Re: twins paradox problem

On Wed, 15 Mar 2006 13:26:20 +0000, dseppala wrote:

On Tue, 14 Mar 2006 15:17:07 -0500, sal <pragmatist@xxxxxxxxxx>
wrote:

On Tue, 14 Mar 2006 14:11:30 +0000, dseppala wrote:

I've never seen an answer to this twins paradox question.

It is because you never looked. You close your eyes in the presence
of answers, and you never invest any effort in finding them
yourself.

You invest lots of effort in finding problems, and none in finding
solutions. So you find problems, not solutions. What a surprise.


In this problem, instead of two twins there is a battery and a
light bulb connected with a pair of wires. An ammeter at the
battery measures that one ampere (one columb per second) is
flowing there. An ammeter at the light bulb measures that one
ampere is flowing through the light bulb.

Now as in the twin's paradox we let the light bulb accelerate to
V, travel for some distance,


Here is your FIRST TASK:

Given that the current through the battery is 1 amp in the rest
frame of the BATTERY, determine the current through the bulb as
measured in the rest frame of the LIGHTBULB.

Either prove that the measured currents match, or if they don't
match, determine what the "moving" reading must be. Use numbers,
algebra, Lorentz transforms, and stuff like that, not just waving
hands.

You have _assumed_ the measured currents match. But is that correct?

No I did not make that assumption. When the battery and light bulb
were at rest, yes each ammeter measured one ampere (the given
information). Now if both current readings remain one ampere while
they are moving, then if time isn't constant then a different number
of columbs flow from the battery than flow through the
light-bulb.

Oops! I feel a breeze! You skipped the calculation.

If the readings don't match, what is the ratio of the readings?
Display your calculation, please.

But, here's the important question which you have glossed over: Where are
the ammeters placed, and how are they wired, in order to obtain these
readings?

And, just to emphasize it: To _which_ frame of reference does each
meter belong?

Be _precise!_ You are still just waving your hands.


This implies charge builds up somewhere. However, the two frames
have a different view as to whether more current flows through the
battery or through the light-bulb,

This is all garbage. You're frame shifting without even realizing
you're doing it and you're trying to conclude something from your
vacuous handwaving. You need to _start_ by comparing meter readings
obtained within a SINGLE FRAME OF REFERENCE.

You have done no calculation here, and what's worse, you have posed
the question very badly and very imprecisely.

Describe _exactly_ what meters you are discussing, and HOW FAST each
meter is moving, whose frame of reference it's at rest in, and exactly
what you'd expect it to read. So far you have not done that.
And you need to describe how each meter is to be connected to the
items it's measuring. That's important; it's not just a side issue.

Compute the current and voltage measured by each meter. (Yes, indeed,
you need to add some voltmeters or you'll never make sense of this
problem.)

Then discuss the relationships between meter readings within a
_single_ _frame_ of reference. Got that? I'll repeat it, because
you probably didn't get it: Meters in a _single_ _frame_ _of_
_reference_.

THEN, and ONLY THEN, you can claim you've found a contradiction, if
you do. But, you won't.

In fact, you won't attempt the calculations, either, I'm quite sure.

Comparing meters at rest in different frames is interesting, but at
this moment you HAVE NO IDEA how their readings should relate to each
other because _YOU_ haven't even attempted to set up the problem in
any precise way.



so if
the ammeters each read the same value, then a volt meter across the
wire at the point where excess charge exists ...


Hogwash and handwaving.

Prove there's a place where excess charge exists. Then, only then,
start worrying about how to account for it and how to measure it.


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