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Having followed @joigus and others in another recent thread I got inspired to check what ChatGPT would produce. (Quotes are cut&paste from chat.openai.com output.) Me: Why is there no faster than light signal in entanglement in quantum mechanics ? I have some small experience from working with (simple) chat bots, let's ask the question slightly different. We (incorrectly) assume that FLT exists in QM to try to trick the AI: Me: how fast is the signal between two entangled particles in quantum mechanics? (The italic part of the first output was reused; I inserted three dots ... to shorten the post.) What are some of the best scientific evidence supporting the above statements? The AI is transparent with it's limitations but are "confident" that the answers given are in agreement with mainstream theories.

https://en.wikipedia.org/wiki/Born_rigidity The "Class A" section contains an entire class of applicable motions. Instantaneous (not generally simultaneous) acceleration using the solution I proposed (different from OP's I think), does not satisfy Born rigidity, because it requires different parts of the train to accelerate at different times, in the 2 rest frames (before and after acceleration) of the train. Therefore the train's length changes in those frames, and its proper length doesn't even seem defined while accelerating. However, it should be the only solution that involves a single instantaneous acceleration at each point of the train, with which the train has the same proper length before and after the acceleration. It would seem not even Born rigidity can be satisfied with an instantaneous acceleration. However, OP's proposal never mentioned anything about a requirement of rigidity. For that matter, they neither required that the proper length of the train is the same before and after, I assumed that. The way I figure it, if you have the back of the train accelerate at time 0, the rest of the train accelerates over time until the front of the train finally accelerates when the length of the train has become L/gamma in the initial frame, where L is its original proper length. By that time, the back of the train has traveled a distance of (L - L/gamma) at velocity v. Therefore the time when the front of the train accelerates would be t=d/v = (L - L/gamma)/v. Then the velocity of the "wave" would have to be d/t = Lv/(L - L/gamma) = v/(1 - 1/gamma) For gamma=2, it seems intuitive that the wave would have to travel at 2v, to reach the front of the train at the same time that the back of the train traveling at v gets halfway there. With v = 3^0.5 c/2, I get a velocity of the wave equal to 3^0.5 c. Like you said this is faster than c, so it's non-causal and needs local forces to accelerate the parts of the train.

This next comment is very important. The Physics an Chemistry of how what we call electricity is very difficult and complicated. Futhermore there is not one single mechanism, but several. And they all have a part to play. As a result, abstract models of how thing behave were developed, models that show measurable quantities like voltage, current and so on. These models are called circuit theory and are set in the mathematics of the relationships between the various measurable quantities. Have you heard of Ohm's Law ? Of course since they are both approaches about the same thing there is a lot of overlap and common stuuf involved. But there are also important differences and flow is one of those differences. Flow appears in artificial abstract circuit theory, but not really in a physical description of what is actually happening. And flow refers to flow of charge, as Mordred said, or current which literally means flow of charge in electricity theory. Anyway the important thing to remember is to know which version you are using. You ask about electric and magnetic fields, so it is important to know just what a field refers to. A field occurs in a region of space (along a line, on an area or in a volume) for which some quantity has a single defined value at every point in the region. The defined quantity may belong to matter or be totally abstract. So a temperature field or a density field are both about properties of matter that can vary from point to point. A placement of arrows on a weather chart showing which way the wind is blowing and where is purely abstract and called a direction field. An electric field shows the strength of attraction (as a force) that would be felt by a unit electric charge at any point. A magnetic field shows the strength of attraction (as a force) that would be felt by a unit magnet at any point. Neither of these are used much in circuit theory, but both have lots of different uses in Physics and Chemistry, often where there is no circuit involved at all.

I agree, I think the "Dark Forest" hypothesis is nothing but paranoia unchained.

What your scenario doesn't take into account, is the almost certainty that in less than 200 years, we will have some kinds of colonies in space. Probably numerous giant space stations, and industrial colonies on the Moon etc. So if aliens want to destroy us that way, their time is running out fast. And vice versa, if we wanted to strike at far-off aliens using your method, it would only work if they had not yet mastered living off-planet. Thats not very likely, if their progress was as rapid as ours. We've gone from being Earth bound to landing machines on Mars in just over 100 years, which is nothing in real time. The aliens could easily be a million years ahead of us, in mastering space living, so wasting their planet would probably be a complete waste of time. We would just be creating an enemy for no gain. And of course, that enemy could have friends, who are even more advanced than they are. You could be making yourself a target, for a NATO like alliance.

Argument from authority I've seen the label, but your comments still don't make sense to me, and I've met way too many trolls on the internet to trust labels. Sorry, but that's more meaningless nonsense. When an object moves relative to an observer, "coordinate time" refers to time in the observer's frame and "proper time" refers to time in the object's frame. This thread is about accelerating a train relative to the ground, so time in the ground's frame is the coordinate time for the problem and time in each car's frame is the proper time for that car. Again, you're throwing around terms like "line element" without knowing what they mean. There are lots of line elements for lots of different objects. The line element of the car's motion is exactly what the clock in the car follows, so each engine clock in a car will measure that car's proper time, not the ground's coordinate time. Blah blah blah blah blah blah blah blah blah blah blah blah. You're using words to intimidate, not to communicate. You're using them incorrectly, and you're not saying anything with them. "Each engine clock will be in coordinate time" is 100 percent, Grade-A baloney.

It's an argument against Dark Forest, which includes the concept of "wiping out all potential threats".

Thymine has a methyl substituent in the 5 position, which uracil does not have. The numbering is just a way to denote the ring substituents. With heterocycles it is normal to pick one of the hetero atoms as position 1 and the others then follow round the ring.

Good analysis +1 Unfortunately no real wave travels faster than c. I will have time to respond further later on RL

The point of what? The OP didn't say a word about turning. No one except you said anything about turning. You talk about signals that nobody mentioned; you talk about turning, which nobody mentioned; every time someone proves you wrong, you change the subject and talk like that's what we were discussing all along. PS: It's "you're", not "your". Your English is almost as bad as your physics.

Unfortunately a simulataneous acceleration of a train would impossible taking into consideration the speed limit of information exchange. This thought experiment would be accurately described via the Rigid Rod under GR. In essence let's make your train one light year hypothetically. If the force for acceleration starts at say the engine. The tail end would not accelerate until one year later. Thats assuming the medium is ideal enough to allow the signal to propagate at c. Which is your speed limit.

The communication between every engine would also be affected so you still wouldn't have simultaneous acceleration not under rigorous treatment with GR being applied.

Proper time would follow the wordline between engines so you still have the same problem

I still believe your missing the point. Even if every single coordinate was effectively it's own engine and you could contrive some means of synchronization. Once the train needs to turn you would end up with differing accelerations. So once again we're stuck with needing communication. The reason I asked how much GR you understood is that I wanted an idea of your math skills. Are you familiar with the four momentum in mathematical form ?

your welcome. the criteria to meet is given in the first equation that the distance does not change between any two particles. \[ V(r,t)=V_0(t)+\Omega(t)r\] is the solution to the first equation \[\Omega(t)\] being an antisymmetric tensor that's the criteria. the rest of the article deals with the examination Ok your not familiar with GR terminology fair enough https://en.wikipedia.org/wiki/Coordinate_time please note that the following from the article.

trolling tactics you are aware I am a Resident Expert on this forum correct ? Any clock at a given reference frame is the coordinate time. Proper time is a clock that follows the Worldline given by the line element of the applicable geometry. usually denoted by the separation distance between two events. For Euclidean geometry ( I did provide links earlier to coordinate time and proper time ) \[ds^2=dx^2+dy^2+dz^2\] The worldline is the null geodesic path which is represented by the line element or if you prefer the affine connections given by the Christoffel connections. The line element is typically easier to understand though lol. Though the geodesic equation includes the Christoffel here is the Minkowskii line element \[ds^2=-c^2dt^2+dx^2+dy^2+dz^2=\eta_{\mu\nu}dx^{\mu}dx^{\nu}\]

Look I'm going to answer questions as I choose to answer them. At any point in time I can back up any statement I make with literature or the mathematics.. I supplied links explaining proper time and coordinate time if you choose not to read those links and attempt to understand what I'm referring to that's your choice. I have also supplied two articles that directly show the rigid rod analysis including taking the time to find a mathematically simplified version.

I see so we have from the topic at hand to you arguing the definitions given by GR that were not set by me. Let's make this simple in GR there is no rest frame unlike SR. In GR all observers frames of reference is the coordinate time. This is because the coordinate time is not invariant.. it is coordinate dependent. The rate of time will vary at any given coordinate as well as the observer. Got that so far ? The only invariant reference frame is the clock that follows the null geodesic worldline it is path dependent. This means it will depend on that worldline between different geometries , flat curved, Schwartzhild metric, Kerr Metric etc. This is why it's the proper time it is the only Lorentz invariant frame of reference in different geometries between different observers If you still have questions on that free to ask. I don't know your math skills but here you go http://web.mit.edu/edbert/Alexandria/notes1.pdf Now why does the wiki link specify the timelike geodesic (null geodesic) ? Well for starters c is Lorentz invariant. All observers measuring the velocity of a photon will measure the same value. Does that help to make better sense of the clock following the null geodesic ?

G GR does not use rest frames all reference frames are inertial . What is the definition of an inertial frame ? A frame under constant velocity. Equal free fall it is not the equivalent to a rest frame. Do you have a reading problem ? The above propertime that clock on the worldline AS PER the WIKI link........ shall I go and quote each instance I stated the clock along the worldline for you for proper time... What don't you understand about that ? Is it the term reference frame ? A reference frame is an inertial frame of reference I already have summarized it's not my fault you refuse to read or understand

I know that, Professor. I was asking md65536 what she thinks, because what she posted is inconsistent. Please either learn how to read or stay out of other people's conversations.

And then the science enthusiast has to deal with trolls who are already established as "Resident Experts" on this board...