Can information travel faster than light?  I read of a thought
experiemnt in which a very long pole stretches from Earth to another
planet.  By moving the pole back and forth slightly you could send a
message using Morse Code.  The messsage would be transmitted faster
than a light beam could reach the other planet.  Ignoring the
technical problems with this idea, the question is: can information
travel faster than light?

In order to answer this we move into the world of quantum physics.  An
experiment which is quite well known for the transfer of information
at speeds faster than light has to do with a Mozart symphony, having
been transmitted with 4.7 times the speed of light.  In the past few
years, some physicists have conducted experiments in which
faster-than-light (FTL) speeds were measured.

U.C. Berkeley has been conducting experiments along this line.  "An
experiment of theirs, where a single photon tunnelled through a
barrier and its tunneling speed (not a signal speed!) was 1.7 times
light speed, is described in "Steinberg, A.M., Kwiat, P.G. & R.Y.
Chiao 1993: "Measurement of the Single-Photon Tunneling Time" in
Physical Review Letter 71, S. 708--711"  - - You can find more
information and other resources at their website (
http://www.physics.berkeley.edu/research/chiao/research.html ) - -
This site provides information of research by the "Chiao Group."  The
study is funded by US GRANT N00014-96-1-0034, so the US government is
taking the study quite seriously.  Most of the information you will
find is in PDF format.  The work is also supported by the Office of
Naval Research and the National Science Foundation.

This site deals with "Cherenkov Radiation from Faster-Than-Light
Photons Created in a ZPF Background"  You will find the physics
involved along with the math equations supporting the theory.
( www.journaloftheoretics.com/Articles/ 3-3/musha-final.pdf ) - PDF
format

Even "teleportation" which is also a faster than light method of
transmitting information (and objects) is becoming a serious study at
IBM.
( http://www.research.ibm.com/quantuminfo/teleportation/ )

Even classic physics is beginning to question.  While this website
states that no thing can go faster than light, there seems to be a
crack developing in the standard light speed theory. - "In the latest
experiment, a group of researchers at the NEC Research Institute in
Princeton, US, observed the peak of a laser pulse leave a small cell
filled with caesium gas before it had even entered the cell (L J Wang,
A Kuzmich and A Dogariu 2000 Nature 406 277). Apparently, the peak of
this pulse is simply not the kind of "thing" to which Einstein's
famous law applies."
( http://physicsweb.org/article/world/13/9/3 ) - this website is
"Physics Web," actually a rather conservative organization.

While nothing is yet proven to the satisfaction of all, the evidence
of faster than light physics and the transmitting of information by
such means is ever growing.  So the answer to the  question of whether
information can be transmitted faster than light would depend on whom
you ask.  If it has any meaning to you at all, my own personal answer
would be, with time, yes.

If I may clarify anything, please ask.

Search Google

Terms - faster than light physics, faster than light quantum physics,
faster than light experiments, superluminal physics

Cheers
digsalot

---

Request for Answer Clarification by halejrb-ga on 06 Oct 2002 16:32 PDT

I'm somewhat familiar with the experiments you are discussing.  I
thought these experiments had been discredited by showing that none of
the particles involved actually exceeded the speed of light.  The
results were due to flawed measuring techniques rather than actual
particle velocity.

In regards to the comment regarding tachyons, I know of no evidence
that they even exist.  To my knowledge they are not included among the
particles in the Standard Model or String theory.  If I'm wrong please
tell me.

In regards to the comment about information traveling thru the pole at
the speed of sound, I posited that the motion of the pole was being
used to transmit information by moving the entire pole back and forth.
 (You could use Morse Code:  move the pole an inch for a dash and a
half inch for a dot.)  So I'm not talking about a sound wave traveling
down the pole.  Also I said to ignore engineering problems with the
pole idea, such as the motion of the Earth.  (We all know you can't
make a stable pole as long as I'm talking about.)

But just from a theoretical standpoint, could the movement of the pole
be used to send information faster than light?

Given these factors do you

---

Clarification of Answer by digsalot-ga on 06 Oct 2002 19:14 PDT

Actually they have not been disproven as of yet.  That's why the Navy,
among others are still interested in them.

As for your pole analogy. Let's change the pole to a beam of light. 
We don't have to worry about the engineering problems then and the two
analogies can sort of interact.

Pretend there is a lighthouse in the middle of a lake.  The light on
the lighthouse might turn very slowly.  However, the beam of light
sweeps along the shore at a faster speed than the light is turning due
to distance.  If the shore were far enough away, and the bean of light
could theoretically be seen that far, then the speed of the beam
sweeping the shore could exceed the speed of light.

While the photons emitted by the lighthouse will not travel faster
than the speed of light, the information carried by the beam of light
'will' exceed the speed of light as it moves along the distant shore.

To translate that back to the pole analogy with the Earth as the
"lighthouse" and the pole of extreme length as the "beam," then the
answer is 'yes,' the movement of the pole could be used to send
information faster than light speed.  We could 'figuratively' twist
the Earth back and forth in a morse code pattern so that the end of
the pole repeatedly passing the same point in space could carry a
message.

This is a good answer to a difficult question.

If you had the technology to emit controlled bursts of tachyons and
detect them, then you could transmit information faster than the speed
of light.  Einstein's equations allowed for the possibility of
tachyons to exist--they are constrained such that their /minimum/
speed is at or above the speed of light.

I am not an authority on the subject, however.

Dear Halejrb,

Whether or not information can travel faster than light, your thought
experiment is not really a candidate for a technique.  You are
apparently assuming that when the Earth end of the pole is moved, the
other end moves simultaneously; this is not so.  In fact, a
longitudinal mechanical wave would travel along the pole, and it would
be this that caused the other end subsequently to move and so convey
the message.  So the speed of communication would be the speed of this
wave - effectively the speed that sound travels in the material of the
pole - and this would be (very much) slower than the speed of light. 
You wouldn't notice any delay with earth-bound experiments using short
poles, but only because the speed of sound is quite fast in practical
terms anyway - but nowhere near the speed of light.

Carnegie

Digsalot said:

"While the photons emitted by the lighthouse will not travel faster
than the speed of light, the information carried by the beam of light
'will' exceed the speed of light as it moves along the distant shore."


Actually, that's not true.  No _information_ is being transferred at
that speed.

Consider an observer on the lakeside who wishes to receive a
faster-than light message from the lamp operator.  The operator
swiches the lamp on and off to create a Morse code message, and
rotates the lamp fast so that the spot of light on the far shore is
travelling faster than light.  How can the observer receive the
message?

All the observer sees as the spot of light passes him is a short flash
(or nothing, if the light happens to be off at that point).  The
entire message has been spread out all around the far shore, and the
only way the observer can read it is to have it all sent back to his
particular location.  And can happen only at the speed of light.

The distance between the observer and the furthest point of the shore
increases as the distnce to the light is increased, so no matter how
far the observer is away, he can never read the message in less time
than it would take if it were sent to him direct.

Hi Michael-ga

Where your theory about a hypothetical situation misses the mark is
that you have the light operator switching the light "off and on." 
The unblinking light is a steady state object, just as the pole is. 
The question deals with the "motion" of the beam/pole rather than
energy pulses.  That's why I used it as an analogy.  You mentioned
that all the observer would see is a flash of light as the beam sweeps
by.  That's true.  That flash of light would be the same as the end of
the "pole."  Rather than turning the light off and on, which is not
part of the equation, the operator would simply move the lighthouse
lantern back and forth in a given pattern, sort of like moving a beam
of sunlight back and forth with a mirror which is already used as a
communication technique. As the mirror reflected beam of sunlight
repeatedly passes a given point where the observer is located, the
message is delivered. The same is true in this case. The observer on
the far shore would then see repeated flashes of light which contain
the message.

LOL, I'm not involved with physics in any way.  I'm an archaeologist
and my inspiration for the answer to the hypothetical question came
from Pharos, the ancient lighthouse of Alexandria rather than any
knowledge of tachyons or Einstein's equations.  So maybe I'm just not
explaining things clearly in the language of physics.  But when
halejrb-ga made the clarification request and I finally understood the
question, he/she did say to ignore the "engineering problems" which I
read as 'eliminate any practical barriers' and answer the question
based only on the information given.  No other considerations need
apply.

Hi again Digsalot

I of course understand that we have to ignore engineering
considerations in this:  that's what physicists do all the time.  But
what we don't do is to ignore the laws of physics!  In your proposal,
the lighthouse beam is left constantly on, but is rapidly moved back
and forth across the observer.  With that approach, the speed of the
'flying spot' as it passes the observer does indeed exceed the speed
of light, but you should not confuse that speed with the speed at
which the message (ie information)is actually being sent.

The time the message takes to get to the observer is determined by the
separation distance and the time the photons take to arrive (since the
observer obviously can't see anything until they do).  The speed of
oscillation of the lamp just controls the amount of information that
can be sent per second, not the speed at which that information
actually arrives.

If you used your method to send a message to an observer in alpha
centuari, the message would take 4 years or so to arrive, no matter
how fast you oscillated the lamp, as that's how long it takes the
photons to get there.  Doubling the oscillation speed from, say, once
to twice per second would simply send twice as many pulses (but still
taking the same time to arrive).

The critical thing to understand is that as you rotate a light beam,
the end point does not follow instantaneously with the rotation of the
lantern.  The spot of light at the observer moves only after photons
produced from the lamp in its new rotated position have had time to
arrive.  So a beam of light, in this context, can no more be
considered a 'rigid pole' allowing action at a distance than can the
(ideal) pole in the original question.

Aha! - I do understand what you are saying.  But in this case we do
have to ignore the laws of physics.  The question is based on a
"pretense" that the pole, or in this case the beam of light IS rigid,
even though in reality we know that cannot be the case, just as we
have to "pretend" that I can twist the rotation of the Earth back and
forth to do morse code. (I even have to pretend that I know morse
code)  We also have to "pretend" that the pole already reaches Aalpha
Centuari or any other selected spot, and we have to "pretend" that the
whole contraption moves in unison.  That "pretention" is what the
whole question is based on.  When we read "Lord of the Rings", we also
have to 'mentally pretend' Middle Earth really exists or the story
would make no sense at all.

The question is an exercise of the mind, not an exercise of physical
laws.  Physical laws have limits, the mind does not.

1) The pole won't move faster than light.  As was pointed out, elastic
waves will travel down the pole at the speed of sound in the pole,
which has to be less than the speed of light for ordinary matter.  You
can imagine matter where this isn't the case (I believe it means the
pressure > energy density in units where c = 1), but it's never been
proposed to exist.

2) The "Journal of Theoretics" specializes in the science of Fractured
Ceramic Cookware.

If you want to know what's going on with "faster than light" pulses,
Google for group velocity vs. phase velocity.  Information doesn't
travel faster than the speed of light in a vacuum.  Everything
physical obeys "Einstein's famous law".

Tachyons are right up there with vampires - none in captivity.

You can also look for Einstein-Podolsky-Rosen if you want to see
something "happening" at a speed faster than light, although it still
doesn't transmit information faster than light.   If it ever happens,
you'll see it on the news when the person who does it collects his/her
Nobel.

Finally, if you're going to "ignore the laws of physics", then it's
all out the window. I can fly, I have a time machine, I'm a rock star,
I just won the lottery, etc.   The difference between a thought
experiment and throwing it all out the window is what's crucial here. 
We could construct a very long pole in space (we couldn't go to the
nearest star, but it's not physically impossible) and test this. 
Don't expect anyone to do it, though, for the same reason that we
don't launch the shuttle just to see if it'll eventually fall back to
Earth.

Try to understand that the whole question is based on the assumption
of the impossible.  It is the assumption of the impossible that sets
the parameters within which the question must be answered.  It is a
hypothetical construct, not reality, that is the issue here.

I don't believe there is any such thing as "dragon riders" either, but
I sure like reading novels about them.

Now, as enjoyable as this exchange has been, it is time for me to move
on to something different and try to introduce a little confusion into
somebody else's life.

Cheers
digs

I think the question was asking if it was possible, not about what's
possible if physics is disregarded. If it's a philosophical exercise
rather than a question of physics, why did it end up here?

I'm glad you & halejrb are both happy with the exchange.

Digsalot

Well, of course I can't say exactly what halejrb-ga had in mind on
posing the question, but he/she did refer to a 'thought experiment'. 
The Thought Experiment (aka Gedankenexperiment) is an extremely
well-known concept in physics.  Essentially, it means 'can you think
of any way to do this - even in theory - without violating the rules
of physics?'

It IS allowable to use techniques that can't yet be achieved in
practice, because of the current state of engineering or technological
know-how, but it is NOT allowable to include things that could never -
even in theory - be achieved because they are impossible under the
rules of physics as we currently understand them.  For example, a rod
of eg several million miles in length is allowed since, although we
can't (yet) contruct one, there is no physical law that says such a
rod is impossible.

There is a critical difference between practical contraints (which may
be ignored), and the fundamental rules of physics (which may not).

So, in your example, the Thought Experiment cannot include an
'infinitely rigid rod' nor a beam of light that acts like one, since
not only do those things not exist, they could NEVER exist (unless the
laws of physics as we know and love them are totally wrong).

If we were allowed to include devices that breach all known physical
laws then the answer would be rather easy:  I could just say "Yes,
infomation can travel faster than light because the writers of Star
Trek have produced a 'thought experiment' that allows this.  It's
called sub-space radio".

Thenextguy-ga is quite correct.  I'm afraid you're attempting to
defend a position that wouldn't be accepted by any physicist,
anywhere.   To be honest, you were lucky in the score you were given
by Halejrb-ga.

Going back to your original question, there is another way to send
messages faster than the speed of light in theory. The theory goes
something like this (in laymans terms)- take a pair of photons
("entangled" particles), separate them and send them off in opposite
directions. Now because of their entangled nature what ever happens to
one, also happens to the other. Therefore if one is changed by an
external force, the other changes in resonance with it at exactly the
same moment irrespective of the distance between them and this can be
observed. Thus information is transmitted from one to the other
instantaneously.

For more information look at
http://anthrax.physics.indiana.edu/~dzierba/HonorsF97/Week1/NYTJuly22.html
which I found by a search for "crystal information faster speed light
twin"

For an example of it being used in fiction check out the marvellous
"gap" saga by Stephen Donaldson (p 299 in the fourth book if you don't
want to read it all).

The problem with using entangled photons is that you don't have a way
of changing one so that the other (distant) one also changes. That's
why something seems to be happening faster than light, but it's not
something you can use to send information.  You can both decide to
measure the polarization of the photons, and you can know what the
other person is getting based on what you get, but you can't change
what either one of you actually will measure.

I appreciate everybody's comments.  Let's shorten the pole in the
thought experiment to one mile in length.  Assume the pole is very
hard and doesn't wobble, bend, etc.  The issue then becomes when you
move the pole one inch forward, does the distant end move
instantaneously with the near end? I don't think so.  It's takes a
small interval of time for the molecules in the pole to push against
each other as the force of the push is transmitted down the pole.  If
the pole is very dense then the time interval will be nearly
instantaneous.  But I don't think the molecules pushing against each
other will exceed the speed of light.  On the other hand, no molecules
are actually moving relative to their position in the pole.  Rather
its just a wave of force moving down the pole. Maybe a wave can exceed
the speed of light even though a particle cannot.

Hi halejrb

Since you are changing the nature of the question by bringing up a
"wave" motion, then that brings the purely hypothetical back into the
world of reality and the comments I am defending against are right. 
To answer the question as asked, I had to suspend belief in the laws
of physics and move purely into the realm of imagination.  Since we
are now speaking of wave motion, then every comment above about the
answer was right and the answer I gave has no basis on which to rest.

While I thank you for the 5 star rating, the answer no longer truly
fits the question.  However, it has been an interesting ride which has
led us from the world of physics, into the world of fantasy, where the
question as worded and interpreted properly belongs, and back into the
world of physics, even past an ancient Egyptian lighthouse.

Should you wish to refuse the answer and repost the question, you will
get no objection from me.  Though I do think this bunch would make a
great Sunday afternoon debate circle.

You're correct.  A wave such as you describe (whether a lateral wave
passing along the rod or a compression wave) can't move faster than
the speed of light in a vacuum  (normally referred to as 'c').  And it
will - as was correctly noted by Carnegie-ga - normally move very much
slower.  So, no information or message can ever pass along the rod
faster than c.

Thenextguy-ga has mentioned 'group velocity' which can, indeed, move
faster than c.  I won't go into that here, except to say that it still
provides no way to pass messages faster than c.  If you're interested,
have a look at the online demonstration at

http://www.ee.mu.oz.au/staff/summer/applets/group_velocity.html

Yes. Light is a particle emission, its use in communication depends on
the transfer of the particle.

Inductive and field modulating technologies, such as that designed and
patented by William Stewart of MediaFusion LLC, rely on instant field
propogation. It appears that this corporate operation was taken over
by us military intelligence specialists, and later shut down. As of
january 2003 all content other than that of archive.org has been
whitewashed and eliminated from all public search archives. It is know
that similar technologies are used by the US IC for all human-mounted
communications systems used in covert activity (Many corporate and
Media operations also implement this technology) (I've had one mounted
myself, undesirably.) Wilfred@Cryogen.com

Quantum particle duality theory indicates that peered particles can be
modulated and their characteristics, such as rotation, changed by
interaction with one of the pair. This also relies on advanced field
modulation, where the particles each depend on the same secondary
field for their characteristics. Modulation of the carrier field by
influencing one particle causes the field to influence the
corresponding particle, in instantaneous timeframes.