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Supposedly if an object attains light-speed time stops for that object, and if it exceeds light-speed it goes backwards in time. They say that it is impossible to move an object faster than light-speed because it would take an infinite amount of energy to nudge it up to that speed and so mass approaches
infinity.
That may be true, what-do-I-know, but we 'can' accelerate something close to light-speed as in the case of solar sails in the vacuum of space.
Well, what if that object is a sphere which doesn't go anywhere and the energy imparted is rotational?
If I am standing on the Earths' equator then I am travelling roughly 1000 miles per hour or so relative to the poles, but if I'm standing in Nunavut I am only moving at 150 miles per hour or so.
Would it not be possible to cause the equator of a sphere to exceed light-speed by accelerating a smaller radius of the sphere up to less than light-speed?
If so, would imaging equipment at the equator be able to time-view and allow us to see glimpses into the past for that location.
...and if so, would it only show a view of space because the Earth itself is no longer in that location?
Spinning lens
[pocmloc, Oct 04 2013]
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It's an interesting question. More generally, can a
point on a disc attain near-light speed such that
the rim of the disc exceeds light speed? |
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Alas the answer is no, from which we can work
backwards to the reason. For example, as the rim
of the disc approaches light speed, its mass will
increase perentatically, thereby preventing you
from spinning the nearer point (or anything else)
even faster. |
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The system is basically a lever. So you're asking
"can I move a point on a lever, near to the
fulcrum, so fast that the end of the lever exceeds
light speed?" You might equally ask the question
"can I move the end of the lever faster than light,
so that the point near the fulcrum moves at half
the speed of light?" |
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Thanks for the reply.
So, it would be possible to spin a sphere at close to light-speed though right?
Say it was floating in space and getting up to speed like a Crookes radiometer off of photons from the sun. Once up to speed it would take very little energy to maintain it.
If it was designed like an Hoberman Sphere and forced to shrink using external magnetic fields, could we then cause the equator to exceed light-speed? Or would it take an infinite magnetic field to shrink it? |
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Pointless exercise ? Engineers already know the breaking strength of materials. It takes the gravitational pull from a black hole to bend things moving at light speed (ie: light). Time dilation doesn't work linearly: to get a 2x time dilation you have to be moving at 0.85c |
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No, even shrinking the sphere wouldn't increase the
speed to the speed of light. Remember, pulling
your arms in speeds you up because angular
momentum is conserved, but since as the outer
shell speeds up, it's mass increases, momentum can
be conserved without the same level of velocity
increase. |
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//If it was designed like an Hoberman Sphere and forced to shrink
using external magnetic fields, could we then cause the equator to
exceed light-speed?// |
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What [MechE] said. Think about reversibility - could you spin a small
sphere up so that its equator exceeded C, and then expand it to slow
it down? |
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But kudos for mentioning Hoberman spheres. |
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hmmm, I'm never going to get to see Atlantis at this rate... let alone be able to go back and kill my guidance counselors. |
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If it were //floating in space// then it would have no chance of //getting up to speed like a Crookes radiometer off of photons from the sun// because said device doesn't run on light pressure, it runs on low-pressure gas. |
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It is, indeed, considered possible that rapidly spinning, highly massive objects act as time machines - with some catches. The surface does not need to exceed the speed of light. There's a whole chapter about them in 'Parallel Universes' by Fred Wolf. |
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[pocmloc] True, but a device like (i.e. resembling) a Crookes radiometer, but powered by light pressure, might work in space. Apparently they don't work on Earth because you can't get the friction low enough. |
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