A rod that continuously lengthens and shortens without deforming or
breaking is elastic.
If it were rigid, it could not help but warp or break.
In my animation
https://www.geogebra.org/m/mqejqtkj
the traveling twin rotates the rod AB.
In the terrestrial reference, that rod lengthens and shortens
continuously.
And it's a *rigid* auction.
Since no rigid rod can stretch and contract with impunity (without
bending or breaking), evidently those stretches and contractions are apparent.
Or is there another explanation?
And as always, don't forget the difference between *calculating Lorentz objects* and *looking at Doppler/Einstein objects*.
You should moreover keep in mind (which obviously you don't) that the length contracted object is described by events (at its inner and outer extremities) that are simultaneous in the observing (moving) system, but that are not simultaneous in the rotating rod's (or wheel's) own system!
[[Mod. note -- Yes, there is another explanation: "rigid" only applies
in the rod's own inertial reference frame. Observers in other inertial reference frames may (will) observe non-ridity, but that's an artifact
of their motion and doesn't affect the rod.
wugi il 03/09/2023 09:21:35 ha scritto:
And as always, don't forget the difference between *calculating Lorentz
objects* and *looking at Doppler/Einstein objects*.
I really want to talk about *calculating Lorentz objects* and,
therefore, let's leave aside what is seen (or not seen).
You should moreover keep in mind (which obviously you don't) that the length >> contracted object is described by events (at its inner and outer extremities)
that are simultaneous in the observing (moving) system, but that are not
simultaneous in the rotating rod's (or wheel's) own system!
See my animation
https://www.geogebra.org/m/xzsf765h
There are 2 types of contraction.
One is the contraction of the "space" between D and E (which is what
you measure with your method and about which I have nothing to dispute
about) and another is the contraction of the "body" AC, about which I
have so much to say.
The contracting space DE has no consequences, because the space between
D and E is empty.
But the AC rod is not empty and if it contracts there are consequences
(if the contraction is real).
And this is exactly what I want to get to: does the AC body really
contract or is it just an apparent contraction?
[[Mod. note -- Yes, there is another explanation: "rigid" only applies
in the rod's own inertial reference frame. Observers in other inertial
reference frames may (will) observe non-ridity, but that's an artifact
of their motion and doesn't affect the rod.
If it is an artifact that does not affect the rod, it means that the non-rigidity is only an appearance.
wugi il 03/09/2023 09:21:35 ha scritto:...
There are 2 types of contraction.
One is the contraction of the "space" between D and E (which is what
you measure with your method and about which I have nothing to dispute
about) and another is the contraction of the "body" AC, about which I
have so much to say.
The contracting space DE has no consequences, because the space between
D and E is empty.
But the AC rod is not empty and if it contracts there are consequences
(if the contraction is real).
...Richard Livingston il 05/09/2023 06:01:20 ha scritto:
...
wugi il 05/09/2023 09:21:30 ha scritto:
...Richard Livingston il 05/09/2023 06:01:20 ha scritto:
...
We obviously live in different worlds.
In my world, a body that contracts, compresses.
And a rigid body doesn't become flexible just because it's in motion.
[[Mod. note --
You are taking it for granted that the body does in fact contract
or become flexible. But those observations are made by an observer
who is not at rest with respect to the body!
If observer A (at rest with body X) observes X to be uncontracted,
and observer B1 (moving at velocity v1 with respect to X) observes X
to be contracted by some amount R1, and observer B2 (moving at some
different velocity v2 with respect to X) observes X to be contracted
by some different amount R2, what should we infer? More generally,
there are infinitely many possible observers B1, B2, B3, B4, ...,
each of who will observe a different contraction of X.
In special relativity, the answer is that we privilege observations
made in the rest frame of the body being observed (in this case X).
To put it another way, can you explain why you think it's paradoxical
that observer B1 observes something different from observer A?
-- jt]]
[[Mod. note --
To put it another way, can you explain why you think it's paradoxical
that observer B1 observes something different from observer A?
-- jt]]
[[Mod. note --
To put it another way, can you explain why you think it's paradoxical
that observer B1 observes something different from observer A?
-- jt]]
I do not consider it paradoxical that observer B1 observes something different from observer A.
I think it is paradoxical that observers B1 and A see different things
both real: if one thing is real the other must be apparent and vice
versa.
This is why I speak of reality and appearance.
A simple and clear example is the following.
If observer B1 stands on the carousel, he sees the earth rotate a full
360 degrees in 5 seconds and sees the carousel stationary.
Instead, observer A on the ground sees the carousel rotate 360 degrees
in 5 seconds and sees dry land.
One sees one thing, the other sees another: can both be real? Obviously
not.
If what observer A sees is real, what observer B1 sees can only be
apparent.
In fact, if the Earth really rotated at that angular velocity, it would shatter!
When you look askew at an object, you will see it kind-of contracted, so is that real or not?
wugi il 05/09/2023 09:21:30 ha scritto:
...Richard Livingston il 05/09/2023 06:01:20 ha scritto:
...
We obviously live in different worlds.
In my world, a body that contracts, compresses.
And a rigid body doesn't become flexible just because it's in motion.
A simple and clear example is the following.
If observer B1 stands on the carousel, he sees the earth rotate a full
360 degrees in 5 seconds and sees the carousel stationary.
Instead, observer A on the ground sees the carousel rotate 360 degrees
in 5 seconds and sees dry land.
One sees one thing, the other sees another: can both be real? Obviously
not.
No indeed, "obviously" there are only appearances.
If what observer A sees is real, what observer B1 sees can only be
apparent.
In fact, if the Earth really rotated at that angular velocity, it would
shatter!
Would it? You forget that with Earth, the whole universe is rotating
around B1, so that ultimately it is only B1 who is feeling the "real" rotational force acting upon them, from Earth + Universe.
We obviously live in different worlds.
In my world, a body that contracts, compresses.
And a rigid body doesn't become flexible just because it's in motion.
You fail to understand that there are no "rigid" bodies.
A wooden ruler or metal rod both are mainly empty space
containing matter constrained by various forces, mainly
electromagnetic forces. The space contracts without
any special consideration of the atoms that exist at the
many points between point A and point C. Just as you agree
that there is nothing special about the space between points D and E.
[[...]] I am also ready to accept that at very high speeds
(close to that of light) exceptional phenomena can occur, such as the contraction of the length of the body or the loss of its rigidity.
However, before I really believe it, I would like there to be at least
some proof.
So I ask you: has the contraction or loss of rigidity of a body in relativistic motion ever been measured?
Edward Prochak il 13/09/2023 09:03:51 ha scritto:
I'll tell you what I understand clearly and what I don't.We obviously live in different worlds.
In my world, a body that contracts, compresses.
And a rigid body doesn't become flexible just because it's in motion.
You fail to understand that there are no "rigid" bodies.
Of course, I understand that in my world the rigid body remains rigid
and does not become flexible just because it moves at some speed,
because speed does not act either on the size of bodies or on their
rigidity.
Having said this, I am also ready to accept that at very high speeds
(close to that of light) exceptional phenomena can occur, such as the contraction of the length of the body or the loss of its rigidity.
However, before I really believe it, I would like there to be at least
some proof.
So I ask you: has the contraction or loss of rigidity of a body in relativistic motion ever been measured?
If such a measure never existed, I would have to believe in this
phenomenon only by faith and I am not a believer.
A wooden ruler or metal rod both are mainly empty spaceThis is not a demonstration or even proof.
containing matter constrained by various forces, mainly
electromagnetic forces. The space contracts without
any special consideration of the atoms that exist at the
many points between point A and point C. Just as you agree
that there is nothing special about the space between points D and E.
One is the contraction of the "space" between D and E (which is what
you measure with your method and about which I have nothing to dispute
about) and another is the contraction of the "body" AC, about which I
have so much to say.
Edward Prochak il 13/09/2023 09:03:51 ha scritto:
We obviously live in different worlds.
In my world, a body that contracts, compresses.
And a rigid body doesn't become flexible just because it's in motion.
You fail to understand that there are no "rigid" bodies.I'll tell you what I understand clearly and what I don't.
Of course, I understand that in my world the rigid body remains rigid
and does not become flexible just because it moves at some speed,
because speed does not act either on the size of bodies or on their
rigidity.
Having said this, I am also ready to accept that at very high speeds
(close to that of light) exceptional phenomena can occur, such as the contraction of the length of the body or the loss of its rigidity.
However, before I really believe it, I would like there to be at least
some proof.
So I ask you: has the contraction or loss of rigidity of a body in relativistic motion ever been measured?
If such a measure never existed, I would have to believe in this
phenomenon only by faith and I am not a believer.
A wooden ruler or metal rod both are mainly empty spaceThis is not a demonstration or even proof.
containing matter constrained by various forces, mainly
electromagnetic forces. The space contracts without
any special consideration of the atoms that exist at the
many points between point A and point C. Just as you agree
that there is nothing special about the space between points D and E.
wugi il 10/09/2023 08:37:40 ha scritto:
A simple and clear example is the following.
If observer B1 stands on the carousel, he sees the earth rotate a full
360 degrees in 5 seconds and sees the carousel stationary.
Instead, observer A on the ground sees the carousel rotate 360 degrees
in 5 seconds and sees dry land.
One sees one thing, the other sees another: can both be real? Obviously
not.
No indeed, "obviously" there are only appearances.
If what observer A sees is real, what observer B1 sees can only be
apparent.
In fact, if the Earth really rotated at that angular velocity, it would
shatter!
Would it? You forget that with Earth, the whole universe is rotating
around B1, so that ultimately it is only B1 who is feeling the "real"
rotational force acting upon them, from Earth + Universe.
I am so naive that I have always believed that the man on the in
movement carousel feels the rotational force of the carousel and not
that of the Earth + Universe.
wugi il 04/04/2024 23:24:16 ha scritto:
I am so naive that I have always believed that the man on the in
movement carousel feels the rotational force of the carousel and not
that of the Earth + Universe.
(A late one). He feels the reaction force by Earth+Universe upon the
carousel's rotational action, transmitted through the carousel's
foundation and its own stiffness.
What does the reaction force of the Earth+Universe to the rotating
action of the carousel have to do with the man on the carousel?
The man on the spinning carousel acts-reacts only with the carousel,
not with the Earth+Universe!
Compare with the water in the bucket, which doesn't feel the bucket's
swinging action, but rather the reaction upon the bucket by the rope, by
the hand, by the person swinging the bucket around, by the floor
retaining his feet, by Earth, ...
Here too, the only force that the water in the bucket feels is the
force of friction with the walls of the bucket and not that of the
hands, the rope or the Earth+Universe.
wugi il 09/04/2024 09:00:40 ha scritto:
Better back to your drawing board. Litterally.
Try to draw all intervening action/reaction pairs and check if you haven't sent some force to "nowhere" ;)
Here is the drawing:
https://www.geogebra.org/m/tecb3dkw
For me, only the two blue and red forces act between man and the carousel; and nothing else.
For you?
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