process of a theorectical "computational task" that no information is being transmitted?

Not quite. Information (as in the spooky influence of one particle on another) can pass between particles faster than light using quantum entanglement, but we cannot know what that particular information is, until the outcome of the experiment (or in this case, the operation) is decided. But the issue here is not the speed of the influence, it is the quantum superposition - the concept that a particle can be considered to be everywhere at the same time, until we measure where it really is (but unfortunately we cannot know where it was).

The reason that the task is "impossible" for a classical computer is that it would take too long (think of cracking encryption here). It is impossible to quickly crack encyrption, but with enough computer power and enough time you can do it. It involves working out prime numbers.

But a quantum computer can, if you like, examine all possible answers for each quantum location in its program, at the same time! So suddenly we can work out high prime numbers and crack encryption codes very quickly indeed! This is impossible for a classical computer.

The computers power comes from its exploitation of the superposition, but it uses entanglement in the process. It is what allows the result of all possible outcomes for the superposition to emerge, if I understand it correctly - it is how the wavefunction collapse for each q-bit propagates throughout the system.

Now as soon as we get quantum computers working, we will need to improve encryption methods, and here perhaps there is a use for entanglement, so that the decryption key does not even exist until after the encrypted message has been received! We are back with the delayed choice quantum eraser once more. But yet again, the decryption key would be an arbitrarily generated random quantum sequence we cannot control.

At least, that's how I understand it.

 

[Solifugae]

but I all can see so far is the potential to be able to communicate what is effectively random garbage information faster than light.

Hmmm. I can't think of anything useful. It seems you can only send information that would yield the same result as no information.

A bomb is ten light years away from Earth, and will explode at 55:51 local time when a detector measures that an entangled particle has a certain spin. This particle is entangled with a particle back in the control room on Earth, and the physicists will collapse the wave function of that particle resolving the spin of the particle ten light years away.

While the bomb would have exploded anyway had it measured the triggering spin, collapsing the wave function from the other side instead of the control room, this does not resolve the fact that the physicists have responsibility for triggering the bomb if they had collapsed the wave function, and this trigger is resolved at faster than light speeds. The only way they could trigger it in the conventional sense is if they could choose what spin the first particle will collapse into, therefore collapsing the distant particle into the same state, arming the bomb. I don't think it's possible to force a particle to have a certain spin though, is it?

In another case: If you tried to send a message using a sequence of entanglement you'd have to tell someone what time you were sending the message at, and what the message would be, which would be completely pointless. :?

 

[GreyMatters]

speedfreak, thanks again. very interesting stuff. You answered a lot of questions.