Science > Physics > layman question about speed of information transfer
| Topic: |
Science > Physics |
| User: |
"Jeroen Boschma" |
| Date: |
01 Sep 2005 03:10:46 AM |
| Object: |
layman question about speed of information transfer |
Hi,
If I recall correctly, it is not possible to transfer information with infinite speed. Speed of
light should be the limiting factor, although I read some about pairs of electrons (?) which react
'directly' on eachothers behaviour, even if separated over a long distance.
I have a question about the speed of information transfer, illustrated by two experiments. Suppose
me and a friend are standing at a distance of 100 m, I want him to give me signal at some random
moment.
Experiment 1) My friend turns on a light to give me the signal. It takes some time for the light to
reach me, so the speed of information transfer is limited.
Experiment 2) My friend takes a 100 m long wooden pole, one end is at his position, the other end is
at my position. He gives me a signal by kicking the pole in my direction. If the pole is infinitely
'stiff' and cannot not be compressed, then I can detect his kick without any delay by looking at the
end of the pole at my position, so we have infinite speed of information transfer.
Somehow something should be wrong with my conclusion of experiment 2 I think (maybe there is some
bound, explained from quantum mechanics or so, on the stiffness of materials?), but can anybody
comment on this to get it clear for me?
Thanx,
Jeroen
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| User: "Bjoern Feuerbacher" |
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| Title: Re: layman question about speed of information transfer |
01 Sep 2005 04:49:33 AM |
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Jeroen Boschma wrote:
Hi,
If I recall correctly, it is not possible to transfer information with infinite speed. Speed of
light should be the limiting factor,
Right.
although I read some about pairs of electrons (?) which react
'directly' on eachothers behaviour, even if separated over a long distance.
This probably refers to experiments like the ones by Aspect, about
entanglement etc. Actually, the electrons do *not* "react directly on
each others behaviour" in such experiments. No information is passed there
superluminally.
You could look e.g. here:
<http://www.physics.adelaide.edu.au/~dkoks/Faq/Quantum/bells_inequality.html>
I have a question about the speed of information transfer, illustrated by two experiments. Suppose
me and a friend are standing at a distance of 100 m, I want him to give me signal at some random
moment.
Experiment 1) My friend turns on a light to give me the signal. It takes some time for the light to
reach me, so the speed of information transfer is limited.
Experiment 2) My friend takes a 100 m long wooden pole, one end is at his position, the other end is
at my position. He gives me a signal by kicking the pole in my direction. If the pole is infinitely
'stiff' and cannot not be compressed, then I can detect his kick without any delay by looking at the
end of the pole at my position, so we have infinite speed of information transfer.
Somehow something should be wrong with my conclusion of experiment 2 I think (maybe there is some
bound, explained from quantum mechanics or so, on the stiffness of materials?), but can anybody
comment on this to get it clear for me?
Well, essentially you can conclude from this that a prediction of
Special Relativity is that no matter can be "infinitely stiff".
Exactly this is addressed here:
<http://www.physics.adelaide.edu.au/~dkoks/Faq/Relativity/SpeedOfLight/FTL.html#4>
Bye,
Bjoern
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| User: "Sam Wormley" |
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| Title: Re: layman question about speed of information transfer |
01 Sep 2005 08:06:35 AM |
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Jeroen Boschma wrote:
If I recall correctly, it is not possible to transfer information with infinite speed. Speed of
light should be the limiting factor, although I read some about pairs of electrons (?) which react
'directly' on eachothers behaviour, even if separated over a long distance.
I have a question about the speed of information transfer, illustrated by two experiments. Suppose
me and a friend are standing at a distance of 100 m, I want him to give me signal at some random
moment.
Experiment 1) My friend turns on a light to give me the signal. It takes some time for the light to
reach me, so the speed of information transfer is limited.
Experiment 2) My friend takes a 100 m long wooden pole, one end is at his position, the other end is
at my position. He gives me a signal by kicking the pole in my direction. If the pole is infinitely
'stiff' and cannot not be compressed, then I can detect his kick without any delay by looking at the
end of the pole at my position, so we have infinite speed of information transfer.
Somehow something should be wrong with my conclusion of experiment 2 I think (maybe there is some
bound, explained from quantum mechanics or so, on the stiffness of materials?), but can anybody
comment on this to get it clear for me?
o arbitrary information cannot be propagated any faster than the
speed of light.
o mechanical waves propagate slower. There is no such things
as "cannot not be compressed".
"Acoustic Fields and Waves in Solids, Vol I & II" by B.A. Auld, 2nd edition
(February 1990), Krieger Publishing Company; ISBN: 089874783X
If you think about what a mechanical wave is at the atomic
level, force is conveyed by the photon.
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