/sci/ - Science & Math

[Anonymous No.10662551]

Is it true?

[Anonymous No.10662563]

No. The movement of the stick travels at the speed of sound in whatever material the stick is made out of, which is much less than the speed of light.

[Anonymous No.10662566]

>>10662563
The stick is one giant atom

[Anonymous No.10662569]

>>10662566

[Anonymous No.10662572]

>>10662563

then how does ANYTHING go faster than the speed of sound?

>>10662551

>implying you could generate enough kinetic energy to move a stick 1 light year long

[Anonymous No.10662606]

>>10662566
No, it isn't.

>>10662572
>then how does ANYTHING go faster than the speed of sound?
The speed of sound is the speed at which accelerations travel through a material. It does not restrict the maximum speed an object can attain, it restricts the speed at which force applied to one part of an object start affecting other parts of the object.

[Anonymous No.10662607]

>>10662572
An airplane moving in air can exceed the speed of sound (of air, as usually assumed) which is relative to some average non moving framing of the air mass. The nature by which sound travels is different depending on the medium it travels in as well so that factors in to the question. Think about phonons of a mechanical wave vs rarefaction/compression of air waves. In the question above it's about how fast a force can propagate through a material, which can be summarized by justing saying the speed of sound in that medium, for metal this speed is quite high, usually in km/s.

[Anonymous No.10662639]

>>10662563
yes but he felt the poke immediately there was no time in between the start and finish of this sticks journey to that man. if the stick can travel to another point instantly then it travels faster than light

[Anonymous No.10662650]

Under these false assumptions, the stick wouldn't need to be a lightyear long, it could be any length. The assumption is that applying force on one end means that the other end begins moving instantaneously. In which case, if that happens over any length, it'd have to be faster than light. Applying force results in a wave traveling through the stick. The molecules at the end of the stick begin moving some time after the molecules at the beginning. A short enough stick makes it appear instantaneous.

[Anonymous No.10662963]

>>10662650
>In which case, if that happens over any length, it'd have to be faster than light
Why? I dont see how
>other end begins moving instantaneously
Is a problem. Every part of the stick can just move with the same speed no?

[Anonymous No.10663201]

>>10662566
Changes literally nothing.

[Anonymous No.10663204]

>>10662963
Nothing is infinitely rigid.

[Anonymous No.10663217]

>>10662563
>all movement is sound
>we are sound-stuff
>our every motion is the music of the stars
>we are the universe trying to hear itself

[Anonymous No.10663306]

>>10662551
>>10662566
>>10662569
>>10662572
>>10662639
>>10662963
>>10663217
The absolute fucking state of /sci/

[Anonymous No.10663474]

>>10662551
The stick doesn't travel from your hand to the one you poke, the stick is traveling at the same distance as your hand.
Doesn't matter if the stick is 10 lightyears long or 10 centimetres long, it still travels at the speed of whatever pushes it.
This is like those shitty troll science things, how could you not understand something this simple?

[Anonymous No.10663479]

>>10663217
When you think about it all movement is waves just like all signals are waves, via fourier transforms etc. If you break it down this way you can see exactly how much of your motion is sound, how much is radio, etc.

[Anonymous No.10663613]

>>10663474
The issue with this is that, if the force transmitted instantly, this would imply faster than light communication and break causality. As some anons pointed out, for any real material the speed of transmission of force through it is the speed of sound in that medium. However, the maximum theoretical rate of force transfer, independent of medium, is the speed of light.

[Anonymous No.10663638]

>>10663204
except black hole

[Anonymous No.10663679]

Wait I'm confused.

Isn't it the case that the guy who gets poked will experience it 1 year (minimum) later relative to the guy who pushed it, but for the guy who pushes it, it happens immediately?

This is because time isn't the same in both locations, right? I don't have a background in physics, so pls no bully.

[Anonymous No.10663778]

>>10663679

Physics/Astronomy dual major here, you're actually overthinking the situation. You're talking about relativistic effects by bringing up the potential for the time to be measured differently in two locations, but that's not relevant unless we're in a pretty strong gravitational field or moving an appreciable fraction the speed of light. Otherwise, you don't have to be concerned with those factors, they just don't come into play here.

The problem poised by OP is a common one that's been answered to death many times before. Simply put, the answer is "No." If you had a light-year long stick, pushing one end of it would just result in a compression wave being sent through the material at the speed of sound within that medium (The medium being the material itself). Assuming it didn't dissipate (Which, realistically, it absolutely would), then the person on the other end wouldn't receive a "Poke" until that compression wave traveled to them from the other end, which would take far longer than one light-year.

I remember I use to think about this when I was a kid. I was convinced I found a way to break light speed by taking a long stick and swinging it around the Earth fast enough that the far end of it would definitely move faster than light, but this idea fails on the same principle as just pushing it. Swinging the stick also requires me send a compression wave through it that instigates the movement, which again won't travel instantaneously and so my little genius solution to FTL travel was a bust.

[Anonymous No.10663815]

>>10663778
Makes sense, thank you

[Anonymous No.10664218]

>>10663778
Why at the speed of sound within the medium?

[Anonymous No.10664233]

>>10663217
my sides

[Anonymous No.10664238]

>>10662563
Wrong. Movement of the speed depends on whatever force is applied to the stick. If a shitter applies a 1 kg of force to move 1 light year long stick, it will not move. If a shitter applies infinite amount of force at infinite speed, the other person will feel it instantly. But there's no such thing as infinite speed/force so its kinda useless.

[Anonymous No.10664875]

>>10662551
it would imply a stick not made of matter and with infinite rigidity, so what's the point? you know what makes an actual stick rigid is the electromagnetic interaction between the atom that compose the stick, so the signal still moves at the speed of light at maximum

[Anonymous No.10664891]

>shove stick 1 light year long
>pour water into a pre-filled hose that's 1 light year long
>put electrons into wire that's 1 light year long
>shine light into fiber-optic cable 1 that's light year long
>shoot tachyon particles into true-vacuum tube (not false vacuum like space/universe is) that's 1 light year long

well?

[Anonymous No.10664898]

>>10662566
Jesus fucking christ.