Hogfather, technically the only thing actually 'travelling' is energy, not mass.

You are still deranged.

As far as we can tell, nothing may travel faster than the speed of light. That includes energy, mass, information and your mother's undies (although they do drop pretty f***en quick I admit).

Not "entirely correct" (loosely used here) see here:

http://www.newscientist.com/article/dn16796-fasterthanlight-tachyons-might-be-impossible-after-all.html

That's rather speculative physics Opec.

The basic message that Blue is deranged for persisting with his f***ing interstellar broomstick isn't tarnished because a few scientists have groovy ideas about wholly theoretical particles.

^^^ That's why I said "loosely used here" heh.

The stuff holding the matter in the rod together is electromagnatism. This is at the quantum level right (the very small)?

I thought stuff in the quantum level was unpredictable and unmeasurable ?

Hogfather, technically the only thing actually 'travelling' is energy, not mass.

You are still deranged.

As far as our understanding of physics allows, nothing may travel faster than the speed of light. That includes energy, mass, information and your mother's undies (although they do drop pretty f***en quick I admit).

I can travel faster than the speed of light if it where in a median with a high enough [or low enough?] refractive index in which I was not.

Okay I'll just give my proposed reasoning to why it cannot happen. I couldn't really see a definitive answer in the other thread besides the fact that that the atoms 'squish' together a.k.a Deformation, which I stated would not occur as we're assuming the rod is some amazingly advanced nano tube thing.

I think this is an optical illusion as even a rod with a small radius, spread over 5 light years would have an enormous mass and hence the Work required to move it would be massive, the force would be massive [which would most likely break the bonds as people have said] and even if it didn't break, to move it backwards and forwards at a usable rate [such as Morse code] again would require ridiculous amounts of energy.

rough estimate of the mass:

Let's just say the atoms are tightly compacted to reduce deformation so it's density is similar to steel = 7.85g/cm^3

Volume of 5 light year rod in cm, lets be generous and say it has a radius of 1cm. 5 light years = 47.3 x 10^17 cm

Therefore mass = 1.4859 x 10 ^ 19 grams = 1.485 x 10 ^ 16 Kg which is like 0.25% of the Earth's mass but still, that's gonna be difficult to move.

I'm not up to Kinetics yet so I couldn't tell you the work.

However I think it was already answered, in a real situation it would deform, bend and break. Gravity fields would interfere etc, etc.

Consider also the f***ing inertia of moving a rod several light years long ... even at a couple of atoms wide it would likely have more mass than the Earth!

Your understanding of kinetic energy and matter is flawed, that's all. You think of a physical object being moved all at the same rate when you push one end, because that's what happens according to your senses. This is the same reason people didn't realise that light 'travelled' for a very long time - they couldn't observe it.

Regardless of how it seems, a physical object isn't completely rigid, and a rod that behaved the way you want it to wouldn't just be be some sort of 'super nano thing', it would be a type of matter that simply has not been observed, basically a proton several light years wide.

Consider also the f***ing inertia of moving a rod several light years long ... even at a couple of atoms wide it would likely have more mass than the Earth!

lol just beat you to it :P

Not "entirely correct" (loosely used here) see here

Very, loosely. So loose in fact that the link is worth ignoring.

Just because someone has an idea that is published/blogged/written on the internet doesn't mean that its possibility has shifted from zero or that it has any merit just from being discussed. This applies especially to the physical sciences.

no on here has give a real answer, to is a good question. The mechanical motion, which is essentially a "sound wave," propagates through the material at the speed of sound. When you tap one end of your rod, the other end won't move for a very, very long time.

If you could make a perfectly rigid rod, then yes, the speed of sound in that rod would be infinite, and you would receive the Nobel prize for discovering a limitation of the theory of relativity.

On the other hand, you're not going to find a perfectly rigid material in this Universe, so the theory of relativity is safe and sound.

i propose transforming this thread into a topselling movie of a man and a dream and his desire to overcome all trolllike detractors in his way

Gonna call it the noob who could

no on here has give a real answer, to is a good question.

what
in the very first reply, I linked him to a thread which answers it just fine
since then that thread has been referred to again, and the actual question answered directly at least once

mooby, yer did, just not as well written :D

just read the thread, and i don't understand what you guys aren't getting about this

it's pretty straight forward, the eye can't simply see more than 30 frames per second

Yeah, it won't work.

Bit off topic, but i'll tell you an experiment you may not know - if you take a steel rod and tap it on one end with a hammer (axially) and then tap it again you can get the steel rod to break. You don't have to tap it hard either time - just with the right force and timing for the second tap. How it works is waves propogate along the rod, reflect and propogate back along the rod. The waves propogate proportionally to the speed of sound through the material, which for an isotropic material like steel is a function of the Young's Modulus (E, elastic modulus) and it's density. The second tap you can get new waves meeting the reflecting waves which can cause stresses well above ultimate stress of the material causing catastrophic failure.

Even more interesting, I can simulate this experiment without even doing it on a very average computer these days.

I couldn't really see a definitive answer in the other thread besides the fact that that the atoms 'squish' together a.k.a Deformation, which I stated would not occur as we're assuming the rod is some amazingly advanced nano tube thing.

Let's just say the atoms are tightly compacted to reduce deformation so it's density is similar to steel = 7.85g/cm^3

I think that's oversimplifying. Consider this: you're not even getting started on how tightly you can pack matter. Using that density, the density of steel is 7.85 * 10^3 kg/m^3

Wikipedia tells me this about the density of a neutron star "The neutron star's density varies from below 1×10^9 kg/m3 in the crust increasing with depth to above 6×10^17 or 8×10^17 kg/m3 deeper inside."

I suspect that trying to assert you can find some kind of matter that's incompressible and exists outside of a black hole is probably where you're having trouble with this question. Probably as you approach your wonder material that is so tightly packed it is impossible to deform you're going to find that what you've got is no longer matter at all.

blahnana, density is only part of the problem. Just because something is dense doesn't mean it's not incredibly elastic (which is the other important factor here, since that's the mechanism by which the wave propogates through the object).

For a common example consider:
1. Rubber - dense, highly elastic
2. Polystyrene - not dense, not elastic
3. Foam - not dense, highly elastic
4. Steel - dense, not very elastic

Now I want to go watch event horizon again. Damn you billy.

Yeh same re. Event Horizon :)

I couldn't really see a definitive answer in the other thread besides the fact that that the atoms 'squish' together a.k.a Deformation, which I stated would not occur as we're assuming the rod is some amazingly advanced nano tube thing.

See, what you're saying is that we should ignore some the laws of physics in order to circumvent some other laws of physics, and all the while ignore inertia. It would take truly ridiculous amounts of energy to shunt your massive lightyears-long rod.

You may as well say "lets invent a special kind of light that goes faster than the speed of light" or "use magic to talk to people on Betelgeuse" as this proposal. The physics is just a sensible - you asked a "science question" and got a "science answer".

If you want to invent non-scientific scenarios then go for it.

Now I want to go watch event horizon again. Damn you billy.

liberate tutemae!

Same deal as electricity. The electrons driving your lightbulb don't come all the way from the light switch. The net movement of all electrons in the circuit is what drives the lightbulb. Although this domino effect is fast, it's still bulls*** slower than light. Hence why fibre optics are now used instead of copper wire for telecom.

Although this domino effect is fast, it's still bulls*** slower than light. Hence why fibre optics are now used instead of copper wire for telecom.

Ah no. The twisted pair copper wires are transmission lines that transmit information at the speed of light (well, half the free-space speed of light typically). They absolutely don't transmit information at electron movement speeds (which are very, very slow).

Fibre optics propagate at about the same speed (50-70% of c), and are used mainly because they have incredibly low loss and are immune to EM interference.

last edited by parabol at 00:32:49 19/Mar/10

In it's purest form, does the theory work?

No. Special relativity says faster than light communications violate causality. If you claim to have discovered how to implement FTL comms by touching your rod, physicists would argue that you're only touching your rod.

It would take truly ridiculous amounts of energy to shunt your massive lightyears-long rod.

That's what she said.

Consider also the f***ing inertia of moving a rod several light years long ... even at a couple of atoms wide it would likely have more mass than the Earth!

Your understanding of kinetic energy and matter is flawed, that's all. You think of a physical object being moved all at the same rate when you push one end, because that's what happens according to your senses. This is the same reason people didn't realise that light 'travelled' for a very long time - they couldn't observe it.

Regardless of how it seems, a physical object isn't completely rigid, and a rod that behaved the way you want it to wouldn't just be be some sort of 'super nano thing', it would be a type of matter that simply has not been observed, basically a proton several light years wide.

I understand that a parallel wave affect will be created when energy travels through a median, this was more like a 'perfect scenario'. When studying kinematics we assume that the particle of mass is a singularity, which in real life it is clearly not.

This diagram should express my point in fun picture form:

http://imgur.com/rCOqQ.jpg

Sorry I have not yet mastered the art of posting an image, that is the velocity of the observed energy wave travelling through the median. I was ignoring it [just like in physics when they ignore particle's area and all other form of interference] so that it could be solved at a purer level.

That's why I was saying it was assumed to be a rigid body, when we analyse trusses at a low-level we ignore bending, stress etc. for the same reason.

http://www.w3schools.com/html/html_images.asp

< img src="http://www.xxx.com/images.jpg" />

so that it could be solved at a purer level.

You mean a wrong level?

when we analyse trusses at a low-level we ignore bending, stress etc. for the same reason.

Is that reason so you can get the answer you want?

blahnana, density is only part of the problem

Of course, I was trying to address Blue's specific concerns without get too tangled up.

Blue, seems like in your last post you're pointing out all the places the idea of this miraculous rod breaks down.

When studying kinematics we assume that the particle of mass is a singularity, which in real life it is clearly not.

That's why I was saying it was assumed to be a rigid body, when we analyse trusses at a low-level we ignore bending, stress etc. for the same reason.

So I guess you're the troll.

Btw, the red squiggly line comes from the spell-checker in your browser. Which gets its language settings from your OS, usually. Nothing to do with this site. Fix that.

last edited by blahnana at 09:38:00 19/Mar/10

so that it could be solved at a purer level.

You mean a wrong level?

when we analyse trusses at a low-level we ignore bending, stress etc. for the same reason.

Is that reason so you can get the answer you want?

Well it acts as a stepping stone to more advanced problems in the future [just like with physics] The answer is technically wrong, yet you need to understand the method to obtain those forces as most of these equations are dependent on the same variables.

That's why it takes 4 years to finish the degree, learning all of those stepping stones so that you can build up to the real thing eventually. With the rod, breaking was an obvious answer, the speed at which the energy travels through the median requires some thinking, as does the fact it has a large inertia. Yet if no rules where put in place on the question people would just say "no it would break" and that's not the answer I was looking for.

I'm not trying to troll, I was just trying to create some thread activity and these questions usually do, everyone who has answered has answered correctly so yea.

Dazhel gave you the best answer Blue.

Special relativity says faster than light communications violate causality.

You're basically trying to say that you can invent a time machine with a gigantic rod, or that special relativity (backed up by masses of empirical data) is somehow wrong.

Unless you can get around special relativity somehow, and to imagine doing so usually involves egghead theories about naked singularities, not gigantic rods :)

:P One answer, micro worm holes! Create a small worm hole in the direction of the messages destination and send it through, problem of FTL solved. /:P

Seriously, our understanding of physics says that FTL is impossible and our limited understanding of Quantum physics is even more limited. Give it all another 100 years and maybe something might actually be discovered.