seeing events in reverse order???

[michel123456]

Okay here's an alternative:

- There is no concept of reality battling against observation. Or equivalently: Reality always wins.

- What is measured is representative of reality.

 

 

How about that? SR and GR then fit. It's simple, also consistent.

 

 

Yours seems to be an interpretation of a misunderstanding of relativity. It's not the worst by far. It is probably fine if you intend to never use or understand relativity. It might even be especially useful for avoiding understanding relativity, because it puts up a wall where further understanding clashes with beliefs (eg. "length contraction's not real!"), and allows for inconsistency with a simple explanation that what it models and what is real are not the same (eg. "contradictions caused by length contraction's unreality are okay; this observer's measurements are simply wrong").

You nailed it.

Sincerely, after carefully reading all the arguments, I still remain on my interpretation. Hopefully, I will never teach Relativity to anyone so if I am wrong I will harm myself only.

The fact is I cannot swallow how it is possible to be "normal" in one FOR and contracted in another and both situations be equally "real".

To me there is only one single "reality". As you accept there exist an "invariant mass", I believe (yes it is a belief) there is a single "true" length that is the length one measures in the same FOR invariant mass naturally appears to be.

 

The disappointing thing is that none of us was capable to put forward a decisive argument that could make the other change his mind.

 

 

(If you meant specifically an alternative explanation of the meter stick through the posts, the basic explanation is something along the lines of: the stick makes it through the posts, and this happens in all frames. In the posts' frame, the stick passes through lengthwise, and is contracted enough to fit. In the stick's frame, it doesn't pass both posts simultaneously. The posts are contracted but also skewed allowing the stick to slip through not all at once, as though on an angle. I understand if this is not personally aesthetically appealing, but it is consistent and it works.)

Could you provide a sketch? I cannot figure the situation. If the posts are skewed, then the meter stick must be skewed also. No? I mean, the situation must be perfectly symmetric. Edited April 6, 2014 by michel123456

[Schneibster]

 

The correct term for what you are calling "true" values is proper length, mass, etc.; i.e. the value measured in the objects own frame of reference.

 

You still haven't answered the point that there are infinite number of frames of reference and therefore none of them can be considered preferred.

 

Mmmm, not quite sure that's entirely correct. Technically proper time is the time between two events measured on a clock that passes through the locations of the two events as each one happens. So not all inertial frames can measure proper time.

 

If I understand "proper time" correctly. And the math says I do.

You nailed it.

Sincerely, after carefully reading all the arguments, I still remain on my interpretation. Hopefully, I will never teach Relativity to anyone so if I am wrong I will harm myself only.

The fact is I cannot swallow how it is possible to be "normal" in one FOR and contracted in another and both situations be equally "real".

To me there is only one single "reality". As you accept there exist an "invariant mass", I believe (yes it is a belief) there is a single "true" length that is the length one measures in the same FOR invariant mass nuturally appears to be.

 

The disappointing thing is that none of us was capable to put forward a decisive argument that could make the other change his mind.

 

 

Could you provide a sketch? I cannot figure the situation. If the posts are skewed, then the meter stick must be skewed also. No? I mean, the situation must be perfectly symmetric.

 

michel, could you please answer my question in post 74?

Edited April 6, 2014 by Schneibster

[michel123456]

Here is how i figure Relativity.

 

You are observing and measuring a planet somewhere completely contracted.

You send an astronaut aboard a vessel to go there and check.

As the astronaut approaches, he observes (and measures) the planet less and less contracted.

When arriving on the spot, the astronaut observes and measures the planet perfectly round.

 

The question is: was the planet flat, skewed and round, really?

Or was it round all the time long?

 

IOW, is our Earth a flat disk, really, because some E.T. far away is observing us?

That is how I understand Relativity.

So you're saying you can only measure the "true" length, mass/energy, and time from a frame that is comoving with what you observe?

I say that you can only measure "true" length, mass and time from the same FOR of the object. Once you insert distance (as a comoving FOR), Speed Of Light will be involved and the machinery of Relativity will be at work, I guess.

 

You're going the same place I did. I'm going to try leading michel step by step.

You'll have a lot of work to do. But thank you for trying. Edited April 6, 2014 by michel123456

[md65536]

Hopefully, I will never teach Relativity to anyone so if I am wrong I will harm myself only.

The fact is I cannot swallow how it is possible to be "normal" in one FOR and contracted in another and both situations be equally "real".

To me there is only one single "reality". As you accept there exist an "invariant mass", I believe (yes it is a belief) there is a single "true" length that is the length one measures in the same FOR invariant mass nuturally appears to be.

 

The disappointing thing is that none of us was capable to put forward a decisive argument that could make the other change his mind.

 

 

Could you provide a sketch? I cannot figure the situation. If the posts are skewed, then the meter stick must be skewed also. No? I mean, the situation must be perfectly symmetric.

I hope so too, because for most people going from classical understanding of reality to a relativistic one is very difficult, and if we see others arguing that it doesn't make sense, that can be an "easy way out" of struggling through the understanding. One might say "Other people think it doesn't make sense, so it's okay if I accept that it doesn't make sense."

 

Look at this thread. It started off as a question of the understanding of relativity, and ended up an argument over whether it is even real.

 

There may be only one reality (SR is compatible with that). However, absolute length and time are not an aspect of reality. It's not terribly more complicated than that.

 

I don't think it's terrible that nobody's mind was changed. I think belief and understanding happen in lock-step. It's hard to understand something when you refuse to accept it could be true. If you believe that it could be true it's easier to understand. The more you understand the more believable it is. Eventually everything just clicks. To change beliefs might be a personal choice, not something one person convinces the other of on a forum.

 

 

http://en.wikipedia.org/wiki/Ladder_paradox#Bar_and_ring_paradox

is probably a close enough picture. The posts would be the tips of the ring. I said the posts were "skewed", but their description "rotated" would be more accurate.

Edited April 6, 2014 by md65536

[michel123456]

At the time there exist a FOR in which

_mass is invariant

_length is maximum

_time is mininmum

 

There is a barrier, where things stop to change.

That's where Relativity stops.

 

It is another thing to say "everything is relative" and get masses from zero to infinity, lengths and times from zero to infinity, not telling you should insert negatives and get values from minus infinity to plus infinity.

That kind of Theory I could accept.

But not the one we have at hand.

[Schneibster]

I say that you can only measure "true" length, mass and time from the same FOR of the object. Once you insert distance (as a comoving FOR), Speed Of Light will be involved and the machinery of Relativity will be at work, I guess.

 

You'll have a lot of work to do. But thank you for trying.

 

Actually the involvement of relativity in those cases is still explicit, but its values are all poles/zeroes. So t time equals tau time, mass equals rest mass, and length equals rest length.

 

This seems an obvious place to define a zero frame: it's motionless. Here's the problem: there's nothing to make it motionless relative to. So this both works (your local frame to the observed object) but also doesn't work (what's "moving" mean?). Are we OK so far?

Edited April 6, 2014 by Schneibster

[Janus]

Here is how i figure Relativity.

 

You are observing and measuring a planet somewhere completely contracted.

You send an astronaut aboard a vessel to go there and check.

As the astronaut approaches, he observes (and measures) the planet less and less contracted.

When arriving on the spot, the astronaut observes and measures the planet perfectly round.

 

The question is: was the planet flat, skewed and round, really?

Or was it round all the time long?

 

IOW, is our Earth a flat disk, really, because some E.T. far away is observing us?

That is how I understand Relativity.

I say that you can only measure "true" length, mass and time from the same FOR of the object. Once you insert distance (as a comoving FOR), Speed Of Light will be involved and the machinery of Relativity will be at work, I guess.

 

You'll have a lot of work to do. But thank you for trying.

It's more like this: You look at an object and see a circle. Someone else looks at it and sees an oval. Which is the "true" shape? Both and neither. You are looking at an oblate spheroid from different directions. Each of you are seeing a difference silhouette of the same object. The same is true with "reality". We can only directly experience "silhouettes" of the "reality" of Space-time, and inertial frames at different velocities are privy to different silhouettes. No one silhouette has precedence in terms of being "true" over any other.

[michel123456]

It's more like this: You look at an object and see a circle. Someone else looks at it and sees an oval. Which is the "true" shape? Both and neither. You are looking at an oblate spheroid from different directions. Each of you are seeing a difference silhouette of the same object. The same is true with "reality". We can only directly experience "silhouettes" of the "reality" of Space-time, and inertial frames at different velocities are privy to different silhouettes. No one silhouette has precedence in terms of being "true" over any other.

 

So you concede it is all about observation, don't you?

 

Actually the involvement of relativity in those cases is still explicit, but its values are all poles/zeroes. So t time equals tau time, mass equals rest mass, and length equals rest length.

 

This seems an obvious place to define a zero frame: it's motionless. Here's the problem: there's nothing to make it motionless relative to. So this both works (your local frame to the observed object) but also doesn't work (what's "moving" mean?). Are we OK so far?

 

 

 

 

I don't know why you say that it doesn't work. It works (admitting distances are small- but then again absolute distance come in play). I agree (with Swansont) that it doesn't help much. You need some other tool to explain other kind of observations.

Let's say I am ok so far.

[Schneibster]

Define motion.

 

If you do your interpretation will fail.

[Strange]

IOW, is our Earth a flat disk, really, because some E.T. far away is observing us?

 

It is in their frame of reference (1) but not in ours.

 

(1) Interestingly, it will still look round in theirs, but that could be described as an illusion.

 

So you concede it is all about observation, don't you?

 

Maybe the problem is what you mean by "reality". We can only know about anything by observation. Therefore what we observe is reality.

[Schneibster]

Strange, do you have any answer for my question in post 77?

[Strange]

Strange, do you have any answer for my question in post 77?

 

What question was that? There is only a question for michel123456 in post #77

[Schneibster]

 

Mmmm, not quite sure that's entirely correct. Technically proper time is the time between two events measured on a clock that passes through the locations of the two events as each one happens. So not all inertial frames can measure proper time.

 

 

What question was that? There is only a question for michel123456 in post #77

 

Well, it was implicit, but I indicated that your use of "proper time" appeared incorrect. If I'm right it invalidates your argument. Could you please explain this apparent discrepancy, or ask questions if you're not sure what it is?

 

[Strange]

 

Well, it was implicit, but I indicated that your use of "proper time" appeared incorrect. If I'm right it invalidates your argument. Could you please explain this apparent discrepancy, or ask questions if you're not sure what it is?

 

 

I'm not sure there is a discrepancy. Proper time is the the time measured by a clock (between two events); i.e. the time that elapses for that clock. If that isn't what I said then it is what I meant.

 

I assume that by "So not all inertial frames can measure proper time" you mean that a clock measuring (its own) proper time may not (always) be in an inertial frame. That is true. (But I thought we were discussing inertial frames.)

Edited April 6, 2014 by Strange

[Schneibster]

In the interest of absolute accuracy I will point out that the clock passes through both events as they occur.

 

This means there is no definition of "proper time" between events that are outside one anothers' light cones.

 

Are we on the same page? I'm very careful in relativity discussions it's so hard to go astray.

[Strange]

This means there is no definition of "proper time" between events that are outside one anothers' light cones.

 

Isn't this implicit in the fact it is measured by a single clock?

 

 

Are we on the same page?

 

I think so.

[Schneibster]

 

Isn't this implicit in the fact it is measured by a single clock?

 

 

Yes. Both events must exist in its light cone.

 

I'm sure we're on the same page.

michel could you please define motion?

Edited April 7, 2014 by Schneibster

[Lizzie L]

 

Separated causal events must have the proper order

 

 

Could you explain what you mean by this?

 

 

Alice can see event 1 happen before event 2 while Bob sees 2 before 1, and there's no way for one ordering to be called real while the other is called an illusion.

 

And I'm not arguing otherwise. What I'm saying is that if Alice assumes (on the basis of misleading evidence) that B caused A, she will report B as preceding A, even though a more objective measure gives A as preceding B. That IS an "illusion" brought about by an erroneous assumption of causality, just as the moon looks bigger at the horizon than the zenith because of an erroneous assumption of distance (although, ironically, less erroneous than the assumption that makes the zenith moon look smaller!)

[swansont]

 

 

Could you explain what you mean by this?

 

 

 

If A actually causes B, the A will precede B in all frames.

[Lizzie L]

 

 

If A actually causes B, the A will precede B in all frames.

 

So causality actually defines an absolute temporal order?

[swansont]

 

So causality actually defines an absolute temporal order?

 

Yes, because of the limiting speed of c, there's no way for the events to appear out of order.

[Lizzie L]

 

Yes, because of the limiting speed of c, there's no way for the events to appear out of order.

 

Out of causal order, presumably.

 

But non-causally related events can be witnessed in different temporal orders, right?

[swansont]

 

Out of causal order, presumably.

 

But non-causally related events can be witnessed in different temporal orders, right?

 

Yes, that's possible.

[Lizzie L]

So that suggests that c is the upper speed limit for information transfer?

[xyzt]

 

So causality actually defines an absolute temporal order?

Correct,

 

Causally linked effects are measured to be in the same order in all frames of reference.

Space-like separated effects may or may not be causally linked so they can be measured in contradicting orders in different frames of reference. I gave a rigorous mathematical explanation at the beginning of the thread.

Edited April 7, 2014 by xyzt