FTL communication

[ZetaX]

Welcome to the club nobody of us understands that, we are hypothesizing and trying to find an answer for that.

No, you are not hypothesizing. You are making stuff up that totally contradicts what we know about the universe. Learn some special relativity first.

[WestAir]

It seems like you're suggesting the Universe exists at one super-macro reference frame where C does nothing but get in the way of information transfer, and that if we could lift the vail of C we'd see the universe as it is "now" everywhere with no delay; and that FTL communication does just that.

But that doesn't make any sense to me. Right now I know that Andromeda is 2.5 million lightyears away - but if I were to suddenly accelerate to near the speed of light, thanks to length contraction it will be closer despite my physical distance never changing. Spacetime just contracts on its own and suddenly Andromeda is no longer 2,538,000 years in the "past". When I reach C, suddenly I'm in Andromeda. If by moving at C the time to reach Andromeda is 0, how is that not instantaneous?

[ZetaX]

Because it is only instantaneous in your frame of reference. But nowhere is anything moving FTL. The instanteneous mentioned above is different, as it is instantaneous in a chosen reference frame, e.g. the one earth and mars. We already epxlained that "instantaneous" is ot well-defined at all; you are bashing a dead horse.

[magnemoe]

If you take into account, that the 3rd observer changes position and intercepts messages halfway, than you make everything needlesly complex.

For the sake of my example, don't consider the 3rd observer traveling from mars to earth. He just crosses Mars position at exactly the same moment of Event2. He then relays his observation of Event2 with his FTL com-device back to earth. While he does that, he is still at position Mars.

EDIT: Imagine the 3rd observer isn't actualy an moving observer that changes positon, but just a moving reference frame. Imagine you are a god at the center of the galaxy, and you can measure everything in your reference frame. You can see everything happening without any signal delays because you are omniscient.

If you, as this god-observer would be not moving in relation to mars and earth, then you would see Event1 and Event2 happening at the same time (there is no signal delay, because you are omniscient, you just KNOW that this is happening at this moment from your frame of reference). But if you have a velocity in relation to Mars and Earth, then you would see Event1 and Event2 at different times.

EDIT2: Another way to think about this. Imagine the universe (everything that has happend, is happening and will happen) is a loaf of bread. A single slice of bread is a single moment. An event is a raisin. you can cut a slice out of the bread, so that the slice contains two specific raisins. You would think therefore, that both raisins (events) happend at the same moment.

But different observers cut the bread at different angles, depending on their velocity. So the slice of bread of a moving observer would just contain one of the two raisins. He has to cut a few more times, to get to a slice that contains the second raisin. So for him, both raisins are in different slices. The events happen at different moments.

Yes moving and intercepting signals complicates stuff unnecessarily.

Example 2 is better, but do not see how speed affect the observation, relativity makes your speed run slower, also space in the direction of travel looks compressed.

Not how this would make you observe things at different time.

And even if it does it would not let you send information back in time who I agree would make an impossible mess.

[ZetaX]

Yes moving and intercepting signals complicates stuff unnecessarily.

Example 2 is better, but do not see how speed affect the observation, relativity makes your speed run slower, also space in the direction of travel looks compressed.

Not how this would make you observe things at different time.

And even if it does it would not let you send information back in time who I agree would make an impossible mess.

Also to you: learn special relativity. It implies exactly those things. And it would imply sending information back in time unless you assume a completely different mechanism (those more philosophical ones discussed earlier) forbids this.

[WestAir]

Because it is only instantaneous in your frame of reference. But nowhere is anything moving FTL. The instanteneous mentioned above is different, as it is instantaneous in a chosen reference frame, e.g. the one earth and mars. We already epxlained that "instantaneous" is ot well-defined at all; you are bashing a dead horse.

Sorry for the horse bashing. I haven't read the other 12 pages of this thread, and my only education on astronomy comes from High School. My degree is in aeronautical science, not physics, so you'll find I ask a lot of open ended questions here when I can't follow the conversation.

[ZetaX]

Ok, sorry for being somewhat rude there, was just a bit annoyed by gpisic there I think.

[N_las]

Example 2 is better, but do not see how speed affect the observation, relativity makes your speed run slower, also space in the direction of travel looks compressed.

Not how this would make you observe things at different time.

So you accept that space in the direction of travel looks compressed? (From the traveling objects point of few, it stands still and the universe travels past it in the opposite direction)

Lets start from there. Imagine a rod and a barn. If you lay the rod besides the barn, you can see that it is longer than the barn.

The barn has a front door and a back door. Imagine both doors open. If you throw the rod through the barn, and make a picture of the barn at the right moment, the rod now seems to completely fit in the barn. Thats because from the barns (and cameras) point of few, the rod is moving and thus appears shorter.

But from the rods point of few, the barn is moving, so the barn should be shorter. But that would mean that the rod couldn't fit completely in the barn. How can that be? We have a picture that proofs that the rod fits in there.

No make it harder: Imagine the front door of the barn open, and the back door closed. We invent a mechanism that closes the front door (event1) and opens the back door (event2) at exactly the same moment. Now we throw the rod, and it travels inside the barn. At the right moment, when the rod nearly touches the back door, we open it (and therefore shut the front door, both events happend at the same time). The rod can travel through the barn without crashing into a door (or a door crashing into the rod). This is only possible because the rod fits inside the barn, because it is shorter due to relativity.

But from the rods point of view, the BARN is way shorter. How can it be that the rod traverses the barn, even though we have the open-shut mechanism? Well, from the rods point of view, the back door opens (event2) long before the front door closes(event1). When the back door opens, the front door is still open, and the long rod reaches out of both doors at the same time. Only some time later, when the end of the rod is completely inside the barn, then the front door closes. So from the rods point of view there has to be a time delay between the events. Event2 has to happen earlier than event1.

So from length contraction alone, we see that different observers (barn and rod) disagree about what is instantaneous.

This has nothing to do with different runtimes of signals from the back to the front door. A camera that films the barn from above can have exactly the same distance to both of the doors. If the camera stands still, and makes a photo at the right time, the photo shows Event1 and Event2 happening simultaneously.

If the camera is traveling in the same direction and speed as the rod, and it makes a picture when it is exactly over the barn (so that both doors are at the same distance) then it may catch Event1 on Photo. Or Event2. But not both events in the same photo.

There has to be no additional "magic" to cause this disagreement about simultaneity. Its just a logical conclusion from space contraction.

Edited September 27, 2014 by N_las

[musicpenguin]

Quantum Entanglement is the most likely I presume as others have mentioned.

[ZetaX]

Quantum Entanglement is the most likely I presume as others have mentioned.

Most likely for what¿ Anyway, whatever you wanted to say has probably been discussed or debunked in the last pages.

[musicpenguin]

Most likely for what¿ Anyway, whatever you wanted to say has probably been discussed or debunked in the last pages.

Eh, I've heard that it could be used for Instantish communication. Feel free to prove me wrong though, I am open to any arguments due to the fact I am not "Learned" In this subject.

[ZetaX]

No it can not. This is sadly a very common believe among non-physicists, probably due to many ill-informed pop-science authors and also due to the idiotic naming schemes like "quantum teleportation" and "spooky action at a distance", which are quite bad choices.

What you can do is give each of two persons a random number in such a way that both get the same number, despite them being very very far away (essentially "instant", but that word is quite meaningless as discussed on the past pages; at least it is not bound to the speed of light). But you cannot choose the autcome, making this scheme completely useless to send information. One normally uses it to securely transmit a random key for cryptography, and as such it works well and has been tested many times already, but it cannot do more than that.

You can also find a discussion on that starting at post 68 I think.

[K^2]

idiotic naming schemes like "quantum teleportation" and "spooky action at a distance", which are quite bad choices.

What's wrong with quantum teleportation? Teleportation does not imply instantaneous transportation. Even in sci-fi, it is frequently light speed limited. It only needs to be instantaneous from perspective of whatever's being teleported, and quantum teleportation is that.

[N_las]

Teleportation is exactly the right word. But most people don't see it that way. Most people who get an explanation on quantum teleportation think it sounds just like sending an e-mail. "How has that anything to do with Star-Trek?"

[Alchemist]

So, the main problem of FTL concept is frame of reference recalculation.

Just as for a sublight object we can find inertial frames where it is stationary or moves in opposite direction than for us, FTL object should have different (but still FTL) speeds in different frames, including instant travel and even "backwards in time" (or maybe better to say "faster than time"?). The question is what's the math behind this conversion.

The only time paradox that really matters is if consequences arrive to the point of the cause before the cause happened - any other movement "back in time" is nothing more than prescience devoid of ability to change what "will happen"

[ZetaX]

What's wrong with quantum teleportation? Teleportation does not imply instantaneous transportation. Even in sci-fi, it is frequently light speed limited. It only needs to be instantaneous from perspective of whatever's being teleported, and quantum teleportation is that.

The only thing teleported there are quantum states, unless there is a version I am not aware of. It is quite weird to call a transmission of information "teleportation".

The problem is simply that a lot of people think, and this is partially due to that name, that you are teleporting matter like seen in Star Trek there, and as far as I know, you are not. This has nothing to do with speed.

Edit: maybe to explain myself more:

Why not calling it, e.g., "quantum transmission" instead¿ (as you are sending quantum states) I claim that some of those names originated simply to sound cooler than they actually are. I can even imagine the actual reason to be getting more money and/or publicity.

Edited September 28, 2014 by ZetaX

[N_las]

The only thing teleported there are quantum states, unless there is a version I am not aware of. It is quite weird to call a transmission of information "teleportation".

The problem is simply that alot of people think, and this is partially due to that name, that you are teleporting matter like seen in Star Trek there, and as far as I know, you are not. This has nothing to do with speed.

In Star Trek, do they really send the individual atoms to their destination? The transporters in Star Trek work like this: "Transporters convert a person or object into an energy pattern, then "beam" it to a target, where it is reconverted into matter."

One could argue, that this energy pattern they are talking about is the quantum state.

[ZetaX]

Yes, one could argue that way, but why should such pattern be the quantum state¿ And why does such a sketchy description in SciFi make it right to use such a misnomer¿

[N_las]

Yes, one could argue that way, but why should such pattern be the quantum state¿ And why does such a sketchy description in SciFi make it right to use such a misnomer¿

The name quantum teleportation fits perfectly. If you have the quantum state of an atom, you can't measure it and apply it to a different atom, you can't copy it and send the copy to a different atom. To get the quantum state from one point to another, you could just send the atom in question via mail, but that would be simple "transportation".

But sending the quantum state from its original atom to a different destination atom, without disturbing it, that fits the name "telportation". The original atom has lost this specific quantum state, and the destination atom has gained this specific quantum state.

Most people see it as just measuring a specific state of the atom, sending the information about this state to a different lab, and then applying that state to a different atom. I can understand why nobody would want to call that "teleportation".

[ZetaX]

I do not dispute that transfering the quantum state to another atom is as good as sending that atom there (ignoring the lost state on the target and the new state on the source). I just find the naming to be too pompous, or more accurately, I see in those naming schemes one of the reasons why people have such false expectations on what is possible with quantum mechanics. That's why I would prefer "quantum transmission" or something similiar, it is still a correct description, but has not this SciFi-ish touch.

[rtxoff]

I hope you are aware that you are talking in a thread that is tagged as [sci Fi Theory].

[ZetaX]

That changes nothing¿ How is the name of a thread influencing my claim that the naming scheme is pompous¿ Is the correctness of 1+1=2 now dependant on the thread title¿ Seriously, this is completely irrelevant.

Also: SciFi does not mean future fantasy. Serious SciFi extends on the known laws of physics, never ignores them.

[rtxoff]

Yeah, trying to change the name of something that is already established is completely irrelevant too.

Good luck searching for serious science in a thread tagged as [sci Fi Theory] in a forum dedicated to a game where little green humanoids named kerbals live. I am not saying explicitly you won't find it, just relax next time when someone says something stupid.

Also things like:

Ok, sorry for being somewhat rude there, was just a bit annoyed by gpisic there I think.

are rude too. If anybody feels annoyed by someone that one may also ignore the thread/post whatever.

This forum is also used by people not beeing scientists, you will have to live with annoying questions when posting here.

[TheFlyingPigs]

What is this, Enders Game?

(If you get the reference, you get a big no-prize)

[ZetaX]

Also things like: [...] are rude too.

If anybody feels annoyed by someone that one may also ignore the thread/post whatever.

Implying I want to be nice to someone who completely ignores what people tell him, despite his rambling being as unscientific as it gets. I will be nice to people that actually want to learn something, or to people that have interesting things to say or teach. But I will not always be nice to someone who repeatedly ignores others that actually know physics, and who tends to throw his unscientific comments into every second discussion.

And that is why I won't ignore such behaviour: it is spreading misinformation. Your posts actually tell people wrong things, and thus they need to be corrected. And ideally, you should stop making them, but I gave up on that part.

This forum is also used by people not beeing scientists, you will have to live with annoying questions when posting here.

The problem are not those asking questions. The problem are those that claim to have an answer despite actually not having a clue about physics. This is not politics where things generally get down to more or less founded oppinions.

I am happy to answer questions, but prefer if people would read the last few pages of a thread before answering to it, as responding to the same stuff three times in the span of a few hours is just annoying. Anyway, if you are actually seeking an answer and not just search for confirmation of your weird theories, you are welcome to ask.