A stick two light years long.

My Dad swears he lost a fish that big...

You'd get sound inside the stick. "Sound" simply meaning compression waves.

 

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James, would a compression wave through a material in space travel at a vastly
different speed than a sound wave at sealevel? If not, it would take something like
16.7 billion years to reach the end of a 2lyr long stick. Could a compression wave
last that long??

 

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So it is possible the other end of the stick would move very little, if any?

 

It can also propagate in space.
Sounds in Space: Silencing Misconceptions
Trivial, I know

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so we are now saying that the stick wouldnt move at all...lol

 

first of all, if you would, some how, construct a stick two light years long, made of a material strong enough to avoid it shatter in pieces when you try to move it, you would have a gravity so strong that it would simply collapse on itself, the gravity you would have with something that big would simply made of it a black hole or something simillar, just try to imagine a stick, let's say, with one end in the sun and another end in jupiter, a stick like that will be heavier than our sun and it wouldn't have a structure or a quantum mechanism to suport it's outstanding gravity, it will simply collapse on itself, our universe doens't allow the existence of single objects that big, but to answer the question first posted, if you would break all laws of physic and the only law you would respect was the speed of light, then when you pushed one end, the stick would slowly shatter like a train chrashing into a wall, and after two years, "your stick", would be so compressed that it will have just a few millions of Km's

 

of course the distance between jupiter and the sun is not 2 light years long, what I was saying was, if you had a stick that long, it will be sufficient for it to collapse on itself, and we're talking about 20 light minutes aprox. , maybe not to form a black hole, but it would collapse on itself, now when we're dealing with objects light years long, we're breaking the laws of physics

"the speed of force?"

there is no such thing, force means energy, and energy's max. speed is the speed of light, and every "force" in the universe respect this law, for instance, "gravity force", if you would remove the sun from our star system, only 8.5 minutes later the earth will feel this effect, our current physical knowledge of the universe tells us that there isn't any effect in the universe that "happens" faster the speed of light, that's why no one understands what happens when you have a singularity, but that is a total different field, within our knowed universe everything happens at the speed of light, and no faster, that is the velocity at wich a string vibrates, and if string theory is correct, a string is the simpliest form of mater/energy in existence

 

but a galaxy isn't an object, a galaxy is a system, it is a "giant bag" of objects, a star is an object, a planet is an object, grabbing your point of view, then I would say the universe is billions years long, but like I was saying it isn't a single object, but a giant number of them

 

This theory should be very easy to prove by doing experiments with a smaller stick say 1 Km and then calculate for the light years case.

P.S. Use a large hammer if the stick is not in zero G space.

 

Hmm... let's say you had a very long bar (long section welded rails?)
Smack it with a sledge hammer. The compression wave will reflect off the other end and come back to you... be careful! I don't know how much energy would be lost in the travel!

You'll need a pretty long bar to notice a time difference, though. Sound in iron goes at about 5km/s.

 

Picture all states of matter as a liquid or picture all atoms as waves. Imagine throwing a rock into an extremely calm lake. What happens? The rock displaces a certain amount of water which cause waves to travel in all directions due to the laws of physics. The wave obviously takes to time to move and reach the calm liquid around it. Thus, when one moves a 2 light year long stick on one end, the effects of that action are NOT immediately noticable on the other end. I'm not trying to be prententious here, but...damn I'm good! Can you feel it? *humps air*

 

Someone raised an interesting question. Since I am sure the compression wave loses SOME energy in travelling such vast distances, is it possible that every time u push such a stick that it does indeed get noticably and permanently shorter? In fact if u push anything it gets shorter! This is because the compression wave is partly turned into random thermal energy.

 

But when the rock collides with the water a certain amount of energy is being transfered from the rock into the water causing these waves. The rate at which the energy is transfered is much slower in water and will eventually disperse ending this wave effect. Where is the energy transfer in the stick and why would energy be needed to move this 2 light year long stick?

Off topic question: What exactly is difference between force and energy transfer (is there even a difference?)

I believe the effects would be immediate and the other end of the stick will move just as fast the beginning end, unless, of course, the stick will compress like you said, but isn't that due to the material not the laws of phsyics?

 

All of this is why "perfectly rigid" materials are impossible in relativity. The "push" would be transmitted along the stick as a wave at a speed (less than c) determined by its elastic property.

 

I thought I already explained this?! Most of the energy goes into moving the stick (each individual atom) and some will give rise to internal energy.

U can have energy transfer without the application of (what physicists usually refer to as) force.

Nothing is instantaneous in the universe (other than quantum entanglement effects i suppose

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).

 

Another question concerning this hypothetical stick. If we were to grab one end of
the stick and begin to swing it around, how fast could we calculate the speed at the
other end to reach? I know if special relativity is applied to the other end, it will never
reach "c", a different frame of reference will come into effect, with length contraction
and time dilation for the movement at that end. Does this mean the same stick could
be in two frames of reference at once, a different frame for each end? If we calculate
the velocity of the other end by the speed of our rotation and the 2lyr length of the stick, we can arrive at a speed greater than "c", so how would the Lorentz transformations be applied in this instance? All hypothetical, I know.

 

God, sorry. Im not going to read every single post, only the most recent ones X.x

 

As the energy in the compression wave dissipates, the wavelength gets longer, but the total movement induced in the stick by the wave will stay the same.