From: KELSEY@SLACVM.SLAC.STANFORD.EDU (KELSEY, Michael H.)
Newsgroups: rec.arts.startrek.tech
Subject: Re: Why the "starbow"/"rubber-band" effect? Speculation
Date: 10 Apr 92 18:05:31 GMT
 <1992Apr10.135713.16014@ucunix.san.uc.edu>
Distribution: na
Organization: Stanford Linear Accelerator Center

In article <1992Apr10.135713.16014@ucunix.san.uc.edu>, balesej@ucunix.san.uc.edu
(Eric J Bales) says:
>
>In article <Y2j+kj+@engin.umich.edu> (Brad Books) writes:
>>In article <1992Apr6.153129.24015@acsu.buffalo.edu>,
>v116r8ac@ubvmsd.cc.buffalo.edu (Chris Nasipak) writes:
>>>
>>> A number of people once asked for an explanation of the "rubber-band"
>>> effect when the E-D went to warp speed.  This bothered me for a while, too,
>>> but I believe I have an explanation for it.
>
>Not really to comment on the previous message, but I thought if this
>while sitting in the lab here...
>
>If, when something goes faster than the speed of sound (while moving in
>a sound-carrying medium, of course), there is a sonic boom, then would
>there be a 'photonic boom' if something went faster than the speed of
>light?  (In a medium with light present, like space.)

[ WARNING:  This is a simplified layman's description.  Those of you with
  technical backgrounds, please accept the approximations and somewhat vague
  language that I have used.  Jargon should be avoided whenever possible :-) ]

Light doesn't have to be present.  This is simply the Cherenkov effect,
which is quite well known and used today in nuclear and particle physics
to measure particle velocity.  In a medium with a (real) index of
refraction n > 1, the speed of light *in that medium* is c/n (that's how
refraction works: the speed of light in one medium is different than in
a neighboring medium, and the waves bend if they cross the boundary at
an angle).  Now let us shoot a charged particle (say an electron, 'cause
it's easy to make them go *fast*) into this medium with a velocity
GREATER than c/n (but of course less than c).  The moving electric field
of the electron will develop something analogous to a "shock front," and
a conical electromagnetic wave will be produced, with an apex angle given
by cos($) = 1/Bn, where $ is the apex angle, B = v/c is the velocity of
the charged particle, and n is the index of refraction of the medium.

The Cherenkov spectrum peaks in the ultraviolet, but there is plenty of
visible light produced at the blue end of the spectrum.  In nuclear
reactors where the fuel cells are stored in open pools of water, the
water glows blue because of the beta-decay electrons producing Cherenkov
light as the pass through the water.  In high energy physics, one method
of distinguishing different kinds of particles is to measure momentum
with a magnetic field (particles bend, and the radius of curvature goes as
1/p), and measure velocity using Cherenkov radiation (either measuring
the apex angle directly, or using layers of material with different n,
and seeing which ones light up and which ones don't).  You can then get
the mass of the particle, and hence it's identity, from the ratio p/v.

There have been experimental searches for (charged) tachyons which have
looked for the production of Cherenkov light in air or vacuum.
Presumably, a large physical object travelling faster than c in space
would produce Cherenkov light from it's constiuent electrons and nuclei,
which could "explain" the flash/starbow effect when the Enterprise
engages its warp drive.

                                                 -- Mike Kelsey
[  My opinions are not endorsed by SLAC, Caltech, or the US government  ]
What is your _name_?    "kelsey@slacvm.slac.stanford.edu"
What is your _quest_?   "To get a Ph.D. in high-energy physics"
When will you _finish_? "I don't know.   Waaaaaaaaahhhhhhhh..."