V

1 "joseph levy" |
Is Lorentz contraction a real process | vrijdag 10 september 2004 16:10 |

2 "Harry" |
Re: Is Lorentz contraction a real process | vrijdag 10 september 2004 17:27 |

3 "Tom Roberts" |
Re: Is Lorentz contraction a real process | zondag 12 september 2004 3:29 |

4 "Nicolaas Vroom" |
Re: Is Lorentz contraction a real process | dinsdag 12 oktober 2004 21:57 |

5 "Tom Roberts" |
Re: Is Lorentz contraction a real process | dinsdag 12 oktober 2004 22:38 |

6 "Nicolaas Vroom" |
Re: Is Lorentz contraction a real process | donderdag 14 oktober 2004 8:55 |

7 "Harry" |
Re: Is Lorentz contraction a real process | donderdag 14 oktober 2004 9:12 |

8 "John Anderson" |
Re: Is Lorentz contraction a real process | vrijdag 15 oktober 2004 4:29 |

9 "Harry" |
Re: Is Lorentz contraction a real process | vrijdag 15 oktober 2004 8:56 |

10 "Nicolaas Vroom" |
Re: Is Lorentz contraction a real process | vrijdag 15 oktober 2004 14:17 |

joseph levy"
I agree with you. Lorentz transformations are not general.
Assuming that they are universal generates a lot of paradoxes
such the one you mentioned, or the fact that the kinetic energy
needed to carry out a certain work appears to be frame depen-
dant, (that is, when you measure the energy needed to move
from one inertial frame S to another S' you get a different result
according to whether the measurement is made from frame S or
from any other inertial frame. This result is at variance with mass-
energy conservation).
Sincerely, Joseph Levy

>
Dear Eugene

The extended space-time I have derived allow to remove all the
paradoxes generated by SRT.

The new space-time theory is developed in my book, "From
Galileo to Lorentz and beyond" which has been reviewed by
Prof. Jean Pierre Vigier. Please consult the publisher's
web site, http://redshift.vif.com and my web site
http://levynewphysics.com

Hmm... Take for example "7- According to conventional relativity the contraction of moving bodies is observational and reciprocal, (which implies that there is no real contraction)."

What do you mean with "no real contraction", and your subsequent comment that real contraction implies "no reciprocity"? According to Lorentz and Poincare it's real in a certain sense (that of observer-independent nature) but reciprocal in another sense (that of observations).

Harald

Dear Harald

According to aether theories rod contraction is a real process depending
on the speed of the rod with respect to the aether frame.
Conversely, for relativity theory, there is no aether frame. the length of a
rod depends on its speed with respect to other inertial frames. Since there
is at the same time an infinite number of inertial frames moving with respect to
the rod, this one possesses at the same time an infinite number of lengths,
which is irrealistic.

One is therefore obliged to assume that according to relativity, length contraction
is only observational. It is not a real process.

According to aether theories a rod which moves from S to S'(for example)
contracts,
but if the rod returns to S it recovers its initial length.

According to relativity, viewed from S the rod in S' appears contracted, but
viewed from S' the rod in S appears contracted in the same ratio. This apparent
reciprocity does not exist in aether theories.

Best regards, Joseph

"joseph levy"

> |
joseph levy" |

> > |
Dear Eugene
I agree with you. Lorentz transformations are not general.
Assuming that they are universal generates a lot of paradoxes
such the one you mentioned, or the fact that the kinetic energy
needed to carry out a certain work appears to be frame depen-
dant, (that is, when you measure the energy needed to move
from one inertial frame S to another S' you get a different result
according to whether the measurement is made from frame S or
from any other inertial frame. This result is at variance with mass-
energy conservation). Sincerely, Joseph Levy |

> |
Hmm... Take for example "7- According to conventional relativity the contraction of moving bodies is observational and reciprocal, (which implies that there is no real contraction)." What do you mean with "no real contraction", and your subsequent comment that real contraction implies "no reciprocity"? According to Lorentz and Poincare it's real in a certain sense (that of observer-independent nature) but reciprocal in another sense (that of observations). Harald Dear Harald
According to aether theories rod contraction is a real process depending
on the speed of the rod with respect to the aether frame.
Conversely, for relativity theory, there is no aether frame. the length of a
rod depends on its speed with respect to other inertial frames. Since there
is at the same time an infinite number of inertial frames moving with
respect to
the rod, this one possesses at the same time an infinite number of lengths,
which is irrealistic. Best regards, Joseph |

Dear Joseph,

I still wonder how real and unreal these things are in the Einsteinian interpretation. I know that Feynman didn't care much about such issues, according to him what *appears* to be true for someone *is* true for that person... But here's the crucial thing about the Lorentzian interpretation which has no ambiguity:

According to Lorentz' theory a rod which moves relative to the ether contracts. Consequently, when a rod moves relative to a random observer frame S, we can't know if it is more *or less* contracted than when it was stationary in S. With that interpretation, reciprocity between two frames of observation S and S' is due to an unknown mixture of correct observation and distorted observation in each frame.

Of course, based on that interpretation it seems plausible that fast particles such as in accelerators are truly contracted, simply because we could suppose that the earth has a small speed relative to such an ether frame.

Harald

> | I still wonder how real and unreal these things are in the Einsteinian interpretation. |

In SR, no rod "contracts" in any way due to its velocity relative to any inertial frame; similarly no clock "dilates" in any way due to its velocity relative to any inertial frame. Just think about it -- since all inertial frames have equal standing, and there are an infinite number of them moving with different velocitites, how could a rod or clock possible "change" due to any such relative velocity?

In SR what changes is the relationship between the rod or clock and the various inertial frames. Measurements in each inertial frame, of course, depend on that relationship, and this leads to "length contraction" and "time dilation".

This is purely geometry in spacetime, and is PRECISELY what happens in Euclidean geometry -- consider the projection of a line segment's length onto the X axis of an X-Y coordinate system on the plane, and compare to the projection of the same line segment's length onto the X' axis of an X'-Y' coordinate system on the same plane, rotated relative to the first. The line segment did not "change", and yet its projection onto the different coordinate systems' X axis does change. In SR, in the X-T plane, the analog of rotation in that Euclidean plane is relative velocity; in the X-T plane, projection onto X is "length (distance interval)" and projection onto T is "time interval".

Tom Roberts tjroberts@lucent.com

"Tom Roberts"

> | Harry wrote: |

> > | I still wonder how real and unreal these things are in the Einsteinian interpretation. |

> |
In SR, no rod "contracts" in any way due to its velocity relative to any inertial frame; similarly no clock "dilates" in any way due to its velocity relative to any inertial frame. Just think about it -- since all inertial frames have equal standing, and there are an infinite number of them moving with different velocitites, how could a rod or clock possible "change" due to any such relative velocity? In SR what changes is the relationship between the rod or clock and the various inertial frames. Measurements in each inertial frame, of course, depend on that relationship, and this leads to "length contraction" and "time dilation". |

Starting point of any discussion if Lorentz contraction is real should be considering only one reference frame i.e. the rest frame of an observer at rest.

Before answering your question let us discuss what
happens if you put a clock in a space ship and your
space ship travels to the moon and returns.

When you compare the time on the moving clock
with a clock at rest you will see that your moving clock
runs behind (runs slower).

Is this a real effect ? IMO yes.

Is this a physical effect ? IMO yes.

That means the words real and physical are synonyms.
In short time dilation is a real, physical effect.

Now let us see if length contraction is. In order to do that you have to demonstrate length contraction in it most simple form without using clocks.

The easiest way is a demonstration like as discussed
in the book Introducing Einstein's Relativity as in fig 2.13
page 23, but simpler.

We only need one observer A at rest near the track
(under the train) at the centre between the two firing devices.
The firing device are such that both are on when the train
is at rest above the firing devices 1 and 2.

Suppose the strain starts from the left and moves to the right.
There is length contraction involved when observer A
first observes light from firing device 1 and then from device 2.

Accordingly to SR this should happen.

Is this a real effect ? IMO again yes

Is this a physical effect ? IMO again yes.

However there is one mayor problem: it is not possible to perform such an experiment which enough accuracy to demonstrate this. For more detail See the book: "Was Einstein right" by Clifford M. Will page 273.

The next step is to study time dilation and length
contraction simultaneous.

For example you can measure the length of a rod
in a rest frame using a clock at rest and you can perform
the same experiment in a moving inertial frame
with a moving rod and a moving clock.

Accordingly to SR the result should be the same.
i.e both length in both frames should be identical.

The problem ofcourse is that at low speeds this always
seems to work, so you are misleading yourself.

What you should do ofcourse is to measure both effects
independently and that is not possible.

However there are more problems.
In the above experiment the train moves in a straight
line and accordingly to SR there should be length
contraction.

The next question is what happens when the distance
of the train (distance between the firing devices) is
the same but the path is curved (is a circle).

Is there also length contraction ?
The answer is silence.

More problems: is there a difference in length
when you pull or push the train.

Again silence.
Part of the problem is that when there is no difference
than it means that length contraction operates
simultaneous on all parts of the train and this is physical
impossible.

For some people the answer is but your train should be rigid. The question is than what means rigid compared to a normal train.

As you see there are many problems.

IMO the answer on your question: "Is Lorentz contraction a real process" is in principle Yes in practice Undecided.

Nicolaas Vroom

http://users.pandora.be/nicvroom/

See also program 4: "length contraction - a visible illusion"

> |
Before answering your question let us discuss what
happens if you put a clock in a space ship and your
space ship travels to the moon and returns.
When you compare the time on the moving clock
with a clock at rest you will see that your moving clock
runs behind (runs slower). Is this a real effect ? IMO yes. Is this a physical effect ? IMO yes. That means the words real and physical are synonyms. In short time dilation is a real, physical effect. |

IOW: you use words far too loosely.

> | Now let us see if length contraction is. |

"Tom Roberts"

> | Nicolaas Vroom wrote: |

> > |
Before answering your question let us discuss what
happens if you put a clock in a space ship and your
space ship travels to the moon and returns.
When you compare the time on the moving clock
with a clock at rest you will see that your moving clock
runs behind (runs slower). Is this a real effect ? IMO yes. Is this a physical effect ? IMO yes. That means the words real and physical are synonyms. In short time dilation is a real, physical effect. |

> |
EXCEPT -- what you describe is not "time dilation", it is "different values of elapsed proper time over different paths through spacetime". The former is related to differences in tick rate between clocks, while the latter is a difference in the total number of ticks between a specified pair of events. The former cannot be considered "real" in any sensible way; the latter can be and usually is. IOW: you use words far too loosely. |

> > |
Now let us see if length contraction is. |

> |
If time dilation is not "real", then neither is length contraction. They are both instances of geometrical projection, not any kind of "real" phenomenon. |

"Introducing Einstein's Relativity" by Ray D'Inverno

Page 33 Chapter 3.3 Length Contraction:

"This (MMX) is rather different from the length contraction of special relativity, which is not regarded as illusory but is a very real effect.

Page 33 Chapter 3.4 Time dilation

"Thus moving clocks go slow by a factor 1/SQR(1-v*v/c*c) This Phenomenon is called time dilation. The fastes rate of a clock is in its rest frame and is called its proper rate. Again this effect has a reciprocal nature"

What is the purpose of science if the laws that they discover are not real, in the sense that they would not describe real physical phenomena ?

For someone who describes or better draws or paints not real objects please visit the home page of M.C. Escher http://www.mcescher.com/

Nicolaas Vroom

http://users.pandora.be/nicvroom

"Tom Roberts"

> | Nicolaas Vroom wrote: |

> > |
Before answering your question let us discuss what
happens if you put a clock in a space ship and your
space ship travels to the moon and returns.
When you compare the time on the moving clock
with a clock at rest you will see that your moving clock
runs behind (runs slower). Is this a real effect ? IMO yes. Is this a physical effect ? IMO yes. That means the words real and physical are synonyms. In short time dilation is a real, physical effect. |

> |
EXCEPT -- what you describe is not "time dilation", it is "different values of elapsed proper time over different paths through spacetime". The former is related to differences in tick rate between clocks, while the latter is a difference in the total number of ticks between a specified pair of events. The former cannot be considered "real" in any sensible way; the latter can be and usually is. IOW: you use words far too loosely. |

Indeed, he took a short-cut: likely he meant that from the reality of the difference in total ticks as measured in any inertial frame, he concludes that the therewith related time dilation also must be a real, physical effect. I conclude less loosely that time dilation involves a real, physical phenomenon - although the amount of time dilation itself can't be called real.

SNIP

> | Here's a simple "razor" to determine if a given effect can be considered to be "real" or not: if the quantity in question is not invariant over coordinate transforms then it cannot be considered to be "real" in any sensible way (coordinates are figments of human imaginations, and nothing "real" can depend on such figments). |

Exactly.

Harald

> |
"Tom Roberts" |

> > | Nicolaas Vroom wrote: |

> > > |
Before answering your question let us discuss what
happens if you put a clock in a space ship and your
space ship travels to the moon and returns.
When you compare the time on the moving clock
with a clock at rest you will see that your moving clock
runs behind (runs slower). Is this a real effect ? IMO yes. Is this a physical effect ? IMO yes. That means the words real and physical are synonyms. In short time dilation is a real, physical effect. |

> > |
EXCEPT -- what you describe is not "time dilation", it is "different values of elapsed proper time over different paths through spacetime". The former is related to differences in tick rate between clocks, while the latter is a difference in the total number of ticks between a specified pair of events. The former cannot be considered "real" in any sensible way; the latter can be and usually is. IOW: you use words far too loosely. |

> > > |
Now let us see if length contraction is. |

> > |
If time dilation is not "real", then neither is length contraction. They are both instances of geometrical projection, not any kind of "real" phenomenon. |

> |
"Introducing Einstein's Relativity" by Ray D'Inverno Page 33 Chapter 3.3 Length Contraction: "This (MMX) is rather different from the length contraction of special relativity, which is not regarded as illusory but is a very real effect. |

It depends what you mean by "real". Do different observers measure a different length for the same object? Yes.

Does the length of the object really change? According to SR, No. According to ether theory, Yes.

John Anderson

"John Anderson"

> | Nicolaas Vroom wrote: |

> > |
"Tom Roberts" |

> > > | Nicolaas Vroom wrote: |

> > > > | Before answering your question let us discuss what happens if you put a clock in a space ship and your space ship travels to the moon and returns. When you compare the time on the moving clock with a clock at rest you will see that your moving clock runs behind (runs slower). Is this a real effect ? IMO yes. Is this a physical effect ? IMO yes. That means the words real and physical are synonyms. In short time dilation is a real, physical effect. |

> > > |
IOW: you use words far too loosely. |

> > > > |
Now let us see if length contraction is. |

> > > |
If time dilation is not "real", then neither is length contraction. They are both instances of geometrical projection, not any kind of "real" phenomenon. |

> > |
"Introducing Einstein's Relativity" by Ray D'Inverno Page 33 Chapter 3.3 Length Contraction: "This (MMX) is rather different from the length contraction of special relativity, which is not regarded as illusory but is a very real effect. |

> |
It depends what you mean by "real". Do different observers measure a different length for the same object? Yes. Does the length of the object really change? According to SR, No. According to ether theory, Yes. John Anderson |

In reality ;-) it depends who you ask. A recent paper about this claims that according to SRT, it must be real (see my thread of 28/9): "the contraction is not "apparent" (due to the process of measuring length), but "real"." -Am. J. Phys. 72 (10) Oct. 2004, 1316-1324

Harald

> | Nicolaas Vroom wrote: |

> > |
"Introducing Einstein's Relativity" by Ray D'Inverno Page 33 Chapter 3.3 Length Contraction: |

> |
It depends what you mean by "real". Do different observers measure a different length for the same object? Yes. |

In my original reply dd 12/10/04 I explained an experiment
with only one observer based on the above mentioned
book by Ray d'Inverno page 23 with only one Observer and
without any clocks and under two conditions:

1) with the train at rest 2) with a moving train

The question is does the Observer (at the track, at rest,
at the centre of the lights) under the second condition
(with a moving train) see the lights simultaneous ?

IMO Accordingly to SR the answer is NO. That implies length contraction is a physical, real effect and using the words by Ray is not illusory.

> | Does the length of the object really change? According to SR, No. |

See http://users.pandora.be/nicvroom/length.htm

and select Example:
http://users.pandora.be/nicvroom/calc1.htm

> | According to ether theory, Yes. |

I will not give my opion regarding the ether theory.

Accordingly to Isaac Newton the answer on the above experiment should be Yes (No length contraction)

However there are many more interesting question than the above question i.e. question 1.

Does the Observer sees the light simultaneous

2) When the path of the track is bended ?
With observer at center of circle.

3) When you push the train (compared with 1)

4) When you pull the train (compared with 1)

And as a bonus question: Suppose the above question uses a normal rod. What are the answers on the same 4 questions when you use a rigid rod.

Nicolaas Vroom

http://users.pandora.be/nicvroom/

Created: 26 November 2004

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