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David Cooper:"I hope that helps."No, it only confuses the experiment, as I laid it out, with your own conditions.The rules of engagement for a thought experiment are set by its author's conditions.You say:QuoteIt will fit in the cargo bay for a moment, but it has to keep moving relative to the cargo bay in order to do so, with the result that it will only fit in it for a moment, so you're going to need a cargo bay with open doors at both ends. If you slow it to a halt or accelerate the shuttle to its speed so that you can capture the alien ship, it will then be too big to fit.I said that the shuttle pulls alongside of the probe and finds that it is way longer than the 10 meters it was measured to be from earth. Yes, it will "be too large to fit", which was my point illustrating that its "contracted length" is much shorter than its actual length, as observed from its own frame of reference "alongside" it. The bay is a standard shuttle bay, not "open at both ends" for a brief fly-through by the probe. It either will fit in a 10 meter bay or it will not.
It will fit in the cargo bay for a moment, but it has to keep moving relative to the cargo bay in order to do so, with the result that it will only fit in it for a moment, so you're going to need a cargo bay with open doors at both ends. If you slow it to a halt or accelerate the shuttle to its speed so that you can capture the alien ship, it will then be too big to fit.
QuoteActually, there may be a better way to illustrate things: you could do away with the door at the far end of the cargo bay and have some kind of device to decelerate the whole ship in an instant without crushing it, this being done by applying a levitation kind of force to it (as has been done with a frog), but obviously much stronger.This is blatant obfuscation of the thought experiment as I presented it.The project was to retrieve the probe. The question was, will a shuttle with a 10 meter cargo bay contain it? The answer is no, and the reason is that the "contracted length" of the probe as measured from earth is not its actual, intrinsic length, as it was built.
Actually, there may be a better way to illustrate things: you could do away with the door at the far end of the cargo bay and have some kind of device to decelerate the whole ship in an instant without crushing it, this being done by applying a levitation kind of force to it (as has been done with a frog), but obviously much stronger.
... And your 'evangelism' above is not helping the credibility of this thread. I expect it will be closed primarily because of your continuing rants, like about "The Church of Einstein" and such. You are hijacking this thread with your radical opinions.I am still hoping for an intelligent replies to my experiment as I presented it.
I fully agree that any property like the shape of an object measured by an observer in a moving frame is totally valid, and the extrinsic shape that s/he observes must be regarded as the actual shape of the object by such an observer who wishes to do consistent physics in their own frame, but it clearly differs from its intrinsic shape.
Are intrinsic and extrinsic the usual technical terms used here? It's been a while since I studied special relativity, but I don't recall ever learning terms other than "rest ____" to describe properties measured in the rest frame.
Any object does have intrinsic properties. That is not a matter that hinges on any observational result -- it is a matter of definition. An intrinsic property of any object is one that is measured in or calculated to an observation in the inertial frame of reference that is stationary with respect to that object's centre-of-mass.This definition automatically gives rise to the fact that an inertial frame of reference that is stationary with respect to the centre-of-mass of an object is a privileged frame in that it allows an observer to directly measure the object's intrinsic properties.
Ok. So, which is the intrinsic property of a monocromatic light (or X-ray, or gamma ray) beam coming from a very distant star? If you say "the frequency", I ask you "in which frame?" And if you reply "in the source frame" I can reply that the star which have emitted it, now can be non existing anylonger, and its ancient position can be non identifiable.
His ship screen out all radiation except those wavelengths that for the Earth frame were harmless visible light. Due to Doppler Effect the light that penetrates the ship will be now gamma-ray.
SR definitely has invariant quantities, which may be defined in terms of some formula entirely in terms of local measurements (in any inertial reference frame), and which turn out to be constant, no matter which reference frame is chosen. Rest properties seem a bit different, since they require a reference frame to be fixed. However, it seems at first glance that (aside from light) you could always use local measurements to figure out the required transformation into a rest frame of the measuree and then transform whatever measurements you make to that rest frame. However, Lightarrow's example of light certainly causes a bit of an issue for this definition of rest properties=intrinsic. Light has no rest frame, yet a photon clearly has invariant mass which seems to be intrinsic. It also has spin, which certainly meets the criteria most folks would set for intrinsic (and indeed, it is technically termed an intrinsic property in relativistic QM).
The project was to retrieve the probe. (Traveling near ‘c’’ toward Earth and measured, from Earth to be 10 meters in length.) The question was, will a shuttle with a 10 meter cargo bay contain it? The answer is no, and the reason is that the "contracted length" of the probe as measured from earth is not its actual, intrinsic length, as it was built.
The dictionary definition of "intrinsic" is "belonging to a thing by its very nature". The Earth has an "intrinsic" shape ...
It is only through the operation of these definitions that we are able to make generalizations such as "the (intrinsic) shape of any sufficiently large and plastic planet must be an oblate spheroid of revolution", and similar issues that were quite legitimately worrying old guy around posting #30 of this thread.
Does this claim that Earth changes shape as it is measured from different frames of reference?
Certainly. In a frame of reference which is still with respect of our planet, the Earth is spherical...; in another, moving, frame, it's not (and of course every human being is flattened too). Where is the problem?
The "problem" is that, "in the real world" Earth does not change shape with every different possible measurement of it.
...misconception that the length contraction is not "real" - ie that it is merely an artifact of vision/observation rather than an actual consequence of frames in relative motion.
I still have received no unequivocal answer to the “will it fit?” question, illustrating the difference between the intrinsic length of the probe measured from at rest with it and the extrinsic , contracted length measured from Earth’s frame.A very brief recent summary from my post 79, edited (...) for clarity of detail:QuoteThe project was to retrieve the probe. (Traveling near ‘c’’ toward Earth and measured, from Earth to be 10 meters in length.) The question was, will a shuttle with a 10 meter cargo bay contain it? The answer is no, and the reason is that the "contracted length" of the probe as measured from earth is not its actual, intrinsic length, as it was built. As I said, “I am still hoping for intelligent replies to my experiment as I presented it.”