Would this accidentally spacetime?

[Der Anfang]

You know how you can pick up a stick or a flashlight or whatever, and swing it from one end of the room to another, pointing it? Hypothetically, let's say you have an unusually long pole (which the pole is not massless) that you pick up and realize it is half an astronomical unit long, yet it is somehow light enough for you to pick it up with Ease, and the pole is impossibly rigid. Now, you decide to point the pole at... say, the Sun, which is peeking just over the horizon. Then, you decide to swing it all the way to the opposite side of the horizon respective to the Sun to point at another distant random star in the sky.

 

Would the end of the pole have surpassed the speed of light? 

[Steel]

Please watch this, for basically the same problem with a laser pointer, or the first minute or so of this for your problem.

Also any *real* pole is that force propagation through it is limited by the speed of sound in the material, so all you'd really end up with is a wave in the material that would travel the length of the pole at the around speed of sound in the material, like a wave on a string, except the losses would probably stop the wave fairly quickly. 

The issue when people say "can this completely unphysical thing break the laws of physics?" is that it usually can, because the laws of physics have already been broken to introduce that thing.

Edited January 5, 2016 by Steel

[Wjolcz]

 

I'm no expert but it would if it was possible and AFAIK no material is able to whitstand such lenght/acceleration and be rigid enough to not be a wet noodle at the same time.

Edited January 5, 2016 by Veeltch

[problemecium]

What steel said.

This is very similar to the old proposal about getting a giant steel beam to span the solar system and then pushing on one end. Intuition tells the layman that the other end moves instantly, so the end of the pole on the other end of the solar system will receive a force faster than light (and then the universe would explode?).
Really the layman's intuition is an illusion caused by the fast speed of sound. When you push on, twist, or otherwise manipulate one end of an object, the other end will not react until the mechanical stress has propagated all the way through the object - and it does this at the speed of sound in that object. Since this is very fast, particularly in the case of a steel rod where it's significantly faster than the speed of sound in air, the rod appears to react instantly. Really, what's happening, as can be verified with an extreme high-speed camera, is that the rod is squishing and flexing like a big floppy noodle, or a slinky that someone's flicked at one end, and a wave is traveling along it.
So with the giant steel rod, you'd grab one end and run off with it (in your EVA suit or whatever) - feel free to go quite a long distance: compared to the rod that distance will be rather small - and you'd create a huge wave moving along the rod at the speed of sound (again, in the rod). For real materials, the speed of sound never exceeds the speed of light (even for Unobtanium ;P ), so the other end not only would remain still for several minutes, but due to the flexibility of the rod would have no trouble traveling below the speed of light and gradually shifting over to where you wanted it to go.

[Shpaget]

Guys, your explanations are not relevant. Laser dot on the moon is not a physical object and such a dot can move faster than c. There is no matter or information that is traveling faster than c.

Speed of sound through the rod explanation is also not applicable since OP is not talking about acceleration, but the final speed. So what if it takes a while for the end of the stick to accelerate? The question is, can the end of the stick break the speed limit of c?

While the answer is still a "no", it is because of a different reason. Even if your stick is very strong (but still flexible) and angular acceleration is low enough to not cause the break in the stick, the end of the stick will still never surpass c because as any mass approaches c, its mass increases and approaches infinity, so it would take an infinite torque to swing a stick and break the c barrier.

[problemecium]

^ Yes, all of the this. Sorry I wasn't more specific.
Acceleration aside, the end would have no reason to be forced to try to go faster than light because of the wet noodle thing I and some others mentioned. In a rigid object, one might get that impression, but if OP had asked about a giant solar-system-sized whip, there would probably be little confusion.

There's also time dilation. The end of the pole and its final speed are all based on its own perception on the incoming mechanical force - in its own reference frame. Due to relativistic effects, as it nears light speed it will experience time waaayyy slowed down, so an astronaut standing there might well convince himself he is getting whipped around at ludicrous speed and that the rest of the pole is simply trying to catch up to him. But to outside observers he's still under light speed.

Edited January 6, 2016 by parameciumkid
Wibbly wobbly timey wimey.

[KerbMav]

Wild guess: Because what appears to us as a solid coherent object is in reality just an accumulation of particles?

[YNM]

A massless pole : that's just light, no effect.

A sliightly massed pole : as soon as you do it, either it break in half, or it break in half a while later. Certainly not going to be rigid in any way though.

[Findthepin1]

Poke someone with a stick a lightyear long. You're at one end, and they're at the other end. They get poked instantly when you push the stick, but they have to wait a year before seeing you push the stick. Does that break physics?

[Shpaget]

2 minutes ago, Findthepin1 said:

Poke someone with a stick a lightyear long. You're at one end, and they're at the other end. They get poked instantly when you push the stick, but they have to wait a year before seeing you push the stick. Does that break physics?

No. They get pushed a lot later than seeing you pushing them.

The "push" travels at the speed of a longitudinal wave through whatever material the stick is made of.

[justidutch]

No, because I won't get poked instantly by the stick, for the reasons the others mentioned above.  It takes time for the force you exert on your end of the stick to make its way to my end.

Edited January 6, 2016 by justidutch

[cantab]

If the pole is "impossibly rigid", then it's impossible to swing it fast enough for the other end to move faster than light, no matter what non-zero mass the pole has. The energy required to do so is infinite, which makes the force required to be exerted on the pole also infinite. This applies regardless of the length of the pole.

[Andem]

The issue with this is that it is an impossible object that defies the laws of physics. Now, if the part in question obeyed the laws of physics, than yes, it would. now, the real issue between the pole and the moon-laser concept is that the dot isn't moving, the light has just been changed to a different angle, creating a clever illusion, like Shpaget said. now, with a physical object, the force would be diluted to  a point where it would not surpass the speed of light.

Edited January 10, 2016 by Andem