I've seen BOTH episodes on the subject and I did a bit of researching on my own. The sails would be a better target than the boat. The sails would catch fire and then fall onto the deck where ther supposed "Roman Fire" was, torching the boat.
Also, Roman boats would idle out of arrow range for about a day before moving in on the beach. Now, if Archamedes could count how far they were out, he could adjust the Greeko-Roman mirror to torch the sails.
-Latifundia

i was just coming on here to suggest the same thing, i totally agree with this being more plausible at the very least

For a while I have been wondering how long it would take Mythbusters to figure out how to make the Death Ray work. I am sorry for those of you who have heard too much of the myth already but I am new to this site and therefore new to this myth. I am no history buff but I don’t see a problem with the level of technology that they would have had. Only the idea is a present day thing, Artemetis should have been able to think of it.
If you have the capability to craft mirrors then you have at least a moderate understanding of how to shape and create glass. If you can do that wouldn’t it be fairly easy to create a lens? The idea is to create a large satellite to focus the light only a little distance away from the mirrors, you then use a lens to create a constant stream of light. The nature of a satellite is to receive a weak signal and amplify it to the maximum possible degree. The piece in the center is the receiver. When this concept is applied to light it should work the same. The lens, if it bends light at the correct angle, should counteract the tendency of light to focus. Instead it would create a constant stream of light similar to a laser. I sometimes have troubles putting my thoughts into words so I created a diagram in Microsoft Paint. Please let me know what you think. The link is http://s148.photobucket.com/albums/s7/quearitoveritas/?action=view¤t=Satelliteshapedmirror.jpg

Quaerito Veritas
Seeker of Truth

Great stuff has been suggested here, but unfortunately mirrors were made of highly polished metals,(usually bronze), during this time.
I confess I haven't researched the glass thing, but I'm not sure if they had glass tech at this time either. 212 B.C.E.

I have researched the siege of syracuse where this,"Death Ray", was supposedly used.
[quote]Roman boats would idle out of arrow range for about a day before moving in on the beach[/quote]

Sorry, no beach.
Sorry, no military reason at all for,"idling".
The romans assaulted the city of syracuse from both land and sea.
In battle,(especially this one), the ships of the time were powered by banks of oars, sorry, no un-furled large sails.

The syracusians targets would be the anchored roman artillery ships and any ladder barges that survived artillery, lifting/tipping mechanisms and drop-wieghts called,"Dolphins".

If this,"Death Ray", was even made and put to use, one would think it would be pounded off the top of the wall,(or where-ever it may have been), with a well placed artillery barrage.

Given Archimedes fields and methods of study, and the hot climate the battle took place in and the elaborate measures of defence of the city; I too vote plausible. But just barely.

I only watched the first,"Test", done in San Fransisco bay. A temperate climate. A sort-of array with anachronistic mirrors and a,"Boat", put together with modern materials and methods.

Did they test this on the second try with closer to real factors? In a hot mediterranian climate? And at a boat made from materials and methods of the time? With pitch and oakem caulking?

In the 2st test they did indeed do a more realistic version. they used a real wooden boat with sails rope included. While they did get alot of smoke the boat never caught fire until they bought it with in 10 FT. And they actually DID used polished bronze for this test also. They just couldn't get enough sunlight to focus on the boat to catch it on fire. Thus they pronounced it busted.

HOWEVER!!!!
They were missing 2 key factors in this test.

1. One of the mainstay weapons used during this time were flaming arrows. The archers that would shoot them had jars of FLAMMABLE oil with them setting right on the deck. They would soak the raged arrows in them before taking them out, lighting them, and then shooting them at the enemy. Conceivably if Archimedes had aimed his ray at these jars they would have caught on fire much easier than the wood of the boat, the cloth of the sails, or the ropes. And all it would take was one jar one fire to spill and set the entire boat ablaze. Also alot of the oil would drip and spill on the decks as the Archers had to quickly soak and light more arrows in rapid succession. This could also be lit to catch the oil soaked deck of the boat on fire.

2. The beam of light was also hot enough to easily burn the crew and solders on the boats too. Even with all that armor there was still exposed skin on the soldiers. Not to mention that the light would also super hear the armor and cause it to start burning the soldiers making them fell like they were on fire.

So instead of directly trying to catch the boat itself on fire, Archimedes could have used his "death ray" to actually either set smaller fires that would spread by lighting the oil jars, or by actually using it on the soldiers themselves to burn them to death thus making it a true "death ray." (Brutal yes, but effective)

At the very least the bright light could be used to blind the enemy.

That's what I'm saying. Archamedes, even though he was WAY before any of the Physics and Formulas and Equations we did today, would probably be smarter than Adam and Jamie in the key fact that they can't be Archamedes themselves. Noone was there that is alive today, but in order for the Full effect of the experement to work, you would need about 20 of Buster's cousins, Flammable oils and Phosphorous (Roman Fire) on the decks in open Jars, and, yes, they did have sails to get from Rome to Greece. (You are thinking about the Greeks, not the Romans, buddy.)
-Latifundia

reposting this from another thread..

Why not focus the beam through Glass? Wouldn't that magnify the light and intensify the heat? Perhaps you could use a tower that can somehow capture the sunlight at any point of the day with a moveable mirror which would reflect the beam down through a glass surface then onto the the ray itself (because it has a focussed central beam can be moved in almost any direction and not lose any intsenity). The scale may be huge, but I don't know how long it took you guys to do all these, and to put thought into it.. no more than 2-4 weeks... these people had a lifetime to devote their thoughts and energies into making this work.. with what you had you got half-way there, in 3 weeks.. I think you should redefine this myth as plausible

or you could also have the beam going down a set path of angled mirrors and could cover the openenings of the tower so that you could generate and store the heat.. then open the door and blast the enemy with hot rays of stored light.. you could make it like a furnace, that would explain the practibility of it, and you would not have to wait for it to heat up, theoretically.