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'[OT] : Challenging...(another thought)'
2004\06\25@035827 by reinaldo

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Wow! this must be good stuff i'm smoking!
Imagine this....
there's a limited number of pixels in any monitor, yet it
can display any image, so, if you wrote a program to set
pixels at every possible colour intensity combination in
sequence, eventually you'll get real images!! it could be
anything, things that already happened and things that will
happen!!and ofcourse a lot of made up things, like a photo
of me and john lennon drinking coffe together, it'll be
there. what's even more scary, what happens when this
sequence eventually runs out? it means any possible and even
impossible event that could or could not happend, has
already been in the sequence...
it means nothing else can happen, you'd think that was
infinate, BUT the number of pixels is limited, and so are
all possible combinations of this...
wierd hey.

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2004\06\25@044920 by Daniel Chia

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Well, the problem presents itself in that there are many, many combinations.

Lets say we take 24bit colout, Red 8, blue 8, green 8 combination. thats 512
possible colours per pixel.

now lets say we have an avg resolution of 800 x 600.

now that works out to
512^480000 combination. no small no.

I am a competitional programmer in school and computers normally hit about
100,000,000 loops per second.. So generating all the permuations is kinda
hard.

------------------------------------------------------------------------
Daniel Chia

"Genius is one percent inspiration and ninety-nine percent perspiration."

    - Thomas Edison

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2004\06\25@045956 by William Chops Westfield

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On Jun 25, 2004, at 1:55 AM, Daniel Chia wrote:

>
> Lets say we take 24bit colout, Red 8, blue 8, green 8 combination.
> thats 512 possible colours per pixel

24 bits is 16million possible colors...

Reminds me of a physics book I had in college that attemped to
demonstrate "impossible" by applying actual analysis to the "lots of
monkeys at lots of typerwriters" problem...

BillW

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2004\06\25@050617 by Hopkins

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So how long would it take?
*************************************************
Roy Hopkins   :-)

Tauranga
New Zealand
*************************************************

{Original Message removed}

2004\06\25@052107 by Daniel Chia

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Ah yes my bad. i took 8^3 rather thank 2^8^3 which is 16777216 about 16
million.

And hmm. how long will it take. Not worth waiting..
Its an exponential algorithm and these things are notorious for the slow
speed.
------------------------------------------------------------------------
Daniel Chia

"Genius is one percent inspiration and ninety-nine percent perspiration."

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2004\06\25@062901 by William Chops Westfield

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Let's be nicer and use a 256x256 display ("poor" TV quality) with
8 bits of color (256 values.)

That's "only" 256^65536 possible combinations.

There are about 10^79 electrons, atoms, and neutrons in the universe.

BillW

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2004\06\25@065842 by Peter van Hoof

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maybe you can generate 100,000,000 images a second but even the best of
monitors can only display 200 different ones a second and even the best of
humans can view at most a few a second

Peter

{Original Message removed}

2004\06\25@073415 by Robert B.

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In attempting to carry out similar calculations and convert to years, Matlab
keeps returning "infinity" as the answer.  So I guess that solves it!

{Original Message removed}

2004\06\25@081025 by Daniel Chia

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Hahaha maybe you should get better software. =P just kidding.

anyway mathematic returns me no of years which has about 160000 digits
roughly.

Wow. what a small no
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Daniel Chia

"Genius is one percent inspiration and ninety-nine percent perspiration."

    - Thomas Edison

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2004\06\25@100713 by Russell McMahon
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Various thoughts on this thread.

1.    The inter-star bending rod is subject to the "laws" of relativity and
will not allow peturbatuions greater than light speed to travel
along/through it. Alas.

2.    Look at waves hitting a beach or ripples hitting the edge of a pool
etc. If the wave front is slightly off square, watch what happens to the
contact point as the wave hits the edge or shore. Whiel nothing on the wave
moves faster than wave speed, the contact point is related to the arctan of
the contact angle. For very small angles, the contact point can travel at
speeds of 100's of kilometres per hour when the wave is travelling under 10
kph. Nothing physical is actually moving this fast but the motion can be
very clearly observed. (The cutting point on a pair of scissor blades does
the same thing but with a multiplier of only a few times).

Now take a light wave meeting a surface at a small angle ...  :-)

3.    Beyond monkeys and pictures on a screen there is the number of
locations in the universe. Space is quantised in units of Planck length (PL)
and time in Planck time (PT). The total possible number of locations in a
universe of dimension L (whatever that may actally mean) is about (L /
Planck_length)^3. While this number is large it is finite. Similarly you can
define all possible locations in space and time for a universe of age T by
(L / PL)^3 x (T/PT). The universe has a finite number of possible locations
in time and space ;-). Now set your monkeys to work to do something useful
with that.

4.    The two (arguably) major competing theories for the formation of the
universe are

i.    that it was creating by an external pre-existant entity (where eternal
and pre-existant are meaningless terms because neither time or space existed
prior to their existing :-) ) OR

ii That it was created out of nothing by nothing.

Both theories have their problems, but I find the second requires far more
faith to believe than the former :-)

5.    Did John Lennon drink coffee ?

6.    Nothing of Einstein's forbids travelling faster than light. Just AT
the speed of light. Hawkings has shown (and it may or may not be true) that,
even though NOTHING can escape from a black hole, BH's radiate because
particles can "tunnel" across the Shwarzchild radius / event horizon. (There
are other ways of looking at this feat but tunneling is as valid (or not) as
any.) Tunnel diodes also operate by quantum tunneling where an energy
barrier is passed through without being crossed over.

So, IF it is possible to tunnel the light speed energy barrier, all sorts of
interesting things happen. Energy gains a sqrt(-1) term whose significance
is as yet (and may always be) unknown. BUT Plotting 0.5 m x V^2 and allowing
for relativistic mass shows that energy required DECREASES past light speed
to a minimum about (AFAIR) 10 x light speed and then again increases towards
infinity. IF you can tunnel light speed there are TWO equal energy points
you can jump to. One is slightly above light speed and the other about 10 or
more times light speed. You can't get to either until you are travelling at
(AFAIR) about 0.9C and odds are that to tunnel you need your  "'ship" to be
at around 0.999C +, so we aren't going to see this any time soon.

But non zero-rest-mass particles MAY be able to be persuaded to play these
games.

Now, go and write that science fiction story ....

7.    Quantum Mechanics says (rightly or wrongly) that causality is broken
at the foundational level. If you build something on an insecure foundation
it is necessarily insecure. While you may be able to take many steps to
shore it up, the basis of causality is lost if the foundation is non causal.
But it still all seems to hang together and work very nicely anyway.
Interesting.

8.    There are ABOUT as many grains of sand on the beaches of earth as
there are stars in the universe (around 10^21 give or take).
But, Abraham knew that :-)



       RM

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2004\06\25@120835 by Robert Ussery

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{Quote hidden}

d00d, lay off the stuff... ur scarin' me! LOL... :O)


- Robert

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2004\06\25@131720 by Dipperstein, Michael

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{Quote hidden}

Unfortunately, capturing an event in space-time and rendering it as a 2D image
on even the best monitor is a lossy compression.  There are many pieces of
information that are lost.  What appears to be you drinking coffee with John
Lennon, would look exactly like:
- A picture of you drinking sewer water John Lennon
- A picture of you drinking coffee with a well costumed space alien dressed as
John Lennon
- A picture of John Lennon drinking coffee with a well costumed space alien
dressed as you
- A picture of a well costumed space alien dressed as you drinking brownish
alien liquid with a well costumed space alien dressed as John Lennon
- A picture of any of the above in the company of the invisible man
- A picture of a picture of any of the above

Then there's the loss of time and locational information too.

What you would get though is every possible image that could be displayed on the
monitor that you used.

If you want to put the recording industry out of business, you can create and
copyright every single bit pattern recordable on a CD.  Every time they release
a CD, you can sue them, because you already have a copyright on that bit
pattern.  If they release recordings on another media, you can digitize the
recording and put it on a CD, find the matching CD and sue them for transmitting
and reproducing your copyrighted material without your express written consent
(and the consent of Major League Baseball).

-Mike

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2004\06\25@203722 by William Chops Westfield

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On Jun 25, 2004, at 7:07 AM, Russell McMahon wrote:

> 2.    Look at waves hitting a beach or ripples hitting the edge of a
> pool
> etc. If the wave front is slightly off square, watch what happens to
> the
> contact point as the wave hits the edge or shore. Whiel nothing on the
> wave
> moves faster than wave speed, the contact point is related to the
> arctan of
> the contact angle. For very small angles, the contact point can travel
> at
> speeds of 100's of kilometres per hour when the wave is travelling
> under 10
> kph. Nothing physical is actually moving this fast but the motion can
> be
> very clearly observed.


There's a similar phenomena for EM/etc; either the 'group velocity' or
'phase velocity' of the waveform corresponding to something like a
fundamental packet;  (IIRC, it goes something like this.  A particle is
like a wave, right?  but you apply forier analysis to get something
that looks like the discontinuous waveform of a particle, and the
individual frequencies involved have to have propagation velocities
faster than C.
Unfortunately, you can do anything useful with those parts...)

BillW

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2004\06\26@115637 by John Ferrell

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So how much delay is there in a hydraulic system? My intuition is telling me
it is faster that a sonar signal.
John Ferrell
http://DixieNC.US

{Original Message removed}


'[OT] : Challenging...(another thought)'
2004\07\25@232947 by Robert B.
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A bit of googling found this:

5000 m/sec: speed of sound in structural steel
1500 m/s : speed of sound in water (temp. dependent)
1600 m/s : speed of sound in hydraulic fluid/oil
330  m/s : speed of sound in air (STP)
3e8 m/s  : speed of light in a vacuum

However, I seem to recall reading some theory in which electrons in a wire
are viewed as "marbles in a tube", and thus electricity can apprear to move
faster than the speed of light.  The theory went that since the "tube" was
already full of "marbles", putting one in the end spits one out the other
end instantaneously, though no single "marble" really moves that fast.  I
don't remember the source, but I'll poke around some of my old electronics
books and see if I can find it.



{Original Message removed}

2004\07\25@234023 by Anthony Toft

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>  3e8 m/s  : speed of light in a vacuum

All though this is considered the speed limit of the universe by most. I
read somewhere that royalty exceeds it, the heir to the throne becoming
King the moment the former King died. Pratchett I think it was

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2004\07\26@021717 by Jinx

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> I'll poke around some of my old electronics books and
> see if I can find it

Just Google for "marbles in a tube" ;-) !!

http://www.physicsforums.com/archive/t-5367

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2004\07\26@040107 by Russell McMahon

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>  5000 m/sec: speed of sound in structural steel
>  1500 m/s : speed of sound in water (temp. dependent)
>  1600 m/s : speed of sound in hydraulic fluid/oil
>  330  m/s : speed of sound in air (STP)
>  3e8 m/s  : speed of light in a vacuum
>
> However, I seem to recall reading some theory in which electrons in a wire
> are viewed as "marbles in a tube", and thus electricity can apprear to
move
> faster than the speed of light.

The electrons do indeed move slower than the "signal", but the signal speed
does respect the laws of Physics as we presently know them ie  it's always
slower than the speed of light in vacuum. The electron speed is referred to
as the "drift velocity" and can be calculated from the charge required to be
transferred in unit time, the charge on an electron (which together gives
electron flow per unit time) and physical characteristics of the system
(the fatter the "pipe" the slower the flow).

In all such ponderings the principle of TAANSTAAFL almost always applies.

An interesting effect occurs when you inject particles/electromagnetic waves
from eg a vacuum into a medium where the normal propagation speed is lower.
For gamma waves (super energetic photons) the result is "Cherenkov
radiation" - this occurs when gamma rays enter the atmosphere and is used as
a major means of detecting incoming gamma rays. It is also seen as a bluish
white glow when radioactive material is stored under water.

An excellent intuitive graphical explanation of the phenomenon may be found
here

       http://physics.csufresno.edu/akira/SR/Cherenkov.html


       RM

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2004\07\26@041143 by Russell McMahon

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Commenting on my comment -

> The electrons do indeed move slower than the "signal", but the signal
speed
> does respect the laws of Physics as we presently know them ie  it's always
> slower than the speed of light in vacuum. The electron speed is referred
to
> as the "drift velocity" and can be calculated from the charge required to
be
> transferred in unit time, the charge on an electron (which together gives
> electron flow per unit time) and physical characteristics of the system
> (the fatter the "pipe" the slower the flow).

The drift velocity is the effective electron speed, which  doesn't mean that
that is the speed that they travel at when they do "travel".

Electrons ALWAYS travel slower than the speed of light as they have "rest
mass". No particles with rest mass can travel AT the speed of light. ALL
particles with no mass must travel at the speed of light. As far as we know
:-)



       RM

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2004\07\26@100238 by Mike Hord

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This is more of a question of the speed of transfer of information,
kind of like Russell's "marbles in a tube" question.  The marble isn't
travelling faster than light, but the information that marble has been
added to the tube is.

Maybe.  Theoretical physics is not my strongest area.  I just thought
I'd comment on the "Speed of Royalty" (not to be confused with
the "Speed of Goverment" which is markedly slower.)

Mike H.

> >  3e8 m/s  : speed of light in a vacuum
>
>All though this is considered the speed limit of the universe by most. I
>read somewhere that royalty exceeds it, the heir to the throne becoming
>King the moment the former King died. Pratchett I think it was
>
>--
>Anthony Toft <RemoveMEtoftatspamTakeThisOuTcowshed.8m.com>

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2004\07\26@101322 by Jake Anderson

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you are mixing up 2 things
the information can travel faster than the speed of the particle in the
tube.

however the marbles cant travel faster than the speed of light.
so the marbles will compress at their local speed of sound (in the marble
material itself)


> {Original Message removed}

2004\07\26@101736 by D. Jay Newman

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> you are mixing up 2 things
> the information can travel faster than the speed of the particle in the
> tube.

Yes, but according to the currently accepted theories, the information
cannot travel faster than the speed of light. Yes, I'm hoping that there
are some new discoveries that allow for FTL travel, but for now there
isn't even an FTL radio.

> however the marbles cant travel faster than the speed of light.
> so the marbles will compress at their local speed of sound (in the marble
> material itself)

Yes, physical objects compress at their speed of sound.
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2004\07\26@102326 by Jake Anderson

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afaikr theres nothing that says information cant travel faster than light.

nothing says *we* cant travel faster than the speed of light.

you just cant go from below the speed of light to above it ;->

i wonder what the affect on luminal matter (ie stuff below C) would be from
superluminal matter (ir stuff travelling FTL)
ignoring the mechanics of getting there for the time being.
methods of detecting this are left as an exercise for the reader.

what i find interesting also is apparently for a fair while after the big
bang the local speed of sound exceded the speed of light(based on the
density of material).

> {Original Message removed}

2004\07\26@102934 by Robert B.

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Yeah that seems more right, I was confusing it in my head.

BUT... it's still hard to believe that if I had a tube about 2km long full
of marbles, and a really big sledge-hammer to cram another one in, that it
would take a full second after a forceful insertion on the one end for one
to pop out the other end.  I suppose it's true, but perhaps one day if I get
rich and infamous I'll verify it personally, just for kicks.



----- Original Message -----
From: "Jake Anderson" <EraseMEgrooveeespamOPTUSHOME.COM.AU>
To: <RemoveMEPICLISTEraseMEspamEraseMEMITVMA.MIT.EDU>
Sent: Monday, July 26, 2004 10:14 AM
Subject: Re: [OT] : Challenging...(another thought)


> you are mixing up 2 things
> the information can travel faster than the speed of the particle in the
> tube.
>
> however the marbles cant travel faster than the speed of light.
> so the marbles will compress at their local speed of sound (in the marble
> material itself)
>
>
> > {Original Message removed}

2004\07\26@103141 by D. Jay Newman

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> afaikr theres nothing that says information cant travel faster than light.

Physics?

There are some theories that certain things happen faster than light,
especially in quantum mechanics.

However, there is no way to extract information from these things.

This is the accepted wisdom *now*. Hopefully this will eventually be
changed, but for now, I'd study a bit more physics and less SF.

> nothing says *we* cant travel faster than the speed of light.

Again, this is physics. This says that we can't travel faster than the
speed of light. There *may* be some promising loopholes, but they are
only speculative now.

> you just cant go from below the speed of light to above it ;->

This is an extremely common plot concept in science fiction. Please do
not confuse this with currently accepted physics.

> what i find interesting also is apparently for a fair while after the big
> bang the local speed of sound exceded the speed of light(based on the
> density of material).

Again, that is theory. If there was a big bang (and this seems probable)
then the basic constants of the universe were in flux during an extremely
short period. The speed of light may have been much higher at that point.
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2004\07\26@103746 by D. Jay Newman

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> BUT... it's still hard to believe that if I had a tube about 2km long full
> of marbles, and a really big sledge-hammer to cram another one in, that it
> would take a full second after a forceful insertion on the one end for one
> to pop out the other end.  I suppose it's true, but perhaps one day if I get
> rich and infamous I'll verify it personally, just for kicks.

You'd have to use strong marbles and get somebody really strong to do
the hammering. Two km of marbles will have a lot of inertia and something
will probably break.

A better experiment would be to take a long metal rod that is restricted
to only move in one dimension. Then hit one end and measure when the other
end moves. With precision timing you don't need that long a rod.
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2004\07\26@104146 by Robert B.

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The currently accepted physical equations are undefined *only* at the speed
of light.  They work out to real solutions for speeds both above and below
the speed of light.  So I assume thats what he meant by "you just cant go
from below the speed of light to above it", because it would require passing
through that undefined point, speed of light.  Of course its all really
theory anyhow.


{Original Message removed}

2004\07\26@104746 by D. Jay Newman

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> The currently accepted physical equations are undefined *only* at the speed
> of light.  They work out to real solutions for speeds both above and below
> the speed of light.  So I assume thats what he meant by "you just cant go
> from below the speed of light to above it", because it would require passing
> through that undefined point, speed of light.  Of course its all really
> theory anyhow.

Sorry, but these equations are Einstein's Special Relativity. General
Relativity removes this loophole, as does quantum mechanics.

Strangely enough, the equations work very well if you just set c (the
speed of light) to infinity. It simplifies a lot of things. I did this
in college because a prof claimed it would never work and I wrote out
a self-consistent set of equations. (By setting c to infinity, I don't
mean that everything happens simultaniously, but that the definition
of the theory made c the fastest possible velocity in a given medium.)
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2004\07\26@104957 by Jake Anderson

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perhaps my reading of "the" book by the man (relativity) was off but i'm
pretty sure that what he said was to move physical mass at c would take
infinite energy. Nothing was said of traveling faster than c being
impossible. (in fact if i read it right you would need infinite energy to
slow down to c if you did happen to excede it)

the problem is to go from traveling at < c to > c without being = c.




> {Original Message removed}

2004\07\26@105617 by D. Jay Newman

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> perhaps my reading of "the" book by the man (relativity) was off but i'm
> pretty sure that what he said was to move physical mass at c would take
> infinite energy. Nothing was said of traveling faster than c being
> impossible. (in fact if i read it right you would need infinite energy to
> slow down to c if you did happen to excede it)

Yes, Specific Relativity has these equations. They are only a simplification
of General Relativity.

> the problem is to go from traveling at < c to > c without being = c.

Yes, the equations in Specific Relativity do that. However, that is
just one part of the picture. When you add the other parts in, going
faster than c is (according to these theories) impossible.

Now, it does seem that certain information *does* travel faster than
light (perhaps even instantaniously). However, this information is on
a level that we can't make use of.

For example, if you produce two particles of opposite spin (this happens
from certain collisions) and measure one, the other becomes the opposite.

On the other hand, this could merely be quantum mechanics strangeness that
only happens to make the theories look good.
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2004\07\26@174252 by William Chops Westfield

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On Jul 26, 2004, at 7:01 AM, Mike Hord wrote:

> This is more of a question of the speed of transfer of information,
> kind of like Russell's "marbles in a tube" question.  The marble isn't
> travelling faster than light, but the information that marble has been
> added to the tube is.

No, in an electrical circuit, the electrons themselves move quite
slowly; it's the information that travels at about c (0.7c or so for
most wire.)  In a tube full of marbles, the individual marbles move
very slowly and the info moves at the speed of sound (in marbles.)

Certain waveforms have certain component velocities higher than c, but
the info transfer is still c...

BillW

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2004\07\27@174359 by Peter L. Peres

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>BUT... it's still hard to believe that if I had a tube about 2km long
>full of marbles, and a really big sledge-hammer to cram another one in,
>that it would take a full second after a forceful insertion on the one
>end for one to pop out the other end.  I suppose it's true, but perhaps
>one day if I get rich and infamous I'll verify it personally, just for
>kicks.

How about a drum of coax cable, a signal generator, and a two channel
scope ? You can substitute fiber if you like.

Peter

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2004\07\27@175021 by David VanHorn

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>
>How about a drum of coax cable, a signal generator, and a two channel
>scope ? You can substitute fiber if you like.

I've seen this done at the SF Exploratorium. They have a big mechanical chopper, and a drum of fiber. The chopper blocks the transmit end, and the receive end at the same time. If you turn the crank fast enough, you start getting light out the end of the fiber, that was put into it a half-cycle ago.

Of course an AVR at 16 MHz can turn an LED on and off before the first light from the LED reaches your eye. :)

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2004\07\27@182959 by Jinx

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> Of course an AVR at 16 MHz can turn an LED on and off before
> the first light from the LED reaches your eye. :)

The Scenix user might ask if you could even see such a LED from so
far away ;-P

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2004\07\27@183207 by David VanHorn

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At 05:30 PM 7/27/2004, Jinx wrote:

>> Of course an AVR at 16 MHz can turn an LED on and off before
>> the first light from the LED reaches your eye. :)
>
>The Scenix user might ask if you could even see such a LED from so
>far away ;-P

Yes, but I still have nice peripherals. He's too busy emulating a timer.
:-P

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2004\07\27@185036 by Mark Jordan

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On 27 Jul 2004 at 17:33, David VanHorn wrote:

> At 05:30 PM 7/27/2004, Jinx wrote:
>
> >> Of course an AVR at 16 MHz can turn an LED on and off before
> >> the first light from the LED reaches your eye. :)
> >
> >The Scenix user might ask if you could even see such a LED from so
> >far away ;-P
>
> Yes, but I still have nice peripherals. He's too busy emulating a timer.
> :-P
>

       I doubt a SX @100MHz would be faster than the new AVR @24MHz...

       Mark Jordan

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2004\07\27@191152 by Russell McMahon

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>         I doubt a SX @100MHz would be faster than the new AVR @24MHz...

Overall maybe not.
For some individual operations and groups of operations, definitely so.
AVR & SX can both do some things at 1 cycle time so SX can be 4 times faster
for some things.


       RM

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2004\07\27@191158 by Russell McMahon

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> > Of course an AVR at 16 MHz can turn an LED on and off before
> > the first light from the LED reaches your eye. :)
>
> The Scenix user might ask if you could even see such a LED from so
> far away ;-P

I'll take that query literally :-):

nS = light foot.
Say on and off in 1 cycle = 1/16 MHz =~60 nS
LED would need to be 60 feet / 20 metre away.
Many ultra-bright LEDs seeable at that sort of distance.

Using a high speed peripheral gated with PLL clock may allow much faster
switching.



       RM

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2004\07\27@192441 by David VanHorn

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At 06:07 PM 7/27/2004, Russell McMahon wrote:

>> > Of course an AVR at 16 MHz can turn an LED on and off before
>> > the first light from the LED reaches your eye. :)
>>
>> The Scenix user might ask if you could even see such a LED from so
>> far away ;-P
>
>I'll take that query literally :-):
>
>nS = light foot.
>Say on and off in 1 cycle = 1/16 MHz =~60 nS
>LED would need to be 60 feet / 20 metre away.
>Many ultra-bright LEDs seeable at that sort of distance.
>
>Using a high speed peripheral gated with PLL clock may allow much faster
>switching.

Whoops. I must be tired, somehow I got 1.6' out of that.
It seemed slow..
Light in water?  :)

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2004\07\27@194555 by Howard Winter

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Russell,

(Pedantic mode: ON)

On Wed, 28 Jul 2004 11:07:01 +1200, Russell McMahon
wrote:

> nS = light foot.

I think you mean:  Light nS = Foot ?

(Pedantic mode: OFF)  :-)

Cheers,


Howard Winter
St.Albans, England

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2004\07\27@203632 by Russell McMahon

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> > nS = light foot.

> I think you mean:  Light ns = Foot ?

To be pedantic, neither, quite. Or both. *
Just a shorthand summary stored in my brain along with many other such for
the "fact" that light travels (about) 1 foot in 1 nS in vacuum

ie V = 3E8 m/s so in 1E-9s it travels 3E-1m =~~ 1 foot.



       RM



* If you said Vlight x ns = feet then I'd agree as the units then work OK.
Maybe I should say ns = light_foot as no multiplication is accidentally
implied.

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2004\07\28@084129 by John Ferrell

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> Light in water?  :)
I think this is covered under the topic "refraction".
I need more cofee to think more on this subject!

John Ferrell
http://DixieNC.US

{Original Message removed}

2004\07\29@150353 by jsand

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Hello Jay & PIC.ers,

>
>A better experiment would be to take a long metal rod that is restricted
>to only move in one dimension. Then hit one end and measure when the other
>end moves. With precision timing you don't need that long a rod.
>--

This can be made really easy too.
Hang any old length of off-cut material (steel, copper rod) horizontally
on a couple of strings. When you knock one end of the piece longitudinally with
a hammer, the impulse sends it away from the hammer head.
This appears to be `instantaneous' but there is a delay due to the need
for the impulse to reach the far end of the strike-ee rod,
change phase 180degree and reflect back to the hammer.
Once it gets there, the two metal pieces separate for the first time.

The time delay can be measured by closing a circuit (hammer / rod) and
monitoring by scope. Voila, speed of sound in metals.


   best regards,   John

email from the desk of John Sanderson.
JS Controls, PO Box 1887, Boksburg 1460, Rep. of S. Africa.
Tel/Fax 011 893 4154,
Cell 082 741 6275,
web    http://www.jscontrols.co.za
Manufacturer & purveyor of laboratory force testing apparatus &
related products & services.

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2004\07\29@165428 by Win Wiencke

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<jsand wrote>
> Hang any old length of off-cut material (steel, copper rod) horizontally
> on a couple of strings. When you knock one end of the piece longitudinally
with
> a hammer, the impulse sends it away from the hammer head.
> This appears to be `instantaneous' but there is a delay due to the need
> for the impulse to reach the far end of the strike-ee rod,
> change phase 180degree and reflect back to the hammer.
> Once it gets there, the two metal pieces separate for the first time.
>
> The time delay can be measured by closing a circuit (hammer / rod) and
> monitoring by scope. Voila, speed of sound in metals.

Great teaching demo

Wonder if a PIC could clock it from contact to rebound.  Probably too
fast.though.

Thanks!

Win Wiencke
Image Logic Corporation

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2004\07\30@083226 by John Ferrell

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I think you just described a sonic delay line. IBM was using these for
storage in the late 60's with lengths up to about 500 ms. That size was
touchy, the 50 ms units were rock solid.

John Ferrell
http://DixieNC.US

{Original Message removed}


'[OT] : Challenging...(another thought)'
2004\08\01@112017 by Howard Winter
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John,

On Fri, 30 Jul 2004 08:33:03 -0400, John Ferrell wrote:

> I think you just described a sonic delay line. IBM was using these for
> storage in the late 60's with lengths up to about 500 ms. That size was
> touchy, the 50 ms units were rock solid.

I think you're wrong there - I believe they were filled with mercury, so were anything but solid!  :-)

Cheers,


Howard Winter
St.Albans, England

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2004\08\01@113054 by Sergio Masci

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----- Original Message -----
From: Howard Winter <KILLspamHDRWspamBeGonespamH2ORG.DEMON.CO.UK>
To: <EraseMEPICLISTspamEraseMEMITVMA.MIT.EDU>
Sent: Sunday, August 01, 2004 4:19 PM
Subject: Re: [OT] : Challenging...(another thought)


> John,
>
> On Fri, 30 Jul 2004 08:33:03 -0400, John Ferrell wrote:
>
> > I think you just described a sonic delay line. IBM was using these for
> > storage in the late 60's with lengths up to about 500 ms. That size was
> > touchy, the 50 ms units were rock solid.
>
> I think you're wrong there - I believe they were filled with mercury, so were
anything but solid!  :-)
>

I have seen some delay lines that consisted of a coil of wire. The coil was
about 8" diameter and only had a few turns (which did not touch each other). I
belive the wire was a nickel alloy.

Regards
Sergio Masci

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