Not quite magic physics [was Re: Quantum Computers]

Robert J. Bradbury (
Sun, 22 Aug 1999 06:33:48 -0700 (PDT)

On Sun, 22 Aug 1999, John Clark wrote:
> Tipler found a solution in General Relativity that shows that an
> infinitely long, extremely dense cylinder made of Neutronium (the stuff of
> Neutron Stars)

Aha, I'll invoke the "Use of Magic Physics" warning when people use terms like "infinitely long", "infinitely dense", "negative mass", etc.!!! Only half :-).

> 2) The very rapid rotation would cause the cylinder to fly apart. This is
> much more than just an Engineering difficulty, no known force in Physics
> would be strong enough to hold the cylinder together, not even the strong
> nuclear force.

John, interestingly enough there is a concept called "momentum transfer" that has shown up in some astroengineering articles I've reviewed for the Dyson shell work. It is used in the recently mentioned "The Saga of the Cuckoo" as well. If your Neutronium "cylinder" were surrounded by a large number of particle accelerators whose beam emissions were perpendicular to the axis of rotation, and the force of the beams striking the outside wall of the cylinder were high enough, it would be impossible for the cylinder to "fly apart". I suppose if you angled the beams slightly, they could impart some of the force required to rotate the cylinder at high velocity.

Now, the thought question for you (since you know more physics than I), is what happens when a beam of protons (or I suppose neutrons if you want really high density beams) hits a neutronium cylinder?

Can neutrons interact in any way so as to produce photons? [It seems kind of strange since there are no electrons involved.]

Do some strange interactions occur so that neutrinos/antineutrinos get produced? [Since presumably those are the only things that can radiate "out" through the incoming mass streams.]

This is related to a question I've wondered about the maximum density of light. Say I have a number of really large lasers (powered by stars) arranged in a large sphere, perhaps like a globular cluster. Say I beam all of those lasers at a single point in space. What happens? Do I generate matter? Do the beams simply pass through each other?

A related question would appear to be -- since a mass density above a certain level will generate a black hole, will an energy density equivalent to that mass density (by e=mc^2) do the same thing?

If so, wouldn't this be a way of generating small black holes that science fiction writers and some physicists use for various purposes?

And finally, if laser light to black hole conversion is feasible, does anyone have any idea how much we would have to juice the laser at Lawrence Livermore to create black holes (of say neutron mass or larger).

Thought questions for the day...


And as an interesting postscript...

One by one the stars blinked and went out as the SIs hurled black holes across the voids of space seeking to destroy each others fuel sources. The fuel that powered the future modelling computers was essential for the prediction of paths that would avoid the ever increasing density of black holes that slowly drained the intelligence from the the universe. Far far away, in a quiet corner, the Anders SI and the Robert SI were watching..., waiting..., knowing that one day those black holes would have to evaporate, providing enough energy to live again. They slept while the universe fell slowly into darkness.