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RE: starship-design: Wild thoughts
L. Clayton Parker writes:
> Steve,
>
> This last response of yours reminds me of something that has been nagging at
> me for a few weeks now.
>
> > -----Original Message-----
> > One amusing feature of relativistic kinematics is that while one
> > photon is massless, two or more photons treated together as a
> > system usually aren't (unless they are all traveling in exactly
> > the same direction). So, for example, if you could create a
> > fiber-optic ring and pump a large amount of laser light into it,
> > you would make it heavier; ...[clip]
>
> It seems to me that there isn't any real difference between a supermassive
> ring rotating at the speed of light and a great deal of energy rotating at
> the speed of light. Although it would probably require more energy than we
> can possibly generate to actually produce the sorts of space warps predicted
> by theory, I would think that we should be able measure some effect inside
> the ring of modern accelerators. Has anybody ever checked for some
> measurable phenomenon such as frame dragging or such?
There is a difference; a supermassive ring can't rotate at the
speed of light. Nothing but photons, gravity waves, and a few
massless particles can go at the speed of light.
I actually have no idea whether a huge bunch of photons
circulating in a ring would produce general relativistic frame
dragging.
Modern particle accelerators only work on very tiny amounts of
mass, so I doubt any such effects would be measurable with them.
My hypothetical fiber-optic ring would require something like
9e10 J of photons (that's a megawatt of power pumped into it for
a little over a day) circulating in it to increase in mass by a
microgram. Any real material would vaporize long before you
could get that much energy into it.