If spacetime is emergent, what does it really mean for anything to be separate?

What If Space and Time Aren’t Fundamental?

If you take space and time out of the equation, what does it even mean for things to be separate?

I had one of those conversations recently that began with quantum entanglement, wandered through wormholes and time travel, passed through the Big Bang, and eventually arrived at a question I haven't been able to shake:

What if our experience of things being separate is partly a consequence of living inside space and time?

I’m not suggesting that I’ve stumbled onto a new theory of physics. Far from it. This is a thought experiment inspired by ideas that physicists and philosophers have been wrestling with for a very long time.

But sometimes a thought experiment is useful precisely because it forces us to examine assumptions that normally feel so obvious we don't even notice we're making them.

And few assumptions are more deeply embedded in us than space and time.

We Can't Help Thinking in Space and Time

Everything about ordinary human experience is organized around them.

Something happened before something else.

An object is here instead of there.

We were born. We live. Eventually, we die.

We move from one location to another and from one moment to the next.

It's almost impossible to construct a sentence about reality without smuggling space or time into it somewhere.

That's not surprising. We're physical organisms existing within spacetime. Our memories point toward what we call the past, our expectations point toward the future, and our experience seems to travel continuously between them.

But relativity already tells us something strange: there is no single universal cosmic "now" shared by every observer.

Observers moving relative to one another can disagree about whether distant events occurred simultaneously. Time and space aren't separate universal backgrounds; they're woven together into spacetime.

That has led philosophers and physicists to seriously consider ideas such as the block universe, or eternalism, in which past, present and future are parts of a four-dimensional spacetime rather than reality being created one universal moment at a time. That's an interpretation rather than a uniquely established consequence of relativity, but relativity makes our intuitive idea of a universal present much harder to maintain. https://plato.stanford.edu/entries/consciousness-temporal/

And that immediately creates an uncomfortable question:

If there is no universal "now," how fundamental is our sensation that reality is moving from past to future?

The Universe Has No Center

Another clue comes from cosmology.

We're often taught the Big Bang using an unfortunate mental picture: everything in the universe compressed into a tiny object sitting somewhere in emptiness and then exploding outward.

But that's not what modern cosmology describes.

There was no empty surrounding space for the universe to explode into. Space itself was involved in the expansion.

NASA's John Mather puts the point particularly clearly: the Big Bang shouldn't be pictured as an explosion with a center. In the standard cosmological picture, expansion occurred everywhere, and there is no privileged central location from which everything is flying outward. https://www.nasa.gov/universe/nasas-james-webb-space-telescope-and-the-big-bang-a-short-qa-with-nobel-laureate-dr-john-mather/

That leads to one of my favorite features of the expanding universe.

From our galaxy, distant galaxies generally appear to recede from us.

Travel to another sufficiently distant galaxy and, on large cosmological scales, the same pattern appears there.

That observer can also describe everything as expanding away from them.

Neither observer occupies the center.

There isn't one.

It's not primarily that galaxies are all racing away from one special point through an otherwise static arena. The distances represented by the cosmic geometry itself evolve.

And now reverse the thought experiment.

Imagine a contracting universe.

From any comoving location, sufficiently distant regions would appear to grow closer. Reverse that process far enough in the classical equations, and spatial separations can approach zero.

It would be tempting to say, "Everything eventually collapses into me."

But every observer could say exactly the same thing.

There is no privileged me.

The more interesting conclusion is that the ordinary distinction between all those separate locations would eventually cease to work the way it does today.

And that's where my philosophical curiosity kicks in.

What Does "Separate" Actually Mean?

Consider two objects.

We call them separate because there is some spatial distance between them.

Now consider two events.

We call them separate partly because there is some temporal interval between them.

So here's the question:

If spatial and temporal relationships aren't fundamental, what does "separate" mean?

I'm not proposing that we can literally delete spacetime from today's physics and see what's left. General relativity is fundamentally a theory of spacetime geometry.

I'm asking something more philosophical.

Suppose spacetime itself emerges from something deeper.

Then perhaps spatial separation isn't fundamental either.

That's not entirely disconnected from contemporary theoretical physics.

Mark Van Raamsdonk, for example, explored the idea that the connectedness of spacetime in certain theories of quantum gravity may be intimately related to quantum entanglement. In his work, reducing entanglement between parts of a quantum system corresponds, in the gravitational description, to spacetime regions pulling apart. https://arxiv.org/abs/1005.3035

That does not mean "entanglement proves everything in the universe is one thing."

That's a philosophical leap.

But it raises a fascinating possibility:

Perhaps geometry itself is something that emerges from a deeper network of relationships.

In that case, spacetime would be real in much the same way temperature is real.

Temperature unquestionably exists. You can measure it, experience it and build equations around it.

But an individual molecule doesn't possess temperature in the same sense that a room does. Temperature emerges from the collective behavior of many microscopic constituents.

Maybe spacetime has an analogous story.

We don't yet know.

Wormholes Make the Problem Even Stranger

General relativity gives us another wonderful playground for thinking about these questions: wormholes.

Certain mathematical solutions allow two otherwise distant regions of spacetime to be connected by a shortcut.

If such a wormhole could exist and remain traversable—and that is an enormous if—the two mouths could even accumulate different elapsed times.

For example, one mouth might undergo strong gravitational time dilation or high-speed motion while another does not.

Researchers showed decades ago that a traversable wormhole of this kind could, in principle, be converted into something resembling a time machine. The catch is substantial: maintaining such a structure appears to require exotic physical conditions, and we have no evidence that usable traversable wormholes actually exist. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.61.1446

Still, the thought experiment is revealing.

A wormhole wouldn't merely be a shortcut through space once its two mouths had accumulated different amounts of proper time.

It would become a shortcut through spacetime.

The distinction between "where?" and "when?" becomes much less comfortable.

That's not science fiction being injected into physics.

It's what happens when we take relativity seriously enough.

And Then Quantum Mechanics Makes Things Weirder

Quantum mechanics adds another layer—but also a warning against getting carried away.

A quantum computer, for example, doesn't simply try every possible answer and average the results.

Quantum states evolve through amplitudes that can interfere with one another. Carefully constructed algorithms make some possibilities reinforce and others cancel, changing the probabilities of the outcomes we eventually measure. IBM's quantum-computing materials give concrete examples of interference being used specifically to alter those measurement probabilities. https://quantum.cloud.ibm.com/learning/en/courses/fundamentals-of-quantum-algorithms/phase-estimation-and-factoring/phase-estimation-procedure

Then we measure.

And we get a definite recorded outcome.

It's very tempting to say:

That's the moment reality becomes real.

I understand the attraction of that sentence.

But physics doesn't actually require that interpretation.

In collapse-based approaches, measurement is described as producing a determinate result. Other interpretations, including Everett-style approaches and attempt to account for definite observations without fundamental wave-function collapse at all. The notorious "measurement problem" exists precisely because the equations and our experience leave room for very different stories about what is happening underneath. https://plato.stanford.edu/entries/qm-copenhagen/

So the experimental fact is comparatively modest:

A measurement produces a definite outcome that we can record and communicate.

Whether consciousness created reality, whether one branch became actual, whether all branches remain, or whether we're asking the wrong question entirely belongs to interpretation.

And I think keeping those categories separate actually makes the mystery more interesting, not less.

Maybe "Here" and "Now" Are Perspectives

This brings me back to the original thought.

We experience the universe from a profoundly local perspective.

I am here.

This moment is now.

That galaxy is there.

Yesterday is gone.

Tomorrow hasn't happened yet.

Those statements are immensely useful. They may even be unavoidable for creatures like us.

But perhaps they're more like coordinates than ultimate features of reality.

"Here" doesn't identify the center of the universe.

It identifies my location.

Perhaps "now" works somewhat similarly.

And if spacetime itself ultimately emerges from something deeper, then both concepts could belong to a layer of reality that is perfectly real without being fundamental.

That leads to the question I keep returning to:

If you take space and time out of the equation, what does it even mean for two things to be separate?

I don't know the answer.

Physics doesn't currently know the answer either.

We don't yet possess a confirmed theory of quantum gravity telling us what spacetime ultimately consists of, or whether asking what it "consists of" is even the right question.

But I find one possibility irresistible to contemplate.

Maybe the universe isn't fundamentally a collection of independent things sitting at different places at different times.

Maybe relationships come first, and objects, distances, locations and perhaps even time emerge from those relationships.

If so, our everyday experience isn't an illusion.

It's a perspective.

A very useful one.

A very real one.

But perhaps not the deepest one.

And somewhere beneath here, there, before and after may be a description of reality in which the question "Where is it?" no longer makes sense.

Not because everything occupies the same place.

But because place itself hasn't emerged yet.A note on speculation

The expansion of the universe, relativistic time dilation, quantum interference and quantum measurement are established physics. Traversable wormholes remain hypothetical. The block universe is an interpretation of time rather than an experimentally established ontology. The emergence of spacetime from quantum information or entanglement is an active theoretical research direction, not a confirmed description of our universe. The idea that these imply some deeper metaphysical "oneness" is philosophical speculation—and that's exactly where I intend to leave it.

References and further reading

NASA physicist and Nobel laureate John Mather gives an excellent explanation of why the Big Bang should not be imagined as an explosion from a central point. NASA — Webb Telescope and the Big Bang

For the physics behind traversable wormholes and their potential connection to closed timelike curves, the classic paper is Morris, Thorne and Yurtsever's 1988 Wormholes, Time Machines, and the Weak Energy Condition. Physical Review Letters — Morris, Thorne & Yurtsever

Mark Van Raamsdonk's Building up spacetime with quantum entanglement is one influential entry point into the idea that spacetime connectivity and entanglement may be related in theories of quantum gravity. arXiv — Building up spacetime with quantum entanglement

For the philosophical debate over whether only the present exists or past, present and future are all elements of reality, Stanford's philosophy resources provide a rigorous overview. Stanford Encyclopedia of Philosophy — Presentism

For the less philosophical nuts and bolts of quantum measurement and interference, IBM Quantum's learning materials are a very approachable starting point. IBM Quantum — Quantum mechanics basics