Solid Faster than Light?

If you had an object that long, wouldn't it warp the fabric of the universe, create a super black hole and suck everything in?

In theory, ignoring laws of physics, everything is possible.

The closest thing to this theory is the lack of electrical resistance in crystals

The rod can be any length, as long as each end can be synchronized/measured precisely. To go to the other extreme, say the rod length is only the diameter of an elementary particle with mass. If you could measure the position of each side as you pushed it, wouldn't each side of the particle move simultaneously, therefore instantaneously? Line 'en up like billard balls as long as you need, with no space between. Maybe the answer is that no particle is really solid, re: String Theory.

This should get them going....

I guess this proves that analogue is still better than digital.

In the navy, our old mechanical fire control computers are still faster than the fastest digital computer in the world.

...control computers are still faster than the fastest digital...

Maybe not a "Mechanical Brass-Mind", just an old-type electronic trajectory plotter and fire-control, but immediate-response, sure;

Those weren't programmed with "Visual-Studio", only had "right-to-the-point" type of firmware, hence, no "Residual-Garbage" to digest.

I bet you that even the new ones, are programmed in highly optimised low-level assembler, rather than a visual this-or-that "application-generator", with an extended Object-Library.

...no particle is really solid, re: String Theory...

No need to go that far, Wolfgang Pauli embedded this in the thirties, and photons passing through each other in a laser tube can prove it daily

Thank you! The voice of reason may yet prevail... That is, if the epicycles are in the proper phase.

One part of relativity states that an object's length is also relative to the speed of light - length contraction is part of the Lorentz transformation as much as time dialation. Also from a physics perspective the length would be measured, I am not sure if this is what you mean by "communicated". From the refrence frame of the rod the length is known, but from the fixed reference frame of the viewer measuring the rod in motion the rod length is relative to the speed of the rod.

I could use the rod to "communicate", or tap out a message, at the other end. Common sense says that one end moves as soon as I move the other. If I push the rod at the same time that a light beam is sent along the length of the rod, the tap would occur at the far end before the light got there. I would therefore be able to communicate faster than light. I've got a team working on it.

I think the point here is that any solid would be compressed. Any material has an elastic modulus, what happens is that something has it too big.

I think in this case, a longitudinal wave would be created, traveling in the speed with the limit to the speed of light (because stress propagation in a material is actually the interation of electric fields among particles).

...If you construct a rod of a "perfect solid" that is unable to be compressed...

Aren't you talking about that "Ether", you know, of Michelson-Morley's negative result from 1900 something?

My kid sister said once: "my mind is faster than light, see, I'm thinking of the edge of the universe, right now".

Indeed, imagination is.

No, let's see the problem by another angle. I'm going to try to explain better my way of thinking.

Imagine now your perfect solid not 1 light year long, but, let's say, 3 meters.

Now, imagine a box with a front opening, measuring 2,95 m in lengh

Let's say that your perfect and incompressible solid is moving towards the box at a high fraction of the light speed. In that speed, your solid would have an apparent lengh of 2,95. Even if it's incompressible, this is the lengh measured due to relativistic effects.

Now, imagine that your perfect solid, that has a so smal mass that cannot destroy the box, enters the box and its tip stops at the rear wall.

Is your solid entirely inside the box? If so, where the remaining 0,05m go when it comes to rest?

The answer is: there will be a "relativistic" shock wave expanding the material from tip to back, because the material will have to expand at some rate to get to the original lengh for an observer at rest beside the box.

That's why I think the feel of the movement will travel at or below light speed. If it's at or near light speed, your material, observed from the guy who's hammering the tip of the long bar, will contract if hit in too much speed. If not, remember, all solids are based on electric field interactions. This means that the feeling is going to be noted at the speed of ... electric fields.

But it's all relativity. Hard even to imagine... better have a beer for some help...

Ignoring everything else (we seem to be doing a lot of that lately), if a rod that is one light year long is pushed, the instrument at the end will broadcast the change in position towards our end. It will still take a light year to get that message.

The position at the other end has changed but we get the data only after a year (if we're using light to signal the change). This same phenomena happens all the time. When you gaze out into the night sky (or the day sky but that might be too dangerous since it's only the sun that can be seen...plus the moon on occasion but lets ignore that...again), you see a star or, via a telescope, a galaxy or nebula, as it was thousands, millions or billions of year ago. In essence, everything that we see actually happened in the past, due to the speed of light. See? I can see myself typing but what I'm actually doing is having a break in the cafeteria .

If no one agrees with me, then...just ignore me .

What a bunch of Aristotelians!!! "It must be an imbalance of the bodily vapors!"

First, a perfect solid?! Yeah! I'm just like a Ken doll, cut me in half and I'm solid. Forget the guts! Second, ANY solid or liquid or gas allows physical impulses to travel at the speed of sound for that particular medium. So, if you hit one side, it's going to take a really long time for the compression wave to reach the other end. People say that "water" is noncompressible, yet even water transmits pressure waves.

Finally, matter can be guaranteed to travel slower than light ONLY in a vacuum. There are many substances where the speed of light through the substance is actually slower than that of a particle. When this is the case, the particle creates an electromagnetic shock wave like a mini sonic boom. The result is a flash of blue light, known as Cerenkov radiation. This is basically how neutrino telescopes work: neutrinos travel faster than light through water, hence (hopefully) a neutrino will travel close enough to an atom to create this shock wave and be detected by a photomultiplier tube.

No; a fallacy; the rod will communicate only as fast as it is pushed. Then, it will take time (the same time or a light year) for the orignal pusher to receive confirmation that the "message" was received. No law's violated. Of course, Jorrie should have a more eloquent explanation.

You people are so SILLY. The bar travels at the velocity it is accelerated to by being pushed. It does not matter if it is one meter or 10,000 light years long. the whole bar moves, but not at the speed of light. Silly people, silly silly silly..this is like a trick question based on faulty logic

Thank you!!!!

If a roster lays an egg on the top of a barn, which side of the roof will the egg roll down?

Er, a rooster/chicken, being male, does not lay eggs. Only a hen/chicken can do that.

Are spherical chickens still on the agenda?

How dare you sir! It's a Cockerel!

"Sir"? Shouldn't that be "Cur"? Any attempt at estimating gender of a subscriber will result in an answer that is around 50% correct in the absence of other data. Even spherical chickens can be differentiated into cockerels and hens with a much higher degree of confidence in the result...

Vibrations travel through a solid at the speed of sound for that material. The speed of sound in neutron material is currently indeterminate, as there is insufficient of that sort of material locally with which to determine it.

A spherical chicken constructed of neutron material 1 light year in diameter would contain sufficient mass to form a black hole without so much as a cluck from a cockerel, and probably roll down the roof much faster than any egg, taking the roof and everything else nearby with it. [High temperature alarm at subsystem Brain 0.0 at this location...]

To save further argument, just roast mine with a hint of garlic.

At least you're paying attention.

YES...COMMON SENSE RULES!!!!!!!!!!!!!

So, ok , it will be true.

Lets consider a spherical chicken with no atrict with the air or with the ground.

The solid will transmitt the movement. But, by the nature of the materia, it will be compressed! Most of materia is actually vacuum, free space. Even the nucleous of atoms are made of elementary particles with nothing among them.

Could you explain what's the nature of the research you're doing on this matter?

Spherical chickens?

What do you think that is easier to imagine: a spherical chicken with no atrict, or a 1 light year incompressible solid? THat's just the way we use to say when you're considering (a lot of) ideal conditions with no practical implementation.

Jorrie?

Jorrie?

Yes. Jorrie, please... we really need your help.

Did anyone send him an e-mail? I will...

Hi bhrescobar, sorry, had a bit of a hectic start to the week, so I missed this interesting one. However, your email got my attention eventually!

Forces propagate in solids at the speed of sound in that material. For a steel rod, it is something like 5 km/s. There is no "perfectly solid" materials, because this would imply the speed of sound to be infinite.

In simple terms, when you push at one end of a rod, the whole rod does not move instantaneously - the particles start to move at a rate determined by the speed of sound in the material.

I'm sorry if I repeat an answer that has already been given, but I just had to quickly scan all the responses and I might have missed some!

Regards, Jorrie

Pushing the end of the bar actually generates a shockwave that travels within the limits of physics. Of course, the hypothetical perfect solid will distort the laws since the density of a perfect solid will result in a black hole. The shock wave will be generated on one side but never "felt" on the other since it can't escape. OK that's enough before I finished my first cup of coffee.

My, I've seemingly opend a can of spherical chickens here. Let me present another analogy. You push that ruler on your desk along it's length. You don't push it at anything near the speed of light, you just push it. The far end moves at the same time as the near end. In reality there is a subatomic compression of the material the ruler is made of so there is actually a miniscule delay between the motion of the pushed end and the far end. This is reality. But, hypothetically, if the ruler was unable to be compressed, the far end would start, move, and stop, at the exact same time as the pushed end. You don't need to receive confirmation that the far end has moved, a receiver at the far end awaits either the pushed end or the simultaneously launched light beam to arrive. How can the light beat the pushed rod? My research team is struggling to make coffee right now.

Fowl play is suspected...

...The far end moves at the same time as the near end...

Got it, got it. Just a ruler, not a year-light long. Not pushing it from zero to light speed. Just a little nudge. By god, I got it.

I don't even see what can go wrong with such an experiment.

Except for explaining the resulted measurement in a formal way, that is...

I think Jorrie's there, just stumped.

...or eggsasperated by those sherical chickens...

Could a spherical chicken cross the road faster than C? If so why would it do it?

...to get to the other side of the road...faster...

Hi guitarhunter, stumped? - not yet mate!

My cricket team is this year's favourites to win the ICC (cricket) world cup. So till we're "stumped", we remain on top!

Here is something that could "stump" most people: "perfect rigidity" has been replaced in relativity by "Born rigidity", in order to get rid of the unphysical notion of "perfectly rigid", that demands an infinite speed of sound in a solid.

Wikipedia's Born rigidity is pretty terse - check it and see if it makes any sense...

Regards, Jorrie

I believe the velocity/mass of light is not a limitation it is more a relative standard measure.

E=MC^2 means to move mass somewhat faster than the velocity of light.

There is no data other than theoretical about the physical dynamics of magnificent velocities.

think of each atom of the rod as an individual point- if you move your end of the incompressible rod, each particle of the rod moves at the same speed that you pushed your end- the speed of light does not figure in at all.

but are we sure that neutrons are "solid"? what about quarks? solidity might be a farce, everything could be energy bonds all the way down to a self-propagating bond

Thank you Jorrie. "A body rigid in itself would violate special relativity, as its speed of sound would be infinite." - Wikpedia. That explains the reality of the situation. But, could an infinite solid exist? Could something like a Bose-Einstein condensate, in theory, form a perfect solid? Is my "pushed rod" scenario not possible because the physics is impossible or because relativity dosen't allow it? Wait, that's the same thing, isn't it?

Your perfect solid would require no space between particles. And because we know there's lots of space everywhere, even inside a neutron, your perfect solid is so dense that it has infinite mass. So you can't push it.

Good point. Even if you consider just the mass of the nucleous of atoms, not the elementary particles, you'd end with a density of something like 10 tons/cubic centimeter.

Now, do you start to realize what you are proposing here?

And, have you checked the link Jorrie kindly gave us?

The movement of the rod will travel at the speed of sound through the rod. No solid is continuous, it's just the nature of the solids, no matter if in earth, in mars, or near a supernova.

As I implied in my post (#10), when you ignore certain things, anything's possible.

Hi guitarhunter, you asked: "Is my "pushed rod" scenario not possible because the physics is impossible or because relativity dosen't allow it? Wait, that's the same thing, isn't it?"

Hmmm..., yep - it's essentially the same thing.

The answer given below by another poster on infinite density, infinite mass etc., i.e., a singularity, is perhaps a better 'killer' of the concept!

Regards, Jorrie

I am the "SILLY" guest. If you push the end and send a beam of light at the same time, the light will travel at the speed of light and the rod will travel based on the force applied and the mass of the rod. Since this rod is not of infinite mass, what mass, according to your discussions, would it take before your relativity assumptions kick in? What if this thin long rod is exchanged for a shorter fat rod of the same mass, like the distance from earth to jupiter?

And what if it a fibreoptic rod and you shane a beam of laser light and push it at the same time?

Guest asked: "And what if it a fibre-optic rod and you shane a beam of laser light and push it at the same time?"

The speed of light in most fibre optical bundles (basically glass) is around 0.66c. The speed of sound in a glass rod is around 4km/s, or 10^-5c. So the light pulse will still easily beat the sound wave caused by the push. What it means is that the single light pulse will travel the length of the rod in the time L/c, regardless of the push.

It will be different if you keep on pushing while sending a series of light pulses down the fibre rod, because once the whole rod is in a state of acceleration, the light will take longer to travel the length of the rod.

Regards, Jorrie

Hi "SILLY" guest, you asked "Since this rod is not of infinite mass, what mass, according to your discussions, would it take before your relativity assumptions kick in? What if this thin long rod is exchanged for a shorter fat rod of the same mass, like the distance from earth to Jupiter?"

There is actually no relativity assumptions here! The "push effect" propagates at the speed of sound in the rod and the light travels at c - one huge difference in speed!

The only difference with a "shorter fat rod" is that the speed of sound along its length will be different for the same material, but I don't know by how much.

Regards, Jorrie

Has there ever been an actual experiment with a Born Solid to measure the motion on different parts of the rod, or is this only a math exercise?

Yet another Guest asked : "Has there ever been an actual experiment with a Born Solid to measure the motion on different parts of the rod, or is this only a math exercise"

Essentially a math exercise, using Einstein's special relativity.

One thing you must remember, is that once a pushed rod, rocket, or whatever has reached a steady acceleration, i.e., the stresses has been taken up by the whole length and it is lengthwise compressed, it behaves virtually identically to Born-rigid movement. This has been done many times in practice.

A tall building is, by the equivalence between gravity and acceleration, undergoing "quasi Born-rigid motion"! What you find there is that the clock at the top of the building ticks slower than the clock on the ground and that the gravitational acceleration at the top is marginally lower than on the ground.

Regards, Jorrie

Thank you for starting this thread. I remember asking this very question many, many years ago in High School, and I still remember the dismissive scoff from my Physics teacher. I've always wondered about the answer. Another way to look at it is that a 'perfect solid' would require infinite density. Of course, I may merely be restating what a previous poster said regarding String Theory. Thanks, sumanth p.