sakellog,
I believe it was Mr. Churchill, also dyslexic as I am, who said "Anyone can spell a word the same way twice. It takes true creativity to spell it uniquely each time"
I can't be insulted. I was a systems administrator once. 🙂
Did you know light travels slower in a fiber than electrons in a cable?
I believe it was Mr. Churchill, also dyslexic as I am, who said "Anyone can spell a word the same way twice. It takes true creativity to spell it uniquely each time"
I can't be insulted. I was a systems administrator once. 🙂
Did you know light travels slower in a fiber than electrons in a cable?
Does it? Electron drift velocity due to a current is very low. Thermal velocity is higher but depends on temperature. Light in a fibre travels quite fast, a significant fraction of c.
i did not know that.
on one hand.....ok, in a cable the electrons out are not the ones u put in. like a garden hose, put 1 ounce in a full hose and one ounce comes out, but not the same ounce.
but fiber the light u put in has to go all the way...right.
still @ the speed of light.
i love the quote.
you know your bad when the spell check in outlook says"huh"?
it has every word known to man at its finger tips but i screw it up all the time.
on one hand.....ok, in a cable the electrons out are not the ones u put in. like a garden hose, put 1 ounce in a full hose and one ounce comes out, but not the same ounce.
but fiber the light u put in has to go all the way...right.
still @ the speed of light.
i love the quote.
you know your bad when the spell check in outlook says"huh"?
it has every word known to man at its finger tips but i screw it up all the time.
I was at a conference last week with "folks who know" for real. At data communication speeds, light is a fiber is quite a bit slower than electrons in a wire. I did not get the numbers. The difference is enough to cause issues and choices. You need to remember, these are the kinds of folks who curved the backplane to make the wires shorter by an inch or so. I was surprised. If I remember, in cat 5 it is in the 60% range of C. In fiber, it is not just the refractive index, which is in the 70% range, but some other density kind of effect that makes it quite a bit slower.
Interesting! I'll have to look that up.
Speaking of the speed of light, the other day I ran across some ultra-high speed photography done by MIT that is "faster than light". Well, not exactly, but it does show a pulse of light as it moves across the scene. Imagine the old high speed photos or films of a bullet going thru an apple. This was similar, but a 5mm long pulse of light as it moved across the target. Target was a roll of tape, an apple, a back plate. Seeing a pulse of light move at almost 300,000,000 meters per second is pretty damn fast! A bullet's got nothing on that.
Speaking of the speed of light, the other day I ran across some ultra-high speed photography done by MIT that is "faster than light". Well, not exactly, but it does show a pulse of light as it moves across the scene. Imagine the old high speed photos or films of a bullet going thru an apple. This was similar, but a 5mm long pulse of light as it moved across the target. Target was a roll of tape, an apple, a back plate. Seeing a pulse of light move at almost 300,000,000 meters per second is pretty damn fast! A bullet's got nothing on that.
thatt is cool. i would love to add that to my collection.
hint hint. is there anyway i can get that, or get to that to download. dad is a comunications guy for the railroad. i remember playing with fiber and 100 pair cable when i was little. he tought me the resistor color code and the com code when i was 7. i only remember the resistor colors....but who can forget violet giving willingly
Yea, I saw that topic. Stuff going on in science these days really warps one's mind. MIT, Berkeley Labs, all over. I still can't understand how hitting something with lasers can cool it.
Here is the ultra-fast femtosecond stuff:
Visualizing Light at Trillion FPS, Camera Culture, MIT Media Lab
It's done by successive scans, not all at once. Still very impressive. Took me awhile to wrap my head around it. You don't expect to see photos of the movement of a burst of light.
Visualizing Light at Trillion FPS, Camera Culture, MIT Media Lab
It's done by successive scans, not all at once. Still very impressive. Took me awhile to wrap my head around it. You don't expect to see photos of the movement of a burst of light.
I think you (or they) may be confusing electron speed with wave speed. I can well believe that signals may travel slower through a fibre than through a coax cable, but that is not what you said.tvrgeek said:
Based (maybe) on the speed of light etc,
What is the speed of movement?
If I hit a solid of 1m length at one end, how long until the other end moves?
Common sense would say it moves instantly, yet the "signal" of movement would have travelled faster than light.
Chris
What is the speed of movement?
If I hit a solid of 1m length at one end, how long until the other end moves?
Common sense would say it moves instantly, yet the "signal" of movement would have travelled faster than light.
Chris
Where as with light, it is the same photon that comes out as went in, it is not necessary the same electron coming out as went in until we are in the quantum realm, so yes.
Information is conveyed by two different methods, the light being the slower of the two. How's that?
Information is conveyed by two different methods, the light being the slower of the two. How's that?
Chris,
Your analogy makes the false assumption that a solid object exists. So far, the only transference of information faster than the speed of light is as Einstein called it "spooky action at a distance", now referred to as quantum entanglement. But that gets into the problem if time exists or if it is a construct we invented to understand our location.
Your analogy makes the false assumption that a solid object exists. So far, the only transference of information faster than the speed of light is as Einstein called it "spooky action at a distance", now referred to as quantum entanglement. But that gets into the problem if time exists or if it is a construct we invented to understand our location.
Think speed of sound, when hitting a solid rod.
For comparing coax with fibre, the main issue is permittivity/refractive index. RI=sqrt(relative permittivity). It is quite possible that the material in a fibre has a higher permittivity than the dielectric in a cable, so EM waves travel more slowly. In addition, some fibre types support propagation modes which can be loosely described as a zig-zag, so the distance travelled by the light is longer than the linear length of the fibre.
For comparing coax with fibre, the main issue is permittivity/refractive index. RI=sqrt(relative permittivity). It is quite possible that the material in a fibre has a higher permittivity than the dielectric in a cable, so EM waves travel more slowly. In addition, some fibre types support propagation modes which can be loosely described as a zig-zag, so the distance travelled by the light is longer than the linear length of the fibre.
Solid rod: Mythical construct that does not exist in nature. Not even a black hole is solid, or by best guess as I have never seen one. Oh yea, black hole. That is where your reimbursement request for business travel goes. Guess we have proof of their existence.
I asked about the propagation mode and was told that was not the primary effect.
I asked about the propagation mode and was told that was not the primary effect.
I suppose the simple answer would be to take the speed of movement = 3x10^8 m/s, then time = distance/speed = 1/(3x10^8)
This assumes infinite density, I suppose (making Z tend towards infinity?).
I know there's no such thing as a solid object - we're all 99.9% nothing anyway, and the forces between atoms/molecules are only electrostatic so have a certain amount of "squish" between them.
I suppose acoustic impedance comes into this: we covered this a little in a medical physics unit, but we haven't been taught enough to cover this question.
Reading to be done.
Chris
As I said, speed of sound (in the rod - fast, but well below c). I'm sure its not quite that simple, but should be a good approximation.
There are two processes in play...the hammer strike compresses the faces of the hammer and rod in inverse proportion to their respective stiffnesses. As they rebound the "square wave" input excites the rod at its resonant frequencies and this compression/rarefaction pressure wave does indeed propogate down the rod at the speed of sound in the rod. At the same time the force input to the inertial mass of the rod delayed and smoothed by elastic compression of the rod accelerates the rod away from the hammer as an integration of the time variant force divided by the inertial mass.
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