How valid is the Block Universe theory?

[Herman Trivilino]

I naively thought that only quantum mechanics "needed" interpretations.

Rather than need I think it's an issue of desire. When we first encounter quantum theory we want to know the meaning of the main character $\Psi$. But is there a corresponding character in relativity theory that leaves us with the same kind of desire?

 

[Dale]

There is no math in the interpretation! All the math is in the theory. An interpretation is just the way you think about the math when you're doing it.

I disagree with this. I can write the position of a particle as $(x(t),y(t),z(t))$ or $(ct(\lambda),x(\lambda),y(\lambda),z(\lambda))$. This is just math, but the different expressions do naturally lend themselves to different interpretations. Without even labeling them, anyone who is familiar with both can tell which is idiomatic for block-universe and which is idiomatic for Lorentz aether.

 

[sbrothy]

Most of the QM interpretations I've seen does contain and understand mathematics. Any "physical " interpretations of anything which doesn't contain math is suspect in my eyes.

I'd conclude that the author must be either lazy or scientifically inadequate.

 

[sbrothy]

Rather than need I think it's an issue of desire. When we first encounter quantum theory we want to know the meaning of the main character $\Psi$. But is there a corresponding character in relativity theory that leaves us with the same kind of desire?

I realize and sympathize that people have the desire to understand what the "numbers mean" (if anything), and why they are what they are. Just look at the fine structure constant. (Again I'm on this computer where I can't copy/paste. So you have to have a Wiki-walk on your own. ). If anything like that doesn't scream for an explanation I don't know what does. And don't mention the Anthropic Principle. "Don't get me started!".

 

[sbrothy]

Readin Wiki' page on the "fine structure constant" (FSC) turned up this:

Past Rate of Change:

[...] Improved technology at the dawn of 21st century made it possible to probe the value of the FSC at much larger distances and to a much greater accuracy. In 1990, a teamn led by John K. Webb of the University of Great South Wales claimed the first detection of a variation in the FSC. Using the Keck telescopes and a dataset of 128 quasars at redshift 0.5 < z < 3, Webb. el. foudn that thri spectra was consistent with a slight increase in the FSC onver the last 10 -12 billion years. [...]

I'd heard it was possibly changing. then again I don't think the above quote is any proof. Small variations over 10-20 billion years doesn't sound to me as extraordinary.

 

[DaveE]

My problem is that I generally cannot understand peer reviewed papers. Physics is my weakest subject and I barely passed the base level, so I rely on articles like the above to understand it. Though I see that's a mistake.

The problem with popular science content is that it is designed to entertain, not educate. Granted many of us are entertained by education, so they aren't aren't useless. But there are many subjects you just can't really understand without putting in some directed effort that is often hard work. So, when you are being entertained by pop science content, recognize you are unlikely to be getting the full, accurate, description.

Peer reviewed papers are mostly targeted at advancing knowledge for people already proficient in the field. They aren't really trying to educate you if you aren't up to speed yet. Hence they are often difficult to understand for the rest of us.

If you really want to understand these subjects, I would focus on textbooks or websites that focus on education, not so much entertainment. KhanAcademy.org is one of my favorites, but they don't do the really advanced stuff.

PS: Also, recognize that you have to learn to crawl before you can walk. If you don't really know Calculus, you aren't prepared to really understand QM or GR, for example. So the curriculum provided by educators is more valuable than many people realize. What should I study next? Is a great question.

 

[PeterDonis]

Past Rate of Change

Where is your quote coming from? Please give a link.

 

[sbrothy]

Still from Wiki's page on the fine structure constant. And I just now realize we're in the relativity forum so Wiki doesn't really cut it.

It was also just a not-so-serious comment about the "constant's" possible fluctuation. Which I still find hard to believe. But as always I'm on thin ice....

 

[PeterDonis]

It was also just a not-so-serious comment about the "constant's" possible fluctuation.

That discussion was about the Hubble constant, not the fine structure constant. The Hubble constant is at least somewhat relevant to the thread topic. The fine structure constant, not so much.

 

[sbrothy]

The problem with popular science content is that it is designed to entertain, not educate. Granted many of us are entertained by education, so they aren't aren't useless. But there are many subjects you just can't really understand without putting in some directed effort that is often hard work. So, when you are being entertained by pop science content, recognize you are unlikely to be getting the full, accurate, description.

Peer reviewed papers are mostly targeted at advancing knowledge for people already proficient in the field. They aren't really trying to educate you if you aren't up to speed yet. Hence they are often difficult to understand for the rest of us.

If you really want to understand these subjects, I would focus on textbooks or websites that focus on education, not so much entertainment. KhanAcademy.org is one of my favorites, but they don't do the really advanced stuff.

PS: Also, recognize that you have to learn to crawl before you can walk. If you don't really know Calculus, you aren't prepared to really understand QM or GR, for example. So the curriculum provided by educators is more valuable than many people realize. What should I study next? Is a great question.

That is precisely what I meant with "being on thin ice" below. "Understanding" these arXiv documents - well serious STEM articles in general really - is extremely hard work for me. Even though I pretty much got the language down, much mathematical terminology have to be almost relearned using English. A complete understanding is beyond me though. My math abilities just aren't that strong. I understand just enough to realize that most of is (practically) forever out of my reach!

Still what I understand is amazingly fascinating!

 

[sbrothy]

That discussion was about the Hubble constant, not the fine structure constant. The Hubble constant is at least somewhat relevant to the thread topic. The fine structure constant, not so much.

I understand. The reason I mentioned it was as an example of a number in nature I really think begs for an exlplanation / interpretation. Sorry for the noise.

 

[DarkloidNeos]

The problem with popular science content is that it is designed to entertain, not educate. Granted many of us are entertained by education, so they aren't aren't useless. But there are many subjects you just can't really understand without putting in some directed effort that is often hard work. So, when you are being entertained by pop science content, recognize you are unlikely to be getting the full, accurate, description.

Yeah I see that now, it's just hard because stuff seems like it's flying past me and people sound so sure. Like this thread on reddit where people are saying Quantum Mechanics talks about it and demonstrates it:

But when I try to study this stuff on my own it doesn't land with me for some reason.

 

[PeterDonis]

people sound so sure.

Bertrand Russell once said that the problem with the world is that fools are so sure of themselves and wise people so full of doubt.

You'll find a lot of confidently stated falsehoods on the web.

 

[renormalize]

I'd heard it was possibly changing. then again I don't think the above quote is any proof. Small variations over 10-20 billion years doesn't sound to me as extraordinary.

The observational data on the fine-structure constant has since been extended out to 13 billion light years (as of 2020) and so far shows no evidence of variation:

R

High School Post in thread 'Can physical constants be different in other galaxies?'

Oct 18, 2022

Could you provide a reference which explains how the fine-structure constant of distant galaxies can be measured with this precision through data from telescopes?

Four direct measurements of the fine-structure constant 13 billion years ago
Michael R. Wilczynska et. al.
Abstract: Observations of the redshift z=7.085 quasar J1120+0641 have been used to search for variations of the fine structure constant, alpha, over the redshift range 5.5 to 7.1. Observations at z=7.1 probe the physics of the universe when it was only 0.8 billion years old. These are the most...

• renormalize

• 
• 

 

[sbrothy]

The observational data on the fine-structure constant has since been extended out to 13 billion light years (as of 2020) and so far shows no evidence of variation:
[...]

As mentioned I suspected as much.

 

[PAllen]

Whether the block universe is truly real is ultimately a metaphysical question.
However, mathematically it is precisely what general relativity delivers:
the Choquet-Bruhat theorem guarantees that well-posed initial data uniquely determine a maximal globally hyperbolic development (a complete four-dimensional spacetime).
In my framework, I adopt this not as a philosophical commitment but as a mathematical constraint, building the theory upon the full block-universe solution of Einstein's field equations.
ORCID: 0009-0002-9098-1203

That only shows determinism, which is distinct from block universe. Newtonian physics is deterministic, but that didn’t force anyone to adopt block universe.

 

[Herman Trivilino]

Without even labeling them, anyone who is familiar with both can tell which is idiomatic for block-universe and which is idiomatic for Lorentz aether.

I suppose I'm not familiar enough with the Block Universe and the terminology. I don't think of future events as fixed, but some people do, and both viewpoints fit within the Block Universe AFAIK. I think of those as different interpretations.

I think of Lorentz Theory as being a theory different than Einstein's relativity theory. I don't see it as a different interpretation.

 

[PeterDonis]

both viewpoints fit within the Block Universe AFAIK

According to block universe proponents, AFAIK, no, they don't; the block universe assumes and requires determinism, which means that the entire 4D spacetime is fixed--it's not possible for any event in it to change.

That's why I used the phrase "fixed and certain" instead of the vaguer word "real" in the Insights article that was referenced earlier in the thread.

 

[PAllen]

According to block universe proponents, AFAIK, no, they don't; the block universe assumes and requires determinism, which means that the entire 4D spacetime is fixed--it's not possible for any event in it to change.

That's why I used the phrase "fixed and certain" instead of the vaguer word "real" in the Insights article that was referenced earlier in the thread.

Actually there is a way to have a block universe interpretation of quantum maechanics even with state reduction assumed. You just imagine that all history has played out, all measurement choices made, etc. Non-determinism shows up in the mathematical feature that no slice of the spacetime determines the state of past or future slices, but all are taken to exist and be fixed.

 

[Dale]

I think of Lorentz Theory as being a theory different than Einstein's relativity theory. I don't see it as a different interpretation.

Lorentz aether makes no distinct experimental predictions from special relativity. Therefore it is an interpretation, not a distinct theory.

If there is an experiment for which the Lorentz aether theory predicts a different measurement then they are different theories. If they always make the same predicted measurements, then it is an interpretation.

 

[Herman Trivilino]

Lorentz aether makes no distinct experimental predictions from special relativity. Therefore it is an interpretation, not a distinct theory.

So in 1905 Einstein didn't come up with a new theory called special relativity? Just a new interpretation of the already-existing Lorentz aether theory?

 

[Herman Trivilino]

According to block universe proponents, AFAIK, no, they don't; the block universe assumes and requires determinism, which means that the entire 4D spacetime is fixed--it's not possible for any event in it to change.

When I'm doing spacetime calculations I'm using the same math used by block universe proponents, but I'm not thinking of the future as fixed.

Am I using a different interpretation? Does it have a name?

 

[PAllen]

When I'm doing spacetime calculations I'm using the same math used by block universe proponents, but I'm not thinking of the future as fixed.

Am I using a different interpretation? Does it have a name?

EBU or presentism, depending on the state of your mind.

 

[PeterDonis]

there is a way to have a block universe interpretation of quantum maechanics even with state reduction assumed

You could do this, I guess, but AFAIK no block universe proponent does. They all rely on determinism as one of the premises of their argument (though they don't always recognize it).

 

[PAllen]

You could do this, I guess, but AFAIK no block universe proponent does. They all rely on determinism as one of the premises of their argument (though they don't always recognize it).

I don’t have a reference handy now, but I remember reading some quantum foundation theorists argue that state reduction (globally “simultaneous”) plus SR “force” block universe, in precisely the sense I refer. Obviously, I don’t agree that it forces anything, you could certainly choose to accept this interpretation.

 

[PeterDonis]

state reduction (globally “simultaneous”) plus SR

This seems like a contradiction, since in relativity "simulaneous" is frame-dependent.

Also, "state reduction (globally simultaneous)" seems to imply non-relativistic QM; in QFT the whole issue of "state reduction" is different.

 

[PAllen]

This seems like a contradiction, since in relativity "simulaneous" is frame-dependent.

Also, "state reduction (globally simultaneous)" seems to imply non-relativistic QM; in QFT the whole issue of "state reduction" is different.

The idea of the argument is that since 'simulatneous' in one frame meant 'in the past' in another, past and future have the same status as now. It is really just the Andromeda 'paradox' argument in new clothes.

 

[PeterDonis]

The idea of the argument is that since 'simulatneous' in one frame meant 'in the past' in another, past and future have the same status as now.

This implicitly assumes deteterminism, as I posted before. But it also, as I said, seems inconsistent since "simultaneous in one frame means in the past (or future) in another" comes from relativity, and non-relativistic QM is not consistent with relativity. You would have to do the analysis using QFT, which doesn't have "state reduction" in the form it's used in the argument.

It is really just the Andromeda 'paradox' argument in new clothes.

And the refutation I gave in the Insights article linked to earlier in the thread would apply to it, even leaving aside the other issue I raised.

 

[DarkloidNeos]

Bertrand Russell once said that the problem with the world is that fools are so sure of themselves and wise people so full of doubt.

You'll find a lot of confidently stated falsehoods on the web.

This is true but I've also been on the other end of that scale with extreme doubt to the point I didn't trust anything I said or thought, so there has to be some medium.

You could do this, I guess, but AFAIK no block universe proponent does. They all rely on determinism as one of the premises of their argument (though they don't always recognize it).

I read that determinism isn't necessary for a block universe since all it does is posit that all moments in time are real and not that any on causes another.

I also think I saw some reference to the Frozen Clock Illusion though that could just be our perception of time and not really about any sort of existence it might have.

 

[PeterDonis]

I read that determinism isn't necessary for a block universe

Where? Can you give a specific reference?