# Special Relativity nonsense

Discussion in 'Pseudoscience' started by Zeno, Apr 8, 2018.

1. ### ZenoRegistered Senior Member

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This should be an easy answer because it's the same moment between both frames of reference. For the person on the ground, the back end of the train is inside the tunnel because the train is length-contracted. For the person on the train, the tunnel is length-contracted and the back end is outside of the tunnel. So what is wrong with this answer? Maybe you can elaborate.

3. ### NotEinsteinValued Senior Member

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Except that it's not. Look at the video again, and notice the clocks at 3:47 and onwards. Clearly, the idea of two different events happening "at the same moment" isn't an open-and-shut case.

I've already elaborated, and you've promptly ignored those elaborations multiple times. You are laboring under a mistaken notion of simultaneity. Go read up about it.

5. ### ZenoRegistered Senior Member

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215
Actually, you haven't elaborated. The only thing you've replied with is 'simultaneity doesn't work like that'. You haven't explained why. You haven't explained what actually happens. That's just basically a non-response. You haven't explained anything. You haven't fully explained why this isn't a paradox. Please explain how the back end of the train being both inside and outside the tunnel are not simultaneous if this occurs at the same time that the front of the train reaches the end of the tunnel and this event is simultaneous between both frames of reference.

Last edited: Apr 8, 2018

7. ### NotEinsteinValued Senior Member

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1,584
Which is the elaboration I was talking about.

As any introductory textbook will explain: it's a logical consequence of the postulates of SR.

May I point out that you've done the same thing? You've not explained where your notion of simultaneity comes from, or why you consider your notion to be valid in the context of SR.

There's perfectly good introductory textbooks out that explain it better than I can. As I said, go and read them.

8. ### exchemistValued Senior Member

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He won't. He is a creationist, anti-science troll, who revels proudly in his stupidity. Just look at his posting history.

Perhaps he's a researcher for "Conservapaedia".

9. ### NotEinsteinValued Senior Member

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I'm starting to suspect that, yes. Ah well, his/her loss.

That doesn't sound very hopeful, no. Guess I won't spend any further energy on this, if (s)he isn't willing to learn.

Well, I suppose asking people online still is a better way of learning about the truth than blindly believing what some unknown person wrote down over a thousand years ago.

10. ### DaveC426913Valued Senior Member

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Because the long-form explanation of why it's true is outside the scope of this thread.

You'll have to do some reading on this. Not internet word-snippets; you'll need a book's worth of groundwork laid out to get to this place.

It's like somebody not believing in calculus. It does work, but the deep level explanation essentially requires them to learn calculus to actually see how.

We've all done this. You don't have to trust us (in fact, I urge you not to) but it will take some work on your part to sort out the underlying misconceptions you have, one-by-one.

The key, as several people have said, is that there is no single moment in time for two observers. Simultaneity of events is relative to each of their frames of reference.

The common example is Einstein's Train Thought experiment. There are many descriptions of it, but I urge you to do some solid reading. There's just no substitute.

11. ### Janus58Valued Senior Member

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While the observers at the tail of airplane B and at the nose of airplane A agree that their passing each other is a single event taking place at a single moment, this is the only time that they agree on a common "now".
The best way to illustrate this is by putting clocks on each plane so that all the clocks on a given plane are in sync with each other according to that plane.

If we stipulate that when the clock at the nose of plane A and the clock at the tail of Plane B both read zero at the moment of their passing each other then this is how events occur according to plane A under the following conditions:
1. the relative velocity between the trains is 0.866c
2. the proper length of the planes as measured in their own frame is 0.866 light-seconds (I know that this makes for a very long plane, but this allows to use time periods that don't need a ton of decimal places)

We start with the moment the nose of plane A and the tail of plane B pass each other. Since the nose of Plane B is at this moment 0.433 ls from the tail of Plane B, this takes place 0.5 sec before the moment that the Nose of Plane B reaches the tail of plane A according to all the clocks on plane A in order for the clock at the tail of plane A to read 0, when the Nose of plane B reaches it. Also, since the clocks on Plane A are time dilated so that they run half as fast as those on Plane A, the clock at the nose of plane B read 0.25 sec before zero in order to satisfy our earlier stipulation. However, due to the relativity of simultaneity, All the clocks on Plane B are not in sync with each other according to Plane A and the clock at the tail of plane B already reads 0.5 sec past 0.

Next we have the moment when the nose of plane B reaches the tail of plane A. Both clocks at this meeting point read zero. For plane A all its clocks read O. For plane B, both clocks ave advanced 0.25 sec, so that the clock at the tail now reads 0.75 sec, just as it passes the mid point of plane A and the clock at that midpoint reads 0

Now we advance to the point where the midpoint of plane B passes the tail of plane A. All the clocks on Plane A have advanced 0.25 seconds, and all the clocks on plane B have advanced 0.125 sec. a clock at the midpoint of Plane B will read halfway between the reading on the nose and tail clocks and read 0.5 sec past zero

Lastly, we move on to the point where the tails of the two clocks pass each other. All the clocks on plane A read 0.5 sec past zero. The clock at the tail of plane B reads 1 sec past zero, and the clock at the Nose of plane B reads 0.25 sec past zero.

Now we consider events from the frame of plane B. We start with the moment where the midpoint of plane A passes the nose of plane B. just like for Plane A frame, the clock at the midpoint of plane A reads 0.5 sec before zero and the clock at the nose of plane B reads 0.25 sec before zero. Now however since we are in the frame of plane B all its clocks are in sync and the clocks in plane A aren't (Relativity of simultaneity). This again is consistent with the fact that that it will take 0.25 seconds for the tail of plane A to reach the nose of plane B according to the clocks on plane A, and the fact that now it is the clocks on plane A that run half as fast due to time dilation and 0.125 sec will have to tick off the clock at the tail of plane A in order for it to read zero upon reaching the nose of plane B.

Advancing 0.25 sec gives us the moment that the tail of plane A meets the nose of plane B and the clocks at both read zero. Looking back at our second image for plane A's frame, we see that at this moment according to plane A, all its clocks read zero, and the clock at the tail of plane B reads 0.75 sec past 0. At this moment according to plane B, all its clocks read 0 and the clock at the nose of Plane A read 0.75 sec before zero as it passes the midpoint of plane B.

Another 0.25 sec later and the tail of plane A is passing the midpoint of Plane B. All the clocks on Plane B have advanced 0.25sec, and all the clocks on Plane A have advanced by 0.125 sec. Just like when the midpoint of plane B and the tail of Plane A passed each other in Plane A's frame, the clock at the Tail of plane A read 0.25 sec past zero and the clock at the midpoint of plane B reads 0.5 sec past zero.

Yet another 0.25 sec later. The clocks on plane B have advanced 0.125 sec. midpoint of plane A is passing the tail of plane B. The clock at the tail of plane B reads 0.75 sec past zero and the clock at the midpoint of Plane A reads O. Again we have complete agreement as what the frame of Plane A said was the readings on these two clocks as they passed each other

Lastly, the tails of the planes pass each other. Again the respective readings on the clocks at the tail of the plane is in exact agreement with what they were according to the frame of Plane A.

The point being that no matter where you put clocks on either plane, both planes will agree as what the respective reading are on those clocks will be as they pass each other. The clock at the tail of plane A will say that when it read zero the clock at its midpoint read zero and the clock at the tail nose of read 0.75 sec past zero as it passed that midpoint, while the clock at the nose of plane B will say that that event didn't occur until 0.75 sec later, but everyone will agree the clock at the tail of plane B read 0.75 sec past zero and the that the clock at the midpoint of Plane A read zero when they passed each other.

12. ### exchemistValued Senior Member

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Yes, fair enough - supposing always that the person asking is doing so on good faith, i.e. is genuinely interested in the answer.

13. ### Q-reeusValued Senior Member

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So which is it Zeno - convinced that SR just has to be wrong based on - what exactly? Theology? Or throwing out a provocatively titled challenge to SR tongue-in-cheek style - but willing to concede in the end SR is probably correct after all?

14. ### RainbowSingularityValued Senior Member

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1,410
conscious individuation of reality.
collectiveness defines its' total entity, however... the nature of all parts still maintain thier individualness.
the shared reality of the entire entity takes up space.
that space can not be completely occupied by the individual all the time.
thus time is different as a collective reality.
rendering time down to an individual moment which extends to all parts of the plane at once is ... interesting

15. ### James RJust this guy, you know?Staff Member

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Janus58:

That's a very useful, detailed response.

I will interested to see whether Zeno replies, or if just disappears from this thread, only to reappear at some future time with some new "challenge" to special relativity.

16. ### ZenoRegistered Senior Member

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215
Let's assume that plane A has a missile attached to the underside of its tail and plane B has a missle attached to the topside of its tail.
From A's viewpoint...
Code:
T------------------------------N     M      plane A
M               <---       N---------T      plane B

From B's viewpoint....
Code:
T----------N   -->              M         plane A
M    N--------------------------T         plane B

So which plane gets blown up and which survives?
Thank you for the response Janus58. However, it looks like complete insanity. You have people that, when viewed from another frame of reference, are doing things that they have not yet decided to do in their own frame of reference.
For example, let's say there is a line of dominos that are standing up and close to each other and it runs from one end of airplane A to the other. At time 0, the person at each end starts the domino chain going. From the viewpoint of airplane A, the ends are started at the same time and the dominos are lying over each other in opposite directions until they meet in the middle. From the viewpoint of airplane B, the tail is started first before the nose. This leads to a paradox. Both situations can't simultaneously be true.

Last edited: Apr 15, 2018
17. ### Q-reeusValued Senior Member

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3,084
Zeno you were asked a question in #30, and have not responded. Are you committed to a Newtonian worldview of absolute time and space? For some particular reason?

18. ### DaveC426913Valued Senior Member

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Really?

A bolt of lightning hits the transformer next to my house. I see a huge flash and simultaneously hear a blast of thunder.
My friend calls me from a mile away, and tells me he saw a bolt of lightning hit near me, and then heard a peal of thunder five seconds later.

Is this a paradox? Both situations can't simultaneously be true?

.

You wrote it yourself:

"From the viewpoint of airplane A..."
"From the viewpoint of airplane B..."

Viewpoints are not objective Truth. Viewpoints are dependent on your frame of reference. There is no objective truth.

19. ### James RJust this guy, you know?Staff Member

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31,670
There's no reason that both situations can't be true. (Your insertion of the word "simultaneously" in that last sentence is a mistake, by the way, since simultaneity is relative.)

Your observers A and B will both agree that the collapsing dominos meet in the middle. But they do not have equal distances to travel to get to the middle in both frames. The only way they can meet in the middle in B's frame is if one end is started before the other.

20. ### James RJust this guy, you know?Staff Member

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31,670
This kind of thing is a common error people make when they discuss relativity: they fail to separate when two events happened from when light from the events was seen. The seeing of the light constitutes two new events.

But I don't think that Zeno is making that mistake here.

We can talk about when the dominos were started falling at each end of the line, in either frame A or B. Those events are quite independent of when an observer on spaceship A or B saw them start to fall. Moreover, those starting-to-fall events are simultaneous in frame A, but not in frame B, and that has nothing to do with when anybody observes the light from the dominos starting to fall.

21. ### DaveC426913Valued Senior Member

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It wasn't meant to be a rigorous example of relativity of simultaneity, just to have Zeno rethink the idea of an objective truth.

22. ### James RJust this guy, you know?Staff Member

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31,670
Yes, but Zeno intends his example to be precisely that - a rigorous example of how the relativity of simultaneity must be nonsense. It fails to be what he thinks it is, because he hasn't yet understood the relativity of simultaneity.

23. ### Q-reeusValued Senior Member

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3,084
But there are plenty of objective truths - in relativistic context at least. A particle collision for instance is a spacetime event agreed on by all observers in all frames. That the order of events can be frame dependent doesn't detract from the event itself being an objective fact. Likewise for quantities like electric charge or angular momentum - relativistic invariants.

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