In any case, here’s a quote from one of the top physicists in the field. He supports my position exactly and the situation hasn’t changed since then:

“It is an amazing fact that there does not seem to exist any direct or simple experimental verification of the Lorentz-Fitzgerald contraction. There is no reason whatever to doubt that the effect exists, precisely as called for by theory. So far, nevertheless, the difficulties – (1) of securing an object of appreciable length that moves with a speed comparable to that of light and, (2) of determining two events, one at either end, which are simultaneous for the observer – have proved insuperable. This very fundamental conclusion of the theory awaits actual proof.”

Albert Shadowitz, Special Relativity, 1968, p. 168 of Dover paperback.

Personally, I am happy to accept the measurements of spectrometers, etc, as the more appropriate way to measure the composition of the Moon and hence show directly that it doesn’t taste of cheese, just as I am prepared to accept interferometric measurements of distance as the appropriate way to measure directly the very small effects of Lorentz contraction in the laboratory.

The fact that no-one has used a meter rule to do so may well be true, but it is entirely uninteresting as using a meter rule to measure such a distance is no more “direct” a measurement than using interferometry, just as the fact that no-one has actually tasted Moon rock may well be true, but is uninteresting because tasting Moon rock is no more “direct” a measure of its cheesiness than using a mass spectrometer.

Was that spelled out explicitly enough this time?

I think we have a case here of people just wanting to keep on pounding their original line out of misguided stubbornness, vanity, or whatever even after a good argument has been made against their perspective. This is as unhealthy as it is dismayingly commonplace.

I congratulate you on a rare moment of insightful introspection.

“What we’ve got here is a failure to communicate!” – the Boss from Cool Hand Luke

Although October 2006 marked the breakthrough, it also marked cancellation of the project by the Bush Administration, which needed the insignificant amount of further engineering development money for the Iraq War.

Here’s a link to a video of a talk about the project Dr. Bussard delivered to Google employees before he died.

Here’s a link to an interview he gave about the technology.

How about it, Cosmic Variance? An article on this would be great.

That is what “direct” means, it is not too strict; you folks are too post-modernistically mushy etc. IMHO. If you use background assumptions and reasoning to infer something, well, it is still “inferred”, good practice or not. I’m not saying it’s wrong to believe in what is well inferred (I believe in LC too for all the same reasons), but I care about good use of wording – shouldn’t you?

Perhaps we should. Perhaps we don’t like being patronized. Or perhaps we are smart enough to recognize that it isn’t that simple. Why is using a ruler the “direct way” to measure a length? Isn’t counting the clicks on a click wheel a direct way to measure a length? Or perhaps sonar, which you have already accepted as a direct measurement, since it involves measuring the time it takes something (in this case a sound wave) to travel at fixed velocity from one end to the other. Why not time a light wave? Or you could lay a bunch of cigarettes of known length end to end and count them, which, I hope you agree, is really just a rather foolish kind of ruler. In fact, you could use any standard rod you like for the measurement: pingpong ball, cricket stumps, you name it. They are all rulers. Or even wavelengths of light of known frequency: you could set up a standing light wave and count the nodes. That would be an interferometer, which, I am sure you now agree, is just a ruler. So perhaps Messrs Michelson and Morley were just using a ruler to make a direct measurement, and we weren’t the ones who hadn’t thought through what constitutes “good use of wording.”

If you are not willing to take the equivalence of frames as a given (from which time dilation gives you length contraction), then you are so crazy as to let anything go. You could measure length contraction but then say, oh, motion creates a mystical field that affects my measurement devices in a systematic way.

You suggest using a spinning disk to get around questions of simultaneity. The resolution of that paradox is far more “background loaded” than barn-pole, but let’s ignore that. I’ll do the experiment, but instead of painting dots on the sphere and watching them go by (your example of a “direct” experiment, I think), I’m going to charge it up and measure the magnetic field. There’s really no way you can separate those two into distinct epistemological categories (unless you have some wacky notion of qualia as ontologically prior — but I doubt you’re a Heideggerian!).

They are on a continuum and no “good use of wording” will make the difference discrete. Indeed, dots-on-a-sphere may require a great deal more background assumptions — about the nature of light propagation, for example — and the visual experience will have to be disentangled because of doppler shifts and so forth! I’m not particularly “post-modern” (whatever that means), but neither am I a logical positivist. This is pretty standard Quine stuff.

As for terminology questions of which mass is the “true” mass. In teaching relativity I find it’s nice to make a distinction between “number of atoms” (proportional to rest mass) and “mass”, the latter of which I define through inertia. Relativity does force us to complexify our intuitive ideas about “mass as stuff”, though, so perhaps we should bite the bullet and call them “zoog” and “zaag”.

That is what “direct” means, it is not too strict; you folks are too post-modernistically mushy etc. IMHO. If you use background assumptions and reasoning to infer something, well, it is still “inferred”, good practice or not. I’m not saying it’s wrong to believe in what is well inferred (I believe in LC too for all the same reasons), but I care about good use of wording – shouldn’t you?

BTW, what do any of you think of the proposition I put upthread, that we should use “mass” in the sense of “relativistic mass”? See my arguments for why it is better than the invariant “proper mass” as a placeholder for “mass” in general.

In general, you need a set of background assumptions to do any kind of science; you can’t establish Lorentz contraction without holding, and inferring from, some other beliefs about the nature of the physical world. Logically speaking, every measurement we’ve made is compatible with the absence of Lorentz contraction, but the amount of background you’d have to alter at this point is huge.

Succumbing to Latex