Is Causality Fundamental?

zzk
Hi Zou,
It is a very interesting article you have posted. It resonates with many of my own ideas on a first read. I think that I will do a deeper dive into it at a later date after I have concluded my tachyonic studies.
Best wishes
Dave

Lorraine Ford
Hi Lorraine,
Your post got me thinking a bit on what is fundamental. With my reductionist hat on, I have boiled Physics down to a couple of force laws, namely attraction and repulsion, together with a reduction of "The principle of least action" to F=ma. I haven't got a clue what charge is, and at the fundamental level I do not understand motion either. So in reality I do not understand either force or motion.
But I didn't let that stop me from developing a Theory of Everything, as there is so much to be gained by just accepting a few axioms. Whilst it may be true that Wheelers equations didn't fly on demand, there are neat algorithms that make my drones fly (with my help of course as well).
Now I best get back to my tachyon studies.
Dave

Claudio Marchesan
Hi Claudio,

Sure, devices like light-cone structures and conservation laws and consistency are seemingly needed e.g. to check the validity of mathematical models, and to predict or narrow down possible outcomes of a model. Light-cones don’t actually exist, except as a concept in the minds of physicists; but they are a useful device.

So, this “causality” that you seem to be describing seems to be mainly about physicists trying to model and predict outcomes of a complicated and slightly unruly real-world system that they are observing.

But that is not genuine causality at all, in the sense of physicists trying to understand and represent the actual causal inner workings of the real-world system. Maybe physicists have given up on that ambition!

I think that the valid point that Wheeler was making is that a set of equations, no matter how many equations, no matter how ingenious the equations, can’t ever represent a viable, moving system. It is just the nature of equations: they can’t do it.

I think Wheeler was in effect saying that if physicists ever had the ambition of representing the actual components needed to make a viable moving (“flying”) real-world system, then something entirely different to equations would be needed, as well as the equations.

DAVE
Hi Dave,

Good luck with your TOE and your tachyon studies !

Claudio Marchesan
Hi Claudio,
I had a look at Wikipedia on tachyons, particularly the Tolman paradox you suggested.
Below is a quote from that article on two way tachyonic communication (with paradox), together with my version using a single frame (with no paradox). Am I missing something?
From Wikipedia, the free encyclopedia
A tachyonic antitelephone is a hypothetical device in theoretical physics that could be used to send signals into one's own past. Albert Einstein in 1907[1][2] presented a thought experiment of how faster-than-light signals can lead to a paradox of causality, which was described by Einstein and Arnold Sommerfeld in 1910 as a means "to telegraph into the past".[3] The same thought experiment was described by Richard Chace Tolman in 1917;[4] thus, it is also known as Tolman's paradox.
A device capable of "telegraphing into the past" was later also called a "tachyonic antitelephone" by Gregory Benford et al.[5] According to the current understanding of physics, no such faster-than-light transfer of information is actually possible.

Tachyonic telephone paradox – two way communication example from Wikipedia in italics.
When Alice's clock shows that 300 days have elapsed since she passed next to Bob (t = 300 days in her frame), she uses the tachyon transmitter to send a message to Bob, saying "Ugh, I just ate some bad shrimp". At t = 450 days in Alice's frame, she calculates that since the tachyon signal has been traveling away from her at 2.4c for 150 days, it should now be at position x = 2.4×150 = 360 light-days in her frame, and since Bob has been traveling away from her at 0.8c for 450 days, he should now be at position x = 0.8×450 = 360 light-days in her frame as well, meaning that this is the moment the signal catches up with Bob. So, in her frame Bob receives Alice's message at x = 360, t = 450. Due to the effects of time dilation, in her frame Bob is aging more slowly than she is by a factor of , in this case 0.6, so Bob's clock only shows that 0.6×450 = 270 days have elapsed when he receives the message, meaning that in his frame he receives it at x′ = 0, t′ = 270.
When Bob receives Alice's message, he immediately uses his own tachyon transmitter to send a message back to Alice saying "Don't eat the shrimp!". 135 days later in his frame, at t′ = 270 + 135 = 405, he calculates that since the tachyon signal has been traveling away from him at 2.4c in the −x′ direction for 135 days, it should now be at position x′ = −2.4×135 = −324 light-days in his frame, and since Alice has been traveling at 0.8c in the −x direction for 405 days, she should now be at position x′ = −0.8×405 = −324 light-days as well. So, in his frame Alice receives his reply at x′ = −324, t′ = 405. Time dilation for inertial observers is symmetrical, so in Bob's frame Alice is aging more slowly than he is, by the same factor of 0.6, so Alice's clock should only show that 0.6×405 = 243 days have elapsed when she receives his reply. This means that she receives a message from Bob saying "Don't eat the shrimp!" only 243 days after she passed Bob, while she wasn't supposed to send the message saying "Ugh, I just ate some bad shrimp" until 300 days elapsed since she passed Bob, so Bob's reply constitutes a warning about her own future.

Now let us look at this with a universal clock since this problem has nothing to do with the sending and receiving of light signals. As both Bob and Alice know their velocity is 0.8c, let us say they both install a universal clock in their spaceship that adjusts for the time dilation factor (ie. It runs faster by 0.6). Now let’s use the universal time clock and distance coordinates in days and light days (t’’, x’’) for a similar scenario but with a much faster tachyonic phone speed of 4c (so as to keep the numbers smaller).
When Alice's UT clock shows that 300 days have elapsed since she passed next to Bob, she uses the tachyon transmitter to send a message to Bob, saying "Ugh, I just ate some bad shrimp" (x’’ = -240, t’’ = 300). At t’’ = 450 days in the UTC frame, she calculates that since the tachyon signal has been traveling away from her at 4.0c for 150 days, it should now be at position x’’ = 4.0×150 -240 = 360 light days in UTC frame (x’’ = 360, t’’ =450), and since Bob has been traveling away from her at 0.8c for 450 days, he should now be at position x’’ = 0.8×450 = 360 light-days in UTC frame as well, meaning that this is the moment the signal catches up with Bob. So, in the UTC frame Bob receives Alice's message at x’’ = 360, t’’ = 450.
When Bob receives Alice's message, he immediately uses his own tachyon transmitter to send a message back to Alice saying "Don't eat the shrimp!".
225 days later in the UTC frame, at t’’ = 450 + 225 = 675, he calculates that since the tachyon signal has been traveling away from him at 4c in the −x′ direction for 225 days, it should now be at position x′ = −4×225 +360 = −540 light-days in the UTC frame, and since Alice has been traveling at 0.8c in the −x direction for 675 days, she should now be at position x’′ = −0.8×675 = −540 light-days as well. So, in the UTC frame Alice receives his reply at x’’ = −540, t’′ = 675. Thus causality is preserved.
I think the paradox arises in the original (italicised) version because of the assertions that “Time dilation for inertial observers is symmetrical, in her frame Bob is aging more slowly than she is, and in Bob's frame Alice is aging more slowly than he is, both by the same factor of 0.6.” In fact Bob and Alice age at the same rate in this example as they are both travelling at the same relativistic speed. Their knowledge of each others time via their UTC’s is in essence the same as having an instantaneous tachyonic phone.

These paradoxes are always incredibly complex and fascinating, so I might be wrong — but I wonder: if Alice and Bob are in relative motion, how can they both have the same UTC clock, at rest with respect to them, to synchronize their time? According to special relativity, a universal time shared between observers in relative motion shouldn't exist.

Hi Dave,

Alice is using relativity to establish when Bob sent the message. In my opinion, the mistake that creates the paradox is that, in the presence of tachyons, time can no longer be compared using traditional methods. It’s not that causality breaks, but that the system for measuring time, as we normally understand it, is no longer applicable. In other words, the paradox arises because we try to use a scheme of synchronization and temporal ordering that doesn’t work with superluminal signals.

Hi Dave, hi everyone, I have thought long about Tolman’s paradox.

Who knows! Perhaps in the future this paradox, with its implications for causality and the nature of communication, will be presented to students in a philosophy lesson, just as today we analyze Zeno's paradox of Achilles and the tortoise to explore the limits of our intuition about the continuous.

To me, the crux of the matter arises from the very nature of the calculation system: does the tachyon break clocks synchronization? This paradox is an invitation to rethink our logical foundations.

But how can the synchronization of clocks belonging to the same light cone be broken?

This story suggests that a tachyonic telephone cannot connect regions within the same light cone: their ability to communicate would produce a causality paradox. However, quantum entanglement exists, and whether or not we call it “tachyon” changes little; therefore, our conclusion is that some form of superluminal communication can occur regardless of the frame of reference. It is evident that whatever the nature of this “mediator”, it does not respect the Lorentz transformation: the gamma factor is imaginary. In Alice's frame of reference, she cannot calculate when Bob will receive the signal, but this does not imply that Bob will not receive it. To know when, she only needs to ask Bob with a traditional communication.

From all this, compact dimensions are not necessarily deduced, and the undivided universe is not excluded.

In the case of entanglement, the measurement performed on particle A causes the collapse of the state of the other, B. This represents a cause-effect relationship, in reference frame B. Here, the cause triggered by A precedes the effect on B, and from this perspective the tachyon cannot reverse the arrow of time, thus preserving causality.

The no-communication theorem, about the impossibility of transmitting information superluminally via entanglement, doesn't change the fundamental issue of its non-local correlations, which remain puzzling in the context of relativity.

Thanks for the tip! I had no idea my tachyonic musings were eligible for premium academic support. Do you guys offer faster-than-light proofreading too? That would really help me get feedback before I even write the post.

We study physics not just to know, but to do, to build, and to continually improve our world. And in doing so, we are compelled to confront the deepest questions about the nature of reality itself, fostering a profound interplay between scientific discovery and philosophical inquiry that drives both practical innovation and fundamental intellectual advancement.
Beyond its practical applications, the study of physics is profoundly intertwined with ontology, the philosophical study of the nature of being and reality. And you're absolutely right: this isn't just an academic exercise in knowledge acquisition.
I personally do not believe that any branch of physics can progress without a deep understanding of what the laws we have formulated actually represent. For physics to truly advance, it's not enough for our laws to merely "work", that is, to accurately predict experimental outcomes. We must also grapple with what those laws ontologically signify.

Claudio Marchesan
What is a signal? If, when driving a car, red light interacts with our eyes, we know it means to stop the car; if green light interacts with our eyes, we know it means we can start moving the car again.

I think, at the particle level, an interaction between low-level matter with a red-light particle or a green-light particle can have no “extra” meaning, i.e. there can be no signals at the low-level matter or particle level. So, there could potentially be knowledge, on the part of low-level matter or particles, of categories like frequency or wavelength, and of the associated numbers, but there could be no extra meaning on top of that which would allow the definition of “signal”.

Re framework: My framework is that, by definition, we live in a standalone, self-sufficient world (universe), with no meddling from the outside because there IS no outside to the world. At the foundations of the world there is no mathematical system etc., there is only something (not a God, with all the nonsense baggage that that entails) that created and knows the mathematical system etc.. And I think that matter (particles, atoms, molecules and living things including human beings) can only be small parts of this whole thing.

Hi Lorraine,

As you might have guessed, I tend to respond from the perspective of physics. You're absolutely right: concepts like particles, mass, and even “signal” (which I’d relate here to wave phenomena) are far from obvious. And this is exactly where quantum mechanics becomes essential.

The double-slit experiment, in particular, challenges our most basic intuitions about the nature of objects and the independence of reality from the observer. In this context, a “signal” isn’t something with intrinsic meaning — but rather an emergent, interpretable pattern within a probabilistic framework.

For a physicist, it’s not enough that Schrödinger’s equation predicts the interference pattern. The desire to understand what the laws actually represent — ontologically — is what drives new theories like hidden variables or many-worlds interpretations. The double-slit experiment is, in a sense, the archetype of this ongoing and necessary interaction between physics and ontology.

Thank you again for your thoughtful message — I truly appreciate this kind of exchange.

Claudio Marchesan
Hi Claudio,

Re "In this context, a “signal” isn’t something with intrinsic meaning — but rather an emergent, interpretable pattern within a probabilistic framework.":

That is exactly what I was saying: no signal or symbol has intrinsic meaning. The problem is: who or what interprets a signal? People interpret signals. But particles and other low level matter don't interpret signals, because it requires a bit of high-level analysis and collation to interpret a pattern or a signal, as we know, e.g. from the number of steps required in computer programs to interpret patterns or signals. And also, the "meaning" or interpretation of patterns or signals doesn't Platonically float in the air, ready to be plucked. So, obviously, low-level matter interacts with other low-level matter; but are you claiming that low-level particles or matter could be signalling each other?

Also, there is a calculatable probability for everything, e.g. the number of people who will be bitten by dogs in a particular town in a year, or something like that. So, Schrödinger’s equation is about probable outcomes; but the equation doesn't predict actual real-world outcomes. The real question is: who or what is assigning new numbers to categories, like the relative position category, in a real-world particle outcome?

Mathematics, with its man-made symbols, can’t exist without the consciousness and agency of mathematicians. However, mathematicians and physicists continue to delude themselves that a viable real-world mathematical system could exist without aspects describable as “knowledge/ consciousness” and “agency/ creativity/ free will”. A viable moving system needs more than just a pile of equations and numbers.

So, a viable moving real-world system, or small parts of the system, needs to have a low-level on-the-spot knowledge/ consciousness of itself, i.e. knowledge of what categories, numbers and relationships are currently true. And matter, with its categories, numbers and relationships, already has an intrinsic, in-built, on-the-spot true interpretation/ meaning from the point of view of itself and other matter.

But while matter might have an intrinsic, in-built true interpretation/ meaning, there are no ARRANGEMENTS of matter that have an intrinsic, in-built, interpretation/ meaning. Signals and symbols are deliberate arrangements of matter, but whether these arrangements are deliberate or not: arrangements of matter have no in-built true interpretation/ meaning.

So, who or what is interpreting arrangements of matter? Obviously, a higher-than-base-level consciousness, that is capable of a bit of analysis and collation, is required to interpret signals and symbols.

Hi Lorraine,

You’re absolutely right — there’s no intrinsic meaning in signals or symbols. Interpretation, as you say, is a complex act, and this is exactly where the interesting questions begin. Low-level matter doesn’t “interpret” in the human sense, but it can — at least in some physical models — respond consistently to patterns that, at a higher level, become interpretable as information.
That’s why, in contemporary physics, information is often seen as an emergent property. What we call a “signal” may simply be a useful description at a certain level of abstraction. But what happens when, in some quantum systems, we observe correlations that seem to “carry information” (as in entanglement)? Is the structure of the theory itself enforcing a kind of coherence that resembles communication?

Perhaps the most surprising part is that, despite all these deep questions, physics works.

As for your second question — who or what assigns definite outcomes in the real world?
When we assign a value to a physical quantity, like a particle's position or momentum, we do so within a system of agreed-upon units (like meters or kilograms). These units are not arbitrary; they are meticulously defined and internationally agreed upon to ensure consistency and comparability of our observations.
At the current stage of our understanding, mathematics remains our best, and perhaps only, tool to describe and model reality, even if it may not capture its full essence.

Perhaps we've all wandered a bit off topic, and it might be time to return to the original thread theme: causality.

Claudio Marchesan
Hi Claudio,

Re the off-topic bit:
What is “information”? People seem to have difficulty conceptualising and explaining what “information” is.

I’m contending that low-level information is subjective; information doesn’t objectively/ Platonically exist. Low-level information is just another word for low-level on-the-spot knowledge/ consciousness, and this low-level information is symbolically representable in something like the following form:

(category1=number1 IS TRUE) AND (category2=number2 IS TRUE) AND (category3=number3 IS TRUE.

I’m saying that the above is the way to symbolically represent information about an on-the-spot situation. But this type of information doesn’t emerge from a system; instead, it is a necessary part of the functioning of a system.

(The same types of symbols (e.g. IF, AND, OR, IS TRUE, and THEN), which seem to represent something about the real world that equations can’t represent, are the symbols one would use to represent the analysis of patterns. And also, these symbols (together with the symbols for categories and numbers) are the symbols one would use to represent the assignment of new numbers to categories, like the relative position category, in a real-world particle jump outcome, in response to a symbolically represented situation.)

However, if something new emerged from a system then it would only be because something else new had been ADDED to the system, e.g. new equations/ relationships between categories, or new numbers had been assigned to existing categories. This seems to happen in the plot of the Mandelbrot set, where something new seems to emerge, but this is only because the man-made algorithm is made to repeatedly and systematically ADD something new to every point on the plane on which it is plotted.

Re causality:
Without any explanation for why anything ever moves, causality assumes a moving system. But I don’t think it is valid to assume that a system would just automatically start to move, or continue to move.

1. The underlying infrastructure of the world is symbolically represented in terms of equations (“laws of nature”), categories like mass or position, and numbers that apply to these categories. But “information” is a word that is bandied around a lot, so how should “information” be symbolically represented?
2. What use is information to a system, if any?
3. Is it true that the symbols IF, AND, OR, IS TRUE, and THEN represent aspects of the world that can’t be represented by equations?
4. Is it true that nothing new can emerge from a system unless something else new is added to the system?
5. Before considering "causality", why does a system ever move, and why does a system continue to move?