Definition of Universe requires clarification, to enable discussion

[Gibsense]

I am loath to shorten o/u (perhaps, except for this) because it 'forever' ties the two essential words together. I suppose I have to draw the line at substituting "Cloud Cuckoo Land" for Universe.

Maybe it is appropriate (CCL)
Anyway, I think attempts to define things artificially limit the concept which is of course the objective. Maybe I can illustrate this
In defining the 'Observable Universe' we forget that any OU is user-specific. The OB of you is different to that of someone nearby and very different perhaps of an observer a few light years away. It could be argued that someone a few years away is not a current situation but that might not always be. Therefore we end up with an OB variability over time as well as space.
The definition further suffers when we realise there are an infinite number of possible OBs and by using OBs as an ultimate we extend the concept to infinity as an attempt to limit consideration/discussion. Maybe it does not work. Maybe

Do you find 'Cosmos' useful?

 

[Catastrophe]

Gibsense, of course you are correct in pointing out massive differences at an individual level.
It is on a 'general' level that there must be agreement to achieve smooth running. We all (well, most) agree on what an hour is (we invented clocks most people understand) and so on. If we did not agree on times, places, nomenclature, numerics . . . . . . . . .

Slightly connected is the idea that there is an infinite number of 'real' universes allowing for every conceivable variation of everything. Why should this apply to humans and not to elephants? not bacteria? not atoms? And, of course, every electron in every galaxy? Infinite possibilities - yes. Infinite realities - no.

It is where the line is drawn between that is important to each of us.

As far as cosmos is concerned, I think it just duplicates the problems with universe.
Much of what you say is very relevant, and applicable to verbal communication in general.

(My apologies. I am sufffering from keyboard duplicating letters. I will correct these as best I can, as I go along.)

Cat

Addendum: On looking at this again, I don't think that you can apply this to me:

In defining the 'Observable Universe' we forget that any OU is user-specific.

I think I made it very clear that o/u is very much individual.

Let us just be happy with "observable universes", but with the proviso that they can be observed, interacted with, and/or detected with instruents, by any entity capable of intelligent observation involving whatever reliable means of investigation available to them.

 

[promytius]

Sure; blame Galileo...

 

[Catastrophe]

With the benefit of a couple of weeks away from the subject, I feel ready to try to return to the question. Hopefully I have made some progress.

First introductory question. Who wants to know? Is one approach better than others?

Case 1. The person in the street. Very easy. "All there is" is a perfectly adequte defnition.
I just want to get on with eating and sleeping and getting by. Who cares anyway.

Case 2. The philosopher, of whatever ilk. Someone who just wants to juggle ideas.
Possibly impress people. Facts are of little importance. Ideas are "The Thing".
This covers an enormous variety, including many organised thought systems.
I want to say as little as possible - just to mention and forget that some systems have been used to control the populace. Others are just for the joy of musing over a pint, or a glass of sherry, or perhaps of lemonade. These are just interested because they like to think about or use ideas of how it all got started, or how it will end. Their particular system of ideas is universally correct (pun intended) and nothing is going to shake them. They can churn out reams of spectacular verbosity but would quake in horror if asked to prove anything. You understand, I am sure.

I do not think scientists should bother with these cases,
If it makes them happy, let them get on with it, . . . . . . . . .
so long as they do not interfer with others' deductions and conclusions.

Case 3. those with a scientific approach. But here we must sub divide.

Case 3A are those with only a strict scientific approach. That is fine.
They will limit their deliberations strictly to what can be obtained by scientific methods.
They will suggest hypotheses which can be tested, and modify their ideas accordingly.

Case 3B are those who adopt the same viewpoint as 3A, but, in addition, are prepared to adopt some metaphysical attitudes but are quite clear and controlled in their thinking about how these knit together with "pure" scientific methods. I regard such subjects as the Big Bang and a Singularity as examples of metaphysics. There is no way we can set up and observe making the first Singularity at billions of billions of billions degrees Celsius temperatures to reduce to only billions in less than one tenth of a second. Likewise, recreating the "real" Big Bang.
Do not misunderstand me. I am OK with shooting elementary particles at each other, in the interests of science, but that is not quite the same thing. If some metaphysics can meet the conditions, and be absorbed into science, as has been happening for centuries, then I am all in favour.

I was tempted to include 3C, which would include scientists who did not know or recognise the difference between science and metaphysics, but I am sure that there are none of these here.
Extraterrestrial life is not accepted as scientific fact, so the logical certainty remains within metaphysics. Some time in the future, there may be some scientific acceptance.

Well, I will leave it there for the time being, but will be back very soon to continue with Case 3.

Cat

 

[Catastrophe]

So we disregard Cases 1 and 2, as inappropriate to this forum.

We have remaining Cases 3A and 3B. Both should be valid here.

Case 3A is fine, but I find it rather limiting.

Case 3B, remember allows logical lines of thought.
Case 3A is fine, but precludes anything beyond human sensory input, albeit a variable and open to expansion by use of instruments.

Case 3B allows sane logical exploration:

A thought experiment is a mental exercise where you imagine a scenario to explore a concept, theory, or problem, often used in fields like physics, philosophy, and psychology to test hypotheses or gain insights. [Google]

For the moment, I would like to pursue 3B. It is up to us to remain within the bounds of concept (et cetera) exploration; particularly avoiding assertions.

So, to return to definition of "Universe" or qualified "universe".

I believe that, for puroses of exploration of the concept, we can examine the flatlander analogy. As shown elsewhere, I believe that one line of thought arrives at the conclusion that The term "universe" (in general) must be relative.
Thus we have only "observable universe"s.

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Briefly, there are unlimited "observable universes" throughout one hypothetical Universe. If you want to question the nature of "The Universe", you must answer the question "according to whom?". An answer, maybe obvious to some, cannot be discussed here, as being too philosophical.
We are not considering here suggestions made by distant predecessors.
Such questioners must, according to our rules, ask elsewhere.

So, from a logical standpoint, we must accept "observable universes" as being de riguer. From this, there follows the suggestion (via flatland) that these observable universes are expanding into a dimension one higher than those experienced by the flatland observer's (observable universe). Thus, to an observer capable of experiencing one dimension higher (as would be humans to flatlanders) the "higher dimensional observer, D+1) would see an unlimited number of "lower" "observable universes".

In brief, I would propose that we should not use the term "Universe" in logical discussion, but use "observable universe" with suitable qualification.

Cat

 

[Catastrophe]

A further comment is needed to tie posts #1 and #55.

I began with:

I believe there is considerable difference still possible in what we understand by Universe, and this goes beyond what we understand by observable universes. We need to look at the "we".

I referred to John Gribbin's definition:

“The Universe is everything that we can see, and interact with, and detect with our instruments.”

The change between posts #1 and #55 is that I have negated the use of we as limited to humanity, and substituted a more general case. This is admittedly metaphysical, but no more so, imho, than the term Big Bang or Singularity.
It may not be observable currently from Earth, but logic requires that, of the billions of galaxies with billions of planets, untelligent life exists in great numbers. Even failing this, "observable" is not limited to "intelligent". There is always a possibility of considering what would be observable from that location, if an observer were present, so let us not get bogged down by semantics.

Cat

 

[Classical Motion]

If we can see back to the beginning doesn't that imply that we can see all that there is?

 

[Catastrophe]

No, unless you suggest "we" can "see" everything since t =0, but not only that. You know that, until only recently, we were unable to "see" via IR, UV, and other wavelengths. Furthermore, one individual is limited to a microscopically tiny portion of spacetime in their "seeing", and the rest is hearsay.

Everything "we" can "see" is secondhand, or more distant, hearsay.

Cat

 

[Classical Motion]

So only local observations are valid? What would you say a time frame is for it to be valid? Or perhaps worth consideration?

 

[Classical Motion]

I agree with your concept of hearsay light. It's a very valid point.

 

[Catastrophe]

So only local observations are valid? What would you say a time frame is for it to be valid? Or perhaps worth consideration?

Why do you assume that only local observations are valid?
By definition, local observations are the basis of observed universe?
But wait . . . . . . do you mean observation of the o/u from local places (and summing them?), or observations of local places only? No comprendo.

 

[Classical Motion]

Pardon me for my confusion, confusing you.

I confused your use of hearsay. You were of course literal. I am not use to such.

You were probably referring to not being able to detect yet. Therefore hearsay.

I was thinking that hearsay meant light that comes from a source that is no longer there.

The confusion was mine.

 

[Catastrophe]

No need to apologise

One meaning is "information you have heard that might or might not be true".

Cat