There are structural parallels between quantum measurement and the experience of "now":
| Property | Quantum measurement | The present moment |
|---|---|---|
| Selects one outcome from many | Yes | Yes |
| Irreversible | Yes (wavefunction collapse) | Yes (past becomes fixed) |
| Creates definite classical reality | Yes | Yes |
| The "before" is indeterminate | Superposition | Open future |
| The "after" is a settled fact | Eigenstate | Fixed past |
| Mechanism not fully understood | The measurement problem | The problem of "now" |
Both involve a transition from indefinite to definite that is difficult to derive from time-symmetric fundamental laws.
Roger Penrose has pursued this connection explicitly. His Orchestrated Objective Reduction (Orch-OR) theory, developed with Stuart Hameroff, proposes that conscious experience of "now" arises from quantum state reductions in neuronal microtubules.
John Wheeler's "participatory universe" idea and Lee Smolin's arguments for the fundamentality of time also touch on related themes, though from different angles.
The mainstream view in physics is that decoherence (irreversible interaction with the environment) accounts for the appearance of measurement without requiring a special role for "now" or consciousness. This remains an open area where physics and philosophy have not reached consensus.
- We do not actually verify a shared present. We each experience our own present and infer agreement. By the time signals travel between observers, each observer's "now" has moved on. Simultaneity is reconstructed retroactively from records, not verified in real time.
- Physics does not need a universal time. Special relativity (1905) eliminated universal simultaneity. Different reference frames disagree on which distant events are simultaneous. This is experimentally confirmed (GPS corrections, particle lifetimes).
- Experimental agreement is about records, not the present. Observers agree on classical data written after the fact. Agreement about the past is not evidence of a shared present.
- Causality does not require shared time. Causality requires only a partial ordering of events (lightcone structure), not a global clock.
Relativity demands it. The Andromeda paradox illustrates this: two people walking past each other in opposite directions on a street have "now" slices through the Andromeda galaxy that differ by days, due to relativity of simultaneity. If "now" were a universal physical fact, whose "now" would determine the state of distant events?
Quantum mechanics is local. Measurement outcomes are local events. When two observers share an entangled pair, the no-signaling theorem guarantees that the ordering of their measurements is frame-dependent. There is no fact of the matter about who measured "first."
Decoherence is local and progressive. The quantum-to-classical transition is not a sudden global event. It propagates outward from local interactions at finite speed.
The word "measurement" in quantum mechanics refers to any irreversible interaction that creates a classical record. It requires no brain, no consciousness, and no complexity beyond a quantum system interacting with a larger environment.
A tree performs quantum measurements continuously:
- Photosynthesis: a photon in superposition is absorbed by a specific chromophore. The photon's state collapses; energy is irreversibly captured. Research (Fleming group, ~2007) has shown quantum coherence plays a role in energy transfer through light-harvesting complexes before this collapse occurs.
- Chemical bond formation/breaking: electrons in superposition of configurations collapse into definite molecular states.
- DNA replication: molecular machinery reads base pairs, irreversibly amplifying quantum-level information into macroscopic chemical structures.
- Cell death: a massive irreversible thermodynamic event involving the collapse of many quantum states.
If "now" is identified with local decoherence events, then a tree does not have a single "now." It has billions of loosely coordinated cellular "nows" with no central integration. A rock similarly has trillions of disconnected micro-"nows." A nervous system's contribution is not to create measurement but to integrate many local measurements into a more unified experience.
If "nows" are local, what constrains their ordering? The answer: causal structure.
| Concept | Meaning | Required by physics? |
|---|---|---|
| Chronological order | A universal clock that all observers share | No |
| Causal order | If A could have influenced B, then A precedes B | Yes |
Events fall into three categories relative to any given event:
- Causal past (inside past lightcone): must have happened before
- Causal future (inside future lightcone): must happen after
- Spacelike separated (outside both lightcones): no defined ordering; different reference frames disagree, and all are equally valid
Distributed version control and blockchain consensus protocols solve a problem structurally identical to the one physics faces:
| Git / Blockchain | Physics |
|---|---|
| Commits / blocks | Decoherence events / "nows" |
| Parent-child edges | Causal connections (lightcone) |
| Branches | Spacelike-separated observers |
| No global timestamp required | No universal "now" required |
| Merge must not conflict | Records must agree when observers meet |
| DAG (Directed Acyclic Graph) | No causal loops |
The key constraint is consistency on merge: when two causal chains come together (two observers meet), their records must be compatible. This is a constraint on the past, not on the present.
If person A's death causally influenced person B (B knows about it, carries A's genes, etc.), then A's final "now" must precede B's current "now" in causal ordering. However, for two events with no causal connection — say, a decoherence event on Earth and one in a galaxy whose light will never reach us — there is no physical fact about which happened first.
- The transition from quantum indeterminacy to classical definiteness (measurement) shares structural features with the experience of "now" — both involve irreversible selection of one outcome from many possibilities.
- There is no physical evidence requiring a universal shared "now." Relativity forbids it; quantum mechanics is compatible with a local, observer-dependent "now."
- Quantum measurement does not require brains or consciousness — any irreversible interaction with an environment constitutes a measurement. Trees, rocks, and all physical systems perform measurements continuously.
- The ordering of "nows" is constrained by causal structure (a partial order / directed acyclic graph), not by a global clock. This structure is analogous to how distributed systems like git and blockchains maintain consistency without shared time.