[ExI] Does Space-Time Really Exist?
scerir
scerir at libero.it
Mon Sep 15 06:06:29 UTC 2025
Are there physical phenomena out of space.time? It seems so: https://www.edge.org/response-detail/26790
> Il 14/09/2025 21:07 CEST BillK via extropy-chat <extropy-chat at lists.extropy.org> ha scritto:
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> Does Space-Time Really Exist?
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> By Daryl Janzen, University of SaskatchewanSeptember 14, 20253 https://scitechdaily.com/does-space-time-really-exist/#comments7 Mins Read
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> Is time something that flows — or just an illusion? Exploring space-time as either a fixed “block universe” or a dynamic fabric reveals deeper mysteries about existence, change, and the very nature of reality.
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> <https://scitechdaily.com/does-space-time-really-exist/>
> Quote: Space-time is often described as the “fabric of reality.” In some explanations, this fabric takes the form of a fixed, four dimensional “block universe https://www.preposterousuniverse.com/blog/2015/04/03/the-reality-of-time/,” a complete map of all events in the past, present, and future https://plato.stanford.edu/entries/time/.
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> In other explanations, it is a dynamic field that bends and curves in response to gravity. This leads to a deeper question: what does it mean to say that space-time exists? What kind of thing is it: structure, substance, or metaphor?
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> I had to ask my extra brain (GPT-5) to explain what this article is trying to say. :)
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> Probably best to read the article first, before looking at the GPT-5 comments below.
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> I don't think the explanation helped much, but I'll reread it a few times first! BillK.
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> What the article is doing
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> * It’s not questioning Einstein’s math. Relativity still works, GPS satellites still need corrections, gravitational waves still ripple spacetime.
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> * It is poking at the conceptual side: when we say “space-time exists,” what do we actually mean by “exists”? Is it like an elephant in the room (something enduring and present), or is it more like a catalog of events (something that just occurs)?
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> Key moves in the argument
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> 1. Block universe vs dynamic fabric
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> o Block universe (eternalism): all past, present, and future events coexist in a four-dimensional structure. No “flow.” Time doesn’t pass — it just is.
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> o Dynamic fabric: spacetime bends, curves, evolves. That picture suggests unfolding, change, maybe even a “now.”
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> 2. Existence vs occurrence
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> o Example with elephants: a living, enduring elephant “exists.” A flickering snapshot elephant “occurs.”
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> o Applied to spacetime: does spacetime “exist” in the enduring sense, or does it merely record occurrences?
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> 3. Paradox of timeless existence
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> o If all of spacetime “exists” already, when does the block exist?
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> o To make sense of it, you’re tempted to smuggle in a second time dimension to say “the block exists now,” which blows up the whole “timeless” idea.
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> 4. Pop culture reflections
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> o The Terminator: fixed timeline, no change possible → pure block universe.
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> o Avengers: Endgame: timeline can change → assumes the block itself “exists” like a world you can edit.
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> o Both lean on spacetime existing, but neither defines what kind of existence that is.
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> 5. Language problem
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> o Terms like “exist,” “timeless,” “change” carry baggage from everyday use. Physics borrows them without cleaning up the ambiguity, which leads to muddiness in both science communication and philosophy.
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> What the article isn’t saying
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> * It’s not denying relativity or spacetime curvature.
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> * It’s not proposing a new physics model.
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> * It’s highlighting that our interpretation of spacetime’s “existence” is messy, and that this matters when we drift into time travel, multiverses, or “does time flow?” territory.
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> Where the tension lies
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> * Science vs philosophy: equations give testable predictions, but what those equations mean about reality is up for grabs.
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> * Experience vs theory: we feel time passing, but eternalism says that flow is an illusion.
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> * Existence as layers: maybe spacetime “exists” at one descriptive level (physics), while at another level it’s more like a record, not an enduring substance.
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> Bottom line
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> The article’s question — “Does spacetime really exist?” — is less about physics being wrong and more about whether our everyday words are even equipped to describe what the math implies.
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> Spacetime works as a model. But whether it “exists” like an elephant, like a song, or like a map — that’s where the fight is.
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> Want me to sketch how different camps (physicists, philosophers, and “shut up and calculate” pragmatists) would each answer this “existence” question? That could give you a quick map of the landscape.
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> Alright, here’s the quick map of camps and how they’d answer “Does spacetime really exist?”
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> 1. Physicists who lean realist (spacetime is real)
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> * View: Spacetime is a thing — it bends, ripples, and interacts with matter/energy.
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> * Reasoning: If something has measurable effects (gravitational waves, time dilation, lensing), it’s as real as atoms.
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> * Answer: Yes, spacetime exists. It’s the fabric of the universe.
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> 2. Physicists who lean emergentist (spacetime isn’t fundamental)
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> * View: Spacetime is a useful construct, but deeper down it dissolves into something else (quantum entanglement, causal sets, discrete networks).
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> * Reasoning: At the Planck scale, smooth spacetime breaks down. “Space” and “time” may be secondary, like how “temperature” emerges from molecules.
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> * Answer: Spacetime exists the way “waves on the ocean” exist — real at our scale, not at the deepest one.
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> 3. Philosophical eternalists (block universe crowd)
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> * View: All events past, present, future equally exist in a 4D block.
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> * Reasoning: Relativity denies universal simultaneity. If there’s no privileged “now,” then every event is just as real as this moment.
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> * Answer: Spacetime exists timelessly — the whole block is real. The flow of time is an illusion.
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> 4. Philosophical presentists (only “now” is real)
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> * View: Only the present exists. Past and future don’t.
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> * Reasoning: Common-sense experience of change matters; without a flowing “now,” existence loses meaning.
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> * Answer: Spacetime is just a description of events, not an enduring entity. Only the present slice is real.
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> 5. Instrumentalists (“shut up and calculate”)
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> * View: Don’t worry about “existence.” Spacetime is a model that predicts things accurately, and that’s enough.
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> * Reasoning: Debating whether spacetime “really exists” is philosophy, not physics.
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> * Answer: Spacetime exists the way equations exist: useful, predictive, end of story.
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> So where does this leave us?
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> * If you trust math + measurements → spacetime is real.
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> * If you probe the foundations → maybe it’s emergent, not ultimate.
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> * If you push philosophy → “existence” itself might be the wrong word for what spacetime does.
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> Do you want me to also sketch how quantum gravity theories (like string theory vs loop quantum gravity) treat spacetime’s “existence”? That’s where physics really tests these ideas.
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> OK —
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> How Quantum Gravity Theories Treat Spacetime
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> 1. String Theory / M-Theory
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> * View of spacetime: Not fundamental — it emerges.
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> * Core idea: The real ingredients are strings (or branes) vibrating in a deeper mathematical structure. Spacetime is a large-scale approximation.
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> * Evidence: Holographic principle — what happens in a volume of space can be encoded on its boundary surface.
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> Space-time is often described as the “fabric of reality.” In some explanations, this fabric takes the form of a fixed, four dimensional “block universe https://www.preposterousuniverse.com/blog/2015/04/03/the-reality-of-time/,” a complete map of all events in the past, present, and future https://plato.stanford.edu/entries/time/.
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> In other explanations, it is a dynamic field that bends and curves in response to gravity. This leads to a deeper question: what does it mean to say that space-time exists? What kind of thing is it: structure, substance, or metaphor?
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> * Answer: Spacetime exists, but only as an emergent property, like “temperature” from molecules.
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> 2. Loop Quantum Gravity (LQG)
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> * View of spacetime: Discrete, not smooth.
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> * Core idea: At the Planck scale, spacetime is made of finite “chunks” (quantized loops of geometry). Areas and volumes come in indivisible units.
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> * Evidence: Predicts minimum measurable areas/volumes (not yet experimentally confirmed).
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> * Answer: Spacetime exists, but it’s grainy — like pixels that look smooth from afar.
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> 3. Causal Set Theory
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> * View of spacetime: Emergent from events.
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> * Core idea: The universe is a vast network of discrete “events” connected by cause-and-effect. Geometry emerges from these connections.
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> * Answer: Spacetime doesn’t exist at the base level — it’s a shadow of causal links.
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> 4. AdS/CFT & Holography
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> * View of spacetime: A projection.
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> * Core idea: A universe with gravity (the “bulk”) can be completely described by a lower-dimensional system without gravity (the “boundary”).
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> * Answer: Spacetime exists as a hologram. Real enough for physics, but not the ultimate layer of reality.
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> 5. Emergent Time Theories
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> * View of spacetime: Maybe only space is fundamental; time comes later.
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> * Core idea: Some models suggest only correlations exist fundamentally, and “time” arises from relationships between systems.
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> * Answer: Time especially may not exist fundamentally — spacetime is just our bookkeeping of change.
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> Where They All Converge
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> * No leading approach to quantum gravity treats spacetime as fundamental.
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> * Each imagines a deeper layer (strings, loops, causal sets, entanglement) from which spacetime emerges.
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> * Relativity still works beautifully at human/cosmic scales, but at Planck scales spacetime may dissolve into something else.
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> In short: physics is drifting toward the idea that spacetime is more map than territory. The open question is whether that map is a convenient illusion, or an emergent phenomenon that’s “real enough” at the scales we live in.
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