I How Does Special Relativity Challenge Our Understanding of Absolute Time?

[Dale]

I was considering that if one neuron was in a different state it would be a different neural state,

A single neuron’s single action potential is 1 ms so that would mean relativistic effects are irrelevant for brains less than about 300 km in size. However, the state of the brain doesn’t change as fast as the state of a single action potential (neurons encode strength in the frequency of action potentials). A better upper limit for that frequency would be the rate of the gamma waves in an EEG, which tops out at about 150 Hz. That would correspond to a brain size of about 2 million m before relativistic effects would be relevant. The human brain is about 20 cm, so essentially a point compared to the relevant length scales.

 

[name123]

A single neuron’s single action potential is 1 ms so that would mean relativistic effects are irrelevant for brains less than about 300 km in size. However, the state of the brain doesn’t change as fast as the state of a single action potential (neurons encode strength in the frequency of action potentials). A better upper limit for that frequency would be the rate of the gamma waves in an EEG, which tops out at about 150 Hz. That would correspond to a brain size of about 2 million m before relativistic effects would be relevant. The human brain is about 20 cm, so essentially a point compared to the relevant length scales.

I can see your point, but I am not sure that the issue is how often a single neuron could fire, or how long it took. I thought it might be the brain state.

If there were say 100 billion neurons in the brain, and say 10% were firing in any given second and that each of those that fired, fired on average 5 times per second. Then there would be 50 billion neural firings per second, and the number of neurons starting to fire any given nanosecond would be about 50 and the number of neurons ceasing to fire for any given nanosecond would be about 50. Also the firings are not "on" "off" affairs, and the action potential will vary over the firing. How significant it would be to the experience I do not know. But presumably it would be slightly significant else if you counted each ns step as equivalent to the next then when considering the sum of lots of such differences you would consider it to make no difference. In the sense that if e₁ = e₂ and e₂ = e₃ and e₃ = e₄ and so on such that e_n = e_n+1 then e₁ = e_n+1. I have ignored brain waves and the extent to which some of the firings might be "synchronised".

Could the experience not be thought to reflect the simultaneity of neural events?

 

[name123]

Of course anything farther than 0 has its timing shifted. It depends on the precision which you can achieve. If you can measure nanosecond delays, 15cm is far enough. If you measure in miliseconds, 100km is close. If the observers move slowly relative to each other, the whole Solar system can be considered small. Lorentz transformation quantifies actual time (and space) shifts.

I was not thinking about measurement, but theoretical implications. Is what you are experiencing a relative truth?

 

[SlowThinker]

I was not thinking about measurement, but theoretical implications. Is what you are experiencing a relative truth?

I really have no idea where this neurobiology talk comes from.
The brain of an astronaut orbiting Earth works just as well as down here, and neither is affected at all by an alien flying around at 0.9c. Also the alien's brain works just fine. Everyone's viewpoint is equally correct.

 

[Dale]

I can see your point, but I am not sure that the issue is how often a single neuron could fire, or how long it took. I thought it might be the brain state.

I can dig up my neurobiology textbook and find references, but this is standard well known stuff in the field. From a neural signaling perspective an action potential is an all-or-nothing event and the information is encoded in the frequency of action potentials.

the number of neurons starting to fire any given nanosecond would be about 50 and the number of neurons ceasing to fire for any given nanosecond would be about 50.

And there would be a million bazillion molecules jiggling in thermal motion and quantum fluctuations and other things that are irrelevant to “the truth regarding what you were experiencing”. Your own subjective experience should confirm that “what you were experiencing” simply doesn’t change on the scale of nanoseconds and even one nanosecond is about 30 cm at c which is already larger than the brain.

Could the experience not be thought to reflect the simultaneity of neural events?

Not in the sense of the relativity of simultaneity.

 

[name123]

I really have no idea where this neurobiology talk comes from.
The brain of an astronaut orbiting Earth works just as well as down here, and neither is affected at all by an alien flying around at 0.9c. Also the alien's brain works just fine. Everyone's viewpoint is equally correct.

The issue is whether what you are experiencing corresponds to the simultaneous brain activity or not. Perhaps you could make your position clear on this matter.

 

[name123]

Could the experience not be thought to reflect the simultaneity of neural events?

Not in the sense of the relativity of simultaneity.

So if what you are experiencing does not reflect the simultaneity of neural events, what were you thinking it does reflect?

 

[SlowThinker]

The issue is whether what you are experiencing corresponds to the simultaneous brain activity or not. Perhaps you could make your position clear on this matter.

I don't understand your question. My brain is always at rest with respect to itself, and so its parts are always simultaneous in the same way, whether I'm in my bed, or flying an airplane.

 

[name123]

I don't understand your question. My brain is always at rest with respect to itself, and so its parts are always simultaneous in the same way, whether I'm in my bed, or flying an airplane.

Well it depends upon what you mean by simultaneous. Let me put it another way. Are you thinking that the truth of what you are experiencing is relative or is there an absolute truth about the matter?

 

[Dale]

So if what you are experiencing does not reflect the simultaneity of neural events, what were you thinking it does reflect?

Neural events simply don’t happen fast enough for the relativity of simultaneity to matter. Simultaneity in the relativistic sense can never cause anything so it also cannot cause “what you were experiencing”.

 

[name123]

Neural events simply don’t happen fast enough for the relativity of simultaneity to matter. Simultaneity in the relativistic sense can never cause anything so it also cannot cause “what you were experiencing”.

You seem to have avoided answering the question. You seem to have denied that what you are experiencing reflects the simultaneity of neural events, but haven't stated what you think it does reflect. Does it reflect something, and if so, what in the model interpretation that you favour?

Which brings me back to the point I made in post #92

But presumably it would be slightly significant else if you counted each ns step as equivalent to the next then when considering the sum of lots of such differences you would consider it to make no difference. In the sense that if e₁ = e₂ and e₂ = e₃ and e₃ = e₄ and so on such that e_n = e_n+1 then e₁ = e_n+1. I have ignored brain waves and the extent to which some of the firings might be "synchronised".

If you state there is no difference in experience between the slightly different neural events, then it is a slippery slope. If you state that there is no difference that you could distinguish (for example there are RGB numbers we cannot distinguish), then there still is a difference, just not one we can distinguish. And how can the difference not actually be different, how could e₁ = e_n+1 for example.

You also have the problem of not knowing what events would be distinguishable and when they would be distinguishable over time. For example if on RGB events, some R changed later than B in some perspective, maybe it would cross the distinguishable boundary..

Regardless you still haven't explained what your experience reflects.

 

[SlowThinker]

Well it depends upon what you mean by simultaneous. Let me put it another way. Are you thinking that the truth of what you are experiencing is relative or is there an absolute truth about the matter?

Maybe you're misunderstanding the "relativity" in Theory of relativity.

Let's imagine you and I go to view some play in a theater. Your seat is more to the left, mine is more to the right. We both see the same thing, yet it looks different. Both of our views are equally correct. There is no "the one correct" view of the play.

Can you use this example to explain what you mean?

 

[name123]

Maybe you're misunderstanding the "relativity" in Theory of relativity.

Let's imagine you and I go to view some play in a theater. Your seat is more to the left, mine is more to the right. We both see the same thing, yet it looks different. Both of our views are equally correct. There is no "the one correct" view of the play.

Can you use this example to explain what you mean?

Yes two people are looking at you and from their perspectives estimate your experience . If they have differing opinions can they both be right, is it relative, or is what you were experiencing absolute. Can there be experiential scenarios (perhaps put forward by observers moving relative to you at a high speed and an extreme distance) that were simply false. You never experienced those. Is the truth about what you experienced relative?

 

[PeterDonis]

You seem to have denied that what you are experiencing reflects the simultaneity of neural events

That's right; it doesn't. Causal influences can't travel faster than light, and whatever you experience is causally influenced by neural events.

What you experience is that some events in the outside world seem to be simultaneous with some other events. But all of those appearances are constructed by your brain based on information in your past light cone, i.e., information that traveled to you at the speed of light or slower. You never experience anything from events which are actually simultaneous with you, because those events are outside your past light cone and you can't have received any information from them.

 

[SlowThinker]

Yes two people are looking at you and from their perspectives estimate your experience . If they have differing opinions can they both be right, is it relative, or is what you were experiencing absolute.

Maybe one of them saw what's behind me, and neither I nor the other observer saw it.
If the two observers are somewhat intelligent, they'll undestand that they only view some part of the full truth. So do I. But their view may be more complete and more correct than mine.

 

[name123]

Maybe one of them saw what's behind me, and neither I nor the other observer saw it.
If the two observers are somewhat intelligent, they'll undestand that they only view some part of the full truth. So do I. But their view may be more complete and more correct than mine.

I suspect this thread is about to be shut down, as considering this seems verboten.

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

 

[PeterDonis]

if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

You are failing to distinguish two different things.

One, the one @SlowThinker is talking about, is where different observers have different information about events. This can happen in relativity if the observers are spatially separated; each one has the information in their past light cones, but their past light cones are not the same.

The other, the one you are implicitly referring to, is an argument about what one particular observer, at one particular point on his worldline, with one particular past light cone, experienced. Such arguments are irrelevant here; in relativity we assume that an observer's experience at a given point on his worldline is determined by what is in his past light cone, so there can't be any argument or difference of opinion about what that one observer experiences at that one point.

 

[SlowThinker]

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

No, false claims are not as valid as true claims.
What we discussed on the first 4 or 5 pages was all true claims.

 

[PeterDonis]

I suspect this thread is about to be shut down, as considering this seems verboten.

No, the point @SlowThinker made was valid; see my previous post.

It is true that this is a forum on relativity, not neurobiology or cognitive science, so questions about the details of how people's experiences are constructed by processes in their brain are not going to go very far here; if you're really interested in that part of it, you should start a separate thread in a more appropriate forum. Unfortunately we don't have one specifically for those topics; the Biology forum is probably the closest.

If you are only interested in the relativity part of it, then please read the last paragraph of my post #107 carefully.

 

[name123]

No, false claims are not as valid as true claims.
What we discussed on the first 4 or 5 pages was all true claims.

So if

there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

 

[PeterDonis]

in relativity we assume that an observer's experience at a given point on his worldline is determined by what is in his past light cone

There is one additional technical point here: if we include an observer's choice of coordinates or reference frame in what they experience, then different observers at the same point in spacetime, and therefore with the same past light cone at that point--for example, two observers flying past each other in spaceships--will have different experiences, because of their different reference frames (due to their relative velocity--there are other further complications lurking here as well, but I'll pass over them). But it's still true that the observer's past light cone, plus their reference frame, determines their experience at that point in spacetime, so there still can't be any argument or difference of opinion about it.

 

[SlowThinker]

So if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

A claim that I didn't see a purple elefant is perfectly true.
A claim that I did is false.
I still fail to see what is your question.

 

[PeterDonis]

So if

He already answered your question. So did I, in posts #107 and #111.

 

[name123]

No, false claims are not as valid as true claims.
What we discussed on the first 4 or 5 pages was all true claims.

So if your experience doesn't reflect the simultaneity of your neural state what do you think it does reflect?

A claim that I didn't see a purple elefant is perfectly true.
A claim that I did is false.
I still fail to see what is your question.

Supposing that a value could be given to your experience, e.g. 1979873987492873498273498273498723984729472984729847298742974928742987
and that another claimed it was 1979873987492873498273498273498723984729472984729847298742974928742986

Can you not comprehend the theoretical issue? Can they both be true? Is the truth of the matter relative?

 

[SlowThinker]

So if your experience doesn't reflect the simultaneity of your neural state what do you think it does reflect?

Different observers won't agree on simultaneity, precisely because it does not affect anything. It's only a viewpoint.
My neural state is defined by neuron charges and dendrite weights. These are the same whether viewed by myself or some fast alien.

Supposing that a value could be given to your experience, e.g. 1979873987492873498273498273498723984729472984729847298742974928742987
and that another claimed it was 1979873987492873498273498273498723984729472984729847298742974928742986

Can you not comprehend the theoretical issue? Can they both be true?

If someone says that I saw something, they'll probably be wrong. In physics we usually talk about ideal conditions and perfect observers. Only in that sense they can argue that perfect me saw some clock in a train doing something.

Who exactly is claiming that I saw ...986 when I saw ...987?

 

[russ_watters]

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

After weeks of discussion, I don't know where you would come up with such a wrong idea. If I see two lights flash simultaneously, someone else who isn't near me but knows were I and the lights are could calculate correctly that I saw the two lights flash simultaneously, even if he saw them flash at different times. There are no differing opinions about what I experienced. No conflict. No problem. There is only one truth about a set of events and everyone who understands how the relevant scientific laws work and has access to the proper information will agree on what it was, even if they didn't observe them the same. This idea of "relative truth" you have is just plain wrong and you really should understand that by now.

 

[PeterDonis]

if your experience doesn't reflect the simultaneity of your neural state what do you think it does reflect?

I already answered this: your experience reflects the information in your past light cone. "The simultaneity of your neural state" doesn't even make sense.

Supposing that a value could be given to your experience

Then this value would be determined by what's in your past light cone.

Can they both be true?

No. What is in your past light cone is an invariant.

Is the truth of the matter relative?

No.

 

[Janus]

I suspect this thread is about to be shut down, as considering this seems verboten.

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

That never happens. Everyone will agree as to what happens to any given observer, though they might disagree as to the timing of some event that led to what that observer experienced.
For example, consider the following scenario.
You have an observer on the tracks and one in a railway car. Flashes of light are emitting by the the red dots and meet at the track observer just as the railway car observer passes him. Thus both flashes reach both observers at the same instant.
Here's those events according to rest frame for the tracks.

Here are the same events according to the railway car rest frame. ( please forgive the fact that I didn't include length contraction with this example)

In this frame, the light are emitted at different times, yet they still meet when the observers pass each other. Both frames agree as to each observer experiences while disagreeing on whether or not the flashes were initially emitted at the same time.

Or we could consider the traditional Train experiment.
The flashes are still emitted at the same moment and reach the the track observer at the same time, however now they are emitted at the moment that the train observer passes the track observer (according to the track observer frame.
Again first we look at the track frame:

Here the train observer runs into the right flash before before the left flash catches up to him. The right flash hits him when about a third of the way to the right red dot and the left flash catches up to him when he reaches the right red dot. The flashes reach the track observer when the rear of the train is about two car lengths away.
Now the same events according to the train.

A few things to note. In the last image, the train fit exactly between the red dots. But this was a "length contracted" train according to the Track frame. In the train frame, the train is its proper length and the tracks are length contracted. As a result, the train no longer fits between the red dots and the front of the train reaches the right dot before the rear of the train reaches the left dot.
The flashes are still emitted when the end of the train reaches a red dot. Thus the flashes are emitted at the different times. The right flash still hits the train obsever when he is ~1/3 of the way between track observer and right red dot and the left flash reaches him when he is next to the right red dot. the flashes still both reach the track observer at the same moment and when the rear of the train is about 2 car lengths away.
So while observers on the train and tracks disagree as to whether or not the ends of the trains reached the red dot at the same time or not and whether or not the flashes were emitted simultaneously or not, they are in perfect agreement as to what any observer on train or tracks directly experiences.

 

[Dale]

You seem to have avoided answering the question. You seem to have denied that what you are experiencing reflects the simultaneity of neural events, but haven't stated what you think it does reflect. Does it reflect something, and if so, what in the model interpretation that you favour?

It most certainly does not reflect simultaneity of neural events, because it would violate the laws of physics for simultaneity to cause anything. Whatever causes any observable (including experience) must be entirely within some past light cone, not on any surface of simultaneity. This is known as causality.

As for what it does reflect, I have avoided answering the question because we don’t know enough to answer the question. However, we are not completely ignorant. We do know some things, and they are not compatible with your suggestions.

If you state there is no difference in experience between the slightly different neural events, then it is a slippery slope.

It isn’t a slippery slope, it is hard data. For example, if there is a coherent visual and auditory stimulus (e.g. a movie), and if the auditory stimulus is delayed anywhere from 0 to about 100 ms, then the experience is the same. The experience is that there is no discrepancy. So it is a clear experimental fact that different neural states lead to the same experience. Any theory of experience that can not accommodate that is already falsified.

then there still is a difference, just not one we can distinguish.

If you can not distinguish it then it certainly isn’t “what you were experiencing”.

Regardless you still haven't explained what your experience reflects.

Along the lines of what I said above, we don’t have a “standard model” of experience yet. So we don’t know that yet and I won’t speculate. All we can do is place some physical and empirical constraints on it.

One key physical constraint is that spacelike separated events cannot be causally related, so the experience cannot be a function of simultaneous neural states. Of course, given how slowly the experience changes and how small the brain is, this really is a non-issue and you can simply think of the brain as a point object wrt relativity and experience. However, even though it is a non-issue (as I have repeatedly shown) you continue to push it.

One empirical constraint is that the experience must be a many-to-one function of neural activity, with substantial “editing”. Another is the relativistically large time delay between the arrival of a stimulus and its experience. Another would be the time scales involved for experience.

For example if on RGB events, some R changed later than B in some perspective, maybe it would cross the distinguishable boundary..

That is simply not physically possible.

Can you not comprehend the theoretical issue? Can they both be true?

Can you not comprehend the answers? The question was answered already, multiple times by multiple people. No, they cannot both be true, therefore any correct model of experience can not depend on non-causally related events (e.g. simultaneous neural states)

 

[Ibix]

A point about the neural states thing - it may be true that I see two of your neurons complete a state change simultaneously while a passing alien does not. But it does not matter because the aluen and I will have different opinions about how fast the consequences of that change propagate, and the result will be that further neuron state changes will happen as expected. So if you have neurons A, B and C in a line, I might say that A and C activated simultaneously and their activation triggerred B to activate. The alien might say that A and C did not activate exactly simultaneously, but the signals of their activation still arrive at B simultaneously, so has no problem with it activating.

As Dale points out, the above is completely irrelevant because of the slowness of state changes. It's also irrelevant because you are at rest with respect to you. If I run towards you then you will appear slightly blue. Do you now expect to suffer anti-blue racism? No - because nothing about you changes because of my state of motion.