History Question: sinking ships using solar power

[iwishihada]

I have a question that I have not been able to find an answer to. I heard many years ago that there was an invading army coming towards a land in ships. The people of the land were very upset as they could see the ships coming and did not know what to do. A Captain in the army on the land gathered 100 men and had them polish the backs of their shields. The Captain had the men line up on the shore and reflect the sunlight using their shields onto the ships.
The ships were slowly destroyed by burning from the reflected light. the survivors were easily picked off by the army onshore.
I do not know the time or location of this battle or even if it is true. Any help would be greatly appreciated. Thanks a bunch

[Amazing_Tiki_God]

Since your a new and all I’m gonna let you in on a little secret. Questions like this belong in the General Questions forum. It’d be good of you to e-mail one of the mods to ask them to move it there for you.

[UncleBeer]

Off to General Questions.

[RealityChuck]

It took place in the Greek city state of Syracuse. The designer of the system was supposedly Archimedes. (Look for “Burning mirror” at this site: http://www.crystalinks.com/archimedes.html)

[UncleBeer]

Thanks for re-posting that RC. You snuck in the other one just as I closed it.

[Popup]

I just posted here, but it looks like my post went into the bit-bucket.

*Originally posted by RealityChuck *
**It took place in the Greek city state of Syracuse. The designer of the system was supposedly Archimedes. (Look for “Burning mirror” at this site: http://www.crystalinks.com/archimedes.html) **

link fixed: Archimedes

According to an article I read a while back this was not generally reagrded as reliable. Until fairly recently when a history buff made a huge bronze mirror using only methods known to the classics. He managed to set fire to a ship-shaped cut-out hundreds of meters away.
However, I cannot find any evidence for this…

An other note. Most shields would have had wooden backs, and even if they were solid the surface would most likely be far to concave, with a focal length of about a meter, instead of the hundreds needed. It’s more likely that Archimedes actually used flat purpose-made mirrors.

[vl_mungo]

Yah Archimedes… he gets my vote as the top scientist of the Classical world. The solar mirror thing was just one of his many excellent inventions… as you will no doubt see if you check out the above links

[MHand]

I’m not sure how reliable that site is. It says:

Another legend describes how Archimedes uncovered a fraud against King Hieron II of Syracuse using his principle of buoyancy. The king suspected that a solid gold crown he ordered was partly made of silver. Archimedes first took two equal weights of gold and silver and compared their weights when immersed in water. Next he compared the weights of the crown and a pure silver crown of identical dimensions when each was immersed in water. The difference between these two comparisons revealed that the crown was not solid gold.

That’s ridiculous. How could he make an identical pure silver crown and why would he want to?! The way I heard it, which makes more sense, is that he measured the volume of the crown by measuring its displacement when immersed in water. He measured its weight. He divided and calculated its density. He then calculated the density of another known piece of pure gold by measuring is volume through displacement and its weight. The density difference let him know that the crown was not pure gold.

[friedo]

…And then he ran through the streets naked singing “Eureka!”

I heard the same version as you, Mhand, and it makes more sense. It sounds like the author of that page is confused about how density and water displacement work.

Another part of the legend is that when Archimedes was trying to figure out how to tell if the crown was real gold, his wife told him to take a break and have a bath. When he stepped in the tub he realized he could measure the volume of the odd shape with water displacement.

[Seraphim]

The mention of Archimedes jogged my memory, so I dug out my old copy of Reader’s Digest presents Strange Stories, Amazing Facts. Sure enough, it had this bit:

According to several ancient writers–including Plutarch and Anthemius of Tralles–he reflected sun rays onto the Roman fleet when it sailed against his hometown of Syracuse between 215 and 212 BC and set the ships on fire.

But their descriptions were discounted by later historians. In 1973, however, Dr. Ioannis Sakkas, a Greek engineer, carried out a series of experiments that proved that the idea was workable.

He focused 50 bronze-painted mirrors on a small rowing boat and reflected the sun’s rays onto it. Within seconds the craft began to smolder, and after two minutes it burst into flames.

Prof. Evenghelos Stamatis, a Greek authority on Archimedes who saw the experiment, said later he had no doubts that the inventor had used solar energy.

The article is accompanied by a photo of 50 men lining the shore, holding up mirrors as large as themselves.

So we know its possible, at least.

[Sofa_King]

Let’s also not forget that Archie, champion of the lever that he was, devised a great many other “war engines” which apparently worked with some success:

… when Archimedes began to ply his engines, he at once shot against the land forces all sorts of missile weapons, and immense masses of stone that came down with incredible noise and violence; against which no man could stand; for they knocked down those upon whom they fell in heaps, breaking all their ranks and files. In the meantime huge poles thrust out from the walls over the ships and sunk some by great weights which they let down from on high upon them; others they lifted up into the air by an iron hand or beak like a crane’s beak and, when they had drawn them up by the prow, and set them on end upon the poop, they plunged them to the bottom of the sea; or else the ships, drawn by engines within, and whirled about, were dashed against steep rocks that stood jutting out under the walls, with great destruction of the soldiers that were aboard them. A ship was frequently lifted up to a great height in the air (a dreadful thing to behold), and was rolled to and fro, and kept swinging, until the mariners were all thrown out, when at length it was dashed against the rocks, or let fall.

–cite (quoting Plutarch)

[Tranquilis]

I saw a reconstruction attempt of Archimedes’ anti-shipping engine. It was, essentially, a traction trebuchet (or perrière) in reverse. In place of a sling, it had a large grappling hook, and the long arm extended out over the water. By hooking onto a ship’s structure, a large-ish group of men were able to haul a solidly-built and fairly modern fishing boat out of the water. The kinds of vessels Archimedes would have been attacking would have been much more lightly built (being galleys), and thus would have comparably easier to upset. While the reconstruction wasn’t a complete success, we have to remember that the scholars are missing a huge amount of information about ancient construction techniques, and were guessing about the actual design to a fair degree, as no accurate contemporary representation of the Archimedeian engines has survived (if any were ever actually made in the first place).