Is existence faster than the speed of light?

  • Thread starter archen
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  • #26
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-Job- said:
I'd say, if the speed of sound in a rope at some temperature is S m/s, then the other end of the rope wouldn't start to come down until the sound wave got there. So if the rope has length L meters, then it would take at least L/S seconds for the rope to start coming down. Of course because a rope stretches, and even if this stretching is very minimal, if the rope is very long, in a fair amount of time it will have stretched significantly, so my end would come down a bit. If it were a wire instead of a rope, then this probably wouldn't be significant. If the speed of sound in the wire is anywhere around 300 m/s then, in order for me to hang from the ground for 10 minutes, i would need a wire of about 10(60)300 = 180 Km. :smile:
I would not want to be under 180 Km of wire falling at 32 feet per second squared.
 
  • #27
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Jay-qu said:
the forces propagate though the material at <c, I have heard some claim that it is at the speed of sound (in that material) but I dont know and Im not willing to do an experiment
Well i don't think so, u might not have heard abt theory of relativity yet. It says if some phenominon the sun just disappears (obviously along with its mass), the force that keeps earth in its motion will also seize, as said by newton it 'd be instantanious but Einstien said it will ony happen when it could be seen what means when the light reachs the earth. Conclusion: forces propagates at c.
Oh and by the way when u mentioned material it think u confussed it with a light light wave (passing through a glass material)
 
  • #28
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.:JimmY:. said:
Well i don't think so, u might not have heard abt theory of relativity yet. It says if some phenominon the sun just disappears (obviously along with its mass), the force that keeps earth in its motion will also seize, as said by newton it 'd be instantanious but Einstien said it will ony happen when it could be seen what means when the light reachs the earth. Conclusion: forces propagates at c.
Oh and by the way when u mentioned material it think u confussed it with a light light wave (passing through a glass material)
I think a rope satisfies the criteria of been a material... and I have previously had a big discussion about the speed of gravity - its finite, c more specifically which means it would take 8 mins till we fell out of orbit - the same time that it would take for us to notice that the sun isnt there.
the forces that take place in the example I answered dont propagate at c, because it is one particle colliding with the next on an atomic level - for the force itself to propagate at c then the particles would have to move at c - hence impossible
 
  • #29
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Jay-qu said:
I think a rope satisfies the criteria of been a material... and I have previously had a big discussion about the speed of gravity - its finite, c more specifically which means it would take 8 mins till we fell out of orbit - the same time that it would take for us to notice that the sun isnt there.
the forces that take place in the example I answered dont propagate at c, because it is one particle colliding with the next on an atomic level - for the force itself to propagate at c then the particles would have to move at c - hence impossible
Take a 200,000 mile long rope and ask two persons to hold its opposite ends, this is the basic appratus. well the radius of earth is 3964 miles, can u calculate how many time would that rope wrap around the earth. And with all due respect, it doesn't seem to make any sense.
but talk but electric current, if "somehow" u can transmit an electron across a 200,000 mile wire, it would definately take some time befor u can detect it on the other end
 
  • #30
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Integral said:
By the way, if you replace your rope with a steel rod the results are the same. Any effort to move the rod, moves through the rod at the speed of sound in the rod. If you apply forces great enough to create a signal which moves faster then the speed of sound in the metal you will deform the rod.

This is probably a noobish question but why is the limit the speed of sound? In that regard, what is the concept that relates speed of sound with speed of light (so that I might read about it)?

Gracias
 
  • #31
ZapperZ
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jhe1984 said:
This is probably a noobish question but why is the limit the speed of sound? In that regard, what is the concept that relates speed of sound with speed of light (so that I might read about it)?
Gracias
Figure out what "sound" is and how it moves in various medium (gas, solids). You'll see that at best, it can only approach the speed of light.

Of course, there are always anomolous exceptions to this that requires us to redefine the things we actually measure as "moving". This happens with the NEC experiment of apparent superluminal group velocity of light. And it may be happening with the speed of sound also that may allow an apparent "superluminal" effect.

http://physicsweb.org/articles/news/9/11/1/1

However, in a common, standard medium, one encounters no such effects.

Zz.
 
  • #32
Danger
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Sound is the transmission of vibrations through a medium. The speed is dependent upon what that medium is, but is always the fastest mechanical action that's possible. While you can physically force something through faster than sound (such as a bullet or aeroplane), you can't create movement of the medium itself above sonic speed.
Light is an electromagnetic wave phenomenon, whereas sound is mechanical. There is no correlation.

edit: Oh, hi Zapper. How do keep sneaking in like that?
 
  • #33
Any thing instantaneous is virtually. Example: If someone was 1000 feet apart, and they sent an instantaneous message to you, then what would happen if someone in the middle of you two received that message? They would have received it before it was sent.
 
  • #34
Danger
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There's no such thing as 'instantaneous' when it comes to propogation of a signal. The limiting factor is light speed. Even quantum entanglement can't deliver a verifiable signal faster than that.
 
  • #35
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Physics

Quote:
Originally Posted by warp darkmatter
It seems to me that the initial question "is existence faster than the speed of light?" has been overlooked by the the initial writer and subsequent responses.
Whilst the question, can anything travel faster than the speed of light? has been answered and has made for interesting reading, the question is existence faster than the speed of light is another concept altogether.
Existence is relevant to the observer and the interactions that the internal and external stimuli effect upon the brain. I am aware of things existing around me, but only as they have occured in the past (the question of what existence means if nothing exists to observe it is a philosophical one). However, what of the awareness of my own existence?
One could argue that existence itself must travel at the speed of light based on the electrical interactions within the brain. But what if the signals are being created by the subconscious before the actions begin? Even at the atomic level, existence must precede an action. If this is the situation, then could it be possible for thoughts to be created before they are thought? If so, then what are the implications for organic computers (if we go down that path) and artificial intelligence?
Unfortunately this is the physics forum, here we must talk of physics. I do not see any evidence of physics in your response.
What exactly is our essence? Electrons pumped through a neural pathway. What is the exact composition of these electrons? In what form are they triggered and in what manner are they received? What is not physics about this? How do we define thought? Many new formulae would be created through understanding of these things to harvest better answers from the world around us.

It's not eccentricity but who says we have to wait until the labrats discover these things before we tamper with them ourselves?
 
  • #36
ZapperZ
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What exactly is our essence? Electrons pumped through a neural pathway. What is the exact composition of these electrons? In what form are they triggered and in what manner are they received? What is not physics about this? How do we define thought? Many new formulae would be created through understanding of these things to harvest better answers from the world around us.

It's not eccentricity but who says we have to wait until the labrats discover these things before we tamper with them ourselves?
You can temper with them as much as you want, but unless it is a discussion based on established physics, you'll have to do it elsewhere, per our PF Guidelines.

Zz.
 
  • #37
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archen, I understand your question. What I'd like to point out is that regardless of the rigidity of the "rope" and the speed of sound, ect., ect. ; If you're pulling one end of the rope and someone else is losing the other, you and your rope can essentially be treated as one body moving through space. If you pull the rope and it instantly jumps away from the other's hands it only means that a very long object is moving. With regard to velocity it'd be no different than pulling a six foot rope out of someone's hands. The rope only moves as fast as you pull it. Of course, the amount of energy required would be ridiculously larger to pull the longer rope. Might need a winch.
 
  • #38
Danger
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If you pull the rope and it instantly jumps away from the other's hands it only means that a very long object is moving.
Again, this is not possible. It will not jump away from the other's hands any faster than the pulling force can be transmitted from one end to the other, which is limited to the speed of sound in the rope.
 
  • #39
jtbell
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archen, I understand your question.
Please take note of the date on archen's original post that started this thread. Furthermore, according to the list of his postings in his profile, his last post on PF was on November 11, 2005! :rolleyes:
 
  • #40
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Again, this is not possible. It will not jump away from the other's hands any faster than the pulling force can be transmitted from one end to the other, which is limited to the speed of sound in the rope.
I understand the whole "speed of sound" argument. It makes perfect sense. But it's simply not necessary to point it out when answering this question. My answer was "regardless of the speed of sound, ect. ect.". In other words, even if the pull was instantaneous, the rope would still be treated as just a long object moving at the speed your pulling it. I am answering the original question with regards to the idea presented. I'm sure the "rope" in the original question was intended to create a visual interpretation of a theory. I seriously doubt archen was inquiring about the physical characteristics of rope when "yanked" on.

Made for fun reading though.
 
  • #41
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Please take note of the date on archen's original post that started this thread. Furthermore, according to the list of his postings in his profile, his last post on PF was on November 11, 2005! :rolleyes:
Yeah, I noticed the date after I replied. lol maybe he'll come back someday and read what he started.
 
  • #42
Danger
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My answer was "regardless of the speed of sound, ect. ect.". In other words, even if the pull was instantaneous, the rope would still be treated as just a long object moving at the speed your pulling it. I am answering the original question with regards to the idea presented. I'm sure the "rope" in the original question was intended to create a visual interpretation of a theory. I seriously doubt archen was inquiring about the physical characteristics of rope when "yanked" on.
I see what you mean, but this is a serious science site. We don't deal with scenarios involving 'if we ignore the laws of physics, this is what might happen'. The laws of physics are not ignored here.
 
  • #43
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I see what you mean, but this is a serious science site. We don't deal with scenarios involving 'if we ignore the laws of physics, this is what might happen'. The laws of physics are not ignored here.
If you're going to take such an aggressive stance I suggest you consider that much of physics is based on theory. Many theories use imaginary objects for illustration. It's to be appreciated. And recognized. Otherwise you might miss the proposed theory altogether while knit-picking the props, as you seem to have just done.

Additionally, if you actually believed your present thrust then you naturally would have knit-picked the basic scenario itself first. 2 people 200,000 miles apart holding a rope? Where and with whose physics did you justify such impossibility before you noticed that the physics of pulling the rope quickly was the part that wasn't possible?

Nice try Dr. Danger.
 
  • #44
AlephZero
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2 people 200,000 miles apart holding a rope? Where and with whose physics did you justify such impossibility before you noticed that the physics of pulling the rope quickly was the part that wasn't possible?
The justification is that the same laws, principles, or theories, (call them what you like) apply whether the rope is 2 inches long of 200,000 miles long.

And THAT principle is one of the most fundamental principles of physics.

As for impossibility or irrelevance, there are plenty of man-made objects that look and behave pretty much ropes and are a of the order of 1,000 miles long. And experimentally, effects don't get propagated from one end to the other instantaneously.

The propagation delay is quite easy to measure in a rope a 2 feet long, for that matter.
 
  • #45
Danger
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I would point out, as well, that a cable of some sort of 200,000 miles length is entirely possible in space. That would be an appropriate dimension for an interstellar hydrogen ram scoop.
 
  • #46
DaveC426913
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I think Idjot might be thinking we're being sticks in the mud about transmission of the force - that's it's a detail.

Idjot, this is not a trivial point - it is the whole point of the discussion.

To merely propose an infinitely rigid object in a thought experiment is to immediately violate SR. SR does NOT allow any matter or any information to travel at greater than c. Period. There's no grey area.

Our universe works the way it does because pulling on a rope takes time to transmit the force.
 
  • #47
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You guys are totally missing the point. 'Suppose' there was something that spanned 3 light seconds in size and it's entire mass could move simultaneously in one direction. Forget the rope and the mere 200,000 miles for a second. Replace the rope with a star and replace the person pulling with gravity. Now maybe the concept can be examined instead of the layman's props originally used to illustrate it. It's really an interesting idea. A little harder to grasp this way, but for some it may be easier to be free of technical distractions involving rope and such.

The original idea was suggesting that if a large object can interact between two points faster than light could interact between the same two points, what does that really mean? It's obviously possible and happens all the time without breaking any laws. But the concept requires an unorthodox method of observation. Hence the props.

Unfortunately, as much as I appreciate the concept, nothing tangible is actually traveling faster than light in such scenarios. It's merely an interaction with a very large object that takes light a little longer to cross. Still worth a few more thoughts, though.
 
  • #48
Danger
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Man, you have got one convoluted thought process happening there. It has nothing to do with the original question. If you insist upon bringing in gravity, then you do in fact have the entire mass being pulled equally... once the gravitational wave has reached each part; and gravity propogates at light speed. You can still not have an instantaneous movement of all parts.
 
  • #49
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The original idea was suggesting that if a large object can interact between two points faster than light could interact between the same two points, what does that really mean? It's obviously possible and happens all the time without breaking any laws.
But it can't, that's the point. The distant points on the large object can't interact more rapidly than the time it would take light to cross the separation distance. It's not possible, and it can't happen. That's not to say the object as a whole can't move with a uniform speed, but in that case the distant points aren't interacting and can't know anything about each other over timescales shorter than the light travel time between the points.
 
  • #50
Danger
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Nice summation, Jeff. :approve:
 

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