[Rockhounds] OT: Death Rays

[Tim Fisher]

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