On Wed, Jun 24, 2015 at 11:30:34PM -0700, xxxxxx@shadowgard.com wrote:
> hits you or it is a *very* near miss (most plausible lasers have a
> very narrow "fringe" of light around the damaging part.

Most plausible weapon lasers have a *huge* fringe of light around the
damaging part.

> Unless there's a lot of dust, smoke or fog, you *can't* see the
> beam.

You don't need to see the beam, just where it's coming from.
Diffracted power density drops off with the cube of distance from the
main axis, but the peak power intensity for Traveller-like weapons is
*incredibly* intense.  Reduction by a factor of a billion would still
leave it bright enough to damage an unprotected eye, and a factor of
10^20 could still be visible in binoculars.  Starship sensor arrays
should be able to pick up the flash from a miss by up to hundreds of
kilometres.

That's even without considering electromagnetic equivalents of "muzzle
flash" -- side effects of creation of the beam.

> Note 2: in atmosphere, weapons grade lasers (SF level ones, not the
> measly few kilowatt ones we currently have) will level *very* visible
> ionization trails in the air. This both cuts down on their range and
> effectiveness, but also makes them stand out like a neon sign. One
> that says "please shoot me"

Yes, and starship beam weapons would blast out a column of superheated
air like unnaturally straight lightning.

- Tim