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Archimedes and the light shields that

• Message 1. 

  Posted by John Paul (U1698054) on Sunday, 31st July 2005

  burned the roman ships, was shown recently on the Ancient Discoveries item.
  
  But I remember from the coverage of the spartans that their shields were round and concave, of metal. from battle experience in hot summer these would have made good wok dishes.
  
  In my military days we tried to fry eggs in simple hot flat metal plates;
  
  I think that these type of shields would have been the ones used by Archimedes. What do you think?
  
  Thanks
  
  John Paul
  
  
  
  

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  Posted by Gilgamesh of Uruk (U211168) on Tuesday, 2nd August 2005

  Most curved shields, including if memory serves, those of the Spartans, were carried with the concave surface towards the soldier, so that at least a degree of "wrap-around" protection was available. If you polished the inside, then that could be used as a concave mirror, I suppose.

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  Posted by Nik (U1777139) on Wednesday, 3rd August 2005

  I am not sure if mentioning of the word 'aspis' implies directly that Archimedes used actuall military shields or that he used shield-like plates. Using military shields would have been highly impractical due to their weight and cost (they were not that cheap!). It is more probable that he ordered from any of Suracuse's workshops thin light and cheap metal plates easily made probably curved at a nice angle and arranged easily on a support to do his job. More simply he would have used these plates to make ... normal glass mirrors (of course, they existed at that time!) and then put them in use.
  
  The basis of Greek shields at all periods were layers of wood/metal, hide/metal, more rarely metal/metal - the layers increasing the level of protection employing less overall weight (there are nice descriptions of that as early as in Ö÷²¥´óÐãr's poems). On the inside the shield would have a leather bordure for more comfort and on the outside layer (most often made of metal), on summer they would add a leather cover to avoid overheating. The drawings on the shields were often on these leather covers rather than on the metal layer.
  
  An experiment organised in 1973 by a Greek archaiologist on a beach in Attica employed some 100 people holding linear (and not curved!) mirrors trying to focus the shine on a small boat floating at a distance in the sea. To increase the difficulty level, the boat used was made of wood that is more resistent to fire: it took some 15 minutes for the boat to start getting burned!
  
  If Archimedes used a system of curved mirrors and taking into account that Roman ships were made of wood less resistent to fire then most probably the whole story is most certainly true and the burning was achieved within the minute!!! No wonder why Romans wanted him alive!

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  Posted by John Paul (U1698054) on Saturday, 6th August 2005

  Enmerkar, thanks.
  
  Best wishes,
  
  John Paul

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  Posted by John Paul (U1698054) on Saturday, 6th August 2005

  E_Nikolaos_E, howzit?
  
  I had never heard the story, and thought it really ingenious! by what ever means, mirrors, flat or curved metal, as the romans would have manouvered to avoid the focus, the handlers would have done the same, keeping the focus on target.
  
  This makes me just love this historical stuff! Is there any record of any other places doing the same to roman ships?
  
  Thanks, best wishes,
  
  John Paul

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  Posted by Nik (U1777139) on Sunday, 7th August 2005

  John, nice question, I thought of it but I do not know. Since the whole design of an apparatus of mirrors projecting the sun on the target is quite easy to memorize and cheap to built, Romans (and others) might have employed it as a weapon in their armies. It is known anyway that since early ages Greeks (and others of course)used to take off their skin-covers and use the shine of their metal parts to blind the soldiers and especially the horses of the enemy.
  However, a weapon of mirrors could not be employed from a ship (since focus is difficult to achieve!),hence only from a well protected port or base against the enemy fleet. However, after Syracuse the Romans did not siege by sea any other important city (even Carthagene was invaded by land and not through sea-siege). Alexandria in Egypt was also invaded by land not by sea-siege. In the next centuries the Romans being uncontested in the sea hence even if they had such weapons they did not use them. In early medieval ages, Eastern Romans (Byzantinians) had already developed a chemical substance that burnt only when shot (its chemical analysis is still a mystery!) shot by means of a pressurised-air canon or by the classical catapelt; the good thing with this 'Greek fire' was that it could be used also from a ship. Hence, the idea of mirrors was never again to be employed (as far as we know currently...).

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  Posted by Landwehr (U1664897) on Sunday, 7th August 2005

  Fans of 1950s "sword and sandal" epics will of course recall the scene at the end of 'Solomon and Sheba' where the Israelites destroy an Egyptian(?)chariot attack by blinding them with their shiny shields!

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  Posted by John Paul (U1698054) on Sunday, 7th August 2005

  Hi, Landwerh,
  
  So that story would have predated Archimedes; and in the Old Testament there is a reference to inventions of war, something to that effect.
  
  The battlefield has a way of triggering ideas; it was brilliant of Archimedes! the romans only understood what was happening too late: they must have thought the locals were trying to blind them, like the blinding of the horses trick. Once the fire started it was panic stations, no time to counter think: put shields on the outside like the vikings, add on balast or water to raise the water line, keep the outside wet,...
  Best whishes,
  John Paul
  

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  Posted by Nik (U1777139) on Friday, 12th August 2005

  ... i read again your last comment John and it reminded me of a story I had heard years back about that navy confrontation in S.America between English and Germans: Germans had their canons calibred for the local gravitational force - English had not ... their canons were aiming in the sea, the Germans were bombarding succesfully english ships - then an ingenious English officer thought of their initial negligence in the middle of the battle and sat down with others and did the calculations to re-adjust their canons thus saving the battle for the Brits!) - I hope I said nothing wrong, cos its years I have heard it.
  
  As for Romans, I thought of it again and think that the Suracusians would most probably aim at the sails of the Roman ships; the sails would burn easily and falling on the deck would aid in setting the whole ship on fire - if first aiming the wood on the sides it would take 1-2 minutes more until a nice fire was set. Most probably no Roman sailor could come near the focus to drop water, he could become instantly badly-'sunburnt' and blinded - quite terrible!
  
  The only thing that Romans could do is to have their ships equiped with large very thin and extra-light metal plates (that can be carried easily by one man) in order to deflect the focus of the enemy mirrors. Perhaps after their first bad experience they equiped their ships as such though that is a guess of mine - I have not heard of such!!!

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