Half a croissant, on a plate, with a sign in front of it saying '50c'
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This would work fine, except in terms of success.

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Simplifying the Story of the Siege of Syracuse

Archimedes used a diverging lens and mirrors (possibly)
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I am making an not so well educated guess that Archimedes used a refracting glass lens at the focal point of a parabolic mirror.

I know that the ability to make glass predates Archimedes by possibly 3000 years and that the actual text describing the incident states that he used a burning glass.

A Diverging lens near the focal point of a large parabolic mirror would create a beam of light that could be directed downward by a mirror at 45 degrees right after it passed through the lens and then aimed by a rotating mirror below - the technology you would have from a telescope.

Telescopes were not supposed to have been invented for 1500 years after this happened, but there are some indications that they may have been in use even before Archimedes (who was an astronomer as well as mathematician).

I think that telescopes were used long before him - There are records from 700 BC that indicate Jupiter had 4 moons and Saturn had 7, as well as text from writings near Archimedes time that stated that the lunar surface was very rough.

A large enough solar parabolic concentrator with a diverging lense to refract sunlight into a small concentrated beam might actually produce a solar "lasar" that could cut ships in half rather quickly.

(does this count as an idea?)

Zimmy, May 12 2008

possible ancient telescopes http://ancientskyscraper.com/224801.html
It would explain a lot of things that you would have to consider very lucky guesses otherwise. [Zimmy, May 12 2008]

Refraction by diverging lense http://www.glenbroo...s/refrn/u14l5b.html
(near the bottom) [Zimmy, May 12 2008]

Archimedes Death Ray do-over http://web.mit.edu/...chimedesResult.html
Yeah, it's possible, even if the mythbusters didn't get it to work. [jutta, May 12 2008]

(05/13/08) " The Cincinnati War was a bloodless territory dispute..." http://www.marriedtothesea.com/
Any relation to this? [normzone, May 13 2008]

Robert Temple article http://www.robert-t...emansonryToday.html
"The oldest actual lenses which I have found are from the 4th and 5th Dynasties of ancient Egypt and date to perhaps 2500 BC." [Zimmy, May 13 2008]

Archimedes http://en.wikipedia.org/wiki/Archimedes
A bit of a brain-box! [DrBob, May 15 2008]


       I don't think he used glass, just a curve of soldiers holding polished metal shields all reflecting the Sun towards the boat.   

       The Moon actually looks rough to the naked eye and i'm pretty sure all the Galileans are visible too.   

       Also, no, i don't really think this is an idea.
nineteenthly, May 12 2008

       sp. "lens", pl. "lenses"
AbsintheWithoutLeave, May 12 2008

       I like the theory that the "burning glass" story was, like the carrots and night vision story that masked the role of radar in WW 2, a bit of counter-intelligence to mask the use of Greek fire.
DrCurry, May 12 2008

       Not an idea as written, but you could have suggested that the combination would work as a "laser". And I'd have told you it wouldn't, for astronomical reasons.   

       The light from the sun isn't parallel, as it comes from an apparent disc. So focus it how you will, it cannot be made into a beam. It will always project out as an image of the sun, covering an area. A perfect system could put the focal point some distance away, but it would have to be a _perfect_ mirror and lens.   

       Here's a handy demo of the spreading. Get a small mirror, and use tape to reduce it to an area about 1/8 inch in diameter. Use that tiny mirror to reflect a spot of light from the sun into a darkened room and onto a white wall. The further the reflection goes, the bigger the spot gets, and, if you look at it, it's an image of the sun. (The smaller the mirror, the sharper the image, though fainter. I first did this to watch a partial eclipse.)   

       For projecting heat onto a small area, a lot of smaller flat mirrors, such as polished shields, would be much better than one big parabolic mirror, a LOT simpler to make and use, and still probably only good for scaring folks. I understand that Archimedes (honor him) had the attackers pretty nervous after a while.   

       As for Archimedes (honor him) making telescopes, glass wasn't that good back then. Clear and flat wasn't happening, or that silly page that you linked to wouldn't have had metal mirrors to show.   

       Telescopes aren't needed to see the four main moons of Jupiter, if one has young, sharp eyes. Figuring out that the moon is rough isn't very hard--it's sustaining a belief in a smooth moon that is rather rough.
baconbrain, May 12 2008

       //mask the use of Greek fire// I think that was a Byzantine technology (i.e., some hundreds of years later).
pertinax, May 12 2008

       I think if you knew you were up against a guy like Archimedes, and you saw weird things were happening on the ramparts (like a bunch of guys with shining shields), that by itself would be enough to give one pause.   

       The Mythbusters where they took this on irritated me. Chielfy because they allowed all the mirrors on the giant device to be smashed at the end, which gave me a frisson of superstition, if a midwesterner is capable of having frissons. But second is that they did not do it right. They should have lined up an entire highschool student body holding mirrors on a hill over a bay on a sunny day and shone the light on a wooden rowboat with a sail.   

       I know there is a ton about this on the web. Bigfoot too. Maybe I just want to believe.
bungston, May 12 2008

nineteenthly, May 12 2008

       [baconbrain], while I didn't know that light from the sun was not noticibly unparallel (it makes sense thinking of sunlight in mirrors), could it be made to be so by putting a lens in front of a parabolic reflector?
Zimmy, May 13 2008

       [normzone], I grew up in central OH & that link is pretty funny to me.   

       (I also heard that Ohio & Michigan went to war over who would get the city of Toledo. Some say Ohio apparently lost).
Zimmy, May 13 2008

       But what if you want to take some pictures of the fascinating witches who put the scintilating stiches in the britches of the boys who put the powder on the noses on the faces of the ladies of the harem of the court of King Catactacus...
gnomethang, May 15 2008

       You can't. They've just passed by.
DrBob, May 16 2008

       sp. Caractacus (alias Caradoc)
pertinax, May 16 2008


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