[ 3 / biz / cgl / ck / diy / fa / g / ic / jp / lit / sci / tg / vr ] [ index / top / reports / report a bug ] [ 4plebs / archived.moe / rbt ]

2017/01/28: An issue regarding the front page of /jp/ has been fixed. Also, thanks to all who contacted us about sponsorship.

/sci/ - Science & Math

View post   

[ Toggle deleted replies ]
File: 404 KB, 640x480, pendulum_1.gif [View same] [iqdb] [saucenao] [google] [report]
9448732 No.9448732 [Reply] [Original] [archived.moe]

suppose we have this pendulum 1 000 000 km long. if we swing the first ball, the last ball also swing immediately. thus we transferred information faster than speed of light

speed of light DEBUNKED

>> No.9448757

>suppose A
>then magic happens
>speed of light debunked!

>> No.9448770

Momentum is only transferred through the chain at the speed of sound.
If you're going to troll, at least come up with something more original, please.

>> No.9448778

If I have a stick 1 million light years long, and sit on one end as a see-saw and I hit the floor; the other end doesn't begin to move for 1 million years, right? is this because of the speed of gravitational waves?

>> No.9448815

Takes longer than a million years. It travels at the speed of sound (in the stick), not the sped of light.

see >>9448770

>> No.9448857

thanks, could you provide some links?

>> No.9448906


http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html#3 (rigid bodies #4)

>> No.9448994

>implying the speed of light is constant
kid, come on.
go back to /ck/ where the only science they need is a mcchicken.

>> No.9450127

>Momentum is only transferred through the chain at the speed of sound
That's no true. momentum transfer immediately. speed of sound exist because there is space between atoms that need to be traveled.
If we take super dense material we can send information faster than light.

>> No.9450140

The kinetic energy of the atoms in the first ball are transferred to atoms in the second etc.... it's the speed of sound in a material. Even the 6+ ball setups aren't instant.

>> No.9450147

If you whacked a neutron star with a hammer, the impulse would only go through at the speed of sound.
Speed of sound would be very high, but still less than lightspeed.
In an Einsteinian universe there are no perfectly rigid materials.
See http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html#3 (rigid bodies #4)

>> No.9450203

If we have something transmitting at the speed of a vibration propagating to medium only...

You're getting close.

>> No.9451516


>> No.9452434
File: 207 KB, 692x960, 1513105417331.jpg [View same] [iqdb] [saucenao] [google] [report]


1) kinetic energy travels at speed of sound

2) the kinetic energy would turn into heat way before it got to the last ball

3) the gravitational pull exerted by all the balls would rearrange them, and make them wobble on their own, independently

4) kys

>> No.9452486
File: 33 KB, 938x560, 1.jpg [View same] [iqdb] [saucenao] [google] [report]

Sadly you don't understand the basic principle. If we add more mediator particles, we reduce the path that particle need to travel to transfer the energy
time = distance / speed. this is basic math, anon.

>> No.9452497
File: 105 KB, 800x811, 1472482838897.jpg [View same] [iqdb] [saucenao] [google] [report]


you forgot to add le troll face

>> No.9452499

This is all of the Discovery Channel science most people here understand

>> No.9452571

Ah yes, the balls are actually points with no mass in a frictionless vacuum on a perfect plane of uniform gravity.

The kinetic energy propagates through the chain at the speed of sound because of inertia, and internal forces/stresses. Stuff takes time to move, acceleration is not instantaneous/infinite. Furthermore, the kinetic energy is not perfectly conserved in the collision, some of it converts to heat and sound. As you extend the chain you lose more and more of the kinetic energy. This is true for both your newton's cradle in the OP as well as the lightyears long stick mentioned elsewhere in thread.

The more dense a material is, typically the faster the speed of sound is. Precisely for the reason you mentioned: particles don't need to move as far after being bumped before they bump the next thing. However, this is still propagation at the speed of sound in the material, and the speed of sound will NEVER surpass the speed of light because of inertia and physical properties of the material (chemical bonds, tension in the atomic structure, internal friction, etc)

>> No.9452581

That animation is wrong. Either the center balls are always still or they are swinging, There is no condition that would make them shift back and forth like that.

>> No.9452590

If the strings are attached to the top in increments less than the diameters of the balls, then the center of mass of the group of balls would shift as the end balls trade back and fourth.

But yes, they would still probably swing a bit too, not just remain stationary after the shift. However, they wouldn't swing very fast or far, and respect to the much greater and faster motion of the end balls, could appear to be basically stationary.. So the animation is close enough

>> No.9452595

>If the strings are attached to the top in increments less than the diameters of the balls,
They aren't, The entire point of a newtons cradle is that all the strings are vertical and there are no horizontal forces on the balls except for the gravitational force caused by their deviation from 0.

>> No.9452596


>> No.9453850


nigger, vibration propagation in different material works like sound but at different speed

Dunno about degenerate material tho

>> No.9454010

>ibration propagation in different material works like sound but at different speed
yes, because in all materials there is a space between atoms.

>> No.9454022

this is correct

Name (leave empty)
Comment (leave empty)
Password [?]Password used for file deletion.