Re: Spaceship Question


Henri Wilson wrote:
> On 25 Jan 2006 03:16:55 -0800, "PD" <TheDraperFamily@xxxxxxxxx> wrote:
>
> >
> >Henri Wilson wrote:
> >> On 24 Jan 2006 13:32:21 -0800, "PD" <TheDraperFamily@xxxxxxxxx> wrote:
>
> >> >> Why do you think that? The ship occupies a length of space. ...as does a metre
> >> >> rod.
> >> >> For convenience, we can define the ship's length as ONE length unit and use it
> >> >> as a universal length standard.
> >> >
> >> >That standard would only apply in a particular reference frame (one
> >> >where the ship is at rest). Length is the result of a *procedure* that
> >> >is inherently observer-dependent. There is nothing about the ship that
> >> >you can call spatial length that is independent of the observer.
> >>
> >> Of course it is. I would say the opposite.
> >
> >You would be wrong. Experiment, by the way, indicates otherwise.
>
> Come on! You know that there is absolutely NO evidence that length contractions
> occur.

That's simply not true. Suggest you google "rapidity segmentation".
It's demonstrated in particle detectors repeatedly.

>
> >> No physical attribute of any object is observer dependent. How could it be?
> >
> >I agree. Except that length is not a physical attribute of the object.
>
> 'Length' is the absolute amount of linear space occupied (in terms of a defined
> standard).

Except that this value is not a constant.

> Measured length can be actual or illusory, depending on how it is measured.
> Measured length in any one frame is real.

And what if the measured length (done identically) in two frames
produces two distinct values? Who's right, and why?

(Hint: experiment shows this does happen. SR explains why and tells you
the relationship between those two values.)

>
> >> >> I think you will now agree that this standard remains the same no matter how
> >> >> the ship negotiates space.
> >> >
> >> >No, I quite disagree. See the above.
> >>
> >> Why are you people so obsessed with observers?
> >
> >Because length is the result of a procedure that is inherently
> >observer-dependent.
>
> No, you are confusing 'length' with 'measured length'.

Please define length, distinct from measured length, and please
indicate
a) how you know such a quantity, inherent to the object and independent
of the state of motion of the observer, exists
b) what value it has, if it is not measurable

>
> The same applies to TIME, which exists as a fundamental 'dimension' whether or
> not we try to measure it with clocks.

Time as a dimension certainly exists, as does space. How *much* time
something takes, and how *much* space something consumes, however, is a
matter of the state of the observer.

>
>
> >> >> You seem obsessed with observers and their measurements. Observers don't change
> >> >> physical properties of observed objects, you know.
> >> >
> >> >That's right, but length is not a physical property of the ship.
> >>
> >> I have explained elsewhere that the ship INTRINSICALLY occupies a length of
> >> space and that this length can, for convenience, be defined as one standard
> >> unit.
> >> Let's perform an experiment.
> >>
> >> Let's produce billions of identical platinum-iridium 1 metre rods and fire them
> >> all into space in all directions.
> >>
> >> Do you think any of them actually changes due to that experience?
> >
> >No, but then again, the change in length does not amount to a physical
> >change in the rods.
> >
> >> Do you think that if two of them are reunited in remote space, their lengths
> >> will be different?
> >
> >No, but if two of them pass a single observer at different speeds, they
> >will be have different lengths.
>
> I think you just contradicted yourself... :)

No, I don't think so. Where is the contradiction?

>
> >> >> >If, however, you cannot free yourself from insisting that length is an
> >> >> >inherent property of the spaceship, then indeed I can understand why
> >> >> >this would be most difficult to comprehend.
> >> >>
> >> >> The ship's length is defined as ONE SPACE UNIT.
> >> >
> >> >That definition would not work for all reference frames. (Or if you
> >> >mandated that it does, then the length of everything else would change
> >> >in space units.)
> >>
> >> Where is your proof of that...or are you just preaching again?
> >
> >The proof is in experiment, HW.
> >
> >>
> >> We have already established that physical properties do not change with
> >> velocity. (they cannot both increase and decrease simultaneously)
> >
> >But length is not a physical property.
>
> you are confusing 'length' with 'measured length'.

See above.

>
>
> >> >> It doesn't alter with velocity changes.
> >> >
> >> >Sure it does. Length is not a physical property of the spaceship that
> >> >is observer-independent. Length is the result of a *procedure* that is
> >> >inherently observer-dependent.
> >>
> >> 'Occupation of space' is the physical property. Length can be quantitatively
> >> assigned by definition.
> >> We are defining the standard length unit as the amount of space between one end
> >> of our spaceship and the other end.
> >
> >Crappy definition. The problem is that two copies of the same standard,
> >traveling at different speeds and observed by the same fella, will have
> >different lengths.
>
> Measurements made in different frames can be and usually ARE illusions.

Why? Explain how to make the measurement of this quantity in such a way
to be free of the illusion. If you can explain that, then we'll be free
of all this.

>
>
> >> >The moving observer would not agree that those standard rods are the
> >> >same length as the standard rod he is carrying with him.
> >>
> >> But he must know that he is deluded if he measures them to have any length
> >> other than the one he assigned to them at rest....because knows that they could
> >> not possibly have been affected by his own movement.
> >
> >What he thinks he knows is irrelevant, as all such "knowledge" should
> >be checked against experiment. What he *measures* is what determines
> >what he knows. What he learns from this measurement is that length must
> >not be an inherent physical property of the object. (Relativity
> >explains *why* it cannot possibly be an inherent physical property of
> >the object.)
>
> Ah! I can identify part of your problem.
>
> You people all believe you are infallible.
> If you see something, you firmly believe it must be real!

If there is a physical property that is unmeasurable, then it is not
real. If there is a physical property that can be, but hasn't been,
measured, then please specify how. Exactly.

>
> >> >
> >> >> Why would you think it would?
> >> >>
> >> >> A_________rod_________B
> >> >>
> >> >> ->O O1<-
> >> >>
> >> >> You seem to be under the delusion that the rod changes length because of the
> >> >> presence of differently moving observers. How strange...
> >> >
> >> >Yes, that's right. Note that nothing is happening to the rod per se,
> >> >though something is happening to its length. That's because length is
> >> >not a physical property of the rod.
> >>
> >> Its length has been given the value ONE by definition.
> >>
> >> Are you saying that it becomes something other than ONE just because observers
> >> move past?
> >
> >Yes.
>
> That's not very logical of you.

I don't see why you'd think so.

>
> >> >> >> The principle is that nothing actually happens to the ship or its clocks when
> >> >> >> its engine is fired for a period. Obviously the length of the period doesn't
> >> >> >> matter if nothing happens anyway.
> >> >> >> Wouldn't you agree?
> >> >> >
> >> >> >Yes.
> >> >>
> >> >> Hooray!
> >> >
> >> >The guy on the ship is not going to measure any difference in the
> >> >period of the ship's clock, no matter how the ship moves.
> >>
> >> Nor is anyone else with proper measuring equipment.
> >
> >Spaceman also believes that time dilation is due to clock
> >malfunctioning. Do you believe that too?
>
> Spaceman does NOT believe that.

You sure?

>
> Spaceman and I both know that 'time dilation' is part of the relativists'
> delusion.
>
> You still haven't defined 'time dilation' anyway.

OK.

>
> >> >That depends on what "they" stands for. If you mean the rods and the
> >> >clocks, then I agree. If you mean the rod's length or the clock's rate,
> >> >as measured on the ship, then I agree. If you mean the rod's length or
> >> >the clock's rate, as measured by any other observer, then I don't
> >> >agree.
> >>
> >> But you have no good reason to hold such a belief.
> >
> >Sure I do. It's called experiment. It's an observed fact.
>
> It would be an observed illusion, if it did happen.

It's only illusion if there is a way to correct it. Got a plan?

>
> >> The rod's 'length' is calibrated against the standard, which is the ship's
> >> length of ONE unit. If nothing physically happens to the rod as a result of the
> >> acceleration experience, it must be exactly the same rod and therefore possess
> >> exactly the same length as before...no matter WHO measures it.
> >>
> >> Anyone who get a different value for its length must be using a faulty
> >> technique.
> >
> >Not if length is not a physical property of the rod. If one defines a
> >standard and then finds that the standard is useless and
> >observer-dependent, then one calls into question the standard rather
> >than assuming the technique is crappy. Especially if one can accurately
> >*predict* how much the "standard" changes with the observer,
> >independent of the method used to measure it.
>
> But the standard is NOT useless. I can take a standard metre rod anywhere,
> anyhow in the universe and know it is exactly as it was before I left.

Not so. A standard meter comes with instructions stamped in the side
that it can only be used at rest in the observer's frame.

>
> >If there were a problem with the technique, then the answer would vary
> >by varying the technique or by altering the device. Since the result of
> >the measurement is *predictably* dependent on the relative speed of the
> >observer and not on the technique, then the implication is that there
> >is something else going on.
>
> M\easuring anything in a frame different from the obserevr is tricky at best.
> It would normally lead to an illusion. Sensible people would immediately
> realize that.

What illusion is that? And how do you measure the quantity free from
the illusion?

>
>
> >> >
> >> >Any quantity that is the result of a procedure that is inherently
> >> >observer-dependent will naturally be affected by remote observer
> >> >movement. This isn't true for quantities that are inherent properties
> >> >of the object, but length of the object and the rate of the process in
> >> >it are not inherent properties of the object.
> >>
> >> I think you are confusing 'length' with 'measured length'.
> >> Measurement always have limits of accuracy.
> >
> >Limits of accuracy are estimable, and this effect has been observed to
> >far exceed the limits of accuracy.
>
> Limits of the illusion are not easily estimable.
> One must try to create the reality behind the illusion when the illusion is the
> only data one has.

??? You mean, like "Imagine the real world without the Matrix?"

>
> >> Those people who originally standardized their gear with the ship's while at
> >> rest with it and who subsequently do NOT measure the spaceship's length to be
> >> ONE unit, are obviously performing flawed experiments.
> >
> >Sorry, that's not obvious. In fact, it's pretty easily ruled out.
>
> If logic proves that the ship's length did NOT change and a particular observer
> DOES measure a change, then it is pretty obvious who is wrong.

No, logic does not rule it out. You only showed that no physical
processes can be acting to affect the intrinsic physical properties of
the rod. You have not demonstrated that length is one of those
instrinisic physical properties. In fact, you have not demonstrated a
meaning or a means to measure a length in any way that observers in
different states of motion could agree on and get a common value.

This isn't something to get overly worked up about. There are lots of
properties that are like this. Kinetic energy or momentum, for example.

>
>
> >> >Maybe you should ask yourself what "length" means.
> >>
> >> ...occupation of space between two points.
> >
> >Let's figure out exactly what that means. How do you measure the length
> >of a moving object?
>
> You don't have to measure it to define it.

I beg to differ.
Define the momentum of any object that is independent of the motion of
the observer.
Go ahead.

> You only have to measure it if you want to quantify it.

Then we're talking about two different things. You seem now to be
talking about the *existence* of length, as opposed to what values it
has, according to different observers.

PD

.

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