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Archimedes Death Ray
Werner Heuser writes "Ancient Greek and Roman historians recorded that during the siege of Syracuse in 212 BC, Archimedes (a notably smart person) constructed a burning glass to set the Roman warships, anchored within bow and arrow range, afire. The story has been much debated and oft dismissed as myth ... Intrigued by the idea and an intuitive belief that it could work, MIT's 2.009ers decided to apply the early product development 'sketch or soft modeling' process to the problem."
I personally thought that they didn't do a very good job at testing it and they could have definitely gotten it to work if they did a better job setting up the mirrors. (of course they like to claim they "busted" something even when it was inconclusive or mostly true)
For what it's worth, the MIT folks said they couldn't unequivocally rule it out. They didn't say it happened. One of the main points on Mythbusters was that it seemed like it might work, but the fleet would have had to remain essentially motionless for the wood to get hot enough for ignition. The MIT folks did nothing to answer that as they the mirrors and the "ship" were motionless until ignition.
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Solar Death Ray
Looks like the renewable energy people are in on it, too
I also remember seeing one in my chemistry book last year... it was in france or somewhere (theoretically temperatures could get high enough to ignite something with a low flashpoint like wood or paper). The mythbusters' argument was that copper wasn't shiny enough and that even with mirrors, the soldiers wouldn't have enough precision to focus on a point for long enough.
-TX297
i saw that episode (as did the folks who did that project, if you read the article). the mythbusters folks didn't really build a parabolic mirror so much as a poor approximation thereof and they didn't really do a good job of focussing it, so it makes sense that they had problems making it work.
Igniting sails, or burning/blinding people is much easier than setting fire to wood (especially a hull that could be wet). I've always thought that the victory was due to the psychological effects of the weapon on morale more than the outright destruction of vessels.
The size of the focused target is way too big for light wave interference to have an effect. Parabolic mirrors are useful because if we take the sun to be a point source (which it isn't, but it's close enough) then all the rays from the sun will converge towards the mirrors focal point. It's the same principle as burning ants with a magnifying glass - if you put a 3 inch diameter patch of sun into a 1/4 inch diameter circle, you'll have a very, very intense spot of sunlight. Here we're using a mirror to focus the sun.
Education is a better safeguard of liberty than a standing army.
Edward Everett (1794 - 1865)
Okay, if we're going to use this argument...
In the MIT experiment, the boat was arguably a very poor replica of a trireme. It was painted black to optimize the energy transfer (which in the end didn't matter). The target was not moving, only the sun. The target was not in water. Highly polished silver on a superflat surface would have been the closest thing that the ancient greeks could have had to simulate those mirrors, and if such a thing were possible, it would have been enormously expensive. The greeks would have had people holding the mirrors, not tables and stands.
At 100 feet, your each soldier's heartbeat would have defocused the weapon, even if he could otherwise hold perfectly still (which he couldn't). To protect the soldiers from archers, Archimedes' weapon would have to hold focus at a much greater distance.
All these things the MythBusters got much close to right and the MIT folks avoided.
Nobody is arguing that focusing the sun on something won't result in transfer of lots and lots of energy. That would be just silly (the web page says they wanted to see if it was at least possible - damn, they had to go to MIT to figure out a finite amount of energy will cause wood to burn?!). The question is could such a thing have been constructed and put into use by the Greeks. And that's something the MIT folks answered far less effectively.
Education is a better safeguard of liberty than a standing army.
Edward Everett (1794 - 1865)
Not only do they make the assumption that their resources are better, which in all honesty is fair in almost all cases, but (in this instance) they make the grave assumption that they're smarter than Archimedes, or even normal, average people for that matter--and that's where they go wrong. I've lost count of the things they screw up that should be evident to many high school physics students. They're entertaining, and It's always fun to watch them blow stuff up, and that's their purpose, after all.
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I remember a Mythbuster episode where Adam & Jamie try to reproduce this myth/story. They were not able to set a boat hull on fire (they built a replica-piece of boat hull from that age). Stronger still they barely managed to get the temperature higher up... iirc it was only a few degrees higher in the focused center of the beam.
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Actually, on Mythbusters they tried to use people, and even with much practice they couldn't align the mirrors to a stationary target with much better than 5 degrees of accuracy. That's when Adam came up with the idea of using a frame to hold the mirrors.
However, in the Guinnes book of world records they had a photograph of a couple hundred of Greek sailors with polished mirrors of about 1sqm each setting a dinghy on fire from about 150m away.
'Be always mindful, even when ditch-digging.' --D. T. Suzuki
Nice project - though since you had a properly shaped parabolic reflector already, you could simply have coated it with aluminium foil - no need for glass, as the mirror stuff on the back of the glass is aluminium. I once saw a documentary showing that some people in the desert areas of China cook food with 1.5m parabolic reflectors and they easily bring a pot or a kettle to the boil with it.
Oh well, what the hell...
The other answer to my post from the AC above probably nailed it. "Why build a factory when you can have slaves do it?" The class of Greeks that had the time to dabble with steam engines had no incentive to build labour saving devices.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
Really, really, really smart people 2000 years ago were probibally really, really smarter than most people now. Additionally Archimedes was very familiar with the materials available. It is very possible that the best and brightest of today would fail because they couldn't believe that a technology of the day would have been able to make sufficiently reflective mirrors etc. Not that these things MUST have worked properly, but who would believe the pyrimids were built if they weren't still standing?
Since the Greeks had gears and ropes, it would have been possible to build a mechanism whereby one person could rotate many mirrors. I'm not saying it would have been easy, or even that it was done this way, only that they had all of the required technology to do it.
A second possibility would have been similar to the sighting mechanism used very successfully by the Dambusters in their attacks in World War II on German dams. They needed to know when they were at a certain height above the water, level, and at a certain distance from the dams. They achieved this by angling the searchlights to cross over at the right height and strike the dam at the right distance. To know if they were level, they used pieces of wood at different distances, which would line up when the aircraft was level.
To line the mirrors up with the ship, you'd need to know when the light from the sun would strike the ship at the right height. Angle of incidence equals angle of reflection, so as the sun moves through the sky, you'd need to shift the mirrors both horizontally and vertically to keep the light on the right spot.
If you had a hole in the mirror and stood behind it, you could swivel the mirror to face the ship. Since the ship would be at water level and the mirror would probably have been much higher, the mirror would have to have pointed at the tallest mast. It would be the only thing visible. To ensure all mirrors pointed the right way, each mirror would need behind it a stick that needed to line up with the mast, but set at an angle such that each mirror would line up differently along a crude parabolic curve. Shouldn't have been hard, with the Greek knowledge of geometry, which they were exceptionally good at.
If the action was brief enough and at the right time of day and at a predictable distance, the vertical angle would be unimportant. If it had to be ready for ANY time of day OR at ANY distance, then you'd need to have the poles on which the mirrors were attached themselves movable.
If you mounted the pole on one end of a see-saw, then added weights to the other end, you would be able to adjust the vertical angle of the mirror to whatever was required. The line of the see-saw would be parallel to the normal of the mirror. You can tilt the mirror such that the reflected light will intersect the ship at the same point that the line along the see-saw intersects the ship. This would guarantee all mirrors get identical vertical alignment.
We now have a guaranteed way of aligning a great many mirrors onto an identical point on a ship at any distance at any time of day, using nothing more than geometry, alignments and pivots. Again, this is NOT to say that this is how it was done - we don't know HOW it was done, or even IF it was done. What this is saying is that the arguments against have largely been based on sophistication, but that the required level of sophistication was certainly achievable had anyone wanted to achieve it.
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Huh, that surprises me. Wasn't pine sap one of the more common incendiaries during the Middle Ages? I suppose that there probably aren't a lot of pine trees in Italy, but presumably they existed somewhere in the Empire, and I imagine that other saps would work alright as well.
"The question of whether a computer can think is no more interesting than that of whether a submarine can swim" -EWD
Don't forget Archimedes acquired a reputation in his lifetime that has lasted more than two thousand years. That is, he was not only considered the smartest man in his generation, but one of the smartest men ever to live for another hundred lifetimes of men, all over the Western world. He was very probably the ancient world's equivalent of Newton, Einstein and Fermi all rolled into one.
Further, given that he was at the time of his supposed feat a powerful figure in Syracuse, and the fact that the fate of a conquered ancient city was dire -- the city leaders would be paraded and killed, and everyone else sold into slavery -- Archimedes probably had access to all the material wealth of the city, and as much willing -- nay eager -- manpower as he could wish.
Given those facts I would hesitate to scoff at the myth on the basis of what can be achieved, or not, by a mere dozen modern men, of average intelligence* and creativity, working with trivial amounts of money, and not nearly as motivated as men facing enslavement, an ugly death, or in many cases both.
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* Yes, I know the MIT students are no doubt above average in intelligence. But the odds that their number includes someone so clever and inventive that his name and accomplishments will still be common knowledge twenty centuries from now seems remote, to say the least.
For one, they do *many* more experiments than they show on air. Check out their website for details - basically, for every one experiment that makes it to air, they did 5. In reference to this episode in particular, you can be sure they tried many different cell models with many different levels of gas. These guys have quite a large budget to work with, they aren't going to skimp out on one cell phone.
For two, in reference to this particular episode, they did bust the myth that a cell phone can cause an explosion *through normal useage*. What they ended up saying, is in all likelihood the reported explosions were not coming from cell phones, but were a result of static electricity buildup at the scene. This is entirely plauseable. In my last car, depnding on the clothes I was wearing, I would often get actual blue sparks coming from my fingers to the door handle if I touched the car in the wrong way while getting out of it.
An explosion from a spark caused by static is much more likely than anything caused by a cell phone. How could useing a cell phone or having it ring *possibly* be any ore dangerous than a car radio? The car radio operates simmilar electronics, and hell, old ones even have rotary contact-based resistors for the volumne, which would be an ample source of spark potential. Any cell phone whose batter is sparking is not going to work properly because the battery is not making proper contact with the battery, so your calls would be constantly dropping. No one would use it.
In the MIT experiment, the boat was arguably a very poor replica of a trireme. It was painted black to optimize the energy transfer (which in the end didn't matter).
Actually a lot of the boats of the time were black. In any case, they would probably have targeted the sails if they were unfurled, being higher and easier targets.
Highly polished silver on a superflat surface would have been the closest thing that the ancient greeks could have had
I think bronze, or white bronze seems a lot more likely.
The greeks would have had people holding the mirrors, not tables and stands.
Because the greeks had not yet invented tables or stands?
At 100 feet, your each soldier's heartbeat would have defocused the weapon, even if he could otherwise hold perfectly still...
Again, because they had not invented stands yet?
To protect the soldiers from archers, Archimedes' weapon would have to hold focus at a much greater distance.
Or they could be standing behind big sheets of bronze.
All these things the MythBusters got much close to right and the MIT folks avoided.
I seriously doubt that. Now I'll be the first to admit, I'm no expert on light, reflection, or focal instruments. Similarly, I'm not an expert on Greek history and technology or Archimedes. I do, however, have my aptitudes, some of which have been touched upon by other Mythbusters episodes. It makes you want to cry when you see them making fundamental mistake after fundamental mistake, applying constants that are wrong by three orders of magnitude, and basically making all sorts of assumptions without any real research. Mythbusters are entertainers. They blow things up and make stuff that looks neat on TV, while trying simultaneously trying to address various topics in a very informal, half-assed sort of way. To assume that these jokers can "bust the myth" that a genius figured out how to do something that they are unable to in their five days of quickly throwing crap together without any real expertise or research is the real joke.
Note, I'm not saying this legend is true, but I am saying I'd never believe that it is not based upon the posturing of these twits.
The parabolic reflector gaves at the focal point a maximum flux of 1000 W/cm2. The experimentations takes place at the focal zone (18 m in front of the paraboloid. The range of available temperature is from 800 to 2500 C (the maximum reachable temperature is 3800 C) for a maximum thermal power of 1000 kW.
http://www.imp.cnrs.fr/foursol/1000_en.shtml