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<p>Are there physical phenomena out of space.time? It seems so: https://www.edge.org/response-detail/26790</p>
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Il 14/09/2025 21:07 CEST BillK via extropy-chat <extropy-chat@lists.extropy.org> ha scritto:
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<h1>Does Space-Time Really Exist?</h1>
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By Daryl Janzen, University of SaskatchewanSeptember 14, 2025<a href="https://scitechdaily.com/does-space-time-really-exist/#comments" target="_blank" rel="noopener">3 </a>7 Mins Read
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</div> <strong>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.</strong>
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<<a href="https://scitechdaily.com/does-space-time-really-exist/" target="_blank" rel="noopener">https://scitechdaily.com/does-space-time-really-exist/</a>>
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Quote: Space-time is often described as the “fabric of reality.” In some explanations, this fabric takes the form of a fixed, four dimensional “<a href="https://www.preposterousuniverse.com/blog/2015/04/03/the-reality-of-time/" target="_blank" rel="noopener">block universe</a>,” a complete map of all events in the <a href="https://plato.stanford.edu/entries/time/" target="_blank" rel="noopener">past, present, and future</a>.
<p>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?</p>
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<p>I had to ask my extra brain (GPT-5) to explain what this article is trying to say. :)</p>
<p>Probably best to read the article first, before looking at the GPT-5 comments below. </p>
<p>I don't think the explanation helped much, but I'll reread it a few times first! BillK.</p>
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<h3>What the article is doing</h3>
<ul>
<li> <p>It’s not questioning Einstein’s math. Relativity still works, GPS satellites still need corrections, gravitational waves still ripple spacetime.</p> </li>
<li> <p>It <em>is</em> poking at the <strong>conceptual side</strong>: 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 <em>occurs</em>)?</p> </li>
</ul>
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<h3>Key moves in the argument</h3>
<ol>
<li> <p><strong>Block universe vs dynamic fabric</strong></p>
<ul>
<li> <p><em>Block universe</em> (eternalism): all past, present, and future events coexist in a four-dimensional structure. No “flow.” Time doesn’t pass — it just <em>is</em>.</p> </li>
<li> <p><em>Dynamic fabric</em>: spacetime bends, curves, evolves. That picture suggests unfolding, change, maybe even a “now.”</p> </li>
</ul> </li>
<li> <p><strong>Existence vs occurrence</strong></p>
<ul>
<li> <p>Example with elephants: a living, enduring elephant “exists.” A flickering snapshot elephant “occurs.”</p> </li>
<li> <p>Applied to spacetime: does spacetime “exist” in the enduring sense, or does it merely record occurrences?</p> </li>
</ul> </li>
<li> <p><strong>Paradox of timeless existence</strong></p>
<ul>
<li> <p>If all of spacetime “exists” already, <em>when</em> does the block exist?</p> </li>
<li> <p>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.</p> </li>
</ul> </li>
<li> <p><strong>Pop culture reflections</strong></p>
<ul>
<li> <p><em>The Terminator</em>: fixed timeline, no change possible → pure block universe.</p> </li>
<li> <p><em>Avengers: Endgame</em>: timeline can change → assumes the block itself “exists” like a world you can edit.</p> </li>
<li> <p>Both lean on spacetime existing, but neither defines what kind of existence that is.</p> </li>
</ul> </li>
<li> <p><strong>Language problem</strong></p>
<ul>
<li> <p>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.</p> </li>
</ul> </li>
</ol>
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<h3>What the article <em>isn’t</em> saying</h3>
<ul>
<li> <p>It’s not denying relativity or spacetime curvature.</p> </li>
<li> <p>It’s not proposing a new physics model.</p> </li>
<li> <p>It’s highlighting that our <em>interpretation</em> of spacetime’s “existence” is messy, and that this matters when we drift into time travel, multiverses, or “does time flow?” territory.</p> </li>
</ul>
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<h3>Where the tension lies</h3>
<ul>
<li> <p><strong>Science vs philosophy</strong>: equations give testable predictions, but what those equations <em>mean</em> about reality is up for grabs.</p> </li>
<li> <p><strong>Experience vs theory</strong>: we feel time passing, but eternalism says that flow is an illusion.</p> </li>
<li> <p><strong>Existence as layers</strong>: maybe spacetime “exists” at one descriptive level (physics), while at another level it’s more like a record, not an enduring substance.</p> </li>
</ul>
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<h3>Bottom line</h3>
<p>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.</p>
<p>Spacetime <em>works</em> as a model. But whether it “exists” like an elephant, like a song, or like a map — that’s where the fight is.</p>
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<p>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. </p>
<p> </p>
<p>Alright, here’s the quick map of camps and how they’d answer <strong>“Does spacetime really exist?”</strong></p>
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<h3>1. <strong>Physicists who lean realist (spacetime is real)</strong></h3>
<ul>
<li> <p><strong>View:</strong> Spacetime is a <em>thing</em> — it bends, ripples, and interacts with matter/energy.</p> </li>
<li> <p><strong>Reasoning:</strong> If something has measurable effects (gravitational waves, time dilation, lensing), it’s as real as atoms.</p> </li>
<li> <p><strong>Answer:</strong> <em>Yes, spacetime exists. It’s the fabric of the universe.</em></p> </li>
</ul>
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<h3>2. <strong>Physicists who lean emergentist (spacetime isn’t fundamental)</strong></h3>
<ul>
<li> <p><strong>View:</strong> Spacetime is a useful construct, but deeper down it dissolves into something else (quantum entanglement, causal sets, discrete networks).</p> </li>
<li> <p><strong>Reasoning:</strong> At the Planck scale, smooth spacetime breaks down. “Space” and “time” may be secondary, like how “temperature” emerges from molecules.</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime exists the way “waves on the ocean” exist — real at our scale, not at the deepest one.</em></p> </li>
</ul>
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<h3>3. <strong>Philosophical eternalists (block universe crowd)</strong></h3>
<ul>
<li> <p><strong>View:</strong> All events past, present, future equally exist in a 4D block.</p> </li>
<li> <p><strong>Reasoning:</strong> Relativity denies universal simultaneity. If there’s no privileged “now,” then every event is just as real as this moment.</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime exists timelessly — the whole block is real. The flow of time is an illusion.</em></p> </li>
</ul>
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<h3>4. <strong>Philosophical presentists (only “now” is real)</strong></h3>
<ul>
<li> <p><strong>View:</strong> Only the present exists. Past and future don’t.</p> </li>
<li> <p><strong>Reasoning:</strong> Common-sense experience of change matters; without a flowing “now,” existence loses meaning.</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime is just a description of events, not an enduring entity. Only the present slice is real.</em></p> </li>
</ul>
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<h3>5. <strong>Instrumentalists (“shut up and calculate”)</strong></h3>
<ul>
<li> <p><strong>View:</strong> Don’t worry about “existence.” Spacetime is a model that predicts things accurately, and that’s enough.</p> </li>
<li> <p><strong>Reasoning:</strong> Debating whether spacetime “really exists” is philosophy, not physics.</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime exists the way equations exist: useful, predictive, end of story.</em></p> </li>
</ul>
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<h3>So where does this leave us?</h3>
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<li> <p>If you trust math + measurements → spacetime is real.</p> </li>
<li> <p>If you probe the foundations → maybe it’s emergent, not ultimate.</p> </li>
<li> <p>If you push philosophy → “existence” itself might be the wrong word for what spacetime does.</p> </li>
</ul>
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<p>Do you want me to also sketch how <strong>quantum gravity theories</strong> (like string theory vs loop quantum gravity) treat spacetime’s “existence”? That’s where physics really tests these ideas.</p>
<p> </p> OK —
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<h2>How Quantum Gravity Theories Treat Spacetime</h2>
<h3>1. <strong>String Theory / M-Theory</strong></h3>
<ul>
<li> <p><strong>View of spacetime:</strong> Not fundamental — it emerges.</p> </li>
<li> <p><strong>Core idea:</strong> The real ingredients are strings (or branes) vibrating in a deeper mathematical structure. Spacetime is a large-scale approximation.</p> </li>
<li> <p><strong>Evidence:</strong> Holographic principle — what happens in a volume of space can be encoded on its boundary surface.</p> <p>Space-time is often described as the “fabric of reality.” In some explanations, this fabric takes the form of a fixed, four dimensional “<a href="https://www.preposterousuniverse.com/blog/2015/04/03/the-reality-of-time/" target="_blank" rel="noopener">block universe</a>,” a complete map of all events in the <a href="https://plato.stanford.edu/entries/time/" target="_blank" rel="noopener">past, present, and future</a>.</p> <p>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?</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime exists, but only as an emergent property, like “temperature” from molecules.</em></p> </li>
</ul>
<hr>
<h3>2. <strong>Loop Quantum Gravity (LQG)</strong></h3>
<ul>
<li> <p><strong>View of spacetime:</strong> Discrete, not smooth.</p> </li>
<li> <p><strong>Core idea:</strong> At the Planck scale, spacetime is made of finite “chunks” (quantized loops of geometry). Areas and volumes come in indivisible units.</p> </li>
<li> <p><strong>Evidence:</strong> Predicts minimum measurable areas/volumes (not yet experimentally confirmed).</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime exists, but it’s grainy — like pixels that look smooth from afar.</em></p> </li>
</ul>
<hr>
<h3>3. <strong>Causal Set Theory</strong></h3>
<ul>
<li> <p><strong>View of spacetime:</strong> Emergent from events.</p> </li>
<li> <p><strong>Core idea:</strong> The universe is a vast network of discrete “events” connected by cause-and-effect. Geometry emerges from these connections.</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime doesn’t exist at the base level — it’s a shadow of causal links.</em></p> </li>
</ul>
<hr>
<h3>4. <strong>AdS/CFT & Holography</strong></h3>
<ul>
<li> <p><strong>View of spacetime:</strong> A projection.</p> </li>
<li> <p><strong>Core idea:</strong> A universe with gravity (the “bulk”) can be completely described by a lower-dimensional system without gravity (the “boundary”).</p> </li>
<li> <p><strong>Answer:</strong> <em>Spacetime exists as a hologram. Real enough for physics, but not the ultimate layer of reality.</em></p> </li>
</ul>
<hr>
<h3>5. <strong>Emergent Time Theories</strong></h3>
<ul>
<li> <p><strong>View of spacetime:</strong> Maybe only space is fundamental; time comes later.</p> </li>
<li> <p><strong>Core idea:</strong> Some models suggest only correlations exist fundamentally, and “time” arises from relationships between systems.</p> </li>
<li> <p><strong>Answer:</strong> <em>Time especially may not exist fundamentally — spacetime is just our bookkeeping of change.</em></p> </li>
</ul>
<hr>
<h2>Where They All Converge</h2>
<ul>
<li> <p>No leading approach to quantum gravity treats spacetime as <strong>fundamental</strong>.</p> </li>
<li> <p>Each imagines a deeper layer (strings, loops, causal sets, entanglement) from which spacetime emerges.</p> </li>
<li> <p>Relativity still works beautifully at human/cosmic scales, but at Planck scales spacetime may dissolve into something else.</p> </li>
</ul>
<hr>
<p>In short: physics is drifting toward the idea that spacetime is more <strong>map</strong> than <strong>territory</strong>. 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.</p>
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