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/sci/ - Science & Math

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6024438 No.6024438 [Reply] [Original]

Not trolling, but would this work?
Why or why not?

>> No.6024443

Distortion of the rod does not propagate faster than light.

>> No.6024447

no the signal/wave will travel along the material at the speed of sound in the material

>> No.6024454

>>6024443
>>6024447
What makes you think the solid rod would distort into a wave when pushed?
[citation needed]

>> No.6024463

>>6024454
http://www.youtube.com/watch?v=eCMmmEEyOO0
Information cannot travel faster than the speed of light

>> No.6024462

>>6024454

The citation is reality.

>> No.6024466

>>6024454
because the speed of sound in solids is not infinity

>> No.6024468

>>6024454
how does one end of the rod know the other is pushed?

>> No.6024473

>>6024454
because the atoms at one end push the next atoms along etc, by a slightly less than 100% rigid mechanism

>> No.6024497

>>6024473
But imagine it WAS a 100% rigid mechanism.
Would it work then?

>>6024463
The slinky analogy is not applicable to the above hypothetical instrument.

>>6024462
If you're not going to be constructive, then please feel free to fuck off.

>> No.6024512

>>6024497
>But imagine it WAS a 100% rigid mechanism.
it is problematic because different points in space do not necessarily have the same time frame in special relativity, so the whole rod moving "at the same time" doesn't make sense. the best it can do if 100% rigid is propagate that push at the speed of light

>> No.6024509

>>6024497
It's not. You can not have a newtonian material that is 100% rigid, it would allow information to move faster than light, making it impossible.

>> No.6024511

>>6024497
>guys just imagine if I could run faster than light
This is how ridiculous you sound.

>> No.6024517

>>6024438

> Implying the "stick" isn't just a goo of particles that is mostly empty space.

The most important info is that right now that you're not dropping through earth, isn't because of an abstract notion of a "solid" but because a very thinly cloud of atoms is having magnetic forces with your fat ass.

>> No.6024519

>>6024509
This, people should really stop questioning this whole information vs light speed thing, it is simply not possible for a particle to move through space faster than light speed. stop questioning it. fuck.

>> No.6024521

>>6024497
relativity does not like rigid bodies
another rigid body paradox
http://en.wikipedia.org/wiki/Ehrenfest_paradox
ugh this is the only version I could find of your experience
http://www.physicsinsights.org/rigid_rods.html

The slinky's information passes down to the bottom of the slinky.
The bottom does not shift down because the information that it had been dropped had not yet reached it.

>> No.6024524

>>6024497
it is a slinky, just a much stiffer slinky

>> No.6024528

>>6024519
what if I took a laser pointer, pointed at one end of the moon and then rotated it so that the laser pointer hit the other side of the moon.
The dot on the moon would move faster than the speed of light.

>> No.6024532

>>6024528
that's totally allowed

>> No.6024537

>>6024528
the photons from laser pointer are still traveling at c

>> No.6024540

>>6024528
my sides

>> No.6024542

>>6024528
but would you see it move faster than the speed of light?

<mindfuck>

>> No.6024555

>>6024497
>But imagine it WAS a 100% rigid mechanism.
>Would it work then?
Yes. Which is why there is no such thing as a 100% rigid mechanism. A rigid body is a simplification used for each of calculation, not a thing you can find in reality.

>> No.6024564

>>6024555
>Yes
no it wouldn't retard. totally rigid would move propagate the push at speed of light, as that's how the underlying space time would deal with such a thing

>> No.6024567

>>6024564
That would be a deformation, which by definition can't happen to rigid objects.

>> No.6024571

>mfw people don't understand the concept of an idea universe

Nothing is ideal. You assume things are ideal in early physics courses so you don't blow your head off halfway through the semester.

>>6024497
Nothing is 100% rigid

Sorry.

>> No.6024572

>>6024567
no it wouldn't, as space itself deforms that way, so to speak

>> No.6024575

>>6024571
>Nothing is 100% rigid
we can model a rigid rod, and it would propagate a push at one end at speed of light

>> No.6024577

> People actually saying "nothing is absolutely rigid"

"Absolutely" rigid?

Do you have any idea that all objects aside some extremities like neutron stars and black holes are mostly empty space? The reason your fat ass doesn't fall through the floor isn't a "solid", it's magnetic forces from a cloud of atoms. A very thin cloud.

>> No.6024581

>>6024571
If nothing is 100% rigid, how come stones don't dissolve into a fucking goo?

I don't get you guys sometimes, how come everything is a goo all of a sudden?

>> No.6024582

>>6024572
>>6024564
shutup. He's saying that there can not be a 100% rigid object because if there was then the push would be faster than the speed of light. Consequently, it isn't possible, so there is no need for warping of spacetime.

>> No.6024578

>>6024577
>magnetic
it's actually pauli exclusion that makes solid things solid, freeman dyson proved this

>> No.6024586

>>6024581
>>>/out/

>> No.6024588

>>6024577
Do you understand that most solids are consisting of structures which all happen to "give" at least a little? Everything vibrates, everything has a melting point

>> No.6024590

>>6024578

> I take my "psychics" lessons from BBC specials.

Gay.

>> No.6024594

>>6024582
protip: there is no notion of "simultaneity" in special relativity. so for one end to move "at the same time as" the other end doesn't make sense

>He's saying
he is wrong

a 100% rigid body would cause propagation at c, not instantly.

the reason there cannot be 100% rigidity is due to the physics of materials, not special relativity

>> No.6024598

>>6024590
no, i take them from my degree in physics. and yes i am gay

FJ Dyson and A Lenard: Stability of Matter, Parts I and II (J. Math. Phys., 8, 423–434 (1967); J. Math. Phys., 9, 698–711 (1968) );

>> No.6024600

Of course it would work, it's like when you tun on the light switch

>> No.6024599

>>6024586
Yeah, tell me to go away instead of explaining it.

>> No.6024603

>>6024598

> Implying you're gay.

I bet you hate all women.

>> No.6024609

>>6024603
you bet wrong child

>> No.6024608

>>6024581

10^65 years: Assuming that protons do not decay, estimated time for rigid objects like rocks to rearrange their atoms and molecules via quantum tunneling. On this timescale all matter is liquid

and since we're on the topic:

It is possible for spin zero particles to travel faster than the speed of light when tunnelling.[3] This apparently violates the principle of causality, since there will be a frame of reference in which it arrives before it has left. However, careful analysis of the transmission of the wave packet shows that there is actually no violation of relativity theory.

yeah, it's all from wikipedia because I don't study physics but I like dicking around through physics-related articles there without actually understanding that shit.

>> No.6024615

>>6024599
rocks are flexible.
just not flexible enough that you notice them flexing

>> No.6024631

>implying that the second your stick even gets close to xorblaxz it doesn't zip away at thousands of kilometers per second

>> No.6024639

>>6024590
>>6024603
>someone knows more than me
>I feel insecure
>better troll them

>> No.6024659

>>6024468
imagine the following:
you push one layer of atoms. that layer pushes the next, and so on. you move matter, which takes much more time, than the speed of light

>> No.6024663

>>6024659
>totally missing the point

>> No.6024684
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6024684

>>6024438
Watch the video of a golf ball getting hit in slow motion.
http://www.youtube.com/watch?v=AkB81u5IM3I

This is what is happening to the rod when you attempt to move it. Waves and such.

>> No.6024692

>>6024684
>still missing the point

>> No.6024695

>>6024663
He is right. The information only travels at the speed of sound in that substance.

>> No.6024708

>>6024695
he's right, but missing the point

in SR we can model a 100% rigid rod and it still propagates any push at the speed c

>> No.6024757

>>6024528
>The dot on the moon would move faster than the speed of light.
I'm not so sure. Wouldn't the beam become more of an arc, like when you flick a water hose?

>> No.6024760

>>6024575
I can model a fucking unicorn; doesn't change reality. What you're asking is basically "if the laws of nature were different, would things be different?"

>> No.6024762

>>6024757
the dot would move faster than light, but the dot is not a single thing. as it moves is not the same thing at any one time as another time

>> No.6024764

>>6024692
>still missing the point

>> No.6024770

>>6024760
some models are useful, others not

the rigid rod thought experiment is a classic of SR and shows how the breakdown of simultaneity messes with your newtonian intuition

so there is no need to get so mad

>> No.6024995

>>6024528
oh god

>> No.6025021

>>6024463
Didn't someone send sound waves through a medium faster than light?

>> No.6025424

Can a solid object of that size even exist? If it's too narrow it'll break, too thick it'll implode.

>> No.6025436

>>6024438
it would be instant because the pole is not traveling at the speed of light, it is traveling at however many m/s that you're pushing it at
sticks, even long sticks, are allowed to be pushed

>> No.6025442

>>6024438
it would take more time than the speed of light for the vibrations of the "poke" to travel through the stick.

>> No.6025455

>>6025442
poking someone with a stick is not a transfer of vibrations, it is a change of location
as long as you are not poking faster than the speed of light then the movement will transfer instantly
the difficulty would be moving an object of that size due to its massive amount of inertia and the many forces of gravity it will inevitably encounter since it spans across lightyears
also if anything runs into it it's fucked

>> No.6025464

>>6025455
Isn't that assuming the object is perfectly rigid? At our scale, it would transfer instantly but certain phenomena that are negligible at our scale are important at different scales. Just like how Van der Waals forces are significant for very small objects, I'd imagine that the molecular vibrations would be important at extremely large scales. I don't know this, but I just feel like that would have something to contribute.

>> No.6025469

When you push on something, it's a cascading compression, similar to a sound wave. So it wouldn't transfer the poke to the other olanet instantly. I believe it would travel at the speed of sound for that material, and certainly not the speed of light.

>> No.6025472

waves, bro

>> No.6025483

>>6025464
if the object was not perfectly rigid then it would snap before the poke even got close to the other planet

>> No.6025488

>>6025455
Do you not understand that all objects are composed of atoms and those atoms are held together with electromagnetic fields? When you push on one end of the stick, you're pushing on the atoms at the surface. They move a little, and that movement changes the local EM field, which in turn causes neighboring atoms to move, etc. The movement is transferred through the solid as a compression wave, which is actually slower than the speed of light, with the latter as the upper limit in some sort of ideal solid with massless point atoms (and even then it probably doesn't work out due to molecular orbitals depending on particle mass).

The better question is, when you push an elementary particle, does the other end move instantaneously?

I have no fucking idea. Maybe a particle physicist is around to regale us with his insights.

>> No.6025490

>>6025483
why?
do you know why things break?

>> No.6025494

>>6025488
when an object is solid, though, the molecules are packed together so tightly that putting a force on one of them would instantly apply the force to the other one

>> No.6025500

>>6024497
the "rigid" bodies are actually a bunch of protons and electrons, the force between then is transferred through electromagnetic fields, and those obey the rules of relativity and the speed of light

>> No.6025499

>>6025490
you would be applying a force to one end of the rod
the rest of the rod has insane amounts of inertia and would not move
this would cause the rod to bend
on a scale that large the bend would become large enough to cause a break

>> No.6025503

>>6025488
elementary particles aren't solid.
they are "shaped" by the fields from elementary forces.
it will compress these fields slightly and then push them out on the other side.

>> No.6025508

>>6025499
that's called buckling and you could push it slightly enough that the wave of buckling won't snap your rigid rod.

>> No.6025541

>>6025494
>the molecules are packed together so tightly that putting a force on one of them would instantly apply the force to the other one
>so tightly
>instantly

Nope. The speed of light is the limit. There is no "instantly". It appears instant on a macroscale for common objects, but it isn't.

Your concept of a solid seems to be one of a tightly packed collection of marbles. It isn't. Even at 0 K (where there are almost no vibrations (i.e. phonons)... yes, there are still some at 0 K because of quantum physics, deal with it), most of the volume is completely empty space. Basically, if the nucleus were the size of a quarter, some of the electrons would be flying around it a whole football field away.

tl;dr: The speed of light is the upper limit and your notions of solid state physics are too simplisitic to allow you understand why.
>>6025503
That's not really that much clearer, but I suppose it helps. I basically expect that at that scale, the usual concepts of matter get a bit fuzzy.

>> No.6025609
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6025609

>>6024708
>Special relativity

>> No.6025653

>>6024528
The dot could then move faster than the speed of light. However, no laws are broken because there still isn't any particle nor information travelling faster than c. The photons that make up the laserlight are going from you to the moon, not from one side of the moon to the other.