Re: Hey Steve! Post-Change Death Ray?

: "Default User" <defaultuserbr@xxxxxxxxx>
: You can certainly make a telescope grade mirror with fairly
: low tech by hand-grinding glass plates. You need glass production and
: decent abrasives. There are various chemical techniques for silvering.
: However, you won't be burning any ships that way, and most of that was
: probably beyond the ancient Greeks.

IIRC, the mythbusters rehash of this issue, using a design for
setup and aiming from some folks at MIT, used a couple hundred
one-or-two-foot-square polished bronze plates. They could set dry
wood on fire at 150 feet, just barely, and an actual, wet-ish boat
afire at 70 feet, and concluded that they'd need something like four
times the surface area to duplicate the alleged greek death-ray feat.
And even then, the target has to stay put long enough to get set afire,
and had better not be painted white, and so on and on. And you'd better
not have any clouds drift across your battlefield at an inopportune moment.

Also, as mentioned elsethread, one of the gadgets used
cut-up-into-inch-square mirror fragments, applied to a parabolic surface.
So, even post-dies-the-fire, if you could just round up enough pre-change
mirrors, you could score them, cut them up, and glue them on a barabolic
framework (oh, say, a pre-change satellite antenna or something) and
get a fairly efficient solar furnace. You wouldn't need to go mine and
alloy and polish to get bronze mirrors. And I think you get something
like a two-to-one or a bit better advantage using silvered glass instead
of bronze.

Bottom line: you could probably do it with ancient greek tech
(and hence, with post-dies-the-fire tech), in the sense that you could
light fires at a distance, but the logistics of aiming, and the need to
keep it on-target long enough to ignite (which was many seconds) mean
it almost certainly wouldn't be a practical weapon. Though you could
probably give your attackers some wicked eyedazzle, which might help.

FWIW, this episode of mythbusters is being rebroadcast a couple of times
over the coming week or two, so it should be easy enough to catch, if
there's interest.

As an aside, since a lot of the issue was aiming and surface area,
I was led to ponder about Niven sunflowers. They might actually work...
presuming they had some way to sense the target with any accuracy.

Oh, and as I post a stray memory hits me: there was a building, I think
in the Chicago area, a museum of some sort, which the architect designed
with lots of neato flowing curves... and a polished near-mirror-like
finish. I think it was polished stainless steel, or something like that.
And caused excess accidentts due to eyedazzle on nearby streets, and
even caused temperature excursions well over 100 degrees F (though not
quite boiling) in some spots in surrounding buildings, depending on time
of day and cloud cover. They had to go back and use abrasives at great
expense to take enough of the shine off the building to make it safe
(which, luckily, didn't really affect the general appearance and style the
architect was going for; it was had shiny "shiny curvy metallic" thing
going, just not quite so ... focussed). Hm. I don't remmeber where I
saw that. Was it on the first mythbusters death ray episode last year?
Or something else? Hm...


Wayne Throop throopw@xxxxxxxxx http://sheol.org/throopw
.

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