# Special Relativity nonsense

I don't know.

I have no idea what you are writing about or what this has to do with the problem as posed.

I have no idea what you are writing about or what this has to do with the problem as posed.

One object can detect another , but the another can not detect the one object .

Let me try to make this more clear...
Ship1 at rest on top
Code:
``````       T-----------------------N
<----- N----------T``````

Ship2 at rest at bottom.
Code:
``````T-------N  ------->
N--------------------T``````

Since T1 and N2 are lined up and the observers can see each other this must be the same moment for both ship1 and ship2.
Remember how, just a few posts above this one, I carefully explained to you how the term "the same moment" is hopelessly ambiguous and therefore practically meaningless in a context like this one?

We can certainly say that both observers can see each other when T1 and N2 are lined up. It would be impossible for the observer at T1 to look across and see another observer at N2, while at the same time observer at N2 looks across and sees some other part of ship 1 (other than T1). There is only one instant, in both frames, at which T1 and N2 are aligned.

Also, events that happen in one frame must happen in all other frames. It would indeed be impossible for an observer in one frame to say "At one instant of time the people in the two passing spaceships could look directly (i.e. perpendicularly) across at one another" while the other says "That never happened, according to me".

Does everyone agree with this? If you do then let's go back a little bit in time....

Ship1 at rest on top
Code:
``````T-------------------------N
<----- N----------T``````

Ship2 at rest at bottom.
Code:
``````T------N ----->
N---------------------T``````

So the observer at N1 can see the observer at T2 and yet the observer at T2 can't see the observer at N1.
But you haven't drawn the same event in these last two diagrams.

Your last diagram should look like this, to depict the event of N1 and T2 lining up:

Ship2 at rest at bottom.
Code:
``````               T------N ----->
N---------------------T``````

There is obviously a problem here because it is an impossible situation.
Yes, and the problem is that you used an incorrect diagram to draw an incorrect conclusion.

If you want to draw diagrams depicting the same event in two frames, you need to actually show the same event on both diagrams.

Now, you're going to complain that my diagram happened later in time than the first diagram for ship 2, which would mean winding ship 2's clock forward from the time of the T1/N2 alignment until we see the N1/T2 alignment, rather than winding it back like you did. And to that I say: of course we have to do that, because in ship 2's frame N1/T2 happens after T1/N2, whereas in ship 1's frame T1/N2 happens before N1/T2. Like I carefully explained to you previously.

Your error is that you wrongly assumed you need to wind both clocks back from the T1/N2 alignment event in order to get to the T2/N1 alignment event.

Here's the question you need to answer:

Do you agree that the time order of the two events, in which T1/N2 are aligned and T2/N1 are aligned, is different for observers on ships 1 and 2?

If your answer to that is "No, because there's a flaw in relativity", then you're just making an error about the theory of relativity, because there's no inconsistency in the theory. If you think there is, I challenge you to do the maths, using the theory, and show me where I'm wrong about this example.

If your answer, on the other hand, is "No, because I just won't believe that the two observers can see the events happening in a different order, no matter what you do to try to convince me" then the problem you're having is just denial on your part, and there's nothing more we need to talk about.

Your argument, such that it is, boils down to "It's impossible, because I don't like the idea." That's not science. That's just ignorant prejudice.

Last edited:
river,

Can you please go away and leave the adults to talk? Clearly this is beyond you. Your nonsense is annoying clutter.

Actually, since nothing you have said has been remotely relevant to the thread topic, I have decided to lock you out of this thread for 7 days. By that time, we should be done, and then you can add in some inanities if you like.

Ship2 at rest at bottom.
Code:
``````T-------N ------->
N--------------------T``````
If I then go back in time a little bit I get this..
Ship2 at rest at bottom.
Code:
``````T------N ----->
N--------------------------T``````
Going back in time doesn't give me this...
Ship2 at rest on bottom.
Code:
``````                                T-------N ------->
N-----------------------T``````
You aren't making any sense whatsoever.

Do you agree that the time order of the two events, in which T1/N2 are aligned and T2/N1 are aligned, is different for observers on ships 1 and 2?
Yes. All of my diagrams are consistent with this aren't they?
That fact does nothing to resolve the paradox.

The problem is that if T1/N2 is simultaneous for both ship1 and ship2 (which it must be) then N1/T2 isn't simultaneous for both ship1 and ship2. If N1/T2 is simultaneous for both ship1 and ship2 then T1/N2 isn't simultaneous for both ship1 and ship2. This problem comes from the fact that each ship considers the other as shorter than itself.

The problem is that if T1/N2 is simultaneous for both ship1 and ship2...
"Simultaneous" is a word that only makes sense when you're comparing two different events in the same reference frame.

Here, you're trying to use the word "simultaneous" to refer to what is a single event in spacetime, which begs the question "simultaneous with which other event (and in which frame)?"

(which it must be)....
All you're saying is that when T1 and N2 are aligned, they are aligned. Similarly, when T2 and N1 are aligned, they are aligned. In neither frame do those events happen simultaneously to one another, as is clear from your diagrams.

...then N1/T2 isn't simultaneous for both ship1 and ship2.
Right. In one frame, that alignment happens before the other one, and in the other frame it happens after the other one. Like I've told you three or four times already.

If N1/T2 is simultaneous for both ship1 and ship2 then T1/N2 isn't simultaneous for both ship1 and ship2.
That sentence is meaningless. Try again.

This problem comes from the fact that each ship considers the other as shorter than itself.
There's no problem. Both alignments happen. All observers in each alignment look across and see the guy on the other ship when they are aligned.

Ship2 at rest at bottom.
Code:
``````T-------N ------->
N--------------------T``````
If I then go back in time a little bit I get this..
Ship2 at rest at bottom.
Code:
``````T------N ----->
N--------------------------T``````
Yes, if you wind ship 2's clock back, that's what you get. I agree.

Going back in time doesn't give me this...
Ship2 at rest on bottom.
Code:
``````                                T-------N ------->
N-----------------------T``````
Correct. That's what you get when you wind ship 2's clock forwards in time, to the point in time where N1 and T2 are aligned, which was the event you were interested in. Like I carefully explained to you.

You aren't making any sense whatsoever.
But we're in agreement about the diagrams now. That's progress. If I'm not making sense, then you're not making sense either. Agree?

Do you agree that the time order of the two events, in which T1/N2 are aligned and T2/N1 are aligned, is different for observers on ships 1 and 2?
Yes. All of my diagrams are consistent with this aren't they?
Then we're done. Aren't we? You agree that the theory of relativity says this. So, not a problem of internal consistency within relativity, then. Right?

That fact does nothing to resolve the paradox.

You just agreed that the two alignments happen in a different time order for the two observers. That agreement resolves any "paradox" you perceived before. Doesn't it?

There is one moment in time when T1 reaches N2. This moment is simultaneous for both ship1 and ship2. If that is the case then the one moment when N1 reaches T2 is not simultaneous for both ship1 and ship2, which is obviously impossible.

If one ship was longer than the other there would be no problem, but because each ship considers the other as shorter than itself it leads to impossible physical situations that can't occur.

There is one moment in time when T1 reaches N2.
Yes, in each frame the clock on the ship registers a single time when T1 and N2 are aligned.

This moment is simultaneous for both ship1 and ship2.
I just taught you how the term "simultaneous" is used. It is used to compare two events in the same frame.

You are only talking about one event here, the event "T1 and N2 are aligned". The word "simultaneous" will not become relevant until you introduce a second event with which to compare this event.

If that is the case then the one moment when N1 reaches T2 is not simultaneous for both ship1 and ship2, which is obviously impossible.
You agreed with me, just above, that the "moment" that N1 reaches T2 occurs before the "moment" when N2 reaches T1 in one frame, and after it in the other frame. That necessarily means those two events are not simultaneous. How could they be, when the two spaceships have different lengths?

Your cries of "obviously impossible" don't apply to a set of facts that you agree occurs.

If one ship was longer than the other there would be no problem, but because each ship considers the other as shorter than itself it leads to impossible physical situations that can't occur.
What's impossible about the physical situation described?

You keep using that term - "impossible" - but so far that only seems to mean that you don't like the implications of the theory of relativity. The universe doesn't care what you like.

Zeno, you've been having this same conversation since April. Isn't it time to go on to something new? Do you have a theory of dark which is actually the absence of light, D=L-D? That could take us through the summer and it would be a different conversation.

river,

Can you please go away and leave the adults to talk? Clearly this is beyond you. Your nonsense is annoying clutter.

Actually, since nothing you have said has been remotely relevant to the thread topic, I have decided to lock you out of this thread for 7 days. By that time, we should be done, and then you can add in some inanities if you like.
Hooray.

There is one moment in time when T1 reaches N2. This moment is simultaneous for both ship1 and ship2. If that is the case then the one moment when N1 reaches T2 is not simultaneous for both ship1 and ship2, which is obviously impossible.

You are only talking about one event here, the event "T1 and N2 are aligned". The word "simultaneous" will not become relevant until you introduce a second event with which to compare this event.
Maybe I should have been more clear.
There is only one moment when T1 reaches N2, but there are 2 events. T1 reaches N2 in the reference frame of ship1. T1 reaches N2 in the reference frame of ship2. These events must be simultaneous for both ship1 and ship2. So there are 2 events that are simultaneous for the ships and there is only one moment when this occurs. Given that fact, if you go back a little bit in time then the event N1 reaching T2 in the reference frame of ship1 and the event N1 reaching T2 in the reference frame of ship2 are not simultaneous which is a physical impossibility. I even made a small diagram to make that clear. So in order to make it so that there is no physical impossibility James R moves ship1 in the opposite direction relative to ship2 without justification.

Maybe I should have been more clear.
There is only one moment when T1 reaches N2, but there are 2 events. T1 reaches N2 in the reference frame of ship1. T1 reaches N2 in the reference frame of ship2.
No. T1 and N2 meeting are a single event, regardless of whether it is being measured from ship 1 or ship 2. To have two events, you would have include an event such as N1 and T2 meeting or T1 and T2 meeting etc. You can say nothing about Relativity of Simultaneity when dealing with a single event such as T1 an N2 meeting. Everyone agrees no matter what frame they are making the determination from that when T1 meets N2, T2 meets T1. What the two ships will not agree upon is the ordering of separate events such as the meeting of T1-N2 and the meeting of N1-T2

Everyone agrees no matter what frame they are making the determination from that when T1 meets N2, N2 meets T1.
That right, and I have already shown that if that is true for T1 meeting N2 then that isn't true for N1 meeting T2 which is impossible.