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Author Topic: Does length contraction actually exist?  (Read 18223 times)

Offline jeffreyH

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Does length contraction actually exist?
« on: 14/10/2014 22:38:46 »
If it does how do we prove it? Any frame we occupy will not show it.


 

Offline lightarrow

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Re: Does length contraction actually exist?
« Reply #1 on: 15/10/2014 00:44:53 »
Lenght contraction is measurable so it exists.

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Offline PmbPhy

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Re: Does length contraction actually exist?
« Reply #2 on: 15/10/2014 02:22:43 »
If it does how do we prove it? Any frame we occupy will not show it.
Length contraction is used to derive many things in applied physics which are borne out by experiment which means that we have confirmation that it's valid.
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #3 on: 16/10/2014 00:42:46 »
If it does how do we prove it? Any frame we occupy will not show it.
Length contraction is used to derive many things in applied physics which are borne out by experiment which means that we have confirmation that it's valid.

Thanks Pete. I thought that would be the answer.
 

Offline PmbPhy

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Re: Does length contraction actually exist?
« Reply #4 on: 16/10/2014 03:09:01 »
Quote from: lightarrow
Lenght contraction is measurable ...
In what sense do you say that it's measureable? Just because something can be measured it doesn't mean that it has been measured. Do you know of any experiments in which length contraction was measured other than in the sense that I said it was?
 

Offline lightarrow

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Re: Does length contraction actually exist?
« Reply #5 on: 16/10/2014 18:55:38 »
Quote from: lightarrow
Lenght contraction is measurable ...
In what sense do you say that it's measureable? Just because something can be measured it doesn't mean that it has been measured. Do you know of any experiments in which length contraction was measured other than in the sense that I said it was?
I intended "indirect measurement".
As an example, look at post # 13 in this thread:
https://www.physicsforums.com/threads/evidence-for-length-contraction.6842/

 ;)

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Offline PmbPhy

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Re: Does length contraction actually exist?
« Reply #6 on: 16/10/2014 20:17:58 »
Quote from: lightarrow
Lenght contraction is measurable ...
In what sense do you say that it's measureable? Just because something can be measured it doesn't mean that it has been measured. Do you know of any experiments in which length contraction was measured other than in the sense that I said it was?
I intended "indirect measurement".
As an example, look at post # 13 in this thread:
https://www.physicsforums.com/threads/evidence-for-length-contraction.6842/

 ;)

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It appears that they say that there is no direct evidence only indirect evidence, which is in essence what I said.
 

Offline Bill S

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Re: Does length contraction actually exist?
« Reply #7 on: 16/10/2014 23:40:48 »
 

Offline yor_on

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Re: Does length contraction actually exist?
« Reply #8 on: 17/10/2014 17:32:45 »
Yeah, is was pretty good before it got rigid. Then again, it's still good but not as open to thoughts as it once was. The 'muon' is a nice example of the complementary idea of time dilations, relative length contractions, frame dependent. What one need to gain there is the realization of it being both 'frame dependent' and as real as can be, from a local measurement.
 

Offline PmbPhy

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Re: Does length contraction actually exist?
« Reply #9 on: 18/10/2014 08:37:05 »
"https://www.physicsforums.com/threads/evidence-for-length-contraction.6842/"

Ah! The "good old days" of PF.   :(

That forum got filled up with nasty people and people get banned at the drop of a hat. The prohibit people who don't think like the do too. E.g. I was banned for explaining what relativistic mass was when people asked why E = mc2 fails to work with photons which have "zero mass" even though relativist mass is used in the domain of mainstream physics.
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #10 on: 18/10/2014 22:03:56 »
"https://www.physicsforums.com/threads/evidence-for-length-contraction.6842/"

Ah! The "good old days" of PF.   :(

That forum got filled up with nasty people and people get banned at the drop of a hat. The prohibit people who don't think like the do too. E.g. I was banned for explaining what relativistic mass was when people asked why E = mc2 fails to work with photons which have "zero mass" even though relativist mass is used in the domain of mainstream physics.

Hi Pete do you have a page on the relativistic mass of the photon? I will be looking into that soon.
 

Offline PmbPhy

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Re: Does length contraction actually exist?
« Reply #11 on: 18/10/2014 22:36:15 »
Quote from: jeffreyH
Hi Pete do you have a page on the relativistic mass of the photon? I will be looking into that soon.
You betcha buddy! The one I myself wrote is at:

http://home.comcast.net/~peter.m.brown/sr/inertial_mass.htm

Scroll down to the section entitled Mass of a Luxon since a photon is a luxon where a luxon is a particle whose proper mass is zero.

Here are some examples from modern relativity textbooks for those who claim that this is non-mainstream physics:

http://home.comcast.net/~peter.m.brown/ref/relativistic_mass.htm
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #12 on: 28/10/2014 00:04:34 »
I am now very uncertain about length contraction. There certainly is an effect but is much less pronounced that time dilation. It is proving to be a difficulty and it won't go away. Which annoys me. It would be much easier without it.
 

Offline lightarrow

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Re: Does length contraction actually exist?
« Reply #13 on: 28/10/2014 18:12:03 »
If it does how do we prove it? Any frame we occupy will not show it.
Not even time dilation, not even twin paradox, no relativistic effect, if you consider one frame only.

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Offline lightarrow

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Re: Does length contraction actually exist?
« Reply #14 on: 28/10/2014 18:15:58 »
I am now very uncertain about length contraction. There certainly is an effect but is much less pronounced that time dilation. It is proving to be a difficulty and it won't go away. Which annoys me. It would be much easier without it.
It would be much easier even if it would be F = m*v instead of F = m*a, or if the gravitational force between two masses would be F = m1+m2, or if Maxwell's equations were E = q (electric charge); B = j (electric current),
...
...

but it's not.

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Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #15 on: 28/10/2014 19:57:42 »
I am now very uncertain about length contraction. There certainly is an effect but is much less pronounced that time dilation. It is proving to be a difficulty and it won't go away. Which annoys me. It would be much easier without it.
It would be much easier even if it would be F = m*v instead of F = m*a, or if the gravitational force between two masses would be F = m1+m2, or if Maxwell's equations were E = q (electric charge); B = j (electric current),
...
...

but it's not.

--
lightarrow

I have no problem with any of the above but length contraction is odd. It can be thought of much like a recursive function.
 

Offline lightarrow

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Re: Does length contraction actually exist?
« Reply #16 on: 29/10/2014 12:57:40 »
I have no problem with any of the above but length contraction is odd. It can be thought of much like a recursive function.
You mean in numerical analysis? You can identify what is negligible (if there is); if B is negligible respect to A, you write the equation using the rate B/A. If, for example, an electron's energy E in an accelerator is much greater than its invariant mass m, you write the equation E2 = (c*p)2 + (mc2)2 in this way:

1 = (c*p/E)2 + (m*c2/E)2

c*p/E = sqrt[1 - (m*c2/E)2]

p = γ*m*v:

γ = (E/m*v*c) * sqrt[1 - (m*c2/E)2].

Now, if (m*c2/E)2 << 1:

γ ≈ (E/m*v*c) * [1 - (m*c2/E)2]

or, if you prefer, writing x instead of (m*c2/E)2 and β instead of v/c:

γ ≈ (1/β*x) * (1 - x2) ≈ (1/β*x) → (since γ2 = 1/(1-β2) ) → γ ≈ 1/x.


Have no idea if all this could have been useful for you, however.

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« Last Edit: 29/10/2014 13:10:14 by lightarrow »
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #17 on: 29/10/2014 20:34:33 »
I have no problem with any of the above but length contraction is odd. It can be thought of much like a recursive function.
You mean in numerical analysis? You can identify what is negligible (if there is); if B is negligible respect to A, you write the equation using the rate B/A. If, for example, an electron's energy E in an accelerator is much greater than its invariant mass m, you write the equation E2 = (c*p)2 + (mc2)2 in this way:

1 = (c*p/E)2 + (m*c2/E)2

c*p/E = sqrt[1 - (m*c2/E)2]

p = γ*m*v:

γ = (E/m*v*c) * sqrt[1 - (m*c2/E)2].

Now, if (m*c2/E)2 << 1:

γ ≈ (E/m*v*c) * [1 - (m*c2/E)2]

or, if you prefer, writing x instead of (m*c2/E)2 and β instead of v/c:

γ ≈ (1/β*x) * (1 - x2) ≈ (1/β*x) → (since γ2 = 1/(1-β2) ) → γ ≈ 1/x.


Have no idea if all this could have been useful for you, however.

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Unless I am mistaken, in the case of time dilation sqrt[1 - (m*c^2/E)^2] becomes imaginary. That is just at first glance. Thanks for this it is gratefully  received and is food for thought.
 

Offline phyti39

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Re: Does length contraction actually exist?
« Reply #18 on: 30/10/2014 19:21:20 »
I am now very uncertain about length contraction. There certainly is an effect but is much less pronounced that time dilation. It is proving to be a difficulty and it won't go away. Which annoys me. It would be much easier without it.
It would be much easier even if it would be F = m*v instead of F = m*a, or if the gravitational force between two masses would be F = m1+m2, or if Maxwell's equations were E = q (electric charge); B = j (electric current),
...
...

but it's not.

--
lightarrow

I have no problem with any of the above but length contraction is odd. It can be thought of much like a recursive function.
When you heat a metal object, its length changes since it is not rigid. Chemistry shows objects to be composed of discrete elements bound by em forces. It shouldn't be surprising then, that in a dynamic universe, with a constant propagation speed for light, em fields are deformable when moving.
Suggested research: "Oliver Heaviside".
Here is why lc is necessary.
https://app.box.com/s/qpoj20wqwt55hjfkl8x6 [nofollow]
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #19 on: 30/10/2014 23:00:36 »
I am now very uncertain about length contraction. There certainly is an effect but is much less pronounced that time dilation. It is proving to be a difficulty and it won't go away. Which annoys me. It would be much easier without it.
It would be much easier even if it would be F = m*v instead of F = m*a, or if the gravitational force between two masses would be F = m1+m2, or if Maxwell's equations were E = q (electric charge); B = j (electric current),
...
...

but it's not.

--
lightarrow

I have no problem with any of the above but length contraction is odd. It can be thought of much like a recursive function.
When you heat a metal object, its length changes since it is not rigid. Chemistry shows objects to be composed of discrete elements bound by em forces. It shouldn't be surprising then, that in a dynamic universe, with a constant propagation speed for light, em fields are deformable when moving.
Suggested research: "Oliver Heaviside".
Here is why lc is necessary.
https://app.box.com/s/qpoj20wqwt55hjfkl8x6

Well you make several interesting points. One of which is the deformation of heated metal. It might seem a trivial point but particles are released through heating and solidify when cooling. It is the input of energy that separates them. When energy is lost due to loss of energy through cooling things solidify. Things are thus brought together through energy loss. If the em forces bring things of lower energy together then it is reasonable to propose that gravitation may operate in a similar way. By taking energy from an amount of distributed energetic mass it naturally brings them together. This could be the force of gravity removing enough energy for the em forces to be able to bring masses together. So in fact gravity's action may not be the attractive force at all. It is merely a catalyst.
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #20 on: 30/10/2014 23:13:25 »
I think I need to go and derive a mass equation.
 

Offline NUFOIB

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Re: Does length contraction actually exist?
« Reply #21 on: 01/11/2014 11:25:49 »
An easy way to understand length contraction, is to first think about reality itself.

Picture yourself having no education within the field of physics at all. However, you are interested in the concept of motion. And so if you then bother to independently analyze the idea of absolute motion that takes place within an absolute 4 dimensional environment known as Space-Time, this eventually leads you to Special Relativity and the derivation of all of its mathematical equations. Anyone can figure it out on their own, if they simply bother to try. This ever so simple analysis of motion, provides you with a full understanding of length contraction, time dilation, velocity addition, and Lorentz transformations.

A casual presentation of this analysis of motion, which starts from scratch, and its outcome, can be found at
list=PL3zkZRUI2IyBFAowlUivFbeBh-Mq7HdoQ
« Last Edit: 01/11/2014 11:27:34 by NUFOIB »
 

Offline phyti39

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Re: Does length contraction actually exist?
« Reply #22 on: 02/11/2014 18:26:11 »
I think I need to go and derive a mass equation.
The cycle time for a photon exchange over a distance d at rest is d/c=t.
The cycle time for a photon exchange over a distance d moving is d'/c=t'= γt (time dilation).
The em force f = Q/d^2.
The effective distance d'= γd.
The effective force f' = Q/(γd)^2 = f/γ^2 < f.
Since f' is equal in x and p (any perpendicular) direction, and the acceleration is in x, this allows compression in x.
Td and lc both result from extended spatial paths for photons, which results from object motion.
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #23 on: 02/11/2014 20:00:28 »
I think I need to go and derive a mass equation.
The cycle time for a photon exchange over a distance d at rest is d/c=t.
The cycle time for a photon exchange over a distance d moving is d'/c=t'= γt (time dilation).
The em force f = Q/d^2.
The effective distance d'= γd.
The effective force f' = Q/(γd)^2 = f/γ^2 < f.
Since f' is equal in x and p (any perpendicular) direction, and the acceleration is in x, this allows compression in x.
Td and lc both result from extended spatial paths for photons, which results from object motion.

What about motion through a gravitational field? This takes account of velocity or acceleration without regard to a gravitational field external to the moving mass.
 

Offline jeffreyH

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Re: Does length contraction actually exist?
« Reply #24 on: 02/11/2014 20:24:28 »
Consider two indistinguishable black holes of equal mass, spin and other properties. Now consider two observers at equal distances from each black hole. The time dilation should be equal. So then information transmitted from one to the other should indicate no time dilation of one observer with respect to the other. Remove one of the black holes and the situation changes radically. The photons are obviously slowed by the gravitational fields of the black holes so time dilation will decrease in the intervening space between the black holes. Therefore the velocity of the light will increase and slow again on its journey. Can we square this situation with length contraction? Or does space remain unaffected with only a change in mass density, energy flux and time.
« Last Edit: 02/11/2014 20:26:41 by jeffreyH »
 

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Re: Does length contraction actually exist?
« Reply #24 on: 02/11/2014 20:24:28 »

 

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