Friction isn’t the problem; simply having mass would make the beads hard to move, and thus the scissors harder to close than without the bead. (Grease up an ultra-heavy bead and put it between some ordinary scissors; it’s going to be hard to shoot it out, just as it would be hard to accelerate it in any more conventional way. When you close the scissors, you’re basically pushing the bead in a roundabout way, and that pushing will take energy. You don’t get something for nothing. You need to put in some more energy to quickly close the scissors than you would without the bead. Same principle here.). In particular, no amount of energy will be sufficient to close the scissors fast enough to get the bead up to the speed of light.
Yes. If you were floating (relatively stationary) near the tip end of the scissors the intersection of the closing blades would pass you at or beyond the speed of light.
Are you saying that both blades are moving a .6C, therefore relative to each other they are moving at 1.2C? If so, that’s not a problem. The speed of light is a limit on the speed relative to any reference frame. In other words, it’s not a problem that those two objects are moving faster than C relative to each other. If your friend was sitting on one of the blades he would say that you are coming at him at .6 C, and that the other blade would be moving at him at some fraction of C.
Sorry, I am just not understanding your argument. I have placed no limit on the amount of force that can be used.
Again, this seems to be saying it can’t happen without saying why. Unless you are suggesting the lack of force is what is preventing the mass (bead) from gaining C.
Dfth, the key feature of special relativity is that as something approaches the speed of light, it’s mass approaches infinity, and therefore the amount of force required to accelerate it approaches infinity. This is what leads to the speed of light being the speed limit.
If you don’t understand why this is so you need to read a basic explanation of special relativity. When you fully understand that, you’ll understand the answer to your question. And when you do fully understand it, would mind explaining it to me to? 
I don’t know how fast the blades would have to be moving to cause the closing intersection (not a actual object with mass) to move FTL. I would guess that it’s much less than you suggest.
From Indistinguishable’s link:
And:
I feel I have a basic understanding. Are you saying, then, that the bead would retain it’s basic current shape yet it’s mass would increase so dramatically as to prevent its being moved?
Do keep in mind that the first thing you quoted was an example of confusion from the questioner; in that example, the blades do not close all the way, so to speak, as soon as the handles close; the blades flex at first and take a long time to straighten out.
It is possible to make the contact point move faster than the speed of light, as the second thing you quoted notes, but the particular analysis of “As soon as I close the handles, the blades are done closing too” is naive and incorrect.
Yeah, basically. (What’s shape got to do with it?). As objects get faster, it gets harder and harder to make them even faster. You get diminishing returns on any particular amount of force. It all comes together in such a way as that no matter how much energy you put in, you can never get the object all the way up the speed of light, although you can, with ever increasing amounts of energy, get up to any speed below that.
I am not trying to be in the least bit insulting when I say that this comment tends to show there are gaps in your basic understanding. It’s a field where all but an elite (that certainly doesn’t include me) struggle. However, as I’ve said, one of the basics is that as an object approaches the speed of light, its mass increases towards the infinite, and consequently the amount of force required to accelerate it does likewise.
Personally, I think an easier example to visualize is a pipe filled with golf balls. Push a golf ball in one end and one will instantly pop out the other end (this analogy also helps explain how electricity works - the electrons “pushed” into one end don’t zip down the cable at the speed of light; they simply push their neighbors, who push their neighbors, etc.)
Now, picture a pipe a million miles long and jam a golf ball into it. If the effects of the small-scale version of the experiment hold, a golf ball should fall out the other end instantly, even though light itself would take almost six seconds to cover this distance. Congratulations, you’ve achieved FTL communication.
Trouble is, the effects don’t hold and applying enough force to roll a million miles of golf balls would crush the first one, breaking the link and ruining the experiment.
But in discussing your example, you don’t mention any essentially relativistic reasoning. Thing is, you could theoretically apply enough force to roll a million miles of sturdy gedankenexperiment golf balls, that’s not the problem; it’s just that the wave would propagate at a finite speed down the whole pipe (a speed less than the speed of light), rather than instantaneously.
In fact, that’s what happens with normal, non-huge pipes too; it’s just that the effect of finite propagation speed is so marginal that it’s negligibly different from simultaneity at those low numbers.
Heck, even if you could get instantaneous transmission of a ball-signal down a pipe only two feet long, that’d still be a signal travelling faster than light. It’s not like you need to inflate the experiment’s size to see the problems.
It’s not only the magnitude of force required - it’s that there isn’t any material that is absolutely rigid and uncompressible.
-And golf balls are an excellent example - they seem rock hard, but are in fact remarkably squashy - I was hoping to find some slow motion footage of a golf ball being struck - IIRC, they deform like a water balloon before they get going.
Please don’t take this attitude. There’s nothing in special relativity that’s inaccessible to anyone with high-school level algebra. General relativity takes rather a bit more math, but special is (or should be) easy.
While I’m here, the interpretation of “mass increases as you near the speed of light” isn’t considered very useful by most physicists. It’s just a dodge to make the formula for momentum look the same as what we’re familiar with. But it makes more sense to change the formula for momentum, or better yet, to change what one means by speed. In relativity, the momentum of an object of rest mass m travelling at speed v is given by p = mgammav, where gamma depends on v and is 1 at small speeds, but approaches infinity as v approaches the speed of light. Now, you can interpret that formula as "relativistic mass is mgamma", so p = m[sub]R[/sub]v. But it’s more natural to say that there’s some sort of “relativistic speed” (actually called “proper speed”, or u), with u = gammav, and p = mu. Working with proper speed instead of the familiar sort makes a lot of things in relativity easier, since proper speed can get arbitrarily large, and it adds according to the familiar rules. Then, you just have to convert proper speed back to regular speed at the end of the problem, after you’ve done all of the calculations.
Isn’t this similar to have a beam of metal 1 light year long…if I push on one end, the other should move so, therefore, I can send a signal faster than light?
I can’t remember why the above wouldn’t work, but may have relevance to the OP.
All the frictionless beads are currently being used as ball bearings in the frictionless treadmill.
It doesn’t work because the beam isn’t infinitely stiff. For that matter, you can’t even send information faster than the speed of sound in such a beam (or shock wave, but let’s not pick nits).
Would this not apply to the scissors as well then?
This one is easy.
You think metal is rigid? It sure is. But it’s not infinitely rigid. Even really strong beams will bend or break if you apply enough force.
Think about it this way. What forces hold a solid metal beam together? The forces that hold the iron atoms together in that metal beam don’t travel faster than light. So if if that metal rod were very very very rigid, when you push on one end the other end doesn’t instantaneously move. Rather you push on some iron atoms at your end, and those iron atoms push on some other iron atoms and those iron atoms push on some other iron atoms and so on and so on and so on, until you reach the end of the “solid” metal beam. And the forces that allow those iron atoms to push against each other don’t propagate at the speed of light, much less faster than light.
And of course this is completely discounting the fact that a really long metal beam would just bend or break, and that the mass of a metal beam a mere thousand miles long would be gigantic, and the force required to move it would be much larger than the inter-atomic forces holding that beam together.
But even with an unobtanium beam of arbitrary strength you’re still limited to below light speed.
Would this apply to the scissors then?