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Author Topic: Pulling String a Universe Wide ?  (Read 6730 times)

Offline neilep

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Pulling String a Universe Wide ?
« on: 01/04/2005 21:37:37 »
Hello Wonderful Scientists The Subjects of my Awe,

err !!...Children eh ?...don't they come up with the most wonderful things ? ...and in equal quantity non-wonderful things ie: " Daddy can we make a worm sandwich ? "..........anyway, my son's imagination must have been fuelled by something on the cartoon channel cos he was watching something and then came and asked me this.

He said " Daddy, if you had a piece of string as wide as the Universe and it was stretched real tight and then you had one person on each end....If one end was pulled would the effect be immediate on the other end ?...oh by the way Daddy you're the bestest daddy ever"...erhhmm...well, I may have added a bit to that question !!!..anyway....I suspect the answer is yes there would be a delay but don't know why as I assume although there is an incredible distance between the two ends 'NOW' is the same in both locations is it not ?


See if you can do better than me and string more than one word together for an answer that will make me look super cool and clever to my son.

Thanks

Neil


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Offline DrPhil

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Re: Pulling String a Universe Wide ?
« Reply #1 on: 03/04/2005 13:56:57 »
I would guess that the propagation of the disturbance would move through the string at some finite wave speed which depends on the elastic properties of the string. The energy of the density wave would travel through the atomic structure by a series of movements as one atom tugs on the next one.
 

Offline neilep

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Re: Pulling String a Universe Wide ?
« Reply #2 on: 03/04/2005 18:25:24 »
Thanks Phil, I am now enlightened. Attempting to dilute it so that my 10 year old son will inderstand, will also be an education for me. What if it was a solid metal pole ?...would that make a difference ?

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Offline Ultima

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Re: Pulling String a Universe Wide ?
« Reply #3 on: 04/04/2005 09:44:34 »
If you have a slinky that's really good at showing wave propagation if you stretch it out a bit, both longitudinal (push one end towards the other) and transverse (swish it side to side), thatís how my Dad taught me :D

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Offline DrPhil

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Re: Pulling String a Universe Wide ?
« Reply #4 on: 04/04/2005 14:22:03 »
quote:
Originally posted by neilep
What if it was a solid metal pole ?...would that make a difference?
I imagine that the density of the material would influence the speed.

Even though a metal rod seems pretty dense to us, at the atomic and subatomic levels there's still a whole bunch of empty space and plenty of "wiggle" room, so the motion would still take some time to reach the other end.

« Last Edit: 04/04/2005 15:04:50 by DrPhil »
 

Offline daveshorts

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Re: Pulling String a Universe Wide ?
« Reply #5 on: 04/04/2005 17:40:41 »
However stiff you tried to make the pole the wave of movement could never move faster than the speed of light, this is because the electric forces between the atoms are passed on by photons, and these can not move faster than the speed of light, so the atoms must move considerably slower than this due to their inertia.

I think possibly the stiffest material we know of is diamond which has a speed of sound of about 12000m/s so you would be waiting a long time for the other end of the rope to move, even just across the solar system :)
 

Offline MayoFlyFarmer

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Re: Pulling String a Universe Wide ?
« Reply #6 on: 05/04/2005 04:33:34 »
electromagnetic farces between atoms are passed by photons????????!!

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Offline DrPhil

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Re: Pulling String a Universe Wide ?
« Reply #7 on: 05/04/2005 11:48:05 »
According to quantum electrodynamics the electromagnetic force is carried by particles called virtual photons.

Google "Feynman diagrams" or "Virtual Particles" for more info.
 

Offline MayoFlyFarmer

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Re: Pulling String a Universe Wide ?
« Reply #8 on: 05/04/2005 23:57:56 »
ah.... ok.... that sounds a little better

Are YOUR mice nude? ;)
 

Offline DoctorBeaver

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Re: Pulling String a Universe Wide ?
« Reply #9 on: 11/04/2005 15:05:08 »
Tries to imagine an interstellar tug-of-war. Could you pop off for a pint before you felt the other team pulling the rope?
 

Offline realmswalker

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Re: Pulling String a Universe Wide ?
« Reply #10 on: 12/04/2005 01:05:44 »
I would just drop my end of the rope into a black hole in an interstellar tug of war! THeyed never know...
 

Offline DoctorBeaver

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Re: Pulling String a Universe Wide ?
« Reply #11 on: 13/04/2005 13:29:17 »
realmswalker - that's cheating! heh
 

Offline realmswalker

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Re: Pulling String a Universe Wide ?
« Reply #12 on: 14/04/2005 06:07:43 »
no worse than tieng your rope around a tree in real tug o war, only in this the other team cant see you!
 

Offline DoctorBeaver

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Re: Pulling String a Universe Wide ?
« Reply #13 on: 15/04/2005 06:09:51 »
I like your style. Are you as good at cheating in pub quizzes? If so, may I invite you to join my team? heh
 

Offline realmswalker

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Re: Pulling String a Universe Wide ?
« Reply #14 on: 17/04/2005 02:24:41 »
pub quizzes whats that?
 

Offline neilep

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Re: Pulling String a Universe Wide ?
« Reply #15 on: 17/04/2005 19:04:52 »
quote:
Originally posted by realmswalker

pub quizzes whats that?



Oh Goody !!..a question I can actually answer  sensibly and without sarcasm!!..
Over here in the UK  we have places called PUBS. A pub is where people go to learn how to become alcoholics. Sometimes, they have special events....one of the most popular is in the form of a thing called a quiz , this is where somebody asks questions and you have to give the answer. If you or your team answer the most questions correctly you might win a prize.

So, there you have it...this is what a 'pub quiz' is.;)

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Offline realmswalker

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Re: Pulling String a Universe Wide ?
« Reply #16 on: 18/04/2005 01:28:20 »
what type of questions are asked?
 

Offline neilep

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Re: Pulling String a Universe Wide ?
« Reply #17 on: 18/04/2005 08:36:16 »
quote:
Originally posted by realmswalker

what type of questions are asked?



Good question. They ask questions about questionable things. general knowledge, sport and hamsters. Aren't questions great ?;)

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Offline realmswalker

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Re: Pulling String a Universe Wide ?
« Reply #18 on: 19/04/2005 00:55:23 »
quote:
Originally posted by neilep

quote:
Originally posted by realmswalker

what type of questions are asked?



Good question. They ask questions about questionable things. general knowledge, sport and hamsters. Aren't questions great ?;)




indeed they are, indeed they are
 

Offline DoctorBeaver

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Re: Pulling String a Universe Wide ?
« Reply #19 on: 19/04/2005 02:09:57 »
I don't recall any hamster questions. Then again, maybe I was in a stupour by that time
 

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Re: Pulling String a Universe Wide ?
« Reply #19 on: 19/04/2005 02:09:57 »

 

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