🚀 go-pugleaf

In article <aqJ4wB1w165w@grizila.pillar.com>, grizbud@grizila.pillar.com  
(Jim Gorges) writes:
> 
> Less than one week ago I finished trying to read "Cosmic Wormholes: the
> search for interstellar shortcuts" by Paul Halpern.
> 
> Now, I'm basically a bonehead when it comes to understanding things
> theoretically and technically advanced and "indistinguishable from
> magic."  So, grad students and postdocs, what's the judgement on
> Halpern's explanations and physics?  Is the book worth the attention of
> someone desiring to be introduced to the concepts and theories, or
> should it be used to keep the computer desk from wobbling?  Inquiring
> minds want to know.....
> 
> --
> Jim Gorges <grizbud@grizila.pillar.com>         | Life is a series of
> GENIE: J.GORGES                                 | adjustments.
> Fidonet: jim.gorges@p15.f34.n147.z1.fidonet.org | (Michael J. Carney - 1985)

Well, I can't speak to the validity of Halpern's claims, but Kip Thorne has 
something to say about wormholes.  Carl Sagan's book "Contact" gives the ref-
erence (I don't have it handy); Thorne's paper is written as an exercise for
students in GR to calculate the stable "wormhole solutions" to the GR equations.

Bottom line: such solutions are possible that would allow travel over large 
distances without suffering huge time discontinuities or nasty tidal effects, 
but the materials and techniques needed are not known in our present understand-
ing of physics.  That is, GR allows it, but QED may or may not.  Also, having
a solution is one thing--Thorne says himself that he can't imagine how one would
obtain a wormhole of macroscopic size.  The solution just allows you to maintain
it once it's there.  He speculates that perhaps one could "expand" a spacetime
defect from the scale at which spacetime is "foamy" (on the scale of a Planck 
length or less), but how one would do that is anyone's (wild!) guess.

As for naturally occuring wormholes, the physics of stellar collapse to a black
hole allow for such solutions, but with distinct disadvantages:

	The collapse would have to be an ideal one (perfectly rotationally
	symmetric, and rotating at the fastest speed possible--with the surface
	rotation velocity approaching c).

	The "window" would last an infinitesimal length of time, and be 
	infinitely narrow.  A "caustic" of sorts (read: an asymptote in the
	solutions).

	The tidal effects would wreck your whole day.

Bottom line here is that a naturally occurring wormhole would be unusable.

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Chris Anderson			Science Operations Specialist
ANDERSON@DEVVAX.STSCI.EDU	Science Planning & Scheduling
				Computer Sciences Corporation
				Space Telescope Science Institute
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