### Eye photoreceptor

Eye photoreceptor

#### Photon induces a cascade [spreading activation]

Photon induces a cascade [spreading activation]

[ Like distributed consensus ] [Or like metastable system]

#### This is an amplifier [later there is averaging]

This is an amplifier [later there is averaging]

[ amplifiers can violate 2nd law ]

#### Amplification is needed to go digital (e.g. for nerve impulses) [i.e. the minimal version of A-to-D converter[

Amplification is needed to go digital (e.g. for nerve impulses) [i.e. the minimal version of A-to-D converter[

### Piston / pressure measurement

Piston / pressure measurement

#### This is an averager

This is an averager

### Clocks

Clocks

Where do you land relative to a counter?

[ cf interferometers etc. ]

AKA how many events do you have, compared to a standardized system having events?

[ counting events per unit time ]

### Base Units

Base Units

[ may be old ]

## Are Measurements Ultimately Events Per Unit Time?

Are Measurements Ultimately Events Per Unit Time?

First you prune to decide which events you care about ; or perhaps you aggregate events...

What macroevents happened per unit time

[ Claim: macroevents can have extent in time, space .... and branchial space ]

#### Macroevents are the results of coarse graining

Macroevents are the results of coarse graining

### Observers prune information, but then preserve it for a while

Observers prune information, but then preserve it for a while

Reduce number of dof; increase time persistence

## Basic Structure of Measurements

Basic Structure of Measurements

Collecting a limited number of dof, and putting them in a form where they can be remembered.

A nonrelativistic eye collects photons from a certain region, amplifies them and records them. Inside the measuring device, there’s rapid interaction compared to the dof outside.

Relativistic eye: the dof inside the eye are knitted together by lots of light signals; the ones from outside come in through a much more limited number of light signals.

cf piston causal graph

Minimal model of the observer is a single coherent timelike event stream. Although to “form a definite memory” it’s got to lots of events.

Consider some event chain as “the observer”, and look at other events relative to that.

For a piston in a gas figuring out pressure, the only relevant information is events per unit time on the wall... Has to compare those events to a clock.

When a measurement happens, the observer has to be largely unchanged ; changing only by having something that records a persistent memory.

Pick the chain of events that is supposed to be the observer; that’s your world line, orthogonal to the reference frame.

So now we can attribute a time t to the event as (t+ + t-)/2 , and the spatial position is (t+ - t-)/2.

With a single worldline we only get to know 1D distance to an event. Just like a telescope imagining in 2D only knows the direction to stars, not their distance. We need to use parallax to find the distance.... [cf triangulating a supernova requires multiple detectors (e.g gravitational wave detectors, etc.)]

<< Is there something about our sensory apparatus that makes us perceive 3 dimensions? >>

< cf. how do we unravel a spacefilling curve>

< cf. how do we unravel a spacefilling curve>

Our perception of 3D is somewhat exploded by the internet.... [because who knows where the servers are...] [if we lived inside a computer, why would know about 3D?] [It would depend only on the connectivity of the network]

#### General principle: some set of events can be elided together to make “an observer” as an integrated thing

General principle: some set of events can be elided together to make “an observer” as an integrated thing

E.g. stat mech: the observer is aggregating some number of dof’s and eliding them to a single “result of observation”

Look at MWCG ; now an observer is a bundle of timelike curves in the MWCG

Every time an “observer bundle” is formed, it has a common starting event; i.e. all parts of the observers are causally connected to some origin

[The parts of the bundle interact a lot, which is why the whole bundle can be considered “rigid”, and elided (like a rigid body can be described just by center coordinates and orientation) ]

[The parts of the bundle interact a lot, which is why the whole bundle can be considered “rigid”, and elided (like a rigid body can be described just by center coordinates and orientation) ]

The lowest-level version of the MWCG involves no merges; any merge must be “in the eye of the observer”

Consider threads in MWCG as computer threads; forking when there is a branch in the MWCG

(it could be that a local region of causal graph is identical to another local region)

When can you use “shared common expressions” to prune the threads?

(it could be that a local region of causal graph is identical to another local region)

When can you use “shared common expressions” to prune the threads?

Pure tree ;;; then add equivalences

#### Observer is a bundle of worldlines in which certain outside events are amplified to affect lots of these worldlines (i.e. many worldlines depend on the outside event; the effect is the persistent memory) but there is still persistence in the bundle; the observer can then be “equivalenced down” to say that a single outcome occurred

Observer is a bundle of worldlines in which certain outside events are amplified to affect lots of these worldlines (i.e. many worldlines depend on the outside event; the effect is the persistent memory) but there is still persistence in the bundle; the observer can then be “equivalenced down” to say that a single outcome occurred

Multiple scales:

scale of whole system

scale of the whole observer [carrier of the memory]

scale of an individual memory

scale of whole system

scale of the whole observer [carrier of the memory]

scale of an individual memory

Scales in terms of time; scales in terms of dof

#### In stat mech, worldlines are at different places in space, but have the same state of motion

In stat mech, worldlines are at different places in space, but have the same state of motion

Many elementary proto-observers are being combined...

#### In relativistic case, the different places in space are close together

In relativistic case, the different places in space are close together

#### In quantum case ... there are pre-proto-observers

In quantum case ... there are pre-proto-observers

Bundled branches are a “multi-observer”

Multiple branches running the same program... We can readily conflate this to a single branch

If an observer is approximated by a single multiway worldline ... then the observer can perfectly well think that they are not branching....

When the observer is a bundle of worldlines ... it becomes implausible for the observer to think they branched (?)

When the observer is a bundle of worldlines ... it becomes implausible for the observer to think they branched (?)

As soon as you coarse-grain in branchial space, you have irreversibility....

## Rulial Observers

Rulial Observers

You can fish out of the ruliad any apparent laws just by making the appropriate interpreter for a universal computer

### What is the origin of the “stability of experience”?

What is the origin of the “stability of experience”?

It just takes a lot of events (i.e. a lot of time) to “get to somewhere different”

#### Claim: rate of change of the observer is slow compared to the rate of change of the universe

Claim: rate of change of the observer is slow compared to the rate of change of the universe

[Imagine we map our whole view of the universe onto a Turing machine .... it would ultimately work, but not in real time]