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[Blargityblarg]

The cheese is of a normal shape, one which you can buy in a shop.

Cheese comes in rectangular prisms, wedges, wheels, globes and snowman-shapes.

[Leafsnail]

Yeah, the ambiguity was part of the question .

You can also buy it in thin strips, which would make the proposed solution actually possible in reality.

[Blargityblarg]

So it involves folding, I take it?

[Il Palazzo]

For the guillotine... nothing's actually moving horizontally, is it?  We just perceive a kindof wave moving along the bottom.  So perhaps you could create an illusion of faster than light travel in this manner.

Right. The point of intersection between the blade's bottom and some arbitrary horizontal line can move faster than the speed of light. Given a sufficiently small angle, it could do it even at relatively slow falling speeds.

Yeah, the point of intersection is just a mathematical concept, so it's not constrained by the laws of physics.

Now, if you remember the scissors, when you think of the point of intersection in that case, can it move faster than light?
The scissors are made of some metal than can't break, but will bend elastically. You can apply infinite force to the handles.
(I'm not actually sure myself about this one)

A similar problem:
There's a long line of train cars lined up one after another, so that they are each in contact with their neighbours. Their total lenght is D.
You hit(apply a force) the first one on whichever end. Will the car on the opposite end start moving:
(c=speed of light)
A.Immediately.
B.After t=D/c time passes.
C.After t=D/V₁ time passes, where V₁ > c.
D.After t=D/V₂ time passes, where V₂ < c.

[G-Flex]

The scissors are made of some metal than can't break, but will bend elastically. You can apply infinite force to the handles.
(I'm not actually sure myself about this one)

Well, you won't find a source of infinite force to begin with, so that part is sort of moot. Secondly, constant force does not equal constant acceleration on a given mass (it does in newtonian physics, but physics at this scale isn't newtonian). A constant force, no matter how long it is applied to something, does not result in giving that object speed at or faster than the speed of light.

[Il Palazzo]

Yes, of course you can't have an infinite force in reality. This, however, being a thought experiment, we can happily assume that you've got a hand of god and can press the handles with such a force if needed be.(same as you sometimes assume weightless pulleys and dragless surfaces)
The question is concerning the scissors themselves, and how would they behave. Specifically, if the cutting point could move faster than light.
Also, I believe there's no need to involve relativistic physics to explain this one, but I might be wrong.

[G-Flex]

Yes, of course you can't have an infinite force in reality. This, however, being a thought experiment, we can happily assume that you've got a hand of god and can press the handles with such a force if needed be.

In a thought experiment about physics, why are you breaking the laws of physics? You can't say "If you can do <impossible thing>, what is the result?" and expect an answer that has much to do with reality.

At any rate, even with infinite force, no, they won't move faster than light.

Also, I believe there's no need to involve relativistic physics to explain this one, but I might be wrong.

Non-newtonian physics are required to answer any question like this. According to newtonian physics (F=ma and all that jazz), going faster than the speed of light is pretty damn easy.

[Il Palazzo]

Yes, of course you can't have an infinite force in reality. This, however, being a thought experiment, we can happily assume that you've got a hand of god and can press the handles with such a force if needed be.

In a thought experiment about physics, why are you breaking the laws of physics? You can't say "If you can do <impossible thing>, what is the result?" and expect an answer that has much to do with reality.

Are you serious? Weightless pulleys? Dragless surfaces? Rings any bells?

You can analyse the physics of a problem while discarding some parts of it, which realistically could not be discarded, and still gain some insights on the physics involved.
In fact, most of the time you have to do so, else you'll be forever stuck trying to solve unsolvable differential equations or whatnot.

At any rate, even with infinite force, no, they won't move faster than light.

I'm talking about the cutting point here. As you could see with the guillotine, it is possible in some cases for it to "move" faster than light.
However, in this here case, there is something different.

And you don't need to involve relativistic physics. Neither here, nor in the "train cars" scenario.

[Leafsnail]

Yes, you could move at the speed of light with infinite force.

Which is why it's impossible to do so (it's actually the same for "absolute zero" temperature - you need infinite energy to get there).

[G-Flex]

I'm talking about the cutting point here. As you could see with the guillotine, it is possible in some cases for it to "move" faster than light.

Right, never mind. I was thinking about the position of the arms themselves.

And you don't need to involve relativistic physics. Neither here, nor in the "train cars" scenario.

Yes, you do in the train cars question, in the sense that you cannot expect anything to happen instantaneously.

Yes, you could move at the speed of light with infinite force.

I think the problem here is that acceleration (with constant force, which we have here) becomes infinitely small as velocity increases, yet the force we have is infinitely large. This brings is to a sort of indeterminate answer where the acceleration approaches 0*∞, which, by itself, isn't particularly meaningful. I'm not sure I know what this would evaluate to because I don't feel like dealing with limits at the moment. Since the force is constant, though, that probably affects it somehow, albeit in a nonsensical, noncontinuous manner.

[Il Palazzo]

O.K., I'll just tell you what it's all about. It's about how the energy(information) gets transferred.
In the case of the scissors, you can have an infinite force pressing on the handles, but that force still needs to get transferred alongside the arms. Which is done via molecules being displaced, and tugging on their neighbours. This creates a sort of wave traveling from the handles outward, and this wave travels just as fast as any other wave in the scissors' material, i.e.the speed of sound characteristic of the metal the scissors are made of.
As for the cutting point, it stands to reason to assume that it won't travel faster than the information in the arms causing them to move and cut.

It's the same with the train cars. As you can see, relativistic physics doesn't need to get involved, as the energy transfer is constrained by the internal structure of the material in question.

I suppose what might've confused you is the uncertainity whether I was asking a purely mathematical question, or asking you to take notice of the physics involved.

[iceball3]

At any rate, no, nothing about it will move faster than (or at) the speed of light, because that just plain can't happen.

Eh. Regarding the scissors problem. Couldn't there be the possibility that there is just a shitload of tunneling occurring on the blades or something? When something tunnels through a vacuum or matter it essentially ends up on the other side of whatever it tunnel instantaneously. So I guess the best explanation of the scissors question would be that any points past the speed of light would essentially begin to "lag" through the air/vacuum. It would still be moving the speed of light, but it would be compensating by teleporting to catch up.

What in God's name are you talking about? Quantum tunneling is a bizarre, super-small-scale phenomenon. None of that needs to come into the question. The fact of the matter is that the longer the lever (in this case, a scissor arm) is, and the heavier it is, the more inertia it has and the harder and harder it is to make it move faster. It won't move at the speed of light unless you have super-magical arms capable of transmitting infinite energy to it. You don't.

Il Palazzo made a much better point than me, but I will go back to my point.
Say you have a wall. You have a small, but non-zero and non infinitely small chance to waltz right through it. The property does apply on large scales, albeit very rarely. Whether it works or not is proportionate to how much energy is involved, how large scale the tunneler is, and what is being tunneled through. If you are putting more energy to moving something than what is needed to make it go light speed, then presumably, you are putting a damn large amount of energy into it.
This of course assumes the scissors are completely rigid.

[Strife26]

No one is going to try my riddle any more?

[G-Flex]

If you are putting more energy to moving something than what is needed to make it go light speed

Nonsensical. Even an infinite amount of energy only causes something to approach the speed of light and no further.


Anyway, yeah, the point of intersection of the scissor blades could never move faster than the speed of light; looking at it again, it IS different from the guillotine problem.

[ILikePie]

Here's an easy one I heard today. A man holds up a picture and says: "I have no brothers or sisters, the man in this picture is my father's grandson." Who is the guy in picture?