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# Time viewing

There has got to be a catch...
 (0) [vote for, against]

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?

 — 2 fries shy of a happy meal, Oct 03 2013

Spinning lens [pocmloc, Oct 04 2013]

 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?

 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.

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?"
 — MaxwellBuchanan, Oct 03 2013

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?
 — 2 fries shy of a happy meal, Oct 03 2013

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
 — FlyingToaster, Oct 03 2013

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.
 — MechE, Oct 03 2013

 //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?//

 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?

But kudos for mentioning Hoberman spheres.
 — MaxwellBuchanan, Oct 03 2013

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.
 — 2 fries shy of a happy meal, Oct 03 2013

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.
 — pocmloc, Oct 04 2013

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.
 — spidermother, Oct 04 2013

[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.
 — spidermother, Oct 04 2013

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