Newsgroups: sci.astro,sci.space.history,alt.astronomy
From: henry@spsystems.net (Henry Spencer)
Subject: Re: 3000 Year Old Telescope?
Date: Fri, 2 Jul 1999 00:24:55 GMT

In article <7lgj0d$9tt$1@plutonium.btinternet.com>,
Edward Lyons <Edward.Lyons@btinternet.com> wrote:
>Does anyone have any info on the Sun-focussing mirror as a weapon?

Archimedes was said to have done this, when the Romans besieged his native
Syracuse.  (He apparently put a good deal of ingenuity into a wide variety
of anti-ship weaponry at the time, to the point where the Roman ships
backed off quickly any time a new object appeared atop the city walls.)

The story was that with a large number of men holding slightly-concave
shields at the right angle, he could focus enough sunlight onto a ship to
ignite things.  This was widely disbelieved until somebody actually tried
the experiment a few years ago, and discovered that it worked.
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.astro,sci.space.history
From: henry@spsystems.net (Henry Spencer)
Subject: Re: 3000 Year Old Telescope?
Date: Sat, 3 Jul 1999 23:25:49 GMT

In article <377E50DD.7515@together.gov>,
John Beaderstadt  <beady@together.gov> wrote:
>...If this really
>happened, and leaving the physics of it aside, then why did it happen
>only the once? Why didn't other nations, *especially* the Romans, who
>were otherwise natural-born engineers, adopt or improve it the way they
>did other foreign innovations?

Probably because some aspect of how it was done wasn't public knowledge,
and the Romans never learned it.  Such losses of technology happened
routinely in those days, when literacy was scarce and patents nonexistent,
and useful knowledge was often kept secret to prevent ripoffs.  (The most
spectacular case of this is the Antikythera mechanism, whose design and
workmanship are on a par with good 18th-century astronomical clocks, but
which was built about 80 BC.  Nothing is known about who built it, and no
predecessor or successors are known.)  In the case of military secrets,
it's not hard to figure out why the knowledge might have been deliberately
destroyed, since the Romans did eventually take Syracuse.

>Did Archimedes have some kind of secret
>technique for grinding and polishing special mirrors, the knowledge of
>which died with him at the end of the siege?

Seems unlikely.  More likely is that coordinating the pointing of the
mirrors took special procedures, which did not survive the city's fall.

>...Where are the shields,
>themselves? Rather than take them as booty to use against the
>Carthaginians (this *was* in the middle of the 2nd Punic War, remember),
>did the Romans grind them into dust? Where is the physical evidence?

Why would you expect ordinary-looking shields to have been given special
attention?  It's conceivable that some of them might exist in museums
today, unrecognized (and unrecognizable).  More likely is that they got
whatever use the Romans had for them, as shields, and were eventually
melted down to make something else, metal being scarce and valuable in
those days.

There is no specific indication that the Romans made use of any of
Archimedes's other gadgets either, and their existence is fairly solidly
established.

>The question may not be "Could" it have happened, but "Did" it happen?

That's an important distinction.  The modern demo established that it was
feasible with the technology of the day, so the stories *could* be true.
Whether they *are* true is a separate issue, one which is unlikely to be
resolved unless somebody finds either a documentary account of the siege
or some of Archimedes's lost writings.

>In either case I have strong doubts, and you're going to have to come up
>with  better evidence than a nebulous TV show which I'll probably never
>get a chance to see.

I'm not sure what you're referring to here -- I don't get my evidence from
TV shows, since I don't own a TV.
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)