Definition of Universe requires clarification, to enable discussion

[whoknows]

'universe' can only mean observable universe.
There may be non-observable universes, which have no observers near enough for light to reach them.

Simply by definition. It is a question of semantics. English language.
To be an observable universe, there must be an observer to observe it. Depending on does not mean congruent with.
One observable universe can be observed by any number of observers.

There must be at least one observer per observable universe.
The number of universes need not be the same as the number of observers.
In fact, "our observable universe" is shared by the population of Earth?

But, to be precise, the observable universe of the population of Earth is not exactly the same for each person. People inside a building do not see exactly the same as an observer outside the building. There is a shared, incorrect, assumption, that we do all share the one observable universe, but, clearly, we do not. But, it just makes life easier, if we assume (strictly speaking, incorrectly) that there is one observable universe shared by the whole of Earth's population. Then, again, do you wish to include non-human observers?



On a large scale, it is true in practice, but not in detail. On a small scale, it is incorrect in detail, It depends on what any observer chooses it to mean.
And are you going to include non-human observers?

Discussing semantics in detail, can turn out to be a waste of terrible time, but, if one must, it is necessary to define one's terms, or risk wasting one's life.

I hope that that clears up the matter, but, if you wish to pursue it further, then you need to define your terms.

Cat

More than happy to pursue the discussion in your thread using your terms.

For starters can you unravel this for me please?

"'universe' can only mean observable universe.
There may be non-observable universes, which have no observers near enough for light to reach them."

 

[Catastrophe]

whoknows,

universe' can only mean observable universe.
There may be non-observable universes, which have no observers near enough for light to reach them.

It seems quite straightforward to me.

universe' can only mean observable universe.

An oversimplified definition of "universe" is "all there is".
One might extend this, through time, all there was, is, or ever will be.

But one must ask "according to whom?".
Already, we know that there are galaxies millions to billions of light years away. This, as you will know, means that light takes millions to billions of years to reach us. A light year is a measure of distance.

For the time being, at least, it is understood that:

Nothing, including matter and information, can exceed the speed of light. The speed of light (approximately 300,000 kilometers per second) is considered a universal speed limit. Only massless particles like photons can travel at this speed. Any object with mass would require an infinite amount of energy to reach the speed of light.

Thus the entirety of the "Universe" cannot be observed, unless you postulate some observer present in all places at all times. Certainly, the entirety of the "Universe" cannot be observed by humans, and never will be, unless you allow changes beyond belief.

and

There may be non-observable universes, which have no observers near enough for light to reach them.

As stated, we can only observe light (or any EM radiation) which has had time to reach us after leaving its source. In the vernacular, "if it ain't got here yet, you can't see it". Remember, we are discussing light (EMR).

Thus, if the "observable universe" were 14 billion light years old, we would be unable to observe anything more than 14 billion years. This is simply a semantic cyclic statement of the definition. Clearly, a non-observable universe would simply have no observers near enough for light to have reached it.

I hope that this is sufficiently simplified to respond to your question:

For starters can you unravel this for me please?

Cat

 

[whoknows]

whoknows,



It seems quite straightforward to me.



An oversimplified definition of "universe" is "all there is".
One might extend this, through time, all there was, is, or ever will be.

But one must ask "according to whom?".
Already, we know that there are galaxies millions to billions of light years away. This, as you will know, means that light takes millions to billions of years to reach us. A light year is a measure of distance.

For the time being, at least, it is understood that:



Thus the entirety of the "Universe" cannot be observed, unless you postulate some observer present in all places at all times. Certainly, the entirety of the "Universe" cannot be observed by humans, and never will be, unless you allow changes beyond belief.

and



As stated, we can only observe light (or any EM radiation) which has had time to reach us after leaving its source. In the vernacular, "if it ain't got here yet, you can't see it". Remember, we are discussing light (EMR).

Thus, if the "observable universe" were 14 billion light years old, we would be unable to observe anything more than 14 billion years. This is simply a semantic cyclic statement of the definition. Clearly, a non-observable universe would simply have no observers near enough for light to have reached it.

I hope that this is sufficiently simplified to respond to your question:



Cat

Excuse my simplicity, are you saying that a universe has to be observable to be objectively real?

 

[Catastrophe]

Excuse my simplicity, are you saying that a universe has to be observable to be objectively real?

This is complicated, as simple words often are, semantically speaking.

Google Search

One suggested definition is:

actually existing as a thing or occurring in fact; not imagined or supposed.

My suggestion would be ask whether, to be real, the object must be observable. Whilst it may not be being observed at this moment, a would be observer must be able to observe it, if being brought into light/sight range.
Thus, to be real (observable) it must be describable as an "observable object".

Can you suggest any other definition of "real", which does not require the object to be observable.

There are further complications, if you wish to follow them.
For example, "observable" by whom/what? e.g., animals.
In a wider context, observable by aliens, possibly with different perceptions, but, perhaps, invisible to humans.

In short: "are you saying that a universe has to be observable to be objectively real?". The answer is yes, because, otherwise, how do you prove that it exists?

Of course, a universe might not be observable by us, being beyond our light/distance limit, but it might be observable by an observer between us and the distant galaxy. We might consider this galaxy real, if we believed the word of the observer. (This observer could be a future human distant traveller.) In this case the bodies would be many light years distant, and any conclusions would not be based on a common "now", but would have to be historical.

Cat

Addendum:

Science is a systematic endeavor that builds and organizes knowledge about the universe in the form of testable hypotheses and predictions. It involves observing, identifying, describing, experimenting, and theorizing about natural phenomena. Science aims to explain and understand the natural world, offering reliable knowledge that is open to revision as new evidence emerges.

 

[whoknows]

This is complicated, as simple words often are, semantically speaking.



One suggested definition is:



My suggestion would be ask whether, to be real, the object must be observable. Whilst it may not be being observed at this moment, a would be observer must be able to observe it, if being brought into light/sight range.
Thus, to be real (observable) it must be describable as an "observable object".

Can you suggest any other definition of "real", which does not require the object to be observable.

There are further complications, if you wish to follow them.
For example, "observable" by whom/what? e.g., animals.
In a wider context, observable by aliens, possibly with different perceptions, but, perhaps, invisible to humans.

In short: "are you saying that a universe has to be observable to be objectively real?". The answer is yes, because, otherwise, how do you prove that it exists?

Of course, a universe might not be observable by us, being beyond our light/distance limit, but it might be observable by an observer between us and the distant galaxy. We might consider this galaxy real, if we believed the word of the observer. (This observer could be a future human distant traveller.) In this case the bodies would be many light years distant, and any conclusions would not be based on a common "now", but would have to be historical.

Cat

Addendum:

"Can you suggest any other definition of "real", which does not require the object to be observable."

Yes, anything that is objectively real, whether observed or not. Why does reality require your blessing?

Your whole argument seems to be subjective, and therefore metaphysics, to this simpleton.

 

[Catastrophe]

whoknows,

please tell me how you know something is "real".

You should check my post:

Is our universe trapped inside a black hole? This James Webb Space Telescope discovery might blow your mind

The James Webb Space Telescope has found perhaps its most profound discovery to date. The uncovered preferred direction for galaxies supports the idea that the universe was born in a black hole. Is our universe trapped inside a black hole? This James Webb Space Telescope discovery might blow...

forums.space.com

I posted:

What is included as observable depends on the location of the observer, the sensory apparatus of the observer, aided as well as unaided, and even the processing of the input by the brain.

"Observing" is not limited to "seeing".

to observe "perceiving something with one's senses" Merriam-Webster

to perceive "to perceive means to become aware of something through one's senses" Merriam-Webster

Cat

 

[Catastrophe]

whoknows, is this closer to what you had in mind?

Google Search

Cat

 

[Catastrophe]

QUOTE

• Physics:
  Quantum mechanics suggests that the act of measuring a property of a quantum system, like the position of an electron, causes it to "collapse" from a state of possibilities into a definite state. This has led to interpretations like the Copenhagen interpretation, which suggests that things don't have definite properties until they are observed. However, this doesn't necessarily imply that the thing doesn't exist before observation; it might exist in a probabilistic state described by a wave function.
  
  
• Philosophy:
  The question of whether something exists independently of observation is a fundamental question in metaphysics. Some philosophical perspectives, like idealism, suggest that reality is fundamentally mental and exists only as it is perceived. Others, like materialism, posit that reality exists independently of consciousness. There are also views that suggest that existence is tied to interactions or that things exist in a state of potential until they are realized.

QUOTE

I think that my best answer must be "yer pays yer money and yer takes yer pick".

yer = non-standard spelling of you, used in representing dialectal speech.

Cat

 

[Astraeus]

QUOTE

• Physics:
  Quantum mechanics suggests that the act of measuring a property of a quantum system, like the position of an electron, causes it to "collapse" from a state of possibilities into a definite state. This has led to interpretations like the Copenhagen interpretation, which suggests that things don't have definite properties until they are observed. However, this doesn't necessarily imply that the thing doesn't exist before observation; it might exist in a probabilistic state described by a wave function.
  
  
• Philosophy:
  The question of whether something exists independently of observation is a fundamental question in metaphysics. Some philosophical perspectives, like idealism, suggest that reality is fundamentally mental and exists only as it is perceived. Others, like materialism, posit that reality exists independently of consciousness. There are also views that suggest that existence is tied to interactions or that things exist in a state of potential until they are realized.

QUOTE

I think that my best answer must be "yer pays yer money and yer takes yer pick".



Cat

ChatGPTs evaluation of Cat's text block.

Physics (Evaluation):​

Claim Summary:

"Quantum mechanics suggests that the act of measuring a property causes it to 'collapse'... leading to interpretations like Copenhagen... things don’t have definite properties until they are observed."

This reflects a mainstream pedagogical interpretation — Copenhagen Interpretation — but it's not the only or universally accepted framework.

Accurate Aspects:​

• The wavefunction collapse idea is real within certain interpretations (Copenhagen, von Neumann–Wigner, etc.).
• In those frameworks, measurement transforms a system from a superposition of possible outcomes into a definite one.
• The phrase "things don’t have definite properties until they are observed" is an accessible summary of the epistemic implications of Copenhagen, but not a literal claim about existence in all interpretations.

Caveats and Nuance:​

• Collapse is not part of the Schrödinger equation. It's an added postulate — not universally accepted in physics.
• Other interpretations deny real collapse:
  • Many-Worlds: All outcomes occur in branching realities — no collapse.
  • de Broglie–Bohm (Pilot-Wave): Particles always have definite positions; wavefunction guides them, but no collapse.
  • QBism: Collapse is a subjective update to an observer’s knowledge, not a physical process.
  • Objective Collapse Theories (e.g. GRW): Collapse is a physical, spontaneous event, not observer-dependent.
• Thus, it’s not accurate to say quantum mechanics "suggests" collapse — only certain interpretations do. The raw math doesn’t favor collapse over no-collapse.

---

Philosophy (Evaluation):​

Claim Summary:

"Some philosophical views, like idealism, suggest reality is mental and exists only as perceived. Materialism posits reality exists independently. Other views propose potentiality as a mode of existence."

This is a thoughtful generalization of long-standing metaphysical positions, though again, clarity is needed.

Accurate Elements:​

• Idealism (Berkeley, later Kantian strands): Reality is fundamentally tied to perception or mind.
• Materialism/Physicalism: Reality exists independently of observers — it has objective properties.
• Potentiality: Echoes Aristotelian ideas (e.g., being-in-potency vs. being-in-act) and shows up in modern interpretations like Heisenberg’s “potentia” idea.
• Relational views (like Rovelli’s Relational Quantum Mechanics): Suggest properties only manifest through interaction, a middle ground between hard realism and observer-dependence.

Important Clarifications:​

• Saying something “might exist in a probabilistic state” is a metaphorical shorthand. Probabilities describe our knowledge (in Bayesian or epistemic views), not necessarily ontological uncertainty — unless you're adopting a specific interpretation.
• Existence in potential is a meaningful philosophical category but not recognized in classical physics, where systems have definite properties at all times (e.g., Newtonian determinism).
• In quantum physics, whether the wavefunction represents reality or knowledge is interpretation-dependent — a live metaphysical debate, not resolved by physics alone.

 

[Catastrophe]

Astraeus, thank you for processing that. Cat

 

[whoknows]

QUOTE



QUOTE

I think that my best answer must be "yer pays yer money and yer takes yer pick".



Cat

God bless ya govner, still seems rather subjective and metaphysical to me. Don't ya need an external objective reality to exist therefore you are in? ( collapsed energy field or whatever).

 

[Catastrophe]

We all sense that there is something which we all sense.
That does not mean that there is something out there which is open to the same perception by all. That would be an objective universe.

It is beyond argument there is no common "Universe".
There are only "observable universes". That is clear.

See post #81. It concluded, referring to the reference, with

I posted:

What is included as observable depends on the location of the observer, the sensory apparatus of the observer, aided as well as unaided, and even the processing of the input by the brain.

"Observing" is not limited to "seeing".

to observe "perceiving something with one's senses" Merriam-Webster

to perceive "to perceive means to become aware of something through one's senses" Merriam-Webster

Please note: "What is included as observable depends on the location of the observer, the sensory apparatus of the observer, aided as well as unaided, and even the processing of the input by the brain."

You still have not replied to this in any satisfactory manner - you try to advise me on semantics whilst denying the definitions of Merriam-Webster.

I tried to give you a way out, so we could just agree to differ:

I think that my best answer must be "yer pays yer money and yer takes yer pick".

but you refused this gesture of good will. Post #86.

God bless ya govner, still seems rather subjective and metaphysical to me. Don't ya need an external objective reality to exist therefore you are in? ( collapsed energy field or whatever).

You have probably noticed that one similar thread has been terminated.
Is that what you want?

i always try to do my best to be polite and helpful on this forum, but you seem to ignore my would-be good will.

May I suggest that you either give some consideration to this post, especially:

Please note: "What is included as observable depends on the location of the observer, the sensory apparatus of the observer, aided as well as unaided, and even the processing of the input by the brain."

I have said that there is something out there to observe, which seemed your point, but I have shown that perception of this "something" can only be subjective.
Just please think about that.

Shall we now either finish this with a mature discussion, or decide to let the dogs sleep?
Do you have the saying "let sleeping dogs lie"?

Cat

 

[whoknows]

May I suggest that you either give some consideration to this post, especially:



I have said that there is something out there to observe, which seemed your point, but I have shown that perception of this "something" can only be subjective.
Just please think about that.

Shall we now either finish this with a mature discussion, or decide to let the dogs sleep?
Do you have the saying "let sleeping dogs lie"?

Cat .

We all sense that there is something which we all sense.
That does not mean that there is something out there which is open to the same perception by all. That would be an objective universe.

It is beyond argument there is no common "Universe".
There are only "observable universes". That is clear.

See post #81. It concluded, referring to the reference, with



Please note: "What is included as observable depends on the location of the observer, the sensory apparatus of the observer, aided as well as unaided, and even the processing of the input by the brain."

You still have not replied to this in any satisfactory manner - you try to advise me on semantics whilst denying the definitions of Merriam-Webster.

I tried to give you a way out, so we could just agree to differ:



but you refused this gesture of good will. Post #86.



You have probably noticed that one similar thread has been terminated.
Is that what you want?

i always try to do my best to be polite and helpful on this forum, but you seem to ignore my would-be good will.

May I suggest that you either give some consideration to this post, especially:



I have said that there is something out there to observe, which seemed your point, but I have shown that perception of this "something" can only be subjective.
Just please think about that.

Shall we now either finish this with a mature discussion, or decide to let the dogs sleep?
Do you have the saying "let sleeping dogs lie"?

Cat

As ever you are conflating subjectivity with objectivity with a massive sprinkling of condescension.

A mature discussion would entail why a universe, independent of observers, - (edit - independent of what observers might experience or think) could not exist and be the reality.

Try and close this discussion if you wish to hang on to your metaphysics.

 

[whoknows]

"It is beyond argument there is no common "Universe".

Why?