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Length contraction in a block universe must be an illusion


34student
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12 hours ago, 34student said:

Since the particles are 1 meter apart and they travel along world lines through time, then doesn't that imply that their world lines are also 1 meter apart?

Here is a simplified picture that may help: 

A white train T moves relative to points A and B
The points A and B are not moving relative one another.
The train T moves from left to right when seen from a position at point A
An Observer on the other side of the train (at location B) will see the train going from right to left.

image.png.be03e00f41cab62a05b259cdf7f761e5.png

Basic observations:
1: There is one train.
2: The number of observers does not affect the number of trains.
3: The concept of left and right depends on point of view. 

Hopefully the above simplified example may help you form the correct questions or identify misunderstandings. 

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1 hour ago, Ghideon said:

Here is a simplified picture that may help: 

Nice one +1

 

2 hours ago, swansont said:

And every observer will agree with this. What it looks like depends on the observer.

Your personal model of how this works is wrong and needs to be abandoned.

 

Again everyone is suggesting you view things in the light of the Principle of Relativity, not something else which can be show not to comply with observation.

Every analysis should be built on verifiable observation, not on some preconceived idea of how things 'should be'.
The ancient Greeks famously made a basic mistake about this.

 

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9 hours ago, Markus Hanke said:

This isn’t a contradiction at all, because these are different observers performing a measurement the outcome of which is observer-dependent, since they’re measuring something that isn’t intrinsic to the train, but describes only their relationship to it.

It seems to me that we are just repeating both question and answer over and over again, to no avail at all it seems. So let me ask you this - are you actually interested in the explanation, or have you made up your mind already that relativity must be wrong? Just be honest.

Well look at your response to me.  You just ignored my post and repeated yourself.

4 hours ago, studiot said:

Sealioning, gas lighting and so forth.

It's all very sad that the only things I seem to be learning lately are different new words for unpleasant activity.

@34student

I have already suggested that you understand the basic principles before proceeding to greater detail.

There are two here.

1.) The Principle of Relativity.

This was actually known long before Einstein and different works have presented it differently, as did Einstein in his turn.

His version is that the laws of Mechanics and of Electrodynamics should appear mathematically in the same form to all observers.

This is very general and too difficult to start with but a consequence is useful and is the version I commend to you.

There are no such things as absolute space or absolute time.

To this Einstein added a second principle and again I will quote it in a suitable form here for your benefit.

2.) The invariability of the speed of light in a vacuum.

Every observer measures the same speed of light relative to himself and also relative to every other observer, irrespecitive of the motion of the source of that light.

As stated above these two Principles generated a restricted form of relativity, called Special Relativity.

A third principle was later introduced to add the laws of gravity to the list and led to General Relativity, which I will not go into further at the moment.

 

 

I know all of this already.  We do not have to go over all of this again.  Nobody wants to directly address my posts.  Everyone just keeps telling me that SR must be true over and over again.

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21 minutes ago, 34student said:

You just ignored my post and repeated yourself.

Just as you have when I have told told there is a difference between the number of things which every observer views as the same and the properties of those things which may be viewed differently.

So the number of atoms, the number of world lines, the number of trains and so on are all seen as the same.

But every observer measures properties of those atoms, trains, world lines differently so comes up with a different answers.

 

I have also told you that the key to understanding relativity is to find things which are the same for all observers.

Finding such things also enables us to develop the details of the theory to calculate all the desirable quantities we want to know.

Edited by studiot
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17 minutes ago, 34student said:

I know all of this already.  We do not have to go over all of this again. 

This is not apparent to the people responding to you

Quote

Nobody wants to directly address my posts.  Everyone just keeps telling me that SR must be true over and over again.

A number of your questions have been answered and points refuted, which are direct responses. SR has been verified countless times, so yes, SR is true. That's the baseline for any science discussion.

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8 hours ago, Markus Hanke said:

The very title of the thread already gave it away right from the start, but I had been hoping that explaining the theory plus listing experimental evidence might have had some effect at least. Sadly though, at this point the best term I can think of to describe this thread is ‘sealioning’.

I know about the experiments and I have a sufficient understanding of SR and a block universe.  Nobody wants to to discuss my examples and directly explain where they fail.  That is why I came here, and that is what I want to explore.

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9 minutes ago, 34student said:

I know about the experiments and I have a sufficient understanding of SR and a block universe.  Nobody wants to to discuss my examples and directly explain where they fail.  That is why I came here, and that is what I want to explore.

Just an observer here, but are you claiming length contraction is an illusion, or are you simply trying to have someone help you understand where you might have gone wrong in your examples?

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1 hour ago, 34student said:

I know about the experiments and I have a sufficient understanding of SR and a block universe. 

In my initial post about muons; where in that example is the illusion you claim exists? 

 

1 hour ago, 34student said:

Nobody wants to to discuss my examples and directly explain where they fail. 

I posted a simple picture above, explaining some of the things you seem to struggle with in the explanations given by other members. Is there any part of the picture and description that you like to be further explained?

 

 

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13 hours ago, 34student said:

Yes, you understand my question.  Now are there also world lines from 2 particles that are 100 meters apart, as measured from an observer on the train?

There are events on the those same 2 world lines that are 100 m apart to that observer, yes. They're on the same world lines, but they're not the same pair of events that are 1 m apart in Bob's frame. The two observers use different time coordinates, and 2 events at the same t and 100 m apart in the train's frame, don't have the same t' value in Bob's frame. The 1 m length of the train that Bob measures is between 2 events on the respective world lines with the same t' value. This is "relativity of simultaneity."

Using world lines instead of lengths isn't going to change the details of the simpler examples you're using them to represent.

10 hours ago, Markus Hanke said:

The very title of the thread already gave it away right from the start, but I had been hoping that explaining the theory plus listing experimental evidence might have had some effect at least. Sadly though, at this point the best term I can think of to describe this thread is ‘sealioning’.

I suppose we persist because we expect a response like "That's something I don't get, let me try to understand that first" instead of "What if I ignore all that and ask the same question in different words?" Block universe, world lines... it's like expecting to find some aspect of relativity for which the rules of relativity don't apply.

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2 hours ago, studiot said:

Just as you have when I have told told there is a difference between the number of things which every observer views as the same and the properties of those things which may be viewed differently.

As I understand it, the train is, in fact, 1 meter in Bob's frame.  This is not suppose to be an illusion.  This is suppose to be the reality for Bob's universe.  How can you blame me for being confused (or right?)

2 hours ago, swansont said:

A number of your questions have been answered and points refuted, which are direct responses. SR has been verified countless times, so yes, SR is true. That's the baseline for any science discussion.

Well, if we had to use past scientific theories as absolute truth, then I don't think we would have gotten very far with it.

1 hour ago, zapatos said:

Just an observer here, but are you claiming length contraction is an illusion, or are you simply trying to have someone help you understand where you might have gone wrong in your examples?

As it stands right now, both.  I know that I am probably wrong, but I have a very strong objection - at least in my mind - that has yet to be show to me to be false.

57 minutes ago, Ghideon said:

In my initial post about muons; where in that example is the illusion you claim exists? 

 

I posted a simple picture above, explaining some of the things you seem to struggle with in the explanations given by other members. Is there any part of the picture and description that you like to be further explained?

 

 

Yes, the muons I will admit are haunting me.  They are the best and only strong counter point that I have seen yet.

As for your diagram, I understand what you are saying.  But my argument implies that there is only 1 distance.  The diagram fails to be a proper analogy of my issue because there is not ever only 1 direction.

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13 minutes ago, 34student said:

I have a very strong objection - at least in my mind - that has yet to be show to me to be false.

It has been shown to be false, even though you remain obstinate and stubbornly and personally incredulous regarding why. 

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29 minutes ago, 34student said:

How can you blame me for being confused (or right?)

I don't blame you , I am trying to help you.

Furthermore the rest of this post is a sensible statement so +1 for encouragement.

29 minutes ago, 34student said:

As I understand it, the train is, in fact, 1 meter in Bob's frame.  This is not suppose to be an illusion.  This is suppose to be the reality for Bob's universe.  How can you blame me for being confused (or right?)

Yes the train is 1 metre in Bob's frame.

Progress !!!

 

But relativity tells us not only that bob's metres are not the same as train metres but it also tells us how to convert one to the other.

I have kept from going into the second part of that statement until you understood the first part.

 

It works like this

All the atoms of the train appear smaller to Bob, as does the space between them.

Yet to the train driver all the atoms have their normal size.

In fact everything in the train's frame appears scaled down at 1/100 scale.

 

Do you want to progress this explanation to more detail?

 

Edited by studiot
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36 minutes ago, md65536 said:

There are events on the those same 2 world lines that are 100 m apart to that observer, yes. They're on the same world lines, but they're not the same pair of events that are 1 m apart in Bob's frame. The two observers use different time coordinates, and 2 events at the same t and 100 m apart in the train's frame, don't have the same t' value in Bob's frame. The 1 m length of the train that Bob measures is between 2 events on the respective world lines with the same t' value. This is "relativity of simultaneity."

Using world lines instead of lengths isn't going to change the details of the simpler examples you're using them to represent.

Okay please stay on this with me.  I feel like something is about to give.

The way I am thinking about all of this is that t' and t are on one timeline since the universe would only have 1 dimension of time.  So t' is going to intersect with some t.  Do you believe that t' is inside the interval t, where t is the from the beginning of the year 2050 to the year 2100, from the OP example?

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26 minutes ago, 34student said:

Yes, the muons I will admit are haunting me.  They are the best and only strong counter point that I have seen yet.

Good, we may examine that later (other members have posted some points that may be simpler to start with)

27 minutes ago, 34student said:

As for your diagram, I understand what you are saying.  But my argument implies that there is only 1 distance.  The diagram fails to be a proper analogy of my issue because there is not ever only 1 direction.

But there is always one direction: A, B in my example will always agree that the train is going forward. 

We know that the train is moving in one direction hence we are able to determine what each observer A and B will see from their point of view; a left-to-right or right-to-left movement. 

(Forward meaning the locomotive comes first, pulling a number of wagons.  An observer on the train will also agree with A and B)

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4 minutes ago, Ghideon said:

But there is always one direction: A, B in my example will always agree that the train is going forward. 

I'm glad someone else is also finding invariants. +1

 

48 minutes ago, 34student said:

Yes, the muons I will admit are haunting me.  They are the best and only strong counter point that I have seen yet.

I keep saying that the muon experiment is better than the train example because it is

1) Simpler

2) Is an actual experiment that not only can be carried out but has been many times since the first one.

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5 hours ago, 34student said:

The way I am thinking about all of this is that t' and t are on one timeline since the universe would only have 1 dimension of time.  So t' is going to intersect with some t.  Do you believe that t' is inside the interval t, where t is the from the beginning of the year 2050 to the year 2100, from the OP example?

"One timeline" is meaningless to me. t' inside t is also meaningless... you're effectively asking if the time measured by one clock is inside the time measured by another clock. But you could say that if Bob leaves the train at 2050 and returns to it at 2100, its world line between those events is within the future light cone of the train in 2050, and the past light cone in 2100, and that's what you want: all observers agree that Bob's trip happened after the 2050 event and before the 2100 event.

However, if Bob didn't start/end near the train and was always far enough away, that's not true for all observers. As well, Bob's cousin Babs, who suppose shares Bob's inertial frame and clock for an inertial part of Bob's trip, but was in the Andromeda galaxy during proper time interval t', is completely outside the light cones mentioned, so in that sense t' is not "inside" t, and far away events occurring at proper time t' can be before, during, or after (depending on frame of reference) the t interval from 2050 to 2100.

 

 

Yes, the block universe has one time dimension, but you can choose it in different ways (as MigL said, "You can have many different 'foliations' of the 4D hypercube, and all are equally valid.") If you have the block universe in coordinates so that the front of the train is always at the same location with one x value, its world line is a straight line aligned with the T axis. But you can rotate (hyperbolicly) the block universe so that Bob's world line is now aligned with the new T' axis, and the train front's world line span different x' values.

This doesn't imply multiple universes, blocks, trains etc. any more than someone in Russia having a different vector pointing "up" than someone in Argentina, implies that there are multiple Earths. Say they each have a y-axis that points "up", you have one Earth described using 2 different sets of coordinates, each more appropriate than the other to some observer.

Edited by md65536
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11 hours ago, 34student said:

Well look at your response to me.  You just ignored my post and repeated yourself.

I am genuinely of the opinion that all my replies were direct responses to something you posted, and didn’t ignore the salient points; and yes, I had to repeat myself - several times over - because there is only one mechanism explaining these observations, so there are only so many responses one can possibly give.

8 hours ago, 34student said:

Yes, the muons I will admit are haunting me.  They are the best and only strong counter point that I have seen yet.

How about the colliding gold ions at the RHIC, which I referenced earlier? I personally feel that’s an even better example, because the experiment can be repeated in a controlled manner in a lab, and contains fewer unpredictable variables.

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8 hours ago, Ghideon said:

Good, we may examine that later (other members have posted some points that may be simpler to start with)

But there is always one direction: A, B in my example will always agree that the train is going forward. 

We know that the train is moving in one direction hence we are able to determine what each observer A and B will see from their point of view; a left-to-right or right-to-left movement. 

(Forward meaning the locomotive comes first, pulling a number of wagons.  An observer on the train will also agree with A and B)

Yeah, I should not have said that.

3 hours ago, md65536 said:

"One timeline" is meaningless to me. t' inside t is also meaningless... you're effectively asking if the time measured by one clock is inside the time measured by another clock. But you could say that if Bob leaves the train at 2050 and returns to it at 2100, its world line between those events is within the future light cone of the train in 2050, and the past light cone in 2100, and that's what you want: all observers agree that Bob's trip happened after the 2050 event and before the 2100 event.

However, if Bob didn't start/end near the train and was always far enough away, that's not true for all observers. As well, Bob's cousin Babs, who suppose shares Bob's inertial frame and clock for an inertial part of Bob's trip, but was in the Andromeda galaxy during proper time interval t', is completely outside the light cones mentioned, so in that sense t' is not "inside" t, and far away events occurring at proper time t' can be before, during, or after (depending on frame of reference) the t interval from 2050 to 2100.

 

Then there must be a t' that equals a t from the t interval (2050 - 2100) on Earth.  Let's call it t*

Is there one or more sizes of train in the frozen 3d universe at time = t* 

Edited by 34student
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3 hours ago, 34student said:

Is there one or more sizes of train in the frozen 3d universe at time = t*

What does ”frozen 3d universe” mean? 

Edited by Ghideon
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4 hours ago, 34student said:

Is there one or more sizes of train in the frozen 3d universe at time = t* 

distance-between-lines.png.517f10eef1c5930e4411f497148d4460.png

What is the length of a line segment that connects line A at point p, to line B? Is it one or more of a,b,c,d,e, or something else?

If line A represented the world line of the front of a train, and B the world line of the back of the train, what is the length of the train?

This doesn't even illustrate length contraction or the rules of relativity. I think you're missing some basic geometry in what you're asking.

 

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On 10/26/2021 at 5:22 PM, 34student said:

Aliens from another dimension are looking at our block universe from 2050 to 2100.  Will they see a 100 meter train or a 1 meter train or something else?

What I am about to say was probably already said in several variations, but you did not get it yet. So here my try:

You cannot simply imagine the 'block' universe as a simple extension of a 3-dimensional block: just add another dimension and voila. The block universe is not a block with just 4 space dimensions instead of 3. Time stands in relation with the space dimensions, but in another way. This is especially true for Pythagoras theorem. So the metric of the block universe is not:

s2 = x2 + y2 + z+ t2 (Invalid!)

When this were the case you would be probably right. But you are then just extending the Euclidian metric with one dimension. Instead you must use the Minkowski metric, in which 'Pythagoras' is:

s2 = x2 + y2 + z - ct2 

This is the so called 'space-time' distance, and it is a distance all observers agree upon: all observers in the block universe agree on its value. Now a god-like high-dimensional alien creature, looking at our block universe would take that as the distance between two events (e.g. the train's passing of a point, first event is the passing of the locomotive, second event is the passing of the last wagon). However when an observer in the block universe prays to the alien, and asks 'how long is that train really in my 3 dimensional space?', the alien must first ask (or look) how the observer is moving in respect to the train. Only then he can answer the question. But the answer will be different for another observer. This is also true for an observer that is in the same inertial frame of reference as the train.

There are conventional reasons to take the length of the train as the length measured in the frame of reference of the train, but these are not physical reasons. 

Edited by Eise
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9 hours ago, Ghideon said:

What does ”frozen 3d universe” mean? 

Really?  Given the context, you have no idea what I mean?  It means a physical state of the universe.

8 hours ago, md65536 said:

distance-between-lines.png.517f10eef1c5930e4411f497148d4460.png

What is the length of a line segment that connects line A at point p, to line B? Is it one or more of a,b,c,d,e, or something else?

If line A represented the world line of the front of a train, and B the world line of the back of the train, what is the length of the train?

This doesn't even illustrate length contraction or the rules of relativity. I think you're missing some basic geometry in what you're asking.

 

Can you please answer my question first.  If you can give a serious attempt at answering my question, then you may understand my issue.

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2 hours ago, Eise said:

What I am about to say was probably already said in several variations, but you did not get it yet. So here my try:

You cannot simply imagine the 'block' universe as a simple extension of a 3-dimensional block: just add another dimension and voila. The block universe is not a block with just 4 space dimensions instead of 3. Time stands in relation with the space dimensions, but in another way. This is especially true for Pythagoras theorem. So the metric of the block universe is not:

s2 = x2 + y2 + z+ t2 (Invalid!)

When this were the case you would be probably right. But you are then just extending the Euclidian metric with one dimension. Instead you must use the Minkowski metric, in which 'Pythagoras' is:

s2 = x2 + y2 + z - ct2 

This is the so called 'space-time' distance, and it is a distance all observers agree upon: all observers in the block universe agree on its value. Now a god-like high-dimensional alien creature, looking at our block universe would take that as the distance between two events (e.g. the train's passing of a point, first event is the passing of the locomotive, second event is the passing of the last wagon). However when an observer in the block universe prays to the alien, and asks 'how long is that train really in my 3 dimensional space?', the alien must first ask (or look) how the observer is moving in respect to the train. Only then he can answer the question. But the answer will be different for another observer. This is also true for an observer that is in the same inertial frame of reference as the train.

There are conventional reasons to take the length of the train as the length measured in the frame of reference of the train, but these are not physical reasons. 

This is very interesting.  I did not know that there was a distance that all observers can agree on.  Is this an absolute distance or something?

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2 minutes ago, 34student said:

This is very interesting.  I did not know that there was a distance that all observers can agree on.  Is this an absolute distance or something?

I see you've been not reading my posts again.

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