Re: twin clock problem - SR experts help!

On Fri, 26 Aug 2005 12:51:40 +0000, Dirk Van de moortel wrote:

>
> "Harry" <harald.vanlintel@xxxxxxx> wrote in message
> news:430f059e$1@xxxxxxxxxxxxxxxxxxx
>>
>> "Dirk Van de moortel" <dirkvandemoortel@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>> wrote in message news:6ZBPe.11200$8d2.3183@xxxxxxxxxxxxxxxxxxx
>> >
>> > "Harry" <harald.vanlintel@xxxxxxx> wrote in message
>> news:430edf05$1@xxxxxxxxxxxxxxxxxxx
>> > >
>> > > "Dirk Van de moortel" <dirkvandemoortel@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>> wrote
>> > > in message news:%uAPe.11197$4b2.4513@xxxxxxxxxxxxxxxxxxx
>> > > >
>> > > > "sue jahn" <susysewnshow@xxxxxxxxxxxx> wrote in message
>> > > news:430ea504$0$18638$14726298@xxxxxxxxxxxxxxxxxx
>> > > >
>> > > > [snip]
>> > > >
>> > > > > A clock simulates the passage of time.
>> > > >
>> > > >
>> > > > That's only for philosophers who never held a clock in their
>> > > > hands.
>> > > >
>> > > > For physicists and engineers and the rest of the world, a
>> > > > clock *defines* the passage of time.
>> > >
>> > > Hmm... a correctly *calibrated* clock defines the passage of time
>> >
>> > No. As soon as you have a clock - any kind of clock, like your
>> > heart beat, you can define time and the passage of time with it,
>> > and even do experiments with it. You can find out that the
>> > distance covered by a falling stone is more or less proportional
>> > to the square of the falling time, which you define as the number
>> > of heart beats that you count.
>>
>> Just try to sell that idea to a normalisation institute. ;-) - On a
>> serious note: when it was discovered that the solar clock is
>> irregular compared to atomic clocks, the atomic clock standard took
>> over for a more precise (regular) calibration. From then on the
>> solar clock does not anymore define the "passage of time", as it's
>> not anymore the reference standard.
>
> When you are alone in the desert without an atomic clock or wrist
> watch or sun or stars,

In a desert without sun or stars?

What desert might that be? Deserts I'm familiar with are all very
dry, and generally provide an excellent view of the sun during the day
and the stars at night.

I suppose you could be referring to a polar desert in white-out
conditions, but if I were wandering around alone outdoors in such a
situation I would certainly not be thinking about physics experiments.


> you can define time and "the passage of time"
> with your heart beat, and do physics and engineering.

Alone in the middle of white haze, unable to see anything, in sub-zero
temperatures ... most likely _far_ subzero ... and you're doing
physics _and_ engineering.

That's what I call dedication!


> You don't need reference standards. You need a clock,

No you don't, you need a compass! Preferably one of those cool Sagnac
gyro-compasses, since you may be too close to one magnetic pole or
another for a magnetic compass to do much for you.

You may need sunglasses, too, come to think of it, white haze or not.

And did I mention long underwear?


> something that does pom pom pom pom pom pom. You count the poms and
> call it time. When you have more than one kind of clock, you can
> compare one against the other and compare the times you define and
> read on those clocks.

You're alone in the Antarctic wilderness in the middle of a white-out
and your backpack turns out to be stuffed with nothing but clocks, of
all different kinds.

This does not reflect good planning.


> If you can define regularity or "correct calibration" without using
> the concept of time, then I agree with your suggestion that "a
> correctly *calibrated* clock defines the passage of time"

Of course it must be "correctly calibrated".

But "correctly calibrated" is, after all, a rather loose term. A
"time candle" whose stripes are equidistant from each other is
"correctly calibrated", for instance, though it's not likely to be of
much value in a blizzard in Antarctica.

Any heart you happen to have along which goes on going "pom pom
pom..." in a nice soothing regular way while you're stuck out there in
the middle of the ice fields also counts as a "correctly calibrated"
clock, under the circumstances. (You don't want to find out you've
brought along *** Cheney's by mistake, for instance -- if the
batteries in the onboard defibrillator run down before you figure out
the way back to Ice Station Zebra you've got a big problem.)


>
> Dirk Vdm

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