During the siege of Syracuse in 212 BC, Archimedes was purported to have set fire to invading Roman warships by focusing the sun’s rays using glass. The Mythbusters said it couldn’t be done, but a class of MIT students has duplicated the effect: http://web.mit.edu/2.009/www/lectures/10_ArchimedesResult.html
The idea has been proven at least twice before this. The folks at Mythbusters did a pretty poor job of aligning their mirrors – look at the size of the “bright spot” (I can’t really call it a focus) that they obtained. Even with just flat mirror segments they should’ve been able to do much better. (I joined their site just so I could tell them so.)
Check out this guy’s site for details:
Here’s a brief piece on it from the MIT Spec Lab:
Yeah, but ships have a nasty habit of moving through the water and bobbing up and down on waves. How’d Archemedies devise a target tracking system in 212BC. Certainly the MIT students didn’t consider that problem in their experiment.
Archimedes has become sort of the patron saint of Adaptive Optics these days – I’;ve seen him cited in two books on the topic. It’s not entirely fair, since he wasnn’t the one credited with the idea – think Proclus was.
Instead of using a single mirror, you get an army of people, each armed with a little mirror. They all keep their own reflection from the sun fixed on the target.
Exactly how this is to be done isn’t obvious, but several methods were devised for using helioscopes (signaling mirrors) during WWII, and the most successful method would work quite nicely. It’s described in a paper in JOSA and in Hal Clement’s novel “Cycle of Fire”. Using this targeting method, each soldier holding his mirror (or mirrored shield, or whatever) keeps it positioned on the target. Even if the ship moves, the focuas folows it around.
See the references in the Spectrograph paper.
Mythbusters didn’t do this, by the way, which is one reason they failed. The Greek guy who did this back in the 1970sd probably did. So did Buffon, after a fashion. To be honest, I doubt if Proclus or Archimedes knew it, so, while they could have done this, I don’t think they actually did.
A good thing about the Mythbusters is that they’ll revisit old myths and they won’t hesitate to admit if they were wrong the first time. Maybe we’ll see Archimedes’s death ray tested again in a future episode.
I don’t think Archimedes did it either. I mean the man did have principals.
What did his school administrators have to do with anything?
I just read the link in the OP and came to SDMB to post it.
the FAQ does mention ship bobbing
http://web.mit.edu/2.009/www/lectures/10_ArchimedesFAQ.html
Brian
I don’t know whats worse.
That I was gonna post the same article
or
That I was gonna use the same type of Heading.
Havent been here to long… noooooo
That doesnt say too much about my social life. not at all.