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Author Topic: That length contraction does not apply to large objects (or distances)  (Read 16200 times)

Offline old guy

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Imatfaal, from my “Evidence for Large Scale Length Contraction” thread:

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Perhaps once you have shown (in New Theories please) why earth has an intrinsic nature outside the laws of physics - then we can start afresh.

Imatfaal;
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Yes there are plenty of ways to question accepted ideas.  Arguments from incredulity and naked disbelief are not included - most especially on the main fora.  post as much as you like in New Theories - just keep the main fora to Science Q&A

The argument that Earth does not change shape as it is observed from different frames of reference is not, as you falsely characterize it, just a case of “I don’t believe it so it can’t be true”... “naked disbelief.” It can’t be true because Earth is not a malleable sphere, as real science well knows and has thoroughly document from empirical measurement.

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To answer your last point - you are privileging your notions (and the common and nature notions of humanity) over the scientific method.

No, I am not. The scientific method, specifically the laws of physics dictate that for a solid object to change shape, a force must be applied to it. “Seeing it as” changed in shape does not make it change in shape. That is the difference between the intrinsic property of earth’s naturally formed shape and the extrinsic effect of flying by it very fast and “seeing” it as flattened.

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It has be shown countless times that ideas of intrinsic nature, of an immutable realism, of absolute time and space etc are useful, practically universal, easy to accept, and wrong.  Perhaps once you have shown (in New Theories please) why earth has an intrinsic nature outside the laws of physics - then we can start afresh.

First I do not advocate any "absolutes." (Straw man argument.)
The laws of physics gave Earth its shape as it was formed. It is intrinsically about spherical.
Your insistence that a flattened earth is equally as valid as a spherical earth is, in fact, wrong. It is based on SR theory’s confusion about the difference between intrinsic and extrinsic properties. (I do not deny that the speed of light is constant, as I've said a few times.)

Mass is an intrinsic property. Weight is an extrinsic property. My mass will remain the same on Earth as on the Moon, but my weight there will be about 1/6th what it is on Earth.
Extrinsic properties depend on relationships, like gravity’s pull on me on Earth vs on the moon.
Earth, Moon, all the planets and all the stars are close to spherical in shape,  intrinsically speaking, as earth science and astronomy well know... so formed by the laws of physics. Earth science has known that earth’s intrinsic shape is not flat for a long time. (Nobody "fell off the edge" while circumnavigating Earth. Just a little humor here.)

 Then, along came SR as a “relatively” New Theory and claimed that,...
 'No, it is only spherical if you look at it from at rest with it. Its shape varies with how you look at it. It is in fact flattened like a pancake if you are flying by it very fast observing it.'
That relationship (a near ‘c’ fly-by frame) may well make it LOOK flattened, but there are NO LAWS OF PHYSICS which make planets (etc) change shapes as they are observed differently.

“The flattened Earth” is an extrinsic effect due to the RELATIONSHIP  between the fast flying frame seeing the image of earth differently that the image seen from at rest with Earth.
I'll leave it there for now.
Please stick to the topic.



 

Offline old guy

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Re: Evidence for large scale length contraction?
« Reply #1 on: 08/09/2012 00:30:02 »
Just a little "closure" for me in this thread:
JP said:
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A far better guide in science is logic.  Once you know something is true (by observing or measuring it), you can logically figure out its consequences.

Yes. Let's do logic. Can Earth be both nearly spherical and a very oblate spheroid, commonly called "pancaked?" Logically, no. It must logically be one or the other (or various shapes in between, SR insists, depending of course on the observer... no logic there! No "real Earth.")

Yes, "Once you know something is true (by observing or measuring it), you can logically figure out its consequences ."

 And the consequences of measuring the Earth for hundreds of years including the use of modern space-age technology is that we know it is damn near spherical, and we know exactly how much out of spherical it is. (Not much.)
"The laws of physics" made the earth the shape it IS. Nothing "absolute" about that!
SR theory does not change that. Observers do not change its shape.
« Last Edit: 08/09/2012 00:34:17 by old guy »
 

Offline old guy

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In order to move this thread thread into discussion mode, I will repeat and further comment on the quote from imatfaal in the OP:

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It has be shown countless times that ideas of intrinsic nature, of an immutable realism, of absolute time and space etc are useful, practically universal, easy to accept, and wrong.  Perhaps once you have shown (in New Theories please) why earth has an intrinsic nature outside the laws of physics - then we can start afresh.

First I would like to see the evidence ("shown countless times") that "ideas of intrinsic nature... (are) wrong." Continuing with the example of Earth's shape would keep it in the context I have already presented above.

Next, what do you mean by "immutable realism?" I have already quoted Wiki's version of realism, with which I agree, as follows:
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In philosophy, Realism, or Realist or Realistic, are terms that describe manifestations of philosophical realism, the belief that reality exists independently of observers.
"Immutable?"
The fact that Earth bulges a bit at the equator from spinning all those years makes it "mutable," however trivially. The argument from realism is that it would not shrink in diameter with how it might be observed.

"Absolute time and space?" No. I see space as simply 3-D volume, whatever the scale, finite, with boundaries, to infinite. (What "end of space" could be conceived?)
You already know my take on time. Nothing "absolute" about that either. Things move. It "takes time." That does not make time into an entity, so "time dilation" is a misnomer, even though clocks do slow down at higher velocities (and deeper into a 'gravity well' like Earth's gravity field.)

I have shown that "Earth has an intrinsic nature" without subscribing to your belief that its intrinsic nature lies "beyond the laws of physics." I await your reply.

I again invite respectful discussion of the topic in general and the points above in particular.
Ps: I would  like to refer readers to damocles' last post (#55) in my other thread on this topic in the Physics,etc. section, "Evidence for large scale length contraction?" Quite clear and well written, and I totally agree.
(I was forbidden to post on the topic anymore in that section, as imatfaal did not consider the topic appropriately "mainstream" as required for that section.)
« Last Edit: 08/09/2012 18:18:33 by old guy »
 

Offline simplified

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I don't understand sense of Lorentz's length contraction factor,but Doppler deformation of moving space exists.Therefore we see aberration.
      sin(a)=sin(a')*D
D=1/[L(1+v*cos(a)/c)]
D-Doppler length contraction factor
L - Lorentz's factor of slowing of time
v-speed
a - angle of inclination of telescope
 

Offline David Cooper

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If you imagine a fast moving thing travelling past you at a distance rather than heading towards you or away from you, there will be no Doppler complications to get in the way of seeing the length of that object. For example, imagine that you're standing in the middle of a straight road (with no traffic on it - please be careful if you're doing this for real), while ahead of you there is a crossroads, and on the road which crosses yours there is a fast-moving bus which is crossing your road. You can see its length without the Doppler shift affecting it as the light from both ends of the bus has exactly the same distance to travel to reach your eyes. If the bus is moving at 86.6% the speed of light, the bus will be half its normal length as measured in your frame of reference.
 

Offline old guy

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David Cooper:
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If the bus is moving at 86.6% the speed of light, the bus will be half its normal length as measured in your frame of reference.

May we at least use language precisely in the critical analysis of intrinsic vs extrinsic properties?
"The bus will be" is very different than "the bus will appear."
"... as measured in your frame of reference" means "as it will appear to you" (the extrinsic effect of length contraction.) The bus does not actually intrinsically shrink because of the way it would appear to you.
 

Offline simplified

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If you imagine a fast moving thing travelling past you at a distance rather than heading towards you or away from you, there will be no Doppler complications to get in the way of seeing the length of that object. For example, imagine that you're standing in the middle of a straight road (with no traffic on it - please be careful if you're doing this for real), while ahead of you there is a crossroads, and on the road which crosses yours there is a fast-moving bus which is crossing your road. You can see its length without the Doppler shift affecting it as the light from both ends of the bus has exactly the same distance to travel to reach your eyes. If the bus is moving at 86.6% the speed of light, the bus will be half its normal length as measured in your frame of reference.
You should know distance between me and the crossroads,you should know normal length of the bus then you can calculate length of the bus in my frame of reference.I see the rejected middle of the bus under an angle of 60 degrees relatively of arrival line of photons of the crossroads.I can't see photons radiated by the bus on the crossroads with photons of the crossroads under the same angle.
« Last Edit: 11/09/2012 15:55:32 by simplified »
 

Offline old guy

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JP:
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'Mainstream' in terms of length contraction is Einstein's special relativity, which does predict length contraction.  Criticisms of that idea should be kept to New Theories, as mentioned above.
 

OK, back to basics regarding shrinking objects and distances.
The father of relativity denied that "reality" exists independent of observation.
Einstein:
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“It appears to me that “real” is an empty meaningless category (drawer) whose immense importance lies only in that I place certain things inside it and not
certain others."
[Ref:  Collected Papers of Albert Einstein, Edited by J.J. Stachel and Robert Schulmann (Princeton Univiversity  Press, 1987); Letter to Eduard Study from Albert Einstein dated Sep 25, 1918]

In order to believe that objects and distances shrink with how they are observed, one must first believe, with Einstein, that there is no naturally occurring universe formed by the laws of physics applied universally and independent of what science "places inside the drawer" for observation/measurement.
Philosophically, this is relativity's version of subjective idealism but with the abstract concept of frame of reference substituting for subjective experience as the creator of reality.
The classic example of subjective idealism is expressed in the old cliche', "If a tree falls in the forest and no one is there to hear (observe) it, does it make a sound?" An idealist will say "no," and a realist will say "yes." I belong to the latter camp. Sound is the compression of air into waves. Sound waves do not depend on being heard to exist.
The same goes for claiming that there is no reality but that which is observed.
The Hubble telescope, among others, discovered much of the universe which had never before been seen. No scientist will claim that all new discoveries came into existence only after they were observed. So the claim that reality depends on observation is nonsense.

Relativity is constantly comparing 'reality'  "for observer A" with 'reality' for observer B. In my favorite example (illustrating the absurdity of different 'realities' for the same object,) Earth has no "reality" of its own in this philosophy, independent of how it is observed. "For observer A," it is nearly spherical, while "for observer B" it is flattened like a pancake.
 Anyone who believes that Earth is flattened like a pancake (in any case) has decided in favor of Einstein's version of idealism and has abandoned the realism which grants the world an existence and intrinsic properties (shape, size, etc.) independent of observation/frames of reference.

From (edit) imatfaal's link (in my other thread where I am gagged) on
"Relativity, ten minutes to Alpha Centauri":
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However, what in fact happens is that the distance to Alpha Centauri becomes shorter for the person in the spacecraft.

Late edit: I now see that my reference to this reply in my original "length contraction" thread has been deleted. So not only can I not criticize "accepted science" in that thread, I can not even refer to my replies in this thread. But this, of course, is not censorship, and all the mods apparently agree with Einstein that there is no "reality" independent of observation. "Realism" is forbidden to be spoken there in the Physics section.

It takes light 4.37 years to reach Earth from AC, and nothing with mass can travel that fast. However, by the miracle of granting equal "reality" to all frames of reference, "for observer B" (the spacecraft) the time is shortened to ten minutes, because the ship's clock, traveling near 'c', has slowed way down. And of course, the math reciprocal of such "time dilation" is "length contraction"... so... therefore...
Regardless of how the galaxy and all its stars were originally formed and distributed in space "by the universal laws of physics," there remains no "reality" but what each frame variously "observes."

Meanwhile, what "a year" means is ignored. A year is the elapsed time (et) for one Earth orbit of the sun*... just in case 'time dilation' on the ship has obscured that fact. (*Now standardized by very accurate clocks, as the orbit et does vary slightly.) So while the ship is "experiencing" ten minutes of elapsed time, by its clock, Earth will have orbited the sun more than 4.37 times. All this is just a reality check on the fact that the ship's time is its own small microcosm of slowed down physical processes which does not re-create the macrocosm of earth-orbiting-sun or distances between stars.

...Just to put it into philosophical perspective, in case anyone cares.
« Last Edit: 11/09/2012 22:28:58 by old guy »
 

Offline David Cooper

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David Cooper:
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If the bus is moving at 86.6% the speed of light, the bus will be half its normal length as measured in your frame of reference.

May we at least use language precisely in the critical analysis of intrinsic vs extrinsic properties?
"The bus will be" is very different than "the bus will appear."
"... as measured in your frame of reference" means "as it will appear to you" (the extrinsic effect of length contraction.) The bus does not actually intrinsically shrink because of the way it would appear to you.


I'm a linguistician, so my language is usually very precise, and this was certainly the case above. "X will be Y as measured in Z" qualifies the word "be" with "as measured in", so it's perfectly clear that it's referring to the measurement being Y. An example that illustrates this more clearly is: "John is 32 inches as measured round the waist using this faulty tape measure" - this does not mean he is actually 32 inches round the waist.

However, if we are near to being in the preferred frame (assuming for the moment that there is a preferred frame, and we can assume that there is because a universe without one is a universe that depends on magic to explain the pattern of cause-and-effect written through it while there's no such thing as "before" and "after" in the sense of any kind of Newtonian time), then the bus is literally reduced to half its normal length by its movement, and not simply because we're measuring it.
 

Offline David Cooper

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If you imagine a fast moving thing travelling past you at a distance rather than heading towards you or away from you, there will be no Doppler complications to get in the way of seeing the length of that object. For example, imagine that you're standing in the middle of a straight road (with no traffic on it - please be careful if you're doing this for real), while ahead of you there is a crossroads, and on the road which crosses yours there is a fast-moving bus which is crossing your road. You can see its length without the Doppler shift affecting it as the light from both ends of the bus has exactly the same distance to travel to reach your eyes. If the bus is moving at 86.6% the speed of light, the bus will be half its normal length as measured in your frame of reference.
You should know distance between me and the crossroads,you should know normal length of the bus then you can calculate length of the bus in my frame of reference.I see the rejected middle of the bus under an angle of 60 degrees relatively of arrival line of photons of the crossroads.I can't see photons radiated by the bus on the crossroads with photons of the crossroads under the same angle.

That is not the case, though you did manage to get the sixty degrees part right before misapplying it. The light from the bus and the light from the crossroads follows the same path, but the photons being emitted from the bus have to be sent out from the bus in a direction which appears to be pointing 60 degrees behind the bus from the point of view of someone on the bus in order to make them travel from the crossroads to the observer standing some distance away in the middle of the other road rather than being projected out at an angle thought to be sideways. As light is being reflected off the bus at all angles, this isn't a problem.

If we imagine doing the experiment at night, someone on the bus could shine a laser at us, and to do so (s)he would have to point it 60 degrees behind the bus rather than at 90 degrees, but (s)he would also see us as being in that direction, 60 degrees behind the bus as the bus goes across the crossroads, which leads to an interesting detail which I've never come across before - it can't be a crossroads from the point of view of the bus, and the road crossing the road the bus is on can't be straight, even though we know it's straight. What's going on there?

Edit: correction - it's 60 degrees forwards rather than backwards for the direction in which we're seen from the bus (from the point of view of someone on the bus), but 60 degrees behind the bus that the laser has to be pointed, so it isn't pointed towards the target at all.
« Last Edit: 11/09/2012 21:36:53 by David Cooper »
 

Offline David Cooper

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A good post, old guy, but one bit's maybe wrong (depending on how you interpret the shape of a pancake):-

Anyone who believes that Earth is flattened like a pancake (in any case) has decided in favor of Einstein's version of idealism and has abandoned the realism which grants the world an existence and intrinsic properties (shape, size, etc.) independent of observation/frames of reference.

If there's a preferred frame, the Earth could be travelling at 99.999% the speed of light through that frame (along with most of the rest of the content of the universe - unlikely, but not impossible), in which case it could genuinely be flattened like a pancake [almost - it would not have two flat sides and a measurable edge, but it would be close to pancake shape in terms of it's minimum and maximum dimensions].
 

Offline David Cooper

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...and the road crossing the road the bus is on can't be straight, even though we know it's straight. What's going on there?

It does look as if you can cross a straight line at very high speed at any point along that line and make it appear to have a massive kink in it at that point.
 

Offline old guy

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David Cooper:
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A good post, old guy, but one bit's maybe wrong (depending on how you interpret the shape of a pancake.

Thanks. I use "pancaked" in the loose sense that length contraction of subatomic particles in accelerators are said to be pancaked, and then that principle is falsely applied to large scale objects like Earth.
We know precisely how much Earth bulges at the equator compared to the polar diameter... making it technically an oblate spheroid. Length contraction advocates claim that, if a frame of reference is observing from a fast enough fly-by, the diameter could shrink to as much as 1000 miles in the direction of the frame's travel. That would make it a severely oblate spheroid, of course, not a pancake with two flat surfaces and an edge of whatever thickness.
Let's keep it on the topic without such irrelevant distractions, please.
Earth does not change shapes to accommodate all varieties of observational points of view. Let us keep that fact in mind in this discussion.
 

Offline old guy

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David Cooper:
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X will be Y as measured in Z" qualifies the word "be" with "as measured in", so it's perfectly clear that it's referring to the measurement being Y. An example that illustrates this more clearly is: "John is 32 inches as measured round the waist using this faulty tape measure" - this does not mean he is actually 32 inches round the waist.

The whole point of my criticism of large scale length contraction is that there is a world of difference between how something appears or how it is "measured in" various frames and the naturally occurring, intrinsic properties ( including shape and size) of an object as it was formed by the laws of physics (or built) in the first place.
This point was made abundantly clear in my example (in the Physics section version of this thread) of the alien probe retrieval project.
"As it was measured" in Earth's frame (as it approached at near 'c'), it appeared to be 10 meters long. If it were actually, intrinsically 10 meters long, as it was built, it would fit into a 10+ meter (for sliding in room) retrieval cargo bay. But once the shuttle pulled alongside the probe (at rest with it, in same frame of reference) it would have been seen as it actually was, much longer than the 10 meters "as it was measured" from earth.
The retrieval project would have wasted its time and money to send a shuttle with a 10 meter bay to get it. This was a practical illustration of the difference between the intrinsic length of the probe, as it was built, and the extrinsic appearance of the probe as "length contracted", as seen from
Earth.
This point was successfully ignored in the physics section thread. The mantra is simply repeated (with metaphorical hands over ears), "It all depends on frame of reference," or, "There is no reality independent of measurements from various frames."
This passes for "mainstream science" these days, because criticism of Einstein's philosophy, to the above effect (see quote in thread above), is not allowed as legitimate discussion of SR theory in this forum.

Ps; I propose a " contra-mantra" as stated in summary of my last post:
"Earth (and other solid objects) do not change shapes(/lengths) to accommodate all varieties of observational points of view."
« Last Edit: 12/09/2012 19:19:35 by old guy »
 

Offline David Cooper

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Let's keep it on the topic without such irrelevant distractions, please.

It wasn't irrelevant - there are many people out there who may read through this who take things very literally (I have a few friends with Aspergers syndrome who take everything literally and who are very keen on things like physics) and who could be confused by the pancake shape description - I wanted to ensure that the description was tightened up for their benefit.

Edit: furthermore, my post was pointing out an error in what you'd said which had absolutely nothing to do with the inexactness of the pancake description. You said:-

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Anyone who believes that Earth is flattened like a pancake (in any case) has decided in favor of Einstein's version of idealism and has abandoned the realism which grants the world an existence and intrinsic properties (shape, size, etc.) independent of observation/frames of reference.

And I replied to that by pointing out that you can believe the Earth is flattened like a pancake without deciding in favour of Einsten's SR. If you have decided in favour of Lorentz instead and if you also determine that earth is moving at very high speed relative to the preferred frame (which the entire content of the universe may for all we know be doing), then you could determine that the Earth is flattened like a pancake.
« Last Edit: 12/09/2012 21:24:17 by David Cooper »
 

Offline David Cooper

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The whole point of my criticism of large scale length contraction is that there is a world of difference between how something appears or how it is "measured in" various frames and the naturally occurring, intrinsic properties ( including shape and size) of an object as it was formed by the laws of physics (or built) in the first place.

I'm well aware of that, and I agree with you. The problem is that people can only give definitive answers within the bounds of a theory. That means that if you go with Lorentz (which is where I lean towards), then things are literally shortened in length in the direction they move. If you go with Einstein, it's all relative - you can have your cake and eat it. You have to decide what you think is true based on which theory or interpretation of a theory sounds best to you, and then you can make up your own mind about whether things really contract or not, but there can be no correct answer unless the correct theory can be identified as correct, and that's still open.

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This point was made abundantly clear in my example (in the Physics section version of this thread) of the alien probe retrieval project.
"As it was measured" in Earth's frame (as it approached at near 'c'), it appeared to be 10 meters long. If it were actually, intrinsically 10 meters long, as it was built, it would fit into a 10+ meter (for sliding in room) retrieval cargo bay. But once the shuttle pulled alongside the probe (at rest with it, in same frame of reference) it would have been seen as it actually was, much longer than the 10 meters "as it was measured" from earth.
The retrieval project would have wasted its time and money to send a shuttle with a 10 meter bay to get it. This was a practical illustration of the difference between the intrinsic length of the probe, as it was built, and the extrinsic appearance of the probe as "length contracted", as seen from
Earth.
This point was successfully ignored in the physics section thread. The mantra is simply repeated (with metaphorical hands over ears), "It all depends on frame of reference," or, "There is no reality independent of measurements from various frames."

It was not ignored - I answered it more than once, and I've just answered it yet again over there, this time with a new illustration of events to help you see it more easily.

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This passes for "mainstream science" these days, because criticism of Einstein's philosophy, to the above effect (see quote in thread above), is not allowed as legitimate discussion of SR theory in this forum.

This is a damned good forum, actually, and that's why it's worth working with these people to help them improve its one failing. Let's not attack them, but try to work with them to eliminate claims which overstep the mark.

Quote
Ps; I propose a " contra-mantra" as stated in summary of my last post:
"Earth (and other solid objects) do not change shapes(/lengths) to accommodate all varieties of observational points of view."

That's fine, but Einstein's SR contains no such claim - you have to distinguish between his theory and the baggage which other people try to attach to it. Many aspects of many theories are open to interpretation and you can waste a lot of time attacking things which aren't part of the theory in the mistaken belief that they are key parts of it.
 

Offline old guy

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David,
My answer is in my other thread in the physics section.

I am not "wasting time" attacking any kind of straw man argument here. The length contraction "mantra" and the "contra-mantra" I have suggested express clearly defined differences. Please keep your comments within the parameters of the debate as I have conceived it in both of my threads. This is not the place for your pet theories. My argument is not a personal pet project to debunk SR, as I have explicitly stated several times. My argument is based on realism about the intrinsic properties of objects and the distances between them, as I have quoted Wiki on the meaning and elaborated the implications.
« Last Edit: 12/09/2012 22:19:06 by old guy »
 

Offline David Cooper

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Please keep your comments within the parameters of the debate as I have conceived it in both of my threads. This is not the place for your pet theories. My argument is not a personal pet project to debunk SR, as I have explicitly stated several times. My argument is based on realism about the intrinsic properties of objects and the distances between them, as I have quoted Wiki on the meaning and elaborated the implications.

They were, I wasn't pushing my pet theories, and I'm out - you don't take anything on board and I've had enough of trying to help you. Good luck with your quest.
 

Offline simplified

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Edit: correction - it's 60 degrees forwards rather than backwards for the direction in which we're seen from the bus (from the point of view of someone on the bus), but 60 degrees behind the bus that the laser has to be pointed, so it isn't pointed towards the target at all.
Someone on the bus should send his photons  at 150 degrees relatively of own motion direction.
 

Offline David Cooper

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Someone on the bus should send his photons  at 150 degrees relatively of own motion direction.

Yes - that's what I meant by 60 degrees behind, but you've expressed it better.
 

Offline old guy

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JP, post 132, my Length Contraction thread in the Physics section:
Quote
Now we're at the heart of the matter.  You're discussing metaphysics behind special relativity.  That's a perfectly valid and interesting area, but it's not a matter for this science forum.  If we were a philosophy forum, I'd say go at it!

We had some interesting discussions here, but unless you'd like to discuss science, I'll have to ask you again to keep it to "new theories."


It is difficult to see how a thought experimental practical application of "length contraction"... my "probe retrieval project"... is considered metaphysics rather than the applied physics of length contraction.

Of course the background contrast of Einstein's version of idealism with realism is philosophy, but my question, in that context, remains a real challenge to length contraction advocates:
"Does Earth change shapes with every possible different perspective viewing it. I can't believe that you (edit; anyone) believe(s) that!"

Me, post 131, Length contraction thread in Physics section:
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If you were on the retrieval team, you would know that the observed length of 10 meters, from earth's frame, was not its true length, in its own frame. You would not send out a shuttle with a 10 meter bay to retrieve it.

“In the real world” the probe, observed from earth to be 10 meters, is actually much longer.

Me:
.
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.. Einstein endorsed a form of idealism when he said that there is no reality independent of observation/measurement.
If one is not allowed to disagree with that, then SR has become a realism- intolerant dogma in favor of SR's version of classical idealism.

How about you? (Edit; anyone.) Are you an idealist or a realist. (Rhetorical question. Edit: lets make it a “real” question.) Does the falling tree make a sound without an observer to hear it?

From post 128 to imatfaal in the other length contraction thread:
(He will not be allowed to reply there, so I am moving my reply to him to the “backwaters” here.)

Quote
My argument here simply questions how "real" length contraction is. Does a fast moving ship make stars move closer together? No, but its clock will "tick" more slowly the faster it flies, and its occupants will probably age more slowly.

Do objects have shapes and lengths independent of how they are measured? Yes, there is a "real cosmos with real objects" in it, but they may well appear contracted from very fast fly-by frames.

Can you really " fit the probe (very briefly) entirely within the shuttle's cargo bay?"
No.
Let's make the velocity of the probe relative to earth specific at 86.6 % of 'c.' If the "contracted length" as measured from earth is 10 meters, as established, it will then be 20 meters in its own frame and as measured from the shuttle once it enters that frame, at rest with the probe. A 20 meter probe will not fit into a 10 meter cargo bay, period, no matter how "briefly." Sorry.

I can only take a 'no reply' to this direct challenge as an admission that you, imatfaal, are wrong.
JP,
Since you made me move the discussion here, I hope you will answer my last reply to you (above) here.
 

Offline imatfaal

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Old Guy - if you want a discussion please stop the debating society tactics; the complaints of gagging, the assumption that no reply is an admission of acceptance, and the constant moaning - it's puerile, distracting, and possibly why you are not receiving the engagement that perhaps the question deserves. 


My probe example intended to put some meat on the bones of the question, "What is real?" as a practical application, once we achieve relativistic speeds in space travel, of course. (See quote below.)
The retrieval team must know the "real length" of the probe in order to send out a shuttle with a large enough cargo bay. Obviously the shuttle must "come alongside" the probe, matching velocities, at rest with the probe to capture it. (The conjectures about colliding with the probe would be the result of a very poorly planned mission!)
Our cargo bay, as stated, is 10 meters. The "contracted length" of the probe, as seen from Earth's frame appears to be 10 meters. The point of the whole exercise was that 10 meters is not the probes *real length*, so sending out the above shuttle would be very stupid, because the probe is *really* longer than 10 meters. So there is your functional definition of "What is real?"
But it is a definition - that a) is not needed because the concept of reality as you define it is not important for the mathematical model and b) when the probe is moving very quickly I could get it in the open-ended shuttle bay at rest (with arbitrarily quick closing doors) .  b) does not in my mind, challenge the "reality" of the probe being longer than 10m in it's rest frame - but it shows that differentiation between real and apparent are unimportant, dangerous, and misleading.


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Another example is the observed lifetime of muons in motion and thus their range of action, which is much higher than that of muons at low velocities. In the proper frame of the atmosphere, this is explained by the time dilation of the moving muons. However, in the proper frame of the muons their lifetime is unchanged, but the atmosphere is contracted so that even their small range is sufficient to reach the surface of earth.

Essentially this argues that, because of “time dilation” (their rate of decay slows down at higher velocity), these mouns “live longer” than expected of lower velocity muons, and since length contraction is the math reciprocal of time dilation, for those muons “the atmosphere is contracted."
From “the frame” of the whole picture however (earth and incoming muons) , there is no contracting of the atmosphere around each muon. “For a muon” does not change  the atmospheric science of its thickness/depth.
You cannot have a rest frame which encompasses two objects with relative velocities.  The muons reach the ground - they are not time dilated in their own frame, the atmosphere is contracted in the rest frame of the muon.  It is not merely a mathematical reciprocal - it is part and parcel of SR; and in the few situations that we can test it, we find the observations match the predictions

My argument here simply questions how "real" length contraction is. Does a fast moving ship make stars move closer together? No, but its clock will "tick" more slowly the faster it flies, and its occupants will probably age more slowly.
  Clocks only tick slower when viewed from another frame!  And the fact that the earth bound observers see the space clocks as ticking slowly does not explain how the spacemen (who measure no dilation on their own clocks) reach alpha centauri in less than 4.37 years again according to the spacemen

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Do objects have shapes and lengths independent of how they are measured? Yes, there is a "real cosmos with real objects" in it, but they may well appear contracted from very fast fly-by frames.

Can you really " fit the probe (very briefly) entirely within the shuttle's cargo bay?"
No.
Let's make the velocity of the probe relative to earth specific at 86.6 % of 'c.' If the "contracted length" as measured from earth is 10 meters, as established, it will then be 20 meters in its own frame and as measured from the shuttle once it enters that frame, at rest with the probe. A 20 meter probe will not fit into a 10 meter cargo bay, period, no matter how "briefly." Sorry.
  The whole point of the corollary thought experiment is that the shuttle bay allows the probe in without matching velocity ie it is not in the rest frame of the probe - there is a high relative velocity; and then the probe will fit in!    Can you just confirm to me whether you agree that (with arbitrarily fast doors) a shuttle bay with doors at front and back could hold the probe moving with relativistic velocity compared to and observed by the shuttle at rest?
 

Offline imatfaal

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It is difficult to see how a thought experimental practical application of "length contraction"... my "probe retrieval project"... is considered metaphysics rather than the applied physics of length contraction.

Of course the background contrast of Einstein's version of idealism with realism is philosophy, but my question, in that context, remains a real challenge to length contraction advocates:
"Does Earth change shapes with every possible different perspective viewing it. I can't believe that you (edit; anyone) believe(s) that!"
  The reason it is metaphysics - or philosophy - or something not-science is you are postulating beyond observation, experimentation, and empiricism; the notion of reality, intrinsic nature seems to be either seeking an absolute being that transcends or negates the use of frames of reference.  But SR has shown with massive predictive power and experimental success that frames of reference are essential for understanding space and time. 

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Me, post 131, Length contraction thread in Physics section:
/snipped
snipped as measurements in the rest frame of the probe are clear and unarguable.

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.. Einstein endorsed a form of idealism when he said that there is no reality independent of observation/measurement.
If one is not allowed to disagree with that, then SR has become a realism- intolerant dogma in favor of SR's version of classical idealism.
  It is not that you are not allowed to disagree with that - it's just that it doesn't belong in a science argument.  The reason we (specifically) don't allow it - is that Chris and his team started this forum as a Science Q&A to provide answers to members and guests, and that these answers should be based on the ideas of physics as taught in schools etc.  The cross-section between physics and philosophy is very interesting and disturbing - special relativity, the big bang, the eventual fate of the universe, information theory, non locality, and the quantum theories; but it tends to confuse and members can be lead to believe that actually very sound theories are doubted and unsettled.   


 

lean bean

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Let's keep it on the topic without such irrelevant distractions, please.
Earth does not change shapes to accommodate all varieties of observational points of view. Let us keep that fact in mind in this discussion.

So, you have been whizzing about earth at relativistic speeds to know this is 'fact' ?
Thought experiments may reflect your mis-understandings of things rather than bring to light a crumbling of SR's axioms which have been tested and found holding for many years now.

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Let us keep that fact in mind in this discussion.
So, that ’fact’ is not an axiom then?, and every reply to your thread should accommodate that ‘fact’ for your discussion here.
Anyone saying otherwise is not keeping to your threads ’fact’. and is wasting your time.

« Last Edit: 16/09/2012 11:28:18 by lean bean »
 

Offline JP

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Old Guy, I'm not sure what you want me to reply to.  I've already replied to the points you raise.  Repeating them won't change my response:

Scientific theories deal with predicting the results of experiments.  Metaphysics deals with describing the fundamental nature of the universe.  As far as I can tell, your arguments for "reality" deal with the fundamental question, "what is real?" and they do not contradict any of the predictions that SR makes for measurements.  In that case, this is definitely a metaphysical discussion about interpretations of the math of SR, not a scientific one. 

If you'd like to continue a scientific debate on SR, can you offer a prediction of an experimental or observational measurement that in your model of "real" would be different from SR's predictions?
 

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