# Theory about speed of light and how to be faster

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1. Apr 9, 2015

### fr0zencipe

Hey there, I just got a theory ive been thinking about since a while and want to share it.
So here it comes: imagine, we build a huge centrifuge in space, i mean really huge. It is made of super stable material which will not break in the following process. So we speed up that centrifuge until the outer parts of it reach almost the speed of light. (You all know that the outer part of something that spins is always faster thatn an inner one). What would happen if we enlarge the radius of the spinning object? What would happen, if it reaches the speed of light or faster? And would it be possible if we had enough energy for it and it wont just break because of the centrifuge force? Theoretically it might be possible if we had that material and the energy. or not?

2. Apr 9, 2015

### PWiz

No, you can never accelerate an object with non-zero invariant mass to the speed of light or beyond. For the same force, the increase in speed ( instantaneous velocity) decreases over time, and asymptotically approached 0 as you to tend to the speed of light. Only objects with 0 rest mass travel at the speed of light (in fact, they always travel at the speed of light in a vacuum). Theoretically speaking, you would need infinite energy to accelerate the outer parts of your machine to the speed of light, and we all know that this is a nonsensical statement and is clearly not possible practically.

Last edited: Apr 9, 2015
3. Apr 9, 2015

### rootone

When the rim starts to approach relativistic speed, you would find that the faster you try to spin your ring, (or the more you increase the radius), the more energy you would need to maintain the spin, until the energy required tends toward infinity at a speed somewhat less than c.

Last edited: Apr 9, 2015
4. Apr 9, 2015

### ZapperZ

Staff Emeritus
The other fallacy here in this scenario is that you are forgetting (ignorant?) that the material that makes up your centrifuge is held up together predominantly by electromagnetic forces. This means that the push-pull on every single particle that makes up that material is limited by c. You cannot push and pull any element in that material faster than that. So in principle, the material will fall apart as you approach c.

Zz.

5. Apr 9, 2015

### Vatsal Sanjay

Even theoretically it is not possible. Even if you take care of all the problems (which trust me are many), there are three explanations I can think of for this thing to fail.
1. When you talk about velocity, you need to specify the reference frame. So first of all, in whose reference will that be going at speed greater than the speed of light? Now whatever that frame be, time will slow down in that frame and so the speed observed in that frame will slow down. However even if you can "hypothetically" find a frame in which this speed, you think is more than the speed of light, point 2 i what is going to happen.
2. The very force of interaction keeping the structure intact; the disturbances in it or may be you can say the force carrying particles; themselves cannot travel at speed more than that of light. So as your "expected speed" tends to the speed of light, your structure will blow away.
3. One last thing, the maximum stress to mass ratio of any object that might theoretically exist in universe is $c^2$ .The best ratio we have achieved is of carbon nano tubes and that is not even closer to the value I just mentioned. I think this is what others are trying to say, You need zero mass or infinite energy to achieve this thing. So it is as a matter of fact impossible according to the existing theories to do what you want do (until you prove otherwise by building one).

6. Apr 10, 2015

### harrylin

Hi welcome to Physicsforums.

Others have clearly replied already, but your question reminded me of the superluminal scissors paradox, which you may like as well.