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The operative phrase in length contraction is always some version of "for observer A vs for observer B... the length is measured to be different."Realism insists that the objects themselves do not change even if observed/measured to change. Observers seeing an object differently does not mean that the same object actually changes.
I have always agreed with you on that.
That poses no problem for me, but it does for you because experiments show that length contraction is part of reality.
* It (the probe) was measured from Earth to be 10 meters, approaching at .866c, but at as the shuttle pulls alongside to capture it, it is seen as it is... 20 meters long, twice as long as the shuttle bay. You never did get that one, an expose of... a reality check on... the length contraction fallacy.
If the shuttle is moving with the probe, it is length contracted to 5 metres while the probe remains contracted to 10m. You appear to be the only person here who doesn't "get" your own thought experiment.
Yet we have length contraction "theory" insisting that an Earth with a 1000 mile diameter is equally accurate ("no preferred frame") with the "real animal" which is nearly spherical with a nearly 8000 mile diameter.
No, we have one interpretation of SR insisting on that and you are right to attack it.
David,I did not take your test because different observations do not make things change in length. Given that, your "test" is irrelevant.
You said that you agree, as follows:Me:QuoteThe operative phrase in length contraction is always some version of "for observer A vs for observer B... the length is measured to be different."Realism insists that the objects themselves do not change even if observed/measured to change. Observers seeing an object differently does not mean that the same object actually changes.You:QuoteI have always agreed with you on that.You contradict yourself.
There are no experiments showing length contraction outside of particle accelerators.
There, subatomic particles are flattened ("pancaked") by overwhelming application of force accelerating them.
It doesn't work with Planet Earth, distance to the Sun, or rigid objects on the scale of the examples discussed in this thread. The "contraction", for instance of one arm of the MM apparatus, depends on differences in observation (frame of reference). See again what you agreed to above.
The shuttle bay was built on Earth to be 10 meters long. It stays 10 meters long, even when it is traveling beside the probe, the bay now appearing 5 meters long from Earth. The probe was built 20 meters long, which is why it appears from Earth contracted to 10 meters because of its velocity relative to Earth. The shuttle when at rest with the probe sees it as it is, 20 meters. It is twice as long as the bay. Neither the probe nor the bay changed lengths.Only appearences changed, (called length contraction) due to changes in relative velocity. You still don't get it.
Me:"(Force is required to actually change the shape or length of a physical object, and length contraction posits no such applied force.)"You:"Repeating that over and over again doesn't make it true. The first bit is true,..."You agree that "force is required to actually change the shape or length of a physical object" ("the first bit"), yet you say that repeating it doesn't make it true, implying that it is false. More self contradiction.
The first bit is true, but in some interpretations of SR the shape isn't really changed, while in LET is isn't changed by observation but by movement through space, and the only forces required for the contraction are in action all the time (whether the thing's moving or not).
It is true, and of course repeating it doesn't make it more true.
Different observations do not make the same object change lengths. Believing that reality changes with observation is idealism, not realism.
"For observer A", Earth, the probe appears to be 10 meters. "For observer B" (shuttle at rest with probe) the probe is as it is, 20 meters. It didn't actually ("really") change lengths during the shuttle's mission to capture it.Do you get it yet?
I am not interested in debating the alternative theory you call LET.Start your own thread and make your argument there.
I did not take your test because different observations do not make things change in length. Given that, your "test" is irrelevant.
You didn't answer the two simple questions and the other question which required a little bit of maths because you know that it would destroy your position whether you got it right or wrong
but if you're actually intending part of it to mean that the change in an object caused by its change of speed doesn't change the object, then I don't agree with that part.
You've missed out the Michelson Morley experiment - the one which disproves your "realism".
The pancaking has nothing whatsoever to do with acceleration forces on them - that is a complete misunderstanding of the physics on your part.
...their contradictory measurements cannot both be correct when it comes to the actual shape of the object.
If you're trying to measure length contraction using a ruler which has been length contracted by its movement, you're on a fool's errand.
...LET uses existing forces within the object to contract it simply by maintaining the balance of forces between atoms.
You still claim to know me and my motivations better than I know myself and my reason, as above. If you agree that that different observations do not create different realities (lengths of objects, etc.), then seeing the same object differently does not make it change. Your train does not get shorter with differing observations of it. The details are then moot.
SR theory does not maintain that change of speed physically compacts an object, as a bullet compacts to shorter when fired.
It is always, "For observer A," moving relative to an object, it IS shorter than "for observer B," at rest with the object. SR theory (which is the focus of my argument!) does not claim that application of force compacts the object to make it shorter. And, further, physical objects are not shrunken to shorter by the 'power of observation', which is not a force that can change physical objects.
QuoteYou've missed out the Michelson Morley experiment - the one which disproves your "realism".No. It still depends on the usual "for observer A" vs "for observer B" definition of changing "reality." Again, the reality of physical objects (the length of the apparatus arms here) is not altered by differences in observation. That is idealism, not realism. (See the Wiki definition above... again.)
You are wrong. The machines are built to apply immense force to accellerate minute particles. In the process, they are observed to be flattened in the direction they are traveling. Denying that doesn't help your argument.
No force is likewise applied to Earth, yet mainstream SR (my focus here!) claims that "for an observer" traveling past at near 'c', it is pancaked in diameter in the direction of the observer's travel. It doesn't work. It has a load of false assumptions which do not transfer from the empirical observation of contraction of particles with applied force in an accelerator.
The MM apparatus was built with arms of equal length. Seeing one arm as shorter under no circumstance makes the actual physical arm shorter.
Yet again, regarding my "alien probe retrieval project," you say:QuoteIf you're trying to measure length contraction using a ruler which has been length contracted by its movement, you're on a fool's errand.You are stuck in the belief that physical objects change length when they move relative to an observer... the essence of SR's length contraction. The shuttle bay was built and remained 10 meters long, even when it joined the probe's frame and *appeared contracted* to 5 meters. The probe was built and remained 20 meters long, even as it approached Earth at .866c and *appeared* 10 meters long. As said above, the shuttle's launch and change of velocity relative to Earth did not make it shorter, "in the real world" even though it appeared to shrink as it joined the probes frame.
I repeat, my argument here is with mainstream SR's version of length contraction as advocated by the authorities of this forum, in which there is no force applied to objects to compact/contract them. There is no force applied to Earth to flatten it, but the fly-by guy "sees" it as flattened, and there is no preferred frame, so a flattened Earth is equally valid, they say. I am not interested in what you say about LET. Movement doesn't make objects contract. Only the image of objects gets distorted. They still don't understand the difference.
You:Quote...LET uses existing forces within the object to contract it simply by maintaining the balance of forces between atoms.Nonsense! "Maintaining the balance of forces between atoms" will maintain the object's shape and length. To change an object's shape/length, a force must be applied to change the space between whaterver units, molecules or atoms, of which the object is composed.
"...because LET is realism."Nonsense, as exposed above. You really don't understand realism. Objects remain as they were formed or built until a force is applied to crush or compact them to a shorter length or to way out of spherical shape, in Earth's case.
In the real world, observation is not a force which changes physical things. That is my argument, and I've said all I have to say about your argument... yet again... hopefully.
Again, carry on with your LET argument in a thread of your own.
Fine, but I'm still trying to find out why/whether you think you aren't in an SR camp.
lean bean,If Earth ever develops near 'c' space travel, and if an "alien probe" were discovered approaching Earth at .866c, the true test of "length contraction" would be to determine the real, actual length of the probe in order to send a ship with long enough bay capacity to capture it. It would *appear to be* 10 meters long from earth, if the equations are correct (which I don't doubt.) However, sending out a shuttle with a 10 meter bay would be folly... a very stupid wast of resources... and perhaps fatal to life on Earth if the probe's mission were to kill all life on Earth. So the question, "How long is the probe, really" becomes one of vital importance.Turns out it is not "really" 10 meters, as it appears. It is really 20 meters. A shuttle bay 20 meters long, not 10, will be required.
Here again is the essence of my argument against length contraction:"In the real world,(neither) observation (nor measurement from different frames) is a force which changes physical things."
It is ironic that denying that Earth changes shapes/diameters, as observed from different frames, is now considered a "new theory" not to be taken seriously, because it denies that Earth's diameter contracts, as SR insists.
This basic embrace of a "real physical Planet Earth" with intrinsic properties (size and shape) independent of how it is observed (not changing with changes in how it is observed) is still my answer to D.C."s query:QuoteFine, but I'm still trying to find out why/whether you think you aren't in an SR camp.But I've said this dozens of times... yet you ask the above. SR says that reality depends on how it is observed, that there is no "real, unchanging Earth." They say that "for" a frame of reference flying by at near 'c', Earth is flattened, i.e., contracted in diameter. Re-read the thread if you have forgotten all the insistence by length contraction advocates that earth does change shape with changes in frame from which it might be measured.
The reason I use this as my signature example is because it is so obviously a denial of reality by SR. But the same principle applies to rulers, trains, the MM apparatus arms, my shuttle and probe... and the distance to the sun... which if severely "contracted" would result in Earth's incineration (as a "flattened" Earth would also be destroyed.)meters long, not 10, will be required.
OK, so bizerl and the team of length contraction "experts" here insist that an Earth with a 1000 mile diameter is just as valid a description as the well validated nearly 8000 mile diameter. Please correct me if I am wrong.
QuoteThe fact is that all the observational and experimental evidence that has been gathered so far, indirectly supports the fact that if a 20m spaceship flies through a 10m bay at 0.866c, it will (very briefly) fit exactly inside that bay.You, like almost everyone here misunderstood and/or misrepresented my "alien probe retrieval project." There was no ship (the probe) "flying through" the 10 meter bay of the shuttle. In order to retrieve the probe, the shuttle would by necessity need to match the probe's velocity (come to rest with the probe's frame.) The probe was measured from earth to be 10 meters as it approaced earth at .866c. However, as the shuttle pulled alongside the probe, it was then measured to be 20 meters long, so it would not fit in the 10 meter bay, which did not change after launch.This was offered as a thought experiment (that's all we have to work with regarding lenght contraction on this scale) demonstrating that the "length contracted probe" as seen from earth was not *actually* contracted to 10 meters. Nor would the shuttle bay have *actually* contracted to 5 meters, as it would be measured from earth when traveling with the probe.
Quote from: old guy on 09/11/2012 21:11:04lean bean,If Earth ever develops near 'c' space travel, and if an "alien probe" were discovered approaching Earth at .866c, the true test of "length contraction" would be to determine the real, actual length of the probe in order to send a ship with long enough bay capacity to capture it. It would *appear to be* 10 meters long from earth, if the equations are correct (which I don't doubt.) However, sending out a shuttle with a 10 meter bay would be folly... a very stupid wast of resources... and perhaps fatal to life on Earth if the probe's mission were to kill all life on Earth. So the question, "How long is the probe, really" becomes one of vital importance.Turns out it is not "really" 10 meters, as it appears. It is really 20 meters. A shuttle bay 20 meters long, not 10, will be required.Is that all your worried about …an evil alien probe.Don’t worry old wrinkly, we on earth already know of SR and will know that what we observe travelling at high speeds is length contracted and so will allow for it when we send out a shuttle to retrieve the probe. As I said in my post…“An intelligence without knowledge of SR” will be the ones having your probe retrieval problem. Watch the skies…it may rain.
That is not an argument against length contraction: it's a argument for (or against, depending on whether the brackets are there or not) the idea that observation changes things physically.
Don't attribute it to SR as a whole - you are only attacking one camp within SR.
...you're putting yourself in a position which either requires you to be wrong, to be in the LET camp (which you aren't interested in and don't understand), or to have an alternative theory...
All the camps in SR (and LET) require you to build a >20m long container to hold a 20m long object when they are moving/stationary together. Length contraction only comes into it when calculating interactions between things that are moving relative to each other, so your signature example isn't addressing that issue.
If length contraction is indeed just an illusion created by an observer approaching the speed of light relative to another object, what is the reason for this optical illusion? How does it occur? Why should objects appear shorter if they are travelling really fast?
The point is, if you accept that when travelling at 0.866c, the ship will indeed fit very briefly inside the bay, then saying "the ship is 10m when travelling at 0.866c relative to the observer" is as equally valid description of it as saying "the ship is 20m at rest with the observer".
Throughout this thread I have agrued against the length contraction insistence that physical objects actually change shapes/lengths with differences in frames of reference from which they are observed. SR claims that "length is not invarient," i.e., denies that Earth (etc.) has an intrinsic property of diameter length, i.e., insisting that it IS flattened, as above, not just "appears flattened," based on the dictums, "length is not invarient" and "there is no preferred frame of reference." I've made this case many times and it is you who do not yet get it.
QuoteDon't attribute it to SR as a whole - you are only attacking one camp within SR.As above. I am not interested in your LET "camp" because it insists that physical objects actually do change shapes/lengths as their velocities change.
Quote...you're putting yourself in a position which either requires you to be wrong, to be in the LET camp (which you aren't interested in and don't understand), or to have an alternative theory... See above re your misconception, which I bolded.
"My theory" is none of the above, mainstream SR or LET as you have presented it with objects physically changing with changes in velocity... and it is not "my theory." It is realism, which you do not understand, though I've explained it many times. The "elephant" has its own intrinsic shape as a real animal/object, independent of how it is observed. If you accellerate the elephant to .866c, it will not shrink to half its tail-to-trunk length. An "elephant compactor" would be required for that, and that would definitely kill the elepant.
QuoteAll the camps in SR (and LET) require you to build a >20m long container to hold a 20m long object when they are moving/stationary together. Length contraction only comes into it when calculating interactions between things that are moving relative to each other, so your signature example isn't addressing that issue.My example addresses the SR claim that the probe is contracted to 10 meters as measured from Earth. It is not, and it doesn't grow twice as long after the shuttle enters its frame.
This exposes the "for this frame (Earth) vs for that frame (at rest with the probe)" version of reality as a fallacy.
Quote from: old guy on 12/11/2012 19:06:31This exposes the "for this frame (Earth) vs for that frame (at rest with the probe)" version of reality as a fallacy.No it doesn’t. if two things interact and one is travelling at a relativistic speed relative to the other, then you must treat the situation of time dilation and length contraction as real… how else does the muon reach earth’s surface without decaying, are you saying this is some kind of optical illusion, who is the observer in this case? The detection is only made when the muon reaches the detector at earth’s surface or below surface. skinny
The whole point was that the probe is not 10 meters long as it appears from earth, so the transformation formula must first be applied to get its true, actual, real length before going out to capture it.This exposes the "for this frame (Earth) vs for that frame (at rest with the probe)" version of reality as a fallacy. The probe is and stays 20 meters, even as it *appears* contracted. The shuttle bay is and stays 10 meters. the probe will not fit into the bay, even for a theoretical instant.
Same for the distance to the sun. Never mind that Earth would be incinerated if it were actually a small fraction of the established average of 93 million miles or so from the Sun.
Same applies to the "altered realities" of what D.C. calls LET. He says that the space between atoms in Earth varies with changes in velocity (of Earth relative to near 'c' travelers), thus giving it a 1000 mile diameter in the extreme case. More total nonsense.
Late edit regarding D.C.'s last post: It is trivial and irrelevant whether "LET" is a "camp" within SR.
Earth's diameter does not actually change as its image is viewed from various frames of reference.
That is the point which D.C. is trying to obfuscate here with his pet project, promoting "LET."
Why he doesn't promote it in his own thread, I do not know.
Muon-Frame Observer The muon sees distance as length contracted.
Note that the muon and ground frames do not agree on the distance and time, but they agree on the final result. One observer sees time dilation, the other sees length contraction, but neither sees both
"Time dilation" is a misnomer (time is not an entity) for the observed fact that physical processes (like the ticking of clocks) slow down when they travel at higher velocities.
No force required. Your constant referring to a force is a reflection of your misunderstanding of time dilation and length contraction.
Quote from: lean bean on 14/11/2012 22:05:46No force required. Your constant referring to a force is a reflection of your misunderstanding of time dilation and length contraction.You can also demonstrate that forces can, in fact, be thought of as reshaping things at high speeds. The force holding the probe (in the famous probe example) together are electromagnetic and communicated at light speed. Since electromagnetism travels a the speed of light, and the speed of light is constant as the observer moves, these bonds change length and that changes the length of the probe as it moves. You can interpret this different ways, but it's pretty obvious that it can certainly be interpreted as the electromagnetic force leading to a reshaping of the probe as you fly by it at high speeds.