Constancy of SOL from all objects

[Strange]

I don't care about the one YOU see. Exactly as I don't care about what the billions of other humans see at my wrist.

My clock does not change speed because an E.T. passed by the Earth and looked at it.

 

So if you only care about proper time (what you see) then it doesn't matter if there is 1 or 100 other observers.

So why say 2 is OK but 3 isn't.

[swansont]

Then why do some people here believe that time dilation and length contraction "truly" happen?

 

 

This is an issue of equivocation. "Truly" is being applied in an inconsistent manner in the two situations. You appear to be using it to mean there is one true reality, while others are using it to mean that time dilation and length contraction are not illusions; "reality" is frame-dependent.

I don't care about the one YOU see. Exactly as I don't care about what the billions of other humans see at my wrist.

 

Again, an issue of philosophy rather than physics.

My clock does not change speed because an E.T. passed by the Earth and looked at it.

 

But the issue is this: can you give a physics-based reason that your reading is the correct one?

[StringJunky]

 

....while others are using it to mean that time dilation and length contraction are not illusions; "reality" is frame-dependent.

It's not really much different to ten people spaced around a teapot describing the shape of it from their position. There's only one teapot but it has ten different shapes; which one's the 'true' shape?

[Strange]

It's not really much different to ten people spaced around a teapot describing the shape of it from their position. There's only one teapot but it has ten different shapes; which one's the 'true' shape?

 

That's not a bad analogy. The 2D image of the teapot seen by each observer is different. These could all be combined into a 3D model that is invariant.

 

Similarly, as Markus pointed out, we get different results when we just look at time or just space but when combined, the whole 4D model is invariant.

[Delta1212]

I have a tube 1 meter long with a set of very fast guillotines set up at both ends.

 

I have a stick that is 1.1 meters long.

 

I shoot the stick through the tube such that, in my rest frame, which is also the rest frame of the tube and the guillotines, the stick is length contracted to 0.9 meters.

 

In my rest frame, once the stick is fully inside the tube, I dropped the guillotines, which slice past the openings very, very quickly. In my frame, this does nothing to the stick because it is fully inside the tube. But according to you, the stick cannot actually be 0.9 meters because this is a distorted view of reality and not the real length of the stick, which is the length in its rest frame.

 

In the rest frame of the stick it is never fully inside the tube, but sees the guillotines falling at different times with the far one falling before it fully enters the tube and the rear one falling after it has already started to exit the tube.

 

But if length contraction and time dilation are distortions that do not represent the true reality and the measurement from the rest frame is the "real" one, then the guillotines falling at different times is a distortion, and in reality, they fell simultaneously as that is what happened in their own rest frame.

 

 

Which means that "in reality" a stick measuring 1.1 meters in length entered a tube 1 meter in length with blades at either end that fell at some point after the stick had started entering the tube but before the stick had fully left the tube and managed not to hit the stick despite the fact that the stick was never fully enclosed by the tube and the blades fell at the same time.

 

That is literally impossible if there is only one true reality to things represented by what they are like in an object's rest frame.

[StringJunky]

 

That's not a bad analogy. The 2D image of the teapot seen by each observer is different. These could all be combined into a 3D model that is invariant.

 

Similarly, as Markus pointed out, we get different results when we just look at time or just space but when combined, the whole 4D model is invariant.

Yes, that's a useful extension to the teapot analogy for me; The 3D image is invariant but the 2D isn't.

 

Markus actually put into that way of thinking a bit ago; I found it useful.

[Strange]

...

Bazinga.

 

 

I hope this isn't against the rules, but I am going to quote a post from another forum because I think it gets to a key point:

 

Perhaps we can take an analogy from everyday language. If someone asks "does the Sun really rise and set", the answer to that depends quite sensitively on the goals one has for the word "really". From our subjective perspective, the Sun really does rise and set, with quite significant ramifications for our lives. But when we consider more objectively constructed models, we could say the Sun does not really rise and set, instead the Earth really rotates. So which is it? It depends on our objectives when making the language choices we make. So what really matters is that we understand our own language.

http://cosmoquest.org/forum/showthread.php?161009-Is-Lorentz-Contraction-Real&p=2364615#post2364615

Edited July 29, 2016 by Strange

[Mordred]

Speaking of arguments from other forums. A few years ago I worked out using redshift. How to make a cow appear blue to an observer.

 

Did the cow really change color or did our measurement of said cow merely change?

 

Its a similar argument with the color of trees in the nearby observer sees green but a distant observer sees a shade of blue.

 

According to relativity both observers are correct.

 

To be honest and this may add unnecessary confusion. Its extremely difficult to be in precisely the same frame of reference as an object.

 

Take the wristwatch on your hand. One might think your eyes are in the same frame of reference as your hand. But your hand and eyes are in different gravitational potentials.

 

Yes the time dilation is extremely miniscule that we can safely ignore it but its still present.

Edited July 29, 2016 by Mordred

[Strange]

Take the wristwatch on your hand. One might think your eyes are in the same frame of reference as your hand. But your hand and eyes are in different gravitational potentials.

 

Yes the time dilation is extremely miniscule that we can safely ignore it but its still present.

 

Swansont might have something to say about that. I think we are getting to the point where people in his line of work can't ignore those differences!

[StringJunky]

 

Swansont might have something to say about that. I think we are getting to the point where people in his line of work can't ignore those differences!

IIRC I pointed not long ago to a clock experiment that proposed centimetre altitude accuracy and currently it's at 20-30cm I think Swansont mentioned at the time.

Edited July 29, 2016 by StringJunky

[Mordred]

 

Swansont might have something to say about that. I think we are getting to the point where people in his line of work can't ignore those differences!

He probably would. I would also imagine understanding his location influence is extremely important when he is calibrating atomic clocks.

[swansont]

IIRC I pointed not long ago to a clock experiment that proposed centimetre altitude accuracy and currently it's at 20-30cm I think Swansont mentioned at the time.

 

 

There were some frequency standards calibrated at the same height and then one moved to ~30 cm height difference at NIST, and they measured the frequency difference to reasonable precision in less than a day.

[StringJunky]

 

 

There were some frequency standards calibrated at the same height and then one moved to ~30 cm height difference at NIST, and they measured the frequency difference to reasonable precision in less than a day.

That is such precision ( 1/9th of a Kangaroo ) that it somewhat bemuses me why Michel so stubbornly refutes what relativity predicts; he's really got the blinkers on.

Edited July 29, 2016 by StringJunky

[michel123456]

I have no problem with anything you wrote above.

BUT tell me, when observer B that sees no hole in the donut will extend his arm and take the donut at hand, will he get a better information or not? Will he see the hole in the donut or not? Will the donut "truly" lack a hole?

That is the question.

Who will answer this question?

Speaking of arguments from other forums. A few years ago I worked out using redshift. How to make a cow appear blue to an observer.

 

Did the cow really change color or did our measurement of said cow merely change?

 

Its a similar argument with the color of trees in the nearby observer sees green but a distant observer sees a shade of blue.

 

According to relativity both observers are correct.

 

To be honest and this may add unnecessary confusion. Its extremely difficult to be in precisely the same frame of reference as an object.

 

Take the wristwatch on your hand. One might think your eyes are in the same frame of reference as your hand. But your hand and eyes are in different gravitational potentials.

 

Yes the time dilation is extremely miniscule that we can safely ignore it but its still present.

Same question: if the observer imports the cow into his own frame, will the cow be blue?

[Strange]

Who will answer this question?

 

 

The only question is: what do you mean by "truly"? That is the only point of contention here, the meanings of the words you use.

[Mordred]

Same question: if the observer imports the cow into his own frame, will the cow be blue?

What do you think? The answer should be obvious.

 

Have you never driven towards mountains?

 

Perhaps another question is have you ever seen a mountain with its trees suddenly turn blue because someone else farther away looked at it. Or a cow

Edited July 29, 2016 by Mordred

[StringJunky]

Michel

 

Thinking about your problem. Everything starts from axioms and the one you need to accept is that the act of measuring and its results, regardless of our preconceptions, is king in science.

[michel123456]

So nobody answered the question.

[imatfaal]

So nobody answered the question.

 

Surely we were talking about 2d representations of the donut or teapot - therefore you cannot reach out and check.

 

The 3d representation is invariant whereas the 2d depend on the angle of the viewer. Our simple measurements of length and time are analogous to the 2d representations, whereas the invariant space-time interval is analogous to the 3d.

 

To extend the metaphor perhaps too much - there is no hole in the middle of a picture of a donut. ceci n'est pas un pipe

[Markus Hanke]

So nobody answered the question.

 

 

I think you missed the point. If you change your orientation with respect to the donut, you will see it in a different way, just as I had written - you combine the information of your previous point of view with the information of your new point of view, and with the information about what kind of process you have performed to go from one frame to the other. If you do this many times from different angles and positions, you will be able to write down a general law that tells you how the properties of the object transform under changes of perspective. You will then notice that there are certain quantities that capture aspects of the object which remain the same no matter how you orient yourself - for example the metric on the 2D surface of the donut, or the spacetime separation between events on the donut before and after your change of perspective.

 

The issue is not one about "true reality", but rather about how you describe it. If you are in a 4D spacetime, you need to describe objects using tensors, and not in terms of 3D projections such as "space" and "time". If you project a 4D object onto a lower-dimensional boundary, you loose information, which is why observers disagree on individual measurements of space and time. If they were to describe the object in spacetime instead, then there are no longer any disagreements. It's like a cylinder inside a cube - project the cylinder onto the x-y plane, and you get a rectangle. Project the cylinder onto the x-z plane, and you get a circle. So who has got "the truth" ? The question doesn't make any sense, it is meaningless, because the projections capture only limited aspects of the original object. You need to combine them both to arrive back at the full 3D picture. The same is true in the real world - you can argue ad nauseam about "the truth" when it comes to how observers measure lengths and times, but these are just limited projections - you get the full picture only when you combine them both and look at spacetime instead.

 

It should be remarked however that these projections are still real - a cylinder really does look like a circle from one angle, and a rectangle from another. But there is no contradiction or mystery, because neither one captures all aspects of the original object; they are just limited projections of a higher-dimensional object.

In michel12345's defence, I think it should be noted also that it is quite natural to struggle with this concept. The human mind is intrinsically conditioned to see the world from a 3D Euclidean perspective, because that is how our world of everyday experience is structured. Going from there into a 4D world the geometry of which is not even Euclidean, takes quite a paradigm shift that can be difficult to "perform". I remember when I first learned about relativity, it took me a long time to develop an intuition of what it actually means to do a Lorentz transformation between frames, and I often came up against similar doubts as he expresses. This is one of those things that are just very difficult to understand until one day something "clicks", and you suddenly just "get" it. That experience isn't necessarily something that can be induced by words. This reminds me always of those black and white 2D pictures where you have to de-focus your eyes in certain ways, and suddenly you see it in 3D; this is the same thing, we need to learn to "de-focus" our mind away from 3D projections, and understand it in terms of spacetime instead. This takes effort and practice, though.

Edited July 30, 2016 by Markus Hanke

[michel123456]

Is the cow blue?

1. yes it is blue

2. no it is not blue

 

Please.

[Markus Hanke]

Is the cow blue?

1. yes it is blue

2. no it is not blue

 

Please.

 

 

The colour is not an intrinsic property of the cow, because it depends on the structure of your eyes, and also on how the brain processes that sensory input. The colour has no reality separate from your perception of it, just as space and time have no reality separate from how you measure it.

 

Let me ask you a question - that donut on the table, what does it "look like" in spacetime, instead of just space - if you "drag out" the object along some period of time ? Can you try to roughly picture it in your mind ? What would it be like ?

[michel123456]

 

 

I think you missed the point. If you change your orientation with respect to the donut, you will see it in a different way, just as I had written - you combine the information of your previous point of view with the information of your new point of view, and with the information about what kind of process you have performed to go from one frame to the other. If you do this many times from different angles and positions, you will be able to write down a general law that tells you how the properties of the object transform under changes of perspective. You will then notice that there are certain quantities that capture aspects of the object which remain the same no matter how you orient yourself - for example the metric on the 2D surface of the donut, or the spacetime separation between events on the donut before and after your change of perspective.

 

The issue is not one about "true reality", but rather about how you describe it. If you are in a 4D spacetime, you need to describe objects using tensors, and not in terms of 3D projections such as "space" and "time". If you project a 4D object onto a lower-dimensional boundary, you loose information, which is why observers disagree on individual measurements of space and time. If they were to describe the object in spacetime instead, then there are no longer any disagreements. It's like a cylinder inside a cube - project the cylinder onto the x-y plane, and you get a rectangle. Project the cylinder onto the x-z plane, and you get a circle. So who has got "the truth" ? The question doesn't make any sense, it is meaningless, because the projections capture only limited aspects of the original object. You need to combine them both to arrive back at the full 3D picture. The same is true in the real world - you can argue ad nauseam about "the truth" when it comes to how observers measure lengths and times, but these are just limited projections - you get the full picture only when you combine them both and look at spacetime instead.

 

It should be remarked however that these projections are still real - a cylinder really does look like a circle from one angle, and a rectangle from another. But there is no contradiction or mystery, because neither one captures all aspects of the original object; they are just limited projections of a higher-dimensional object.

In michel12345's defence, I think it should be noted also that it is quite natural to struggle with this concept. The human mind is intrinsically conditioned to see the world from a 3D Euclidean perspective, because that is how our world of everyday experience is structured. Going from there into a 4D world the geometry of which is not even Euclidean, takes quite a paradigm shift that can be difficult to "perform". I remember when I first learned about relativity, it took me a long time to develop an intuition of what it actually means to do a Lorentz transformation between frames, and I often came up against similar doubts as he expresses. This is one of those things that are just very difficult to understand until one day something "clicks", and you suddenly just "get" it. That experience isn't necessarily something that can be induced by words. This reminds me always of those black and white 2D pictures where you have to de-focus your eyes in certain ways, and suddenly you see it in 3D; this is the same thing, we need to learn to "de-focus" our mind away from 3D projections, and understand it in terms of spacetime instead. This takes effort and practice, though.

 

It would be so easy for me to stop here and say oh yes you are right.

But NO. Nothing in the equations of Relativity says anything like what we are measuring is "really' happening. It is an interpretation that some clever academics have provide as if reality was mystical. It is taking something simple and making it unnecessarily complicated.

You were never a dumb student that could not figure out and suddenly "understood" with a click in your brain. You just became accustomed to the concepts that were put in your brain with the help of academic hammer. Please open your mind again. You have been contaminated .

[ajb]

The colour is not an intrinsic property of the cow...

Okay, but one can ask about the wavelength of the light reflected from the cow... and then like just about everything we have to ask 'as measured by who?'

[michel123456]

 

 

The colour is not an intrinsic property of the cow, because it depends on the structure of your eyes, and also on how the brain processes that sensory input. The colour has no reality separate from your perception of it, just as space and time have no reality separate from how you measure it.

 

Let me ask you a question - that donut on the table, what does it "look like" in spacetime, instead of just space - if you "drag out" the object along some period of time ? Can you try to roughly picture it in your mind ? What would it be like ?

You didn't answer again.

i see you master the technique to answer a question with a question.