I was pondering over the thought that infinate energy would be needed to accelerate an object with mass to the speed of light and thought of this mental exercise below which fascinated me.

Supposed you have sphere, say the size of the sun, with two long arms, which are - lets say 1/2 a light year long. The spherical device is able to spin @ half the speed of light before energy requirements become too much to spin any faster.

You attached to the end of one of the arms a ship/probe

you spin the sphere to half of the speed of light.

How fast would the probe be travelling? would it reach/even exceed the speed of light?

Assumptions: Ultra strong, rigid material for the arms which would not bend (Impossible I know). The sphere has enough energy to spin to half speed of light, carrying the arms with it (Impossible I know).

What do you think would happen?

I think that space would twist in this case. There are two satilites in orbit now to test this theory since it's unconfirmed.

so, this sun is half the diameter of the arms? seems unnecesary. it's just a question of rotating any object (bar, sphere, sun, a chevy) such that the outermost point reaches C. what i immediately thought of was a motor and flywheel travelling through space near the speed of light. plausible. then you spin up the flywheel, and try to break the speed of light with the resultant velocity vector of the flywheel's edge, which would be following a helical path.

unfortunately, C for an object whose deBroglie wavelength (lambda = h/p) is too large will never be reached w/o driving the mass of the object to infinity - all due to Einstein's SR. It won't matter whether you're in space or in Iowa.

Ck out Ronald Mallett's paper on rotational hv, however. His idea does apparently not conflict theoretically.

http://www.csmonitor.com/2002/0516/p12s02-stss.html

Hi Insyght,


You said that you are spinning it at only 1/2 the speed of light. Well thats all you are going to get. It is your assumption. According to the Special Theory of Relativity and ignoring other GR effects, you would have some apparent length contraction in the direction of motion and none in a direction perpendicular to the direction of motion. The circumference of the "system" will shrink slightly but the radius will not. You will "invalidate" C = 2R where R remains constant but C will be shrinking the faster it goes.

I suppose you realize you are making an interesting sandwich spread out of the occupants of the probe.

Now assume the arms are made from something "impossible" that will not break and you have the energy to "go as fast as you like". It is going to curve spacetime but ignore that for the moment. The circumference will shrink continuously but not the radius as seen from the plane of rotation internally. What you see will depend on your vantage point and where you are viewing from. The tips (probe) cannot move at the speed of light but the circumference can apparently shrink to near zero. Between the center of the system and the tips the "spokes" will be "wound up" at or near the rim (probe). Actually the probe would be apparently "rotated" almost 90 degrees from the direction of progress into a direction perpendicular to all normal orthogonal directions (length contraction seen as spatial rotation). This is in the literature. Seen from the inside it will be smeared into a continuous band (reflecting the almost zero diameter of the external circle of rotation). This will mostly occur within a few centimeters of the rim and the spokes will otherwise appear unaffected.

The (probe) rim will be almost "suspended" in time due to the Clock Paradox. It will have more frequency character than any temporal reference (1/T instead of T character) in that state with de Broglie phenomena predominating. Its dimensions will not be measurable due to optical rotation (length contraction) It will not be locatable via position and momentum simultaneously with any normal observation. The folding of spacetime will occur but it will be far beyond the normal range of "linear algebra" that tensors are based on that maths will not be able to be correctly applied there without some radical revision. Externally... I "imagine" a kind of "dumbbell" effect where the middle waist will appear to be shrunk to nearly zero circumference with an "optical" halo due to the extreme curvature of the surrounding spacetime forming two "spheres" top and bottom distorting what is seen there. An effect not dissimilar from Einstein's Rings.

Interestingly the "lorentzian rotation" seen on the outside will always be away from the direction of motion and the observer... the same as seen from the inside. You could say it is "curled" into higher spaces!!

Cheers

Wow! That is amazing. I'd never thought... no; the only "thought" I'd had in this topic was to wonder once, many years ago, if it would someday be possible to somehow increase the spin on a single electron dramatically, and get _that_ torqued up to lightspeed -- what would happen? I couldn't imagine. Other than to wonder if the experiment wouldn't somehow "tear" a small hole in spacetime -- a wormhole of some kind, perhaps. Who knows? I don't. Would such an experiment even be interesting? How would it be accomplished?

Hi moron and Insyght,


The "probe" would not be possible to build (so to many it is not "interesting") since any mechanical material structure could not sustain such forces. The radius of the system would shrink to fit the structure and visa versa. If the arms were twice the length it would approach the speed of light much sooner in angular velocity (at lower rotation rate) and length contraction (rotation) would occur there sooner at a greater radius. "Interesting" experiments are contrived to support existing theory not bring it down, this is definitely not an "interesting" place to go since direct measurement will not be possible.

All existing experiment rely on direct measurement. There is another way to proceed but it is harder. For all that it matters it may as well be a rent in spacetime since at that point it will then be no longer possible to do measurements anyway. You are dealing with "Schrodinger's Cat" in a box... not only is it "dead" or is it "alive" but is it licking it paws or watching TV... etc? Quantum Theory does not deal with unobserved phenomena and is a recognized difficulty called the Measurement Problem. All the interesting questions about "what happens next" are taboo to Quantum Theory and have no answers. Do your measurement and you have destroyed the quantum phenomenon. Yet he whole Universe is largely an "unobserved Phenomenon", in our inflated ego we have maintained that nothing occurs without man's personal observation to "collapse" the state of the superimposed systems to one. . A bit much to expect from even ye "gods in the making"! Yet this is the current theory.

The radius of the wheel would remain more or less unchanged again at the larger radius and the problems will only occur close to that radius where once again things would appear to being "wound up". The reason for this apparent compression is the optical effects of approaching the speed of light is highly skewed toward to the last couple of percent of approaching the speed of light and in this system the linear velocity is increasing rapidly for small changes in radius. For the radius inside that last critical percent spacetime will appear relatively normal all the way to the center. Internally increasing the rate of rotation would simply progress the "horizon" down along the arms compressing the tips on to a surface along with the arms. This would follow the velocity of the specific point on the arms that was now approaching the speed of light. At no point would any part of the structure actually reach the speed of light, otherwise it would be a violation of the Special Theory. Stuff that was formerly beyond that point would now appear compressed onto the new "approaching" 2D surface, an optical effect only. It would not be "intelligible" or able to be understood by measurement or observation. It is debatable if you would see anything at all... this phenomena would probably be as invisible as normal quantum events since light will barely be able to progress to or from that region - as I said before it is undergoing "extreme" clock paradox phenomena and for photons to "work" there they need a frequency and this is something they will not have - no time and hence no frequency. I think it will be interaction-less. Events will have "ceased" on this "event horizon".

All these individual effects are able to be calculated "roughly" using Special and General Relativity and by application of be Broglie's Principle and Heisenberg's Uncertainty relationships. Will this operation have quantized spacetime? All attempts to show that it has... have resulted in failure. Quantum Gravity sucks. The attempt goes on to find this granularity, stable states that might be measured. Think about the physical situation and think again.... and again.

The interesting fact is this "probe" would be a physical object that probably does indeed have a position and momentum but is now acting beyond the predictions of Quantum Theory in a space that will not map into a flatspace (3D + T) that Quantum Theory needs for that interpretation since the theory of the Quantum does not have extra dimensions beyond 4. Naturally internally you would begin to see the effects of this General Relativistic Curvature as well. Everything 'falls" apart in this process and only "New Physics" would allow this to be interpreted. I suggest that Special and General Theory alone are capable of handling this process since it already deals with curved spaces and the Quantum Theory does not. Ditch it!

Anybody can comment... with Insyght's permission of course. It is always a good question and it is not engraved in stone. To me it is one of the more important thought experiments in Physics.

Cheers