Re: [Phys-l] fire starter from the sun - revisited

[Brian Whatcott <betwys1@sbcglobal.net>]

At 02:19 PM 4/24/2006, Don P., you wrote:
> The "Myth Busters" TV show had a segment several months ago
> investigation the myth of Archimedes' "Death Ray".  According to the
> ancient myth, Archimedes had invented a means of harnessing the sun's
> energy to destroy enemy galleys by setting them on fire.  The TV
> producers actually got a MIT professor and some of his graduate students
> to try and test the myth.  The MIT group built a series of polished
> metal mirrors (I believe there were something like 50 mirrors and they
> were flat so that the sun's image from many mirrors could be easily
> superimposed given the unknown range of the galley).  They ran a series
> of tests with a wooden barge towed past the bank of mirrors (after first
> running a calibration run where the mirrors were adjusted to produce a
> common image of the sun on the path of the barge).  They did succeed in
> creating smoke and burning a little of the wood on the barge (which had
> been treated with pitch as it might have been in ancient times), but
> never succeeded in really getting a good fire going.  The conclusion was
> that Archimedes "death ray" wasn't exactly a showstopper when Roman
> galleys invaded Syracuse.
>
> Don Polvani
> Northrop Grumman Corp.
> Oceanic and Naval Systems
> Annapolis, MD

The MIT report that I browsed claimed it took as long as 10 minutes
 before the wooden construction burst into flames.   But it needed
the Sun to shine.   Duh!
 They used a gross of glass mirror tiles, 1 foot on a side. At a distance
 of possibly 100 feet.

I would want to suppose that Archimedes might have equiped  his
 warriors' larger brazen shields with  angle bisectors to provide dynamic
 targeting.



Brian Whatcott    Altus OK    Eureka!