if a pole of incredible length was constructed and fixed to a fast spinning asteroid, would it be theoretically possible that given the length of the pole was long enough, would the end of the pole be able to travel at the speed of light...since there is a vacuum in space there would be no drag to slow it.

i know its crazy but i was watching a windfarm out at sea and watching the blades spinning, i knew that the end of the blade would be spinning at around 200-300mph...thats where i got the idea from....

your thoughts on this are most welcome...

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Nice one. I had the same thought this morning about differant spots on a record moving at differant speeds even though it has the same amount of RPM.

Anyway, if you want to boggle your brain, how about this.

Look up at the stars tonight.

Spin around on your heels while still looking at the stars.

Try to figure out at what speed those stars were moving at while you spin.
Relatively - its MUCH faster than the speed of light.

Unfortunately not Mrhamblee, good thinking though!

Let's assume your pole was one light year long and made of iron. Basically what happens when you displace the pole is that you start a compression wave. The force of pushing on it forces the atoms in the pole closer together near the end of the pole. This will increase the force on neighboring atoms due to the repulsion caused by forcing them out of equilibrium. Thus the atoms you displaced cause atoms next to them to displace, and so on and so on. Essentially, you have a region of compressed metal which will move down the pole, and will do so at less than the speed of light. It takes tiny fractions of a second for this to happen on smaller lengths so we observe it as being instantaneous (keep in mind light travels along a 1 foot pole in roughly .000000000008 seconds).

A "pole of incredible length" is not a rigid body. Even though there is no drag, there is the question of accelerating such a pole of possibly incredible mass to sufficient enough rpm. The force applied as torque during the acceleration is transmitted down the pole at quite possibly speed of sound as a stress wave. EM interactions are keeping the solid together. If you were to reach sufficient enough speed, each part of of this pole would want to continue in a tangenial path and eventually (and possibly at low speed) the EM interactions keeping your pole solid would succumb to these forces (through weak spots in material). I've had a (faulty ) CD shatter under high spin - it's not pretty for the player or the CD.

Yeah, each part of the record has an rpm that is the same that's why different r (distance from center) distanced parts have to move at different speeds (to make the same rpm)

Haven't you thought about the top loading washing machine yet? That's a good one too, it only takes a relatively small motor to spin the universe around at high speeds. All very relative, like the laser pointed at the moon - we can make the pointer move awfully fast on the moon

Cheers

I guess that would depend on if accelerations are absolute or not. If they are, then we can say you were the one really moving easily enough. If they're not, it becomes an interesting question.

This is easy to answer, they move at the same rate they did when you were stood still.
any argument against this is simply ignorance of elementary physics.

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guess I'm Super slow today... I don't get it.

why would it move Down the pole? (I'm assuming Down means inward toward the "asteroid" and Up would be outward away from)
Wouldn't the centriforce go Up the pole if anything?

Assuming the pole is made of something that won't shatter, no obstructions, and the speed of rotation and length of pole are variables that can be modified... I'd think it'd be possible... but then like I said I'm slow...

"Down" as they're using it means away from the source of the deformation. So away from the asteroid.

But clearly something has changed or else you wouldn't see stars spinning around you head. The standard way to approach it is to you say you're rotating in an absolute way, the fluid inside the canals in your ear is experiencing ficticious forces resulting in you getting dizzy, the stars are fixed. But as Mr. Spock would say, there are always alternatives.

A spinning earth in a Newtonian absolute isn't dynamically equivalent to a stationary earth with the universe spinning around it. But if we forget about the idea of absolute space that Newtonian mechanics is based on we've got some options.

The answer is really very simple. Although there is no "drag" or source of friction on the pole, and the pole is weightless, still the pole has mass. Accelerating it takes force. The far end of the pole does not get a free ride just because the near end is attached to a rotating body. All the problems that always accrue to accelerating a mass in space apply to this situation.

Consider your windmills. Let's say there's no wind, and you'd like to spin the axle at, say, 10 RPM by grabbing the hub and turning it. That's pretty hard. Now take the blades off and just spin the hub. That's a lot easier, because you are not accelerating the mass of of those blades. Even if you took the same mass and brought it in closer to the hub, you'd have a way easier time achieving 10 RPM, because, as you noticed, 10 RPM way out at the end of the blade is way faster than it is close to the hub. And more acceleration requires more force. TANSTAAFL.

It's the old spinning figure skater problem.

I have actually thought of this myself. In theory it would work, but you would need a ridiculously long pole and an incredible amount of force to move it (if you weren't using an asteroid...).

This really isn't the same thing at all. The stars aren't moving just because you are.... its like if I were to run around a table, the table is not neccessarily moving... the stars will be moving at the same speed no matter if you are moving or not.

No, actually not.

Each of your eyes is just traveling in a tiny orbit in a plane at a given angle to the light path from each star. This does not much change their velocity relative to you. It does not change their velocity at all with respect to each other.

What is the point of the question from the start?


Faster than light is possible. But could never be done by conventional means.

DUH! Keep on drifting.....
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