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Polarization stater* are the spin states by the way.*states, even. I love autocorrect
Here is another “reality check” against large scale length contraction:Say an alien probe is discovered heading toward Earth at a significant fraction of light speed. From Earth’s frame it is measured to be ten meters long, length contracted because of its velocity relative to earth. It is decided to go out and intercept/capture it in one of our very high speed space shuttles (of the future.)Our shuttle has a ten meter cargo bay. Will the probe fit into the bay?... A very practical test of “actual length” vs “contracted length.”The answer is “no” because the probe’s “actual length” must be longer than its “contracted length” for it to appear as ten meters long from earth’s frame in this case.
I will give an illustration. The Alpha Centauri complex (AC) is 4.37 light years away from Earth. It takes light from AC 4.37 (edit) years to reach Earth, and no “thing” with mass can travel that fast.A ship traveling at near ‘c’ velocity from here to there must, therefore take longer than 4.37 years to get there, even though the onboard clock will have slowed down and recorded much less than 4 years passing. Yet Earth will have orbited the Sun (the "year" standard) much more than 4 times during the ship’s journey to AC. So, even though “for the ship” much less than 4 years will have passed, the distance between Earth and AC will not have contracted to way less than 4 light years. The ship’s journey obviously will not make Earth and AC move closer together.
...For a spacecraft traveling at 90% of the speed of light, the distance will only be 1.90 light-years, less than half the distance that an Earth-bound observer would measure! ...
Quote from: lightarrow on 13/09/2012 13:02:39Ok. 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.Interesting point, but I have a quick question.Let's assume there is a distant source (like our Sun) that emits harmless visible light for an Earth observer. The observer take a relativistic ship (0.9999c) and travel toward the source. 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. My question is: Will the observer on ship get hurt by gamma rays? Or in his ship those penetrating gamma rays (that on Earth were visible light) have the same impact as the visible light on Earth frame, i.e. they will be harmless?
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.
The question as to whether the Lorentz contraction really exists or not is misleading. It doesn't "really" exist, in so far as it doesn't exist for a comoving observer; though it "really" exists, i.e. in such a way that it could be demonstrated in principle by physical means by a non-comoving observer.—Albert Einstein, 1911
For those of you who don't mind adapting a thought-experiment... relativity is of course reciprocal; just as we can define the rest frame as the frame in which the shuttle has zero momentum, we can also define the rest frame as the frame in which the probe has zero momentum and the shuttle is approaching it at high velocity (in the opposite direction). From the rest frame of the probe we now see the shuttles cargo bay as length contracted, and the probe is no longer contracted ...and the probe would still all fit in just before destroying itself and the shuttle! The timings are very tough to reconcile, events seem to be switched, and with relativistic speeds you cannot be sure of any simultaneities without the maths; but in the end the same set of events happens - it must be the case because it is the exact same scenario.
There's a nice quote from Einstein on the wiki about "real" and length contraction:http://en.wikipedia.org/wiki/Length_contraction#Reality_of_Lorentz_contractionQuoteThe question as to whether the Lorentz contraction really exists or not is misleading. It doesn't "really" exist, in so far as it doesn't exist for a comoving observer; though it "really" exists, i.e. in such a way that it could be demonstrated in principle by physical means by a non-comoving observer.—Albert Einstein, 1911It also goes on to point out what most of us have been stating, that argument over what is "real" only depends on terminology. If you define "real" to mean "in the rest frame" then your argument is right. If you define "real" to mean "what is measured" then your argument is wrong. In actual science, we don't use muddled terms like "real," and constrain ourselves to describing the predicted measurements, for which there is no ambiguity.In essence, "real" matches your definition of "real" because you defined it to do so from the start.
In addition, even in a non-co-moving frame, direct experimental confirmations of Lorentz contraction are hard to achieve, because at the current state of technology, objects of considerable extension cannot be accelerated to relativistic speeds. And the only objects traveling with the speed required are atomic particles, yet whose spatial extensions are too small to allow a direct measurement of contraction.
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.
I posted a link and quotes to a very interesting blog which I believe correctly showed the principles and unsettling consequences of Special relativity. Skulls in the Stars
From the rest frame of the probe we now see the shuttles cargo bay as length contracted, and the probe is no longer contracted ...and the probe would still all fit in just before destroying itself and the shuttle! The timings are very tough to reconcile, events seem to be switched, and with relativistic speeds you cannot be sure of any simultaneities without the maths; but in the end the same set of events happens - it must be the case because it is the exact same scenario.
What I've also argued against is the introduction of extra complexity to special relativity in order to preserve some preconception about the universe. Science doesn't work that way. We can always hold an infinite number of preconceptions about the universe and introduce extra hidden variables into a model to preserve them. Obviously no one's arguing something this far out, but if I were more comfortable with unicorns causing length contraction, I could always introduce unicorns who zip about the universe shrinking our rulers with magical pony power. As long as the unicorns are undetectable by measurement, and their pony power works identically to Lorentz contraction, I can claim that my results are completely in line with observations. That doesn't this viewpoint valid science, nor does it make other viewpoints with far less absurd preconceptions valid science. Science is generally about using the simplest possible model to describe some phenomenon, not choosing the more complex model because it fits your preconceptions.
Einstein's special relativity is the mainstream scientific explanation because it is the simplest model which introduces the fewest extraneous variables and preconceptions and explains observations.
I am completely confused as to what you want from us. If you want an admission that length contraction is illusory and in some sense not "real" - then you just won't get it (from me at least); mainly because SR deals in maths and not semantics, and secondly because I can fit the probe (very briefly) entirely within the shuttle's cargo bay.
Lorentz doesn't need to add anything else at all for his theory to fit the facts.
There is something extra required for Einstein's theory though, as he still has to explain the apparent pattern of cause-and-effect written throughout the universe - because he has no Newtonian time in his model, he is not able to generate effects from their apparent causes.
Imatfaal:QuoteI am completely confused as to what you want from us. If you want an admission that length contraction is illusory and in some sense not "real" - then you just won't get it (from me at least); mainly because SR deals in maths and not semantics, and secondly because I can fit the probe (very briefly) entirely within the shuttle's cargo bay.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.
Do you really not see that your entire argument hinges on making "real" fit your definition of, and then telling us that's proof that you're right? Of course "real" matches your definition if you tell us that you're redefining it to do so!
Quote from: David Cooper on 14/09/2012 19:02:41 Lorentz doesn't need to add anything else at all for his theory to fit the facts.Lorentz's theory postulates an unmeasurable reference frame, the aether. The Lorentzian theory is essentially a historic holdover from the days when scientists thought matter of some form was required to support light wave propagation. As more and more observations added up, it was found that this aether would have to be invisible and undetectable. Say what you will about anything else, but Lorentz's theory has an extra, unobservable feature, while special relativity doesn't. This is why it's been superceded by special relativity among scientists.
QuoteThere is something extra required for Einstein's theory though, as he still has to explain the apparent pattern of cause-and-effect written throughout the universe - because he has no Newtonian time in his model, he is not able to generate effects from their apparent causes. I'm not sure what you mean. Can you give an example? Special relativity does respect causality--that's one of it's important features.
Quote from: JP on 14/09/2012 21:00:52Quote from: David Cooper on 14/09/2012 19:02:41 Lorentz doesn't need to add anything else at all for his theory to fit the facts.Lorentz's theory postulates an unmeasurable reference frame, the aether. The Lorentzian theory is essentially a historic holdover from the days when scientists thought matter of some form was required to support light wave propagation. As more and more observations added up, it was found that this aether would have to be invisible and undetectable. Say what you will about anything else, but Lorentz's theory has an extra, unobservable feature, while special relativity doesn't. This is why it's been superceded by special relativity among scientists.The unmeasurable reference frame is simply the fabric of space which restricts the speed of light within itself to c. The fact that the aether was originally regarded as something more like matter when these theories were originally being worked out does not disqualify the final form in which the fabric of space does the entire job, and having that fabric of space is not anything extra over having a fabric of space called spacetime. The difference between the two theories is really limited to the nature of time - one has Newtonian time while the other attempts to get rid of that entirely and to replace it with something which is almost identical to a space dimension.
What matters to scientists is which one has an extra undetectable feature and which one doesn't. At least on the count of an undetectable reference frame, the Lorentzian model has it, while special relativity doesn't.
Quote from: JP on 14/09/2012 23:21:47What matters to scientists is which one has an extra undetectable feature and which one doesn't. At least on the count of an undetectable reference frame, the Lorentzian model has it, while special relativity doesn't. The Lorentzian model has a fabric of space which can't be detected, and Einstein's model has a fabric of space called spacetime which can't be detected either. The fabric of space in the Lorentzian model is automatically the preffered frame, so there's no extra undetectable thing tied up in it.
Now, a lot of confusion comes into things if you try to explain things in terms of clocks ticking at different rates on the planet and in the rocket, because if all frames are genuinely equal there can be no difference between the fundamental rates at which clocks tick and you can't have some ticking faster than others.
This can be got round by allowing the rocket to take a shortcut into the future by travelling at a high speed and thereby at a different angle through time, so while its clock is ticking at the same rate, it's also on a different course through spacetime which allows it to get back to the planet far in the future while the planet is still only half way there - the two can still meet up because the future of the planet is already there for the rocket to interact with.
The whole business of clocks ticking is actually Newtonian time, so you must actually get rid of it altogether and just have an eternal block universe where the future is linked to the past by many pathways of different time-dimension lengths.
By eliminating Newtonian time altogether, the rocket doesn't actually move though - it simply is, and all of its atoms are stretched through the model like spaghetti such that they exist in all times. This is what SR does to the nature of the universe.
There is nothing in SR to account for how such a universe can be generated, so it just exists eternally without the future ever having been generated from the past and without causes having any opportunity to generate effects.