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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

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.