[Rockhounds] OT: Death Rays

Thu Nov 8 10:12:26 PST 2007

Back to melting  stone. The MP of silicates rocks is supposedly around 1200
deg C. Which is way above the temps these people are claiming, which are 600
deg at best. And since I don't think they are finding little solidified rock
globules on the surface of these cut stones they required temp would have to
be at the vaporization temp not the melting point.

As for a gold reflector, they say it was two men high. Lets call it 3
meters. A 3 meter disk of gold, say 10 cm thick would weigh about 13000 kg
by my back of the envelope calculation. Now I think that modern mechanical
engineers might find it to be a difficult design task to come up with a
mount that would allow you to precisely aim a 3 meter disk weighing 13,000kg
to plus or minus a millimeter or so. Assuming this system would have to be
in the capabilities of stone age craftsmen to build. And that doesn't take
into account the weight of the mounting system.

BK

On Nov 8, 2007 12:23 PM, Tim Fisher <nospam at orerockon.com> wrote:

> The link you sent is dead. Here is a relevant synopsis.
>
> Archimedes Burn-Off. The original ancient death ray episode generated
> so much rebuttal from fans that the team dedicated an entire episode
> to revsiting this one myth. So after reviewing a whole stack of DVDs
> submitted by fans, two teams are selected to come to San Francisco
> for the small-scale burn off to see if they can set something afire
> at five feet.
>
> The guys have a small parabolic mirror that works well (nine
> seconds!), but it doesn't work at five feet. The girls do okay but it
> takes a couple minutes, and they don't work at five feet either. So
> both teams have 24 hours to come up with new rigs. Neither team does
> all that well, but the guys do manage to set the hemp material on
> fire and are declared the victors.
>
> One guy is invited for the large scale burn-off, to set something
> afire at 100 feet, but his massive mirror is busted up during
> shipping so we never get to see it in action.
> <http://www.imdb.com/name/nm1144726/>Adam also builds a disco death
> ray from an old satellite dish and it seems to do pretty well but it
> doesn't go five feet either, so he is disqualified too.
>
> Luckily it seems that some students at MIT were inspired by the last
> episode and they managed to set a small boat replica afire with some
> mirrors, so some people from MIT are invited to help setup a larger
> test with 300 bronze mirrors to see if it works. They get lots of
> smoke but they can't do it at the full distance and only get fire at
> 75 feet, which is half what they wanted.
>
> In the end, there are seven reasons why this myth is Busted:
>    * The Compass
>    * In San Francisco the noonday sun generated 450 degrees of heat
> from 300 bronze mirrors at 140 feet (the distance of an arrow shot).
> If Archimedes had tried this, the sun would have been weaker,
> producing even less of a result.
>    * The Weather
>    * Clouds can render the weapon useless. Are you going to carry
> more than 300 mirrors into battle on the off chance that it will rain
> that day?
>    * Roman Boats Were Moving
>    * It's a great choice if your opponent will come close enough to
> you that you can focus the beam and then not come any closer. But
> like the weather, those aren't very good odds.
>    * "Inflammable" Sails
>    * The sails being mostly light-colored reflects the heat, plus
> their movement in the wind means they don't even smoke, much less
> catch fire, so they aren't a good choice.
>    * History
>    * The history books don't mention fire for 800 years, and no
> mirrors or "death rays" are mentioned for nearly 1200 years.
>    * Scale
>    * You need some 300 mirrors to produce smoke. How many are
> required to create fire again?
>    * Alternative Weapons
>    * Even a novice archer can fire an arrow 300 feet or so. Set one
> of those on fire and alleviate the need for all those mirrors (and
> the people to aim them, the time to set them and the need to tell the
> other boat to stand still while you do so).
> At 09:02 AM 11/8/2007, you wrote:
>
> >Pete,
> >
> >There was a Mythbusters episode about this... they pretty much busted
> it...
> >Here is a site, <
> >http://web.mit.edu/2.009/www//experiments/deathray/10_Mythbusters.html>
> >
> >Drew
>
> Tim Fisher
> Ore-ROCK-On!
> Email address at http://OreRockOn.com
>
> --
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-- 
J Bryan Kramer
North Florida, USA
photos at:
http://pbase.com/photoburner

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