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### Author Topic: What is a Lorentz contraction?  (Read 12194 times)

#### yor_on

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##### What is a Lorentz contraction?
« on: 14/02/2011 05:20:01 »

"You're making an issue of something that can be seen in everyday life.

Someone in a car driving past you will say they waved to you at (x1',y1', z1', t1') and crashed at (x1',y1', z1', t2') using their space and time coordinates, whereas you claim these events occured at (x1, y1, z1, t1 = t1') and (x2, y2, z2, t2 = t2') in your frame.

Can you see the difference?

There is a difference in the space interval you both measure between these two events, and so you could view it as a space contraction of some sort. Special relativity takes it a stage further with the introduction of a time contraction between events, between different frames."
==

Do you agree to this answer, or is there something you would like to add to it, or subtract, or, well?

In one way this make perfect sense. In another it makes me look at everything with new suspicion :) Also it, to me naturally, lifts up the question of 'speed' and how to define one?

Are we all Lorentz contracted?
If so, are we then differently Lorentz contracted as defined from different speeds?
Simultaneously, with it all being a real effect?

And who/what defines the speed?
Does the universe have a gold standard for 'motion' or not?
It seem to need it for this to be true? And if so, where and, can we use it?

Or am I just bicycling in the great younder :)

#### simplified

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##### What is a Lorentz contraction?
« Reply #1 on: 14/02/2011 18:24:22 »
If Einstein was right,then let's see your very fast travel to Sun.We see your reduced length and travel.However you do not see your travel.You see only contraction of distance from Earth until Sun until length of your body.
Length of your body = distance from Earth until Sun

#### yor_on

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##### What is a Lorentz contraction?
« Reply #2 on: 14/02/2011 19:11:39 »
Yes, and it works too :) The only thing I want to understand, and I guess you too :) is how it 'works'. We have too much evidence for it working to ignore it. and any real 'time dilation/Lorentz contraction won't be seen until you speed up like a muon. And at those speed the hard radiation should punch holes in any ship. For me it's the question of how to see the universe and my place in it that makes me pursue this question. Pompous to a fault, huh :)

Anyway, as I think of it now it seems to me that we're constantly Lorentz contracted, as well as time dilated :) Okay, saying that we are constantly 'time dilated' might seem a little to much, but if we consider a 'time dilation' as something that takes place between frames of reference, then we should be doing it :). That we won't be able to confirm that 'dilation', as we could with the twin experiment, doesn't change the facts. What you might want to argue is that as most everything in our universe is moving uniformly it isn't before 'something' accelerates this 'time dilation' takes place. But as far as I understand uniformly moving frames are 'time dilated' too and so, as soon they are moving relative us, there have to be a theoretic 'time dilation' taking place.
==

My reasoning builds on me looking at it as a relation. In the twin experiment none of the twins at any time will find their own 'time arrow' to differ, which to me makes it a relation. Any relation is defined by needing at least two components that are in 'communication' if you like. The rest becoming a question about how you define 'communication'. Me, I do it by assuming that all objects 'communicate' distance and size being no hindrance to that, just as I assume gravity to be 'everywhere'. The thing defining a meaningful communication to us is light-speed, as expected in 'gravity waves' and lights 'propagation'. To the universe I'm not sure, I can't speak for that one, but we have entanglements and tunneling proved, and used, by nature.
==

If you understand it differently I would like to know how you see it.

And as a Lorentz contraction is one thing that only seems to express itself at those other 'frames of reference' you observe we definitely should have a awful lot of different 'contractions' taking place simultaneously from any of those frames 'observing' us.  You might want to argue that this is only a 'conceptual idea' and that in 'reality' there are no such thing as what I describe, but then again, that argument I as easily can use too, and about the exact same. Proving time dilations and Lorentz contractions by comparing 'frames of reference'. and that's the only way proving one that I know?

Does this mean that I doubt those two? Nope, it just mean I don't see how it works, and using math doesn't help me here. If you have a final definition why I only should consider them at some times, and not at other I'm all ears, well, eyes at least :)

The question I come back to in all of this is how 'real' they are. We definitely expect a time dilation to be real, how about the Lorentz contraction? I expect it to be real too. But where exactly does this 'reality' exist? Only in the eye of the beholder? What is a mirage then, if this is 'real'?
==

To affirm a 'time dilation' only when leaving the same place of origin, and only proved as when arriving back at that same origin, is to me just a way of conceptualize something that should happen between all frames of reference. To assume otherwise makes 'time dilation' a magic thing, only applicable under certain circumstances, and also extremely 'local', if defined that way? Why would the universe only time dilate you relative your origin, and only when leaving the same, coming back? That doesn't make sense to me?
===

So how do we define it. In the muon example the time dilation is what we as observers will see, whilst from the pilot seat of the muon no time dilation takes place, only a Lorentz contraction. As you can see you need both effects to make sense of it, looked at this way. The Lorentz contraction because of that, from your frame of reference as the 'muon pilot', your own 'time' can't differ. And that's perfectly logical as long as we define the time dilation as taking place 'everywhere' you can be in that moving frame, relative the Earth. Then you won't notice it, but you will notice the Lorentz contraction doing the same work as the 'time dilation' will do for the Earthly observers.
« Last Edit: 14/02/2011 22:22:36 by yor_on »

#### simplified

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##### What is a Lorentz contraction?
« Reply #3 on: 14/02/2011 19:39:55 »
Illusion is not science.If we see your length contraction,then you see our lengthening.

#### yor_on

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##### What is a Lorentz contraction?
« Reply #4 on: 14/02/2011 19:52:17 »
You are thinking of two uniformly moving objects meeting right? And that they both are expected to see the other ones clock going slower and their ship being 'Lorentz contracted'?
==

Using that we should expect that if placing two clocks, one on Earth and one in our 'muon ship' we both would see the others clock go slower than ours. But here we have defined one of the frames as 'inertial' when we make that example, namely Earth. But I agree, in any uniformly moving frame relative any other uniformly moving frame, it seems to me that it is up to you to define who is moving and who is 'inertial' relative who. As long as the universe doesn't have a gold standard for defining who is moving relative who. If we would find such a gold standard though? What would it tell us, that all objects move relative each other? Can you see how murky such a argument becomes if used?
==

There is one more argument you can make to differ it, that the 'muon ship' is accelerating relative Earth as it 'falls'. That one I find suspicious as I see it as the 'muon ship' following a geodesic, and looked at that way there is no difference between it falling to a planet or 'falling' in deep space. In fact Einstein himself defined gravity's potential to exist even when not measurable, which some didn't like at all. But I like that way of looking at it, as I see gravity as something permeating all there is.

"...what characterizes the existence of a gravitational field from the empirical standpoint is the non-vanishing of the  G^1ik, not the non-vanishing of the [curvature].  If one does not think intuitively in such a way, one cannot grasp why something like a curvature should have anything at all to do with gravitation.  In any case, no reasonable person would have hit upon such a thing.  The key for the understanding of the equality of inertial and gravitational mass is missing."

And

"as Einstein later recalled, the thought occurred to him while writing this paper that a person in gravitational free-fall doesn’t feel their own weight. It’s as if the gravitational field does not exist. This is remarkably similar to Galileo’s realization (three centuries earlier) that, for a person in uniform motion, it is as if the motion does not exist. Interestingly, Galileo is also closely associated with the fact that a (homogeneous) gravitational field can be “transformed away” by a state of motion, because he was among the first to explicitly recognize the equality of inertial and gravitational mass. As a consequence of this equality, the free-fall path of a small test particle in a gravitational field is independent of the particle's composition. If we consider two coordinate systems S1 and S2, the first accelerating (in empty space) at a rate g in the x direction, and the second at rest in a homogeneous gravitational field that imparts to all objects an acceleration of –g in the x direction, then Einstein observed that

…as far as we know, the physical laws with respect to the S1 system do not differ from those with respect to the S2 system… we shall therefore assume the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system...

This was the beginning of Einstein’s search for an extension of the principle of relativity to arbitrary coordinate systems, and for a satisfactory relativistic theory of gravity, a search which ultimately led him to reject special relativity as a suitable framework in which to formulate the most fundamental physical laws."

"Here's the modern physicist's list (again, not sweating the fine points):

Spacetime Structure;  Spacetime is a 4-dimensional riemannian manifold.  If you want to study it with coordinates, you may use any smooth set of local coordinate systems (also called "charts").  (This free choice is what has become of the General Principle of Relativity.)

Principle of Equivalence; The metric of spacetime induces a Minkowski metric on the tangent spaces.  In other words, to a first-order approximation, a small patch of spacetime looks like a small patch of Minkowski spacetime.  Freely falling bodies follow geodesics.

Gravitation = Curvature

A gravitational field due to matter exhibits itself as curvature in spacetime.  In other words, once we subtract off the first-order effects by using a freely falling frame of reference, the remaining second-order effects betray the presence of a true gravitational field.

The third feature finds its precise mathematical expression in the Einstein field equations.  This feature looms so large in the final formulation of GR that most physicists reserve the term "gravitational field" for the fields produced by matter.

The phrases "flat portion of spacetime", and "spacetime without gravitational fields" are synonymous in modern parlance.  "SR" and "flat spacetime" are also synonymous, or nearly so; one can quibble over whether flat spacetime with a non-trivial topology (for example, cylindrical spacetime) counts as SR.  Incidentally, the modern usage appeared quite early.  Eddington's book The Mathematical Theory of Relativity (1922) defines Special Relativity as the theory of flat spacetime.

So modern usage demotes the uniform "gravitational" field back to its old status as a pseudo-field.  And the hallmark of a truly GR problem (i.e. not SR) is that spacetime is not flat.  By contrast, the free choice of charts---the modern form of the General Principle of Relativity---doesn't pack much of a punch.  You can use curvilinear coordinates in flat spacetime.  (If you use polar coordinates in plane geometry, you certainly have not suddenly departed the kingdom of Euclid.)"

I find Einsteins picture easier to relate too.
« Last Edit: 14/02/2011 21:35:28 by yor_on »

#### yor_on

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##### What is a Lorentz contraction?
« Reply #5 on: 14/02/2011 22:03:41 »
In fact I didn't know this when I started to wonder about gravity, neither did I realize that modern physics treat gravity as a 'localized' phenomena. To me gravity has to be everywhere, in some weird way it's 'space' to me. And one simple reason for treating it that way is Inertia. If you want to treat it as a local effect you will need to free inertia from gravity, alternatively expect it to be non-existent in 'a flat portion of SpaceTime' without any measurable gravity. Or you do as Einstein.
« Last Edit: 14/02/2011 22:08:55 by yor_on »

#### simplified

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##### What is a Lorentz contraction?
« Reply #6 on: 15/02/2011 16:58:14 »
Excuse me ,dear! If you are very fast traveler relatively of Earth and Sun,then you are traveling in gravitation field of solar system.Gravitation field of solar system slows down your time.Your gravitation field does not slow down time of Earth and Sun,because it is tiny.

#### bardman

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##### What is a Lorentz contraction?
« Reply #7 on: 15/02/2011 18:57:51 »
And who/what defines the speed?
Does the universe have a gold standard for 'motion' or not?

There is no "standard" for motion, observers define speed. It is only possible to define relative motion. That is, you must choose an origin and describe the motion relative to it. The origin can be moving with respect to another origin, that is how Lorentz formulas work. One of the fundamental principles for our universe is that there is no preferred perspective, all laws of physics hold in inertial frames. (Inertial frames are non-accelerating) Thus, a speed is different for every observer and each speed is equally acceptable if the point of view is taken into account.

Illusion is not science.If we see your length contraction,then you see our lengthening.

This is not true at all. Two frames moving with respect to each other experience a length contraction and a time dilation of the others frame. Suppose you were in the first frame, you would see the length contracted for the other frame because it is moving at v. Now, if you are in the other frame, the first frame is traveling at -v, where the minus sign only indicates direction. The direction is irrelevant and thus you also see a contraction of the other frame.

#### yor_on

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##### What is a Lorentz contraction?
« Reply #8 on: 15/02/2011 22:55:33 »
Yes Bardman, that's how we define it. But do the universe do so too? When I think of a universe with 'motion' I can't help presuming a principle defining it. It might be 'relative motion' that does it, and if so I feel both length contraction and time dilation being real phenomena, with our whole idea of 'fixed or not fixed distances' becoming a sort of cosmic joke being put upon us.

And if that is true then light being a static phenomena, although a constant 'c' to us, also becomes possible to me, and that puts me in a very weird universe, does it not?

The other way to see it is that motion have a 'gold standard', although none that we can measure directly. In that case we introduce a way of defining who is moving relative who for the universe, although not necessarily for us. You might view it as a question of ' how do a universe 'expand' ' too, if you like. I do :)
==

You might also look at it this way. If there is no 'zero movement' unless defined relative something else, then all uniform motion is a true 'zero motion', unless defined relative something else. And so all uniform motion should be exempt from time dilation and Lorentz contraction, unless you can prove it to 'move' by comparing. And in a black box scenario you can't. That will then mean that as soon as you stop accelerating the universe's 'skewed room time geometry' will instantly become the one you see from any inertial 'unmoving' frame, aka Earth.

You still have the possibility of 'skewing' it by invariant mass of course, but not by 'potential/momentum/relative' mass as I see that as non-existent in any uniformly moving 'frame of reference', until 'interacting' like colliding. All uniformly moving objects has an infinite amount of potential 'relative mass/momentum', simultaneously. Same as 'potential energy' do, as defined by invariant mass and the interaction they create, when colliding for example.

Am I right?

If you accept this statement you will need to accept that 'speed' also becomes a meaningless attribute for uniform motion, as it does not exist in our black box, no matter if we, when observing, find something to change 'position' relative us. The only time you will be able to define a speed will then be relative a non-uniform, non-constant, acceleration. That as all constant acceleration then is equivalent to a 'gravity', which then in our black box will mean that you can't differ it from a heavenly object (planet:).
« Last Edit: 16/02/2011 01:27:11 by yor_on »

#### yor_on

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##### What is a Lorentz contraction?
« Reply #9 on: 16/02/2011 00:32:57 »
So which of those two ways are truest?
Both I would say. To me it's a question of 'relations'. Without any relations speed does not exist, and the black box scenario is one where there exist no outside relation that you can 'use'. So does it mean that speed exist if alone in a universe? That question seems meaningless as it assume something existing there, if that is so you have already introduced 'distance' and to observe it you've introduced 'times arrow'. Those two combined will give you the possibility of speed, even though that there is nothing to compare it against. So does that mean that 'speed' exist by itself? Well, as I don't think such a universe is possible to make sense from I find it difficult to imagine.

The really interesting question to me is why we never find our 'measurements' to change, no matter our 'speed' or 'mass'. The universe may 'contract' but our measurements and durations stay the same.

#### yor_on

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##### What is a Lorentz contraction?
« Reply #10 on: 16/02/2011 16:34:32 »
Does this make it easier to understand though? I have to agree with Sim there, it doesn't. Myself I think and expect that it should be no difference between a uniform motion and a acceleration, I've made arguments for that elsewhere here on TNS. But for arguments sake, let's assume that it actually matter if it's a acceleration or not. What would it make time? A 'field' that when 'compressed' slows the 'compressed' travelers time? And a Lorentz contraction would then include? A whole universe? But only mine??

Mine universe?
What about 'yours' then? As I 'compressed' mine, actually compressing my whole universe, but yours never noticed? And what would it make of three 'travelers' 'compressing' their universe's relative each other?

What kind of existence does that make?
==

Add to that, that in this case it will only be an acceleration that can do it. If I use the arguments presented above. That really would make 'speed' a very weird thing, wouldn't it? And an 'acceleration' even weirder as we would have two kinds, the constant and the non-constant. Speed as such can't have a meaning except 'locally' inside the same ''inertial' frame of reference' if so? Earth I was thinking of there :)
==

And to that you can add that I'm not sure where/if cut offs for 'frames of reference' are? Where do I draw the line? And how? We say that Earth is a inertial frame of reference, don't we? What about the molecules, atoms? They may all 'speed away' at the approximate same 'speed' as our Earth, and solar system, and galaxy etc. but they do have 'speeds' of their own too, don't they? Shouldn't that make them into 'frames of reference' too? it becomes a very 'flowing' concept to me, all depending on where I define my 'system'.
« Last Edit: 16/02/2011 17:14:16 by yor_on »

#### yor_on

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##### What is a Lorentz contraction?
« Reply #11 on: 16/02/2011 17:24:08 »
One simple solution is to redefine the idea of 'speed' so that it works. To do that you need to redefine what a distance is, or time, or both. We don't really know what this universe is, we thought we did, and up to Einstein it all made 'sort of sense', as from our Earth-bound perspective. But with Einstein came a revolution in the way we saw light and time. And with it 'time dilation' and 'Lorentz contraction'. So those days we live in a 'split reality', one in where we although accepting Einsteins ideas still cling to what we know from our own history on Earth, using descriptions we know to be true, like speed and distance. And we still try to make them fit those new ideas.
==

So what is uniquely unchanging in your new universe?
Your own 'frame of reference' I would say.
Does that include mine too?

Well, let's test it. If I make the same experiment as you in a constantly accelerating frame having a same 'gravitational potential' (Earth), will I observe the same as you? How about all uniformly moving frames? If I do, is that a proof for our individual 'frames of reference' originally being the same? Or is it so that we all should be defined different 'frames of reference' individually, but get them 'equalized' by joining this 'greater' frame of reference, as we might consider Earth for this question?
==

Do you find it a philosophical question only. Then I guess your point of view is that by defining a 'system' you lift up a 'part of reality' for inspection, and by using different 'cut offs' you create different 'systems', all valid from your 'systems' point of view. Looked at that way string theory has to be real, and loop quantum theory, as well as any other system that will give you a consistent and mathematically valid view. The problem with that reasoning that you can have several 'systems' simultaneously, inconsistent when compared, but valid in themselves.

« Last Edit: 16/02/2011 17:41:50 by yor_on »

#### simplified

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##### What is a Lorentz contraction?
« Reply #12 on: 16/02/2011 19:18:13 »
Does this make it easier to understand though? I have to agree with Sim there, it doesn't. Myself I think and expect that it should be no difference between a uniform motion and a acceleration, I've made arguments for that elsewhere here on TNS. But for arguments sake, let's assume that it actually matter if it's a acceleration or not. What would it make time? A 'field' that when 'compressed' slows the 'compressed' travelers time? And a Lorentz contraction would then include? A whole universe? But only mine??

Mine universe?
What about 'yours' then? As I 'compressed' mine, actually compressing my whole universe, but yours never noticed? And what would it make of three 'travelers' 'compressing' their universe's relative each other?

What kind of existence does that make?
==

Add to that, that in this case it will only be an acceleration that can do it. If I use the arguments presented above. That really would make 'speed' a very weird thing, wouldn't it? And an 'acceleration' even weirder as we would have two kinds, the constant and the non-constant. Speed as such can't have a meaning except 'locally' inside the same ''inertial' frame of reference' if so? Earth I was thinking of there :)
==

And to that you can add that I'm not sure where/if cut offs for 'frames of reference' are? Where do I draw the line? And how? We say that Earth is a inertial frame of reference, don't we? What about the molecules, atoms? They may all 'speed away' at the approximate same 'speed' as our Earth, and solar system, and galaxy etc. but they do have 'speeds' of their own too, don't they? Shouldn't that make them into 'frames of reference' too? it becomes a very 'flowing' concept to me, all depending on where I define my 'system'.
That is right. Motionless gravitation field does not slow my time if I stand without motion on Earth.And such field does not exist.Because electrons and kernels of atoms create moving gravitation field relatively of me.It slows my time.

#### simplified

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##### What is a Lorentz contraction?
« Reply #13 on: 16/02/2011 19:33:35 »

[/quote]

This is not true at all. Two frames moving with respect to each other experience a length contraction and a time dilation of the others frame. Suppose you were in the first frame, you would see the length contracted for the other frame because it is moving at v. Now, if you are in the other frame, the first frame is traveling at -v, where the minus sign only indicates direction. The direction is irrelevant and thus you also see a contraction of the other frame.
[/quote]I don't need Einstein's truth.I need my benefit.

#### yor_on

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##### What is a Lorentz contraction?
« Reply #14 on: 16/02/2011 20:46:30 »
Yes Sim, you want to define it from invariant mass, right? Or do you include motion? If we look at  the muons? they must be time dilated, and if you define it from their mass only, that mass is all to small without including motion. Also you will need an explanation why nobody ever notices their own personal time 'slowing down', as it then will be the only effect existing, if I got you right. That is, if you find the Lorentz contraction to strange to be possible?

On the other hand, shouldn't we all be 'time dilated' constantly, relative all other 'frames of reference'? If we should, where is the Lorentz contractions? Against that one might argue, as I did before, that it's only a acceleration that creates it? possibly also that in the twin experiment neither twin notice any time dilation, and only the moving twin noticing the Lorentz contraction. but then we come to the question of how 'time' differ between uniformly moving frames, knowing who should age slower? If we argue time dilation only from acceleration, surely there have to be some few objects in SpaceTime accelerating as I write, and as I understand 'frames of reference' this should 'influence' us, although we won't notice it.

Or am I wrong in looking at it as a relation between frames? Should I define it as something (a relation) only existing in its own 'frame' moving? That we then find the twins age differ is not a result of a relation between those frames, but two different relations versus motion and/or invariant mass inside each frame of reference? and with the universe using no 'gold standard' for it other than what happens inside them, frame by frame? That actually makes a certain sense.

I think I'll use that one.

It make sense in that we do seem to have a unique 'unchanging' relation to SpaceTime, from our own perspective. We have our expiration date set, sort of :) no matter where we spend our 'time'. but then the universe uses some guidelines that it has to keep count off it seems, if I stop looking at it as relations between frames. But I still like the idea :)

==

I like this definition as it gives gravity its full importance. But it will need 'constants' defined for it to work. If I ignore invariant mass (for the moment:) and assume that gravity exist everywhere, then maybe that could be one? And then I will use invariant mass for defining 'gravity's potential' but not 'gravity' per se.

He :)

I do like it, it's a weird weird idea, and I'm partial to those :)

===

If you look at it from that point of view there is no need for the universe to differ between uniformly moving frames as each frame defines itself, in its relation to gravity and motion. The problem still being motion or 'speed'? But with each frame defining it there will be needed a constant. And we have it already, the speed of light in a vacuum. I like this one better and better. Probably my downfall waits just around the corner, but, so far so good :)

===

There is one big thing that needs to be explained though, and that is how it all 'binds together' into a seamless universe, including us all as we observe each other, still being unique for each one of us. But that one needs to explained in my older version of 'frames of reference' too. It's one of the weirdest things I know in fact. That we all find it the universe so seamless, when it infact seem to consist only of 'fragmented frames of reference' from the microscopic to the macroscopic, and all flowing into each other, creating 'reality'.
« Last Edit: 16/02/2011 21:40:30 by yor_on »

#### bardman

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##### What is a Lorentz contraction?
« Reply #15 on: 17/02/2011 19:09:33 »
On the other hand, shouldn't we all be 'time dilated' constantly, relative all other 'frames of reference'? If we should, where is the Lorentz contractions? Against that one might argue, as I did before, that it's only a acceleration that creates it? possibly also that in the twin experiment neither twin notice any time dilation, and only the moving twin noticing the Lorentz contraction. but then we come to the question of how 'time' differ between uniformly moving frames, knowing who should age slower?

If we have two relatively moving frames (constant and one being 0 or not), then as I understand it, the time is always being dilated for both and both are being length contracted. Here is what I understand of the twin paradox.

If you end up with two equally aged people moving relative to each other, accelerating to the relative motion is a problem but suppose we ended up with equally aged people with motion relative each other, and they both die at the same age (their life is the same amount of time in their respective frames of reference after the position and time coordinates are synced) Each will have appeared to died after the other in the frame they are in. To a person who also synced up the time and position of the twins and had them moving at equal speed in opposite directions relative to that person, they appeared to die simultaneously, but after the time they did in their frames.

The problem with saying who actually aged more is that relative to each other, they both aged more and the only way to compare clocks is at the proper time, which means you read the clocks at the same point in space. This is impossible unless they turn (or one person turns) around and come back. Then acceleration takes effect. This destroys the formulas for constant motion. When the clocks are brought back to the same point in space, the times read the same and so the twins must have died at the same time.

#### bardman

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##### What is a Lorentz contraction?
« Reply #16 on: 17/02/2011 19:21:24 »
If you look at it from that point of view there is no need for the universe to differ between uniformly moving frames as each frame defines itself, in its relation to gravity and motion. The problem still being motion or 'speed'? But with each frame defining it there will be needed a constant. And we have it already, the speed of light in a vacuum. I like this one better and better.

The Lorentz transformations were first developed to explain the fact that light moves constantly in a vacuum no matter the frame of motion. It couldn't be disproved no matter how hard they tried. Einstein later used it in special relativity. So yes, the constant of motion in all frames is light we use that as a standard.

Personally, the calculations are there, so for me light is the only necessary constant of motion. I don't need a standstill frame if I can just convert all other frames into my space-time coordinates.

#### yor_on

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##### What is a Lorentz contraction?
« Reply #17 on: 17/02/2011 19:41:08 »
Quite pleased to meet you Bardman :)

And yes, you're right. And that's troubling me, sort of :). The description you give actually define each 'frame of reference' as unique. But, let us now look at those frames.

1. where is the 'smallest' defined 'frame of reference' you can imagine?

I don't know, but, as I think of it, its limit should be above Planck size. It's not a planet, it's not a car moving relative a man. 'Frames' can be used all the way down to atoms as I see it. And to me they all will be 'time dilated' and 'Lorentz contracted' relative each other. In a way they are very similar to the idea of a 'system', and you have no limits there, except possibly Planck.

2. Your definition seems to put all 'time dilation' on acceleration? Or am I reading you wrong?

If we assume that, then it seems to me that all Lorentz contraction should disappear in a uniform motion. So then your 'speed' won't contract your SpaceTime, as long as you don't assume Doppler to be a contraction too? If you do, are there any experiments testing that idea?

3. As I read you you support my view of all frames getting time dilated relative each other, even in a definition of that happening only in a acceleration? If we now assume that we share this SpaceTime, which we seem to be doing :) then comes the question of 'time'. One explanation is that 'time' is an illusion, defined through some sort of entropy.

Against that you can point out that all 'frames', when 'joined', seems to become the exact same, which to me seems to hang on two definitions. And here's a funny part, it's not 'acceleration', but 'motion' that seems to define it? And invariant mass (stress/tension of space). If 'entropy' adapts this way, what does that say? That we have a 'same entropy'? That can't be right if we look at the twin experiment, or can it?

I could presume that there is a 'gold standard' for 'entropy', as defined from your measurements inside your own frame of reference, as well as defined by the way anyone sharing that same 'frame of reference' will be able to do the exact same experiment, getting the same exact results. and the best 'thing' about such a definition is that it actually seems valid for all kind of motion, accelerating or not, as well as for any other definition for how gravity can come to be, as invariant mass.

I have some more argument but I need to wake up first :)
« Last Edit: 17/02/2011 19:42:47 by yor_on »

#### yor_on

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##### What is a Lorentz contraction?
« Reply #18 on: 17/02/2011 20:03:29 »
And it's the fact that we have two contra dictionary statements that made me think of it as defined by relations inside those unique frames. It makes it easier for me to define what a time dilation is.

It's not something defined between 'frames', and we do not need to give it some unique name like 'entropy' if we use my idea. It will just be a 'same' arrow of time, defined as a 'gold standard' in each 'frame of reference' you make.

That it will differ, as when we look at the twin experiment, just confirm SpaceTimes game rules. But it will still, as proved by you joining my frame, be the exact same 'frame of reference' for us both.

But when we try to join those frames, that's when I find the problem. But, that problem exist any which way you look at SpaceTime. You will always need a explanation how 'disjoint frames of reference' can give you this 'whole seamless SpaceTime'. And that one is described by 'c' always being 'c' as I think of it. That's also the limit of 'meaningful communication' as we know it, also defined by the way each frame will be unique, although 'the same' when we 'join up'.
« Last Edit: 17/02/2011 20:08:03 by yor_on »

#### yor_on

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##### What is a Lorentz contraction?
« Reply #19 on: 17/02/2011 21:27:08 »
Inside each frame there is one thing we can change as I see it, loosely defining a frame as for example the rocket you might be riding, or Earth. We can 'expend energy' transforming one state to another. And that's it, whatever you do is 'expending energy'.

So, discussing relativity, the only thing I know you can manipulate is this 'energy'. And the 'energy' you find will be the direct result of the interactions made. Those interaction can either be seen as 'something' manipulating on a object like 'forces', or as 'relations', then also defining that object. Even though this sounds like I might imagine everything being a illusion, I do not.

I'm just trying to find a description that will work with what we observe. And there 'relations' allows for a greater span of effects than what defining it as 'objects' does. That way I can define a 'spin' as a relation, a super positioned electron will also be the result of your observation of relations. But then we come to the way it 'join up' into matter, if we from a QM perspective could be described as the result of 'relations', how can we be 'solids'? To make that jump I'm lending from Chaos theory and their 'emergences'. Also it has to do with 'time' I believe. the 'arrow' we see have a relation to our macroscopic reality, Einstein called it SpaceTime, meaning that you should not expect it to be 'split' into 'quantum's'. QM does just that, although accepting Einsteins Relativity they try to prove that it all is 'quantum's', and a lot of it seems to make sense. Now you can choose either one, or both, but if you choose both you need a explanation for how one 'flows' into the other. And that I will define as 'emergences'. also I think 'constants' is what defines 'SpaceTime' and that they, just like Plank scale, exist 'on their own', as observed from inside our SpaceTime. I'm not sure we ever will be able to know what's outside 'SpaceTime'. We don't live there, we're in here, trying to look out. But I'm sure that the more 'constants' we succeed to find the better we will define where 'here' is.

Pompous to a fault  :)

#### yor_on

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##### What is a Lorentz contraction?
« Reply #20 on: 17/02/2011 22:32:46 »
To see it my way we need to use the constants. One is lights speed in a vacuum, the other , possibly, gravity as being something existing on its own, permeating' SpaceTime. A constant is not defined by any relations, although it will have a connection to all relations you will find, expressing itself through them. To me they seem like 'borders' for SpaceTime, telling us where its 'limits' are. and if gravity and light are two 'limits' then all frames will 'interact' through and inside those. This is just an idea I have, no theory although I like it :)
==

Then what we see as a 'time dilation' will be whatever frame we are in, relative any other 'frame of reference', as defined by your frames relations to light and gravity. In a way you might look at those as the canvas upon which SpaceTime paints, but as they are a part of what becomes us, we are a part of that canvas too. and now I'm sounding like a mystic..

Da*n.
« Last Edit: 18/02/2011 00:51:30 by yor_on »

#### bardman

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##### What is a Lorentz contraction?
« Reply #21 on: 18/02/2011 02:49:46 »
The feeling is mutual, yor_on.

I need to examine what you are saying more thoroughly before I decide what parts I agree with but there are couple of statements I would like to address before I delve in deeper.

1. where is the 'smallest' defined 'frame of reference' you can imagine?

As I understand it, frames of reference are all infinitely big. The concept of frame of reference is a space-time 4-coordinate system that extends through the whole of space-time. If you are talking about what size scale is the smallest in which the rules apply, I think that it applies on the quantum level and is useful up until uncertainty takes over.

2. Your definition seems to put all 'time dilation' on acceleration? Or am I reading you wrong?

If we assume that, then it seems to me that all Lorentz contraction should disappear in a uniform motion. So then your 'speed' won't contract your SpaceTime, as long as you don't assume Doppler to be a contraction too? If you do, are there any experiments testing that idea?

I may have misspoken at some point or not made myself clear enough but I did not mean to put dilation or contraction on acceleration.

Suppose you have the origin of two frames of reference moving relative to each other at a constant rate (think of two axes passing each other) and at the point the origins meet, you reset your two clocks from what they are to zero. Then you may start measuring distances and time intervals, observing the contraction and dilation respectively. This is how the Lorentz transforms are set up. You never need introduce acceleration to produce the effect, and in fact lose the effect (unless proper adjustments are made, but this is complicated) if either frame accelerates.

Thus, you don't lose length contractions in uniform motion, they only appear there. Thus, the combined contraction of space and stretching of time leaves velocity untouched (which is the whole point of Lorentz).

I thought more about it and doppler is not a contraction. Doppler is the idea that where a wave is propagating from is changing, thus each peak of the wave is either closer or farther away from where the last one was, making the frequency appear different than the source is emitting. Think of a light moving away and emitting each photon of light at a point farther away than the last, thus the wavelength appears to be longer than it is.

I have never heard of time defined as a type of entropy, but I will continue to read through this. My perception of time was always a fourth, abstract axis on which our "time-momentum" carries us in the direction which entropy is increased, as well as other time related properties of space hold. I have dealt with some aspects of time-reversal in particle physics. But, I'm not sure about how to actually go about the actual physical performance of this.

Against that you can point out that all 'frames', when 'joined', seems to become the exact same, which to me seems to hang on two definitions. And here's a funny part, it's not 'acceleration', but 'motion' that seems to define it? And invariant mass (stress/tension of space).

All frames, when joined in one rest frame together, are only exactly the same if the space and time coordinates were defined in the following way:
All the frames were together at rest and the space and time coordinates were chosen to be the same.

Then, you could take those frames, accelerate them in some directions move them around at constant velocity, decelerate them, bring them back and line their origins up at rest. At this point, all the measurements are synced once again. However, while those frames were moving (accelerating or not) the measurements were not synced up properly.

This syncing of moving frames can only be accomplished if previously moving frames sync up their measurements at some point in time and space. Then, while they continue to move as they were, they continue to have comparable spacetime coordinates.

As far as invariant mass goes, all I know is that the rest mass is invariant in all inertial frames (nonaccelerating). So, I guess this too can be a standard for all motion, but I don't know it's usefulness other than to determine total mass in a frame.

Let me read some more and get back to you.

#### bardman

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##### What is a Lorentz contraction?
« Reply #22 on: 18/02/2011 03:36:58 »
And it's the fact that we have two contra dictionary statements that made me think of it as defined by relations inside those unique frames. It makes it easier for me to define ...

I'm going to take this whole comment at once. First, hopefully I've removed the contradiction. If not, present it to me again. As for the definition of time dilation, let me try and take a crack at it.

Time dilation is the effect of a moving frame (if we consider the other to be a rest frame for our two frame system, Also remember that the frames extend through all space and time, they are just like moving axes. If you have dealt with Lin Alg, then the frames are two different basis for the same vector space, thus they are just different measurements of the same thing). Dilation corrections account for discrepancies in measurements due to motion. This is necessary for the the movement away an event (which changes when the observed light or other signal can reach the observer). If you examine the ladder paradox, this becomes more clear. A person running (relativistically) with a ladder longer than a barn appears to a stationary observer to be completely in the barn at one point in time (even though the ladder won't fit and the runner doesn't see this odd effect) the reason is that the light from the ladder leaving the barn does not arrive until after the light from the ladder finishing entering the barn arrives (because the light moves finitely and is on the same order of magnitude as the velocity of the runner). This is a result of time dilation and the phenomenon is called length contraction (they are a pair). If the proper corrections are made, the time dilation is removed and the order of the events fixes itself. The ladder is then realized to protruded from the barn before the whole thing was inside. However, time dilation would cause an observer to say otherwise.

Also, so I am absolutely clear; you can sync up coordinates of moving frames in order to properly observe Lorentz transforms and when you bring them to rest together, those coordinates will no longer be in sync. It is necessary to maintain inertia for the frames to properly measure coordinates. Also, if you sync moving frames, let them move for a while, then bring them back in the other direction, and then set up the original velocities, the values will sync up again at the same point in space you synced them originally.

As far as seamlessness of space goes, I see no issue. Time dilation and length contraction (it never gets enough recognition) were the corrections Lorentz made in order to explain why a relativistically moving object reports time and space coordinates for an event that is seemingly incorrect.
If you forget these corrections, picture a star exploding and someone on earth observes it, as well as someone in a rocket moving away from earth. The rocket reports the time of the explosion and the point in space incorrectly according to the person on earth. This is because the light reaches the rocket at a different time and point in space, which is only measurable at relativistic speeds. Then, we realize we must correct for this change in coordinates of space and time, that is why we dilate time and contract space.

In essence, time and space do not change in the frames of motion, our ability to interpret them does.

Lets me see if there is anything else to cover.

#### yor_on

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##### What is a Lorentz contraction?
« Reply #23 on: 18/02/2011 03:51:07 »

All frames, when joined in one rest frame together, are only exactly the same if the space and time coordinates were defined in the following way:
All the frames were together at rest and the space and time coordinates were chosen to be the same.

Then, you could take those frames, accelerate them in some directions move them around at constant velocity, decelerate them, bring them back and line their origins up at rest. At this point, all the measurements are synced once again. However, while those frames were moving (accelerating or not) the measurements were not synced up properly.

This syncing of moving frames can only be accomplished if previously moving frames sync up their measurements at some point in time and space. Then, while they continue to move as they were, they continue to have comparable spacetime coordinates.

Hm :)
Enjoyed reading you. Imagine a constantly accelerating rocket. If I now happen to get that 'absolutely synced' to another rocket, could I then say that they share the same frame of reference. One might want to argue that they can't be the exact same invariant mass, but we can still imagine a point where both from the perspective of stressing 'SpaceTime' by motion/invariant mass will create the same effect 'time dilation/Lorentz contraction relative some arbitrarily chosen point of reference, like Earth. Or assume them to be identical in all aspects. Then that would place them in the exact same 'frame of reference' to me. do you agree?

And the same seem to work for all kind of acceleration. And if you accept the idea of combinations of 'invariant mass/motion' being able to create the same effects, including when in uniform motion, it to me seem like we already are 'synced up' into a whole lot of common 'frames of reference', most of them out of reach and knowledge, assuming a universe large enough :). To me it goes back to how to see the universe. Assuming that Lorentz contraction is real, from my perspective in that space-ship the universe actually have 'shrunk' proving that this 'frame of reference' actually is my own unique one, but then, we have those frames 'synced' to mine as outlined above? What would it make of Rindler observers, unknowingly sharing the same 'frame of reference'? Could I assume that they too could be defined as being at rest relative each other, sharing the 'exact same universe'?

If I trust in that all uniform motions can be defined as being 'at rest relative each other' no matter their speed, what would this situation make of it? Nothing, as long as we're talking about a 'black box scenario' I presume? But if they were observing our surroundings, would that make those 'shared frames of reference'  more 'real'? I don't know there, the easiest way out of that one is to assume that all uniform motion will share the same exact 'frame of reference' (black box) and this Rindler situation I was speculating about only will be valid for accelerations.
« Last Edit: 18/02/2011 03:52:58 by yor_on »

#### yor_on

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##### What is a Lorentz contraction?
« Reply #24 on: 18/02/2011 04:02:46 »
"A person running (relativistically) with a ladder longer than a barn appears to a stationary observer to be completely in the barn at one point in time (even though the ladder won't fit and the runner doesn't see this odd effect) the reason is that the light from the ladder leaving the barn does not arrive until after the light from the ladder finishing entering the barn arrives (because the light moves finitely and is on the same order of magnitude as the velocity of the runner). This is a result of time dilation and the phenomenon is called length contraction (they are a pair). If the proper corrections are made, the time dilation is removed and the order of the events fixes itself. The ladder is then realized to protruded from the barn before the whole thing was inside. However, time dilation would cause an observer to say otherwise."

Now, there is the crux for me :)

Either it is a illusion, then you must be right, or it is not a illusion, then there come to be a moment where the pole in fact, as defined from the stationary observer, is inside the barn without 'sticking out'. If the later is true my idea makes sense. With it only being geometrics, as described by light propagating described differently from two different positional systems in SpaceTime, the observer and then from the 'event' itself, I will have to change my reasoning. Myself I see it as there actually is a moment, from the stationary observer point of view, where the pole will 'fit' inside the barn. Not looking at it that way seem to make a Lorentz contraction into a illusionary event?
==

If I assume it would be a matter of geometrics, presented to us by light, then we would have to assume that the muon would be 'time dilated', from its own view as well as from our observer on Earth. that one becomes tricky as we then can't have two uniformly moving observers both observing the other clock ticking slower than its own, as I think of it?

Alternatively you might then want to blame it all on lights 'geometrics' assuming your arrow to be the illusion. But we have the example with two 'light clocks' placed 90 degrees to each other |_ they will not be synchronized from the far observers frame, but will from the observer 'at rest' relative them. And the reason that they still are able to have the same 'time dilation' is, as far as I remember, the vertical light clocks Lorentz contraction, correcting its photons 'distance' as it bounces.
==

What I mean by that is that if you assume a 'time dilation' to be real, as defined by the twin experiment' but assume a Lorentz contraction to be a 'geometric effect' due to lights unvarying propagation, as seen from and in all frames of reference, then there is only one effect left for the muon, or for anything under the influence of motion, relative some other frame of reference? And to then assume that this effect still would be non-existing inside his frame, maybe? It's a possibility. As I said I'm not sure of how to see that, but why would the universe bother with giving us two definitions for one thing?

If we use light clocks for defining a time dilation the assumption is that as seen from any moving frame, the clock will tick 'as always'. If using the argument that the 'photon' bounces through more 'space' the faster you move is correct, then that bouncing should be slowed down inside the moving frame too. As I said, it's a possibility, assuming everything ultimately being 'light', we too then could be assumed to 'jiggle' to the same drummer as our 'bouncing photon' does. That as we too are 'passing' that same 'stretch of space' in our motion :) But doing so, and still accepting an 'expansion' outside matter (galaxies), the reason that they don't expand being defined as them being of a higher gravity, seems to clash a little? Then, if that would be correct, you should expect yourself to 'expand' too, as soon as you leave the galaxy it seems?

As we then can't expect our body's invariant mass to present any problem for 'space' to permeate us, as both concepts discuss 'distance'? On the other hand, the light clock example is not perfect I think, even though it has to be near truth.

==

Maybe one can consider it conceptually, finding no definition of 'times arrow' in any positional system more true than any other? But to do so I first will have to invalidate the arrow that brought me to this point from where I consider the question it seems :) As I then are questioning my own arrow too? I can do that, but doing so there will be no time dilation, as I understand the concept, and no Lorentz contraction either. The twin experiment will then be purely illusionary, no matter the biological difference between our twins, which leaves me a even weirder universe :)

Alternatively look at it as a sliding system, but then you still will have to ask yourself why we don't notice our 'arrow of time' slowing down when in motion? That it doesn't either way you look at it points to there being a 'gold standard' it seems to me? Can you see what I mean? That even though using 'distance' as a argument for 'times arrow' slowing down your measurements will be the exact same inside your black box, except in a acceleration which should create a gravitational blue-shift as observed from the 'gravity well' (Aft wall of your black box relative its acceleration), watching 'in falling' light.
« Last Edit: 18/02/2011 05:31:15 by yor_on »

#### The Naked Scientists Forum

##### What is a Lorentz contraction?
« Reply #24 on: 18/02/2011 04:02:46 »