A not so small discrepancy in Relativity of Simultaneity

[Truden]

1 minute ago, J.C.MacSwell said:

In the ladder frame the connection/touching near the hinge (red points) happens halfway between the time the back door opens then closes, and when the front door opens then closes. It will seem like the system connecting the doors is quite flexible, even if it isn't in the barn frame.

Incorrect. The sequence in the ladder FoR is "door closes and opens, then the other door closes and opens, then the other door... " and so on and so on.
And I feel quite uncomfortable to be in an argument about this. I apologize beforehand if I don't answer some of the comments, but there is very little I can say from here on in this discussion. I'll keep an eye on it though.

[Janus]

5 hours ago, Truden said:

As I said in the OP, do not think of the event as "will not happen".
It happens as part of the experiment construct; the doors stop when they meet at that red dot point. 

I don't see an added event as complexity which needs mathematical work.
I just modified the doors of the experiment, which introduces one more event.
The question is why the event is missing in the ladder FoR.
What math can we use here?

What closes and opens the doors?  For instance, is it a force acting on the axis of rotation?  If so, then that force can only propagate through the material of the doors at the speed of sound of the doors. For even the most rigid doors, this can't be faster than the speed of light. This means that parts of the door near the axis will start moving sooner than parts further away.  And since the closing of the doors are going have to be a significant fraction of the speed of light it is going to be significant relative to the speed of propagation through the doors, and you are going to get a noticeable distortion in the shape of the door.

What stops the doors from closing? is it the contact of the red dots?, if so then this can only propagate through the doors at a fixed speed, and different pats of the doors will stop moving at different times.

But for simplicity of argument, Let's assume that you've arranged for the doors to act as single rigid objects in the Barn's rest frame.  This does mean mean that they will do so in the ladder ladder frame.

The Relativity of Simultaneity doesn't just apply to when the doors close and open, but also to different points of the doors. 

Below we show what happens with the open doors according to the ladder frame (where the barn is moving right to left), and assuming the doors close simultaneously and as rigid objects in the barn's rest frame. The far end of the right door will start moving first,  then the points of both doors where they touch and then finally the far left end of the Left doors. Different parts of the doors will start moving at different times.  So even if the shape of the doors is not distorted in the barn frame, they will be in the ladder frame.

 

if you doubt this, just consider the following image

At the top we show the barn doors as they appear in the open and closed positions in the barn frame. Below that, how they appear in the ladder frame. In both cases in the ladder frame the doors will be length contracted along the left-right direction. However, since they are rotated by 90 degree between the open and closed positions, they have different shapes before and after closing.

The element of rotation for the doors while opening and closing add yet another complexity to the problem.  Since the vector direction of different parts of the doors change relative to the ladder's motion vector direction during opening and closing, the resulting velocity addition for any point of the door changes from moment to moment in the ladder frame (using relativistic velocity addition).  In other words, if a point of the door a given distance from the axis of door rotation has a constant tangential speed relative to the axis as measured from the Barn frame, the ladder frame will measure a changing tangential speed with respect to the axis as that point travels along the path of rotation.

These are some of the complexities to the analysis of the scenario you've introduced with your modifications.

[studiot]

8 hours ago, Truden said:

The question is; is it possible a longer than a garage ladder to fit between the simultaneously closed doors of the garage?

 

8 hours ago, Truden said:

The point is that I cannot explain it better than it is explained in the Wikipedia.

Wikipedia is not the best or most reliable source in this case.

So thank you for trying.

 

Another (and I think better) view is that the same physical reality must pertain in all frames.

This is not about Schrodinger's cat and QM. Relativity is exactly deterministic.

A proposal that suggests something different happens in different frames is flawed, usually by inadequate consideration of the mechanics of the situation.

The same reality must happen in all frames (not events they have a special meaning)

That is what is meant by the phrase the laws of Physics must be the same in all frames.

Einstein himself concluded that must place certain limitations on acceptable laws of physics.

If something is impossible in one frame it it impossible in all frames.

 

I suggest that there is too much emphasis on the doors, which are really a distraction.

The doors could be switch activated vertical light curtains effectively instantaneous in action if their height is tiny compared to the length of the ladder.

Alternatively the whole paradox could be simplified, as I'm not sure there is a clear understanding of it here.

So let the exit door of the garage be permanently closed.
Then there is no need to have an opening / closing mechanism or a discussion about simultaneity of door operations.

Jack and Jill first offer up the ladder to the garage and butt it against the exit door, through the open entrance.
The other end of the ladder can be seen to stick out from the entrance side of the garage.
All this takes place in the common frame of Jack, Jill and the garage.

Then Jack picks up the ladder and walks slowly back a suitable distance to begin his run.
He runs very fast forwards and notes that the ladder has not changed its length but the garage appears even shorter in his new frame.
So he concludes that the ladder still will not fit into the garage space.

Jill remains by the garage and notes that the garage has not changed in size.
She also observes Jack running towards her, carrying a ladder, now appearing shorter than the garage space.
So to Jill the ladder will now fit inside the garage.

The resolution of this 'apparent paradox lies in the word apparent, appears and appearing.

Appearances can be deceptive.

Ask yourself how do Jack and Jill make these measurements and you will find that both have to be adjusted by the Lorenz gamma factor to be brought into a common frame for comparison.

 

[J.C.MacSwell]

48 minutes ago, Truden said:

Incorrect. The sequence in the ladder FoR is "door closes and opens, then the other door closes and opens, then the other door... " and so on and so on.
And I feel quite uncomfortable to be in an argument about this. I apologize beforehand if I don't answer some of the comments, but there is very little I can say from here on in this discussion. I'll keep an eye on it though.

In the set up and sequence we are discussing, there are just two doors and they each just close then open once. This occurs simultaneously in the barn frame...and sequentially in the ladder frame. The red dot touching event is coincident with the simultaneous opening/closing of the doors in the barn frame. (it lasts the duration of the closed doors)

In the ladder frame the back door opens and closes ahead of the approaching ladder and later the front door closes then opens behind the back of the ladder. The red dot touching event happens part way between the two, completely after the first and completely before the second. Movements of all intermediary points occur in succession, such that the "rigid" door/connection systems from the barn frame are distorted in the ladder frame.

I know that is counterintuitive, might seem like it does not make sense...but welcome to SR.

[Truden]

@J.C.MacSwell, you should understand one thing - logic first.
The logic says that in this case a non-simultaneously moving doors cannot touch each other. That's a very simple logic.
Don't try to find the touch point somewhere else. There is no such point for the non-simultaneously moving doors in the ladder FoR.
If you argue this, no offense but I'll have to ignore your arguments.

@studiot, whether you insert "apparent" for a paradox, or you think of it as a real paradox, does not change the fact, that its existence question the validity of a statement.
However, we are not discussing the ladder paradox here, but just using it as a base for discussing the relativity of simultaneity.
You can safely ignore the question whether the ladder passes the garage or not. Our focus is on the event which I introduced in the experiment.

@Janus, I'm sorry, but your notes on the drawings and your sketches don't make any sense to me.
I think that you are confused with my drawings.
The doors stop when they meet at the red dot, and that event of meeting (touching) each other is what you should focus on.
If you don't find that event in the ladder FoR, then there is something wrong with relativity of simultaneity.

Good luck guys.

[studiot]

On 17/11/2017 at 3:00 PM, Truden said:

As I already mentioned in my first post about the gravitation hypothesis, I'm not a physicist.
I work on logic problems.
One such logical problem I saw in the "Ladder Paradox" which explains the relativity of simultaneity.

 

40 minutes ago, Truden said:

@studiot, whether you insert "apparent" for a paradox, or you think of it as a real paradox, does not change the fact, that its existence question the validity of a statement.
However, we are not discussing the ladder paradox here, but just using it as a base for discussing the relativity of simultaneity.
You can safely ignore the question whether the ladder passes the garage or not. Our focus is on the event which I introduced in the experiment.

 

One thing only saddens me.

That you seem not to be genuinely seeking discussion and resolution of your point, rather you seek to provoke reaction so that you can ridicule others with more knowledge than yours, whilst at the same time sidestepping from your earlier statements.

I made my last post for very good reasons, which anyone claiming to work on logic problems would normally ask

"That's an interesting comment why did you say that?"

In particular I stripped out simultaneity from the ladder paradox so that it would not obscure the Physics.

Further I deliberately introduced a situation where no ladder of any length in any frame could  in your words "pass the garage".

 

I have pointed you at the correct resolution of the paradox which basically relies on an incomplete analysis of the situation, but without stating how explicitly.

I take it that you are not actually interested in this.

Edited November 19, 2017 by studiot

[Truden]

15 minutes ago, studiot said:

 

 

One thing only saddens me.

That you seem not to be genuinely seeking discussion and resolution of your point, rather you seek to provoke reaction so that you can ridicule others with more knowledge than yours, whilst at the same time sidestepping from your earlier statements.

I made my last post for very good reasons, which anyone claiming to work on logic problems would normally ask

"That's an interesting comment why did you say that?"

In particular I stripped out simultaneity from the ladder paradox so that it would not obscure the Physics.

Further I deliberately introduced a situation where no ladder of any length in any frame could  in your words "pass the garage".

 

I have pointed you at the correct resolution of the paradox which basically relies on an incomplete analysis of the situation, but without stating how explicitly.

I take it that you are not actually interested in this.

I'm very sorry that you misinterpret my interaction in the discussion.
Very often people on the Internet read the text with the voice intonation they usually use on the others.
Perhaps you feel ridiculed not by me, but by the problem, which seems to be so obvious, but somehow was overlooked by such people like Einstein.
In another conversation the last argument of one of the guys was "Do you think that you are cleverer than Einstein?"

I understood your point in your previous comment, but was afraid that picking it up and unfolding it would be against the forum rules, and didn't want to get red point for trolling.
Let's stay on the topic.

[J.C.MacSwell]

1 hour ago, Truden said:

@J.C.MacSwell, you should understand one thing - logic first.
The logic says that in this case a non-simultaneously moving doors cannot touch each other. That's a very simple logic.
Don't try to find the touch point somewhere else. There is no such point for the non-simultaneously moving doors in the ladder FoR.
If you argue this, no offense but I'll have to ignore your arguments.

 

Based on what assumptions?

Based on SR? Or based on your belief that the rigidity of the door geometry in one frame must hold  in another?

How good is your logic? Is it good enough to work with a set of assumptions that you are not comfortable with?

 

Edited November 19, 2017 by J.C.MacSwell

[Truden]

2 minutes ago, J.C.MacSwell said:

Based on what assumptions?

Based on SR? Or based on your belief that the rigidity of the door geometry in one frame must hold  in another?

How good is your logic? Is it good enough to work with a set of assumptions that you are not comfortable with?

 

Based on LOGIC.
SR cannot go against logic. It is the other way round.
I see that you keep pushing the rigidity argument, although I gave you a door system, where rigidity doesn't have any effect, because the doors stop in to each other.
Why are you ignoring my comments? It looks like you are using it as an escape from the lack of arguments.
Please, do not troll the topic.
 

[Strange]

11 minutes ago, Truden said:

SR cannot go against logic. It is the other way round.

SR can be shown, by logic, to be self-consistent. Therefore there cannot be a paradox created by the correct application of SR.

Edited November 19, 2017 by Strange

[studiot]

43 minutes ago, Truden said:

I understood your point in your previous comment,

Then you can tell us all what it was, without all the theatricals.

I stand by my conclusion that

1 hour ago, studiot said:

I take it that you are not actually interested in this.

Noone will award red points for genuine responses, right or wrong.

It's been literally years since I last posted one.

[J.C.MacSwell]

3 minutes ago, Truden said:

Based on LOGIC.
SR cannot go against logic. It is the other way round.
I see that you keep pushing the rigidity argument, although I gave you a door system, where rigidity doesn't have any effect, because the doors stop in to each other.
Why are you ignoring my comments? It looks like you are using it as an escape from the lack of arguments.
Please, do not troll the topic.
 

You do understand logic must be based on a set of assumptions? The point where the doors stop into each other are spatially separated from the points of opening.

The doors can be open when the stops are closed with respect to other frames. There is nothing logically inconsistent with this...unless you use an assumption that is inconsistent with SR.

[swansont]

40 minutes ago, Truden said:

Based on LOGIC.
SR cannot go against logic. It is the other way round.
I see that you keep pushing the rigidity argument, although I gave you a door system, where rigidity doesn't have any effect, because the doors stop in to each other.
Why are you ignoring my comments? It looks like you are using it as an escape from the lack of arguments.
Please, do not troll the topic.
 

!

Moderator Note

There is nothing in SR that goes against logic, as long as you have incorporated the postulates of relativity. To say you are applying "logic" to the problem does not preclude the possibility that you have a faulty assumption to which you are applying your logic.

That's why we demand rigor, and it's lacking in your posts.

Janus (and others) have made the point that you need to apply relativity to all of these complexities you have added. That you have not is one faulty assumption you have made. It invalidates any conclusion you might draw.

For example, in the scenario with the rods that touch. While the doors are closing or opening, the rods are moving, and will be subject to length contraction. Even though they touch when the system is at rest, they will not while there is any motion involved. So you will find that they will not touch in the scenario you have described, as long as you have not assumed anything unphysical and have properly applied relativity.

Until you are willing to rigorously analyze the problem, we're done here. Don't start up any new threads on the topic if all you're going to do is argue logic without rigor.