Spinning wheels & Lorentz Contraction

[Stumblebum]

There are so many of you willing to answer a layman's question that I hope you don't mind a few more.

 

With my bicycle upside down(changing tire) I spin a wheel. The spokes appear to curve. I assume this is because the outer end of the spoke is travelling at a higher rate of speed than the inner portion. If I were to accelerate the rim to .999999c would the spoke curvatures be so great that the distance between the rim and the wheels hub appear to my eyes as to be close to zero? Could I asume that the apparent curvature of the spokes are now extremely exaggerated to the point where they appear to be flattening out? In other words the rim is closer to the hub.

 

Even when I spin the wheel by hand, if I was to measure the distance between the rim and hub it would be less than when the wheel is stationary? Would the spokes because of their apparent curvature appear longer or do they retain same length even when the rim appears closer to the hub?

 

These questions are harder to write than answer. I hope that wasn't too confusing.

[J.C.MacSwell]

There are so many of you willing to answer a layman's question that I hope you don't mind a few more.

 

With my bicycle upside down(changing tire) I spin a wheel. The spokes appear to curve. I assume this is because the outer end of the spoke is travelling at a higher rate of speed than the inner portion. If I were to accelerate the rim to .999999c would the spoke curvatures be so great that the distance between the rim and the wheels hub appear to my eyes as to be close to zero? Could I asume that the apparent curvature of the spokes are now extremely exaggerated to the point where they appear to be flattening out? In other words the rim is closer to the hub.

 

Even when I spin the wheel by hand' date=' if I was to measure the distance between the rim and hub it would be less than when the wheel is stationary? Would the spokes because of their apparent curvature appear longer or do they retain same length even when the rim appears closer to the hub?

 

These questions are harder to write than answer. I hope that wasn't too confusing.[/quote']

 

The faster you spin it the further it gets from the hub.

[atinymonkey]

With my bicycle upside down(changing tire) I spin a wheel. The spokes appear to curve. I assume this is because the outer end of the spoke is travelling at a higher rate of speed than the inner portion.

No. It's because the human eye is shit at separating out fast moving images. I don't understand why you would use the naked eye to work out the relative speeds.

[Stumblebum]

The faster you spin it the further it gets from the hub.

 

Wouldn't the rim's circumference shorten as lightspeed is approached? I can't see how the rim moves away from the center when there are spokes holding it on to the hub unless they stretch.

[MetaFrizzics]

Whatever effects you are seeing might have to do with an artificial light source like a Sodium street-lamp flickering at 60 cps. What were the conditions of your observation?

Have you ever tried shaking your hand in front of a TV set with other lights off?

Or watched a car-wheel go backwards on film or Television? this has to do with frame-effects, not light speeds.

[Stumblebum]

Whatever effects you are seeing might have to do with an artificial light source like a Sodium street-lamp flickering at 60 cps. What were the conditions of your observation?

Have you ever tried shaking your hand in front of a TV set with other lights off?

Or watched a car-wheel go backwards on film or Television? this has to do with frame-effects' date=' not light speeds.[/quote']

 

Actually all I want to know is what happens to the rim of a bicycle wheel when it is spun at a speed close to light. Does the rim move away or does it get closer to the hub or stay where it is? Let's assume the spokes are unbreakable. I was thinking the circumference would measure less than when stopped, the spokes would also measure shorter and the distance from hub to rim would measure significantly less. Or as it was mentioned does the rim move away. I think that could only happen if spokes and rim stretch because of the high speeds? Not sure of this.

[ydoaPs]

the circumference shrinks and the radius stays the same.

 

am i missing something here?

we have a circle: [math](x-h)^2+(y-k)^2=r^2[/math] where (h' date='k) is the center and r is the radius. we now spin the circle about an axis that is perpendicular to the plane on which the circle lies and it runs through the center of said circle. gravity contracts length (and my the equivelance principle, so does acceleration), so as the 1-sphere spins about the axis, the distance between any two points on it decreases while the radius stays the same. since [math']\pi=\frac{c}{2r}[/math], where c is circumference and r is radius, [math]\pi[/math] no longer is a constant. the circle shrinks, but the radius stays the same. what is going on? does the circle turn into a cone?

 

You have stumbled upon a fanatastic paradox of special relativity

 

As it appears in the history books' date=' this is the very same case that lead Einstein to consider non-euclidean geometries in the physical universe.[/quote']

[Stumblebum]

the circumference shrinks and the radius stays the same.

 

I like that answer, makes one think.

 

If I had 5 rims at different distances from the hub and spun the wheel the same, the outer rim will go faster than the inner rims. No matter how hard I try I can never approach the speed of the outer rim with any of the other rims.

 

I thought of this one day when I was trying to figure out some kind of an example or analogy for light speed as top speed in the universe. Then I had this crazy thought that if the universe was a gigantic spinning wheel then the speed of light may depend on your position on it and because of the vastness of space we don't notice differences, yet.

 

Science is weird, my brain hurts.

[MetaFrizzics]

This is what is known as a 'black bicycle rim'. The rim collapses, swallowing the spokes, which stretch toward the threshold of the outer rim. Then suddenly, time stops, as the air leaks out of the tire. Hawking showed that such objects are really 'gray rims', since they leak air molecules via 'broken-glass tunnelling'. Incredibly, the probability that there will be dogdoo on the outer surface approachs 1 as the cyclist approaches C.

[J.C.MacSwell]

the circumference shrinks and the radius stays the same.

 

This requires a material that has infinite tensile strength/stiffness and results in an infinite force.

[Spyman]

the circumference shrinks and the radius stays the same.[/quote']This requires a material that has infinite tensile strength/stiffness and results in an infinite force.

Around a Black Hole' date=' outside the Event Horizon there is a Photon Sphere, where light can orbit.

Mathematically speaking, the photon sphere occurs at 3/2 the Schwarzschild Radius. It's the only place where light rays can have (very) unstable orbits around the black hole.

http://www.gothosenterprises.com/black_holes/static_black_holes.html

 

So, what is the circumference of the Photon Sphere ?