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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.
The mythbusters set up a more realisitc scenario to test with, they had a real wooden boat that was harder to combust due to the protective resin that was coating the boat, their test was more true to the original myth then what the MIT trial was I think.
MIT's boat wasn't even in the water, they were just pointing mirrors at dry wood.
A boat would have also been damp which would have also made it harder to combust.
This, of course, is where the "Gods From Space" crowd chimes in. Works on TV, but in real life, there's a much more satisfying answer: people are damned fucking clever.
I'll swear there was a MST3K featuring a truly awful film of which the premise was Archimedes had built a death ray. I can't remember the precise name, but god it was awful...
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.
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mythebusters clearly cut part of the card throwing episode. Measurements were taken for metal cards, you can see it in a tivo slomo. It was wither cut for time, or the fact that it was found that the metal cards would cause major damage.
I've never heard a good explanation about who built it, only that it was known that there were repairs done (or deduced from the sections of gears that had been replaced with different material) and that it was made around 50 BC - something like that, I think my dates are wrong. It would be interesting to have someone do a spectral analysis of the metals used (unless being submerged for that long in salt water drastically changed trace element properties in every single bit of metal) to trace back to the region of origin, where the metals were mined. I think I read about doing metalurgical traces by geographic reigon once, where they compared samples from ancient mines to trace amounts in artifacts, and could narrow down where it came from. Back to the whole point of my tirade, it would be interesting to find out, for instance, that the metals used in this device came from india, or china, etc. Might not tell us "who built it" but it might be valuable nonetheless.
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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This was built in mini-form on a show called screensavers. It use to aire on G4 a year or so ago before it go turned into Attack of the Show. They proved that it worked by placing an object infront of the mirror (about 2 feet away) and just about instantly set it on fire.
The problem with mythbusters, and they do this often, is they only did one test to see if it would work in one way. They only aligned the mirrors in one direction, every single one of them at the same degree, meaning that the light that hit the center mirrors wouldnt reflect on the same spot the top mirrors did. If you watch the show they did, you can clearly see the reflection of the mirrors all across the 'boat' from 3 to 6 feet, not on a single point. That means that the mirrors didnt concentrate the light energy in one spot and were only able to get the spot to around 200 degree's.
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.
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It's also possible that the ships were a lot more flammable than the mockups used in the tests, if they were caulked with pitch (it is not known if they were or not).
I saw something on TV about another scientist at the time. This guy developed a device that used steam to cause a ball to spin. The water was boiled in the base, travelled up the support rods, into the ball, and out two ejection ports on the outside of the ball. The mockup they showed spun really fast. If this guy had thought of it as more than a toy, he would have started an industrial revolution.
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...
As to whether Archimedes had steel available to him, it would seem much more doubtful, but not impossible.
you'd probably loose some energy in the infrared spectrum, if a lens is used. now that I think about it why not just use a second mirror? you use one set of mirrors to aggregate the sun light, then use another one to redirect them as a beam so they don't lose focus over long distance.
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.
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I once read part of a book by an ancient Roman engineer in which he talked about how to set up a building site. The first thing he would do is locate water. He would lie down on the ground at the top of a hill before sunrise, and as the sun rose, he would gaze down the hill and notice where mist appeared.
That would be where the water table was close to the surface, and they would dig there to open a spring.
Farewell! It's been a fine buncha years!
One common criticism of this theory is that coordination and aiming would be too difficult to be practicable.
It might be possible to engineer a simple method to coordinate the aiming of many mirrors. First assume that your soldiers are standing in a fixed formation and distance relative to their target. (i.e. a straight line)
Each soldier is holding a mirror which is joined at the base to a board, at an angle of 90 degrees. Put a tiny hole in the mirror, so that a point of light falls on the board to which the mirror is attached. Each soldier now has an indicator of the orientation of the mirror. On each board, an ancient geometer has inscribed a grid. (intersecting parabolic arcs, in the case of a straight line of soldiers) If each grid is drawn appropriately (different for each board), then a commander may call out a row and column and each soldier orients their mirror so that the pinpoint of light falls on the appropriate point.
Implemented as simply as I describe, I doubt this arrangement would be suitably precise, but with a larger (possibly two-person) apparatus and provisions for increased stability, it might be possible to quickly focus the hundreds mirrors required to achieve combustion. The only skill required of the solders would be the ability to stand in a straight line and know the alphabet.
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.
How about using the polished insides of bronze shields? Presumably the greeks would have had plenty of those at hand, considering the situation.
Two points I haven't seen anybody raise.
First, the ship would be constantly moving because of waves. This makes it a tad harder to heat up one spot to igniting and means that the spot would have to be fairly large for this to work. Bigger spot means that we need more mirror surface to heat it enough to ignite.
Second, solid mirror would have fixed focal distance. That means such weapon would have fairly limited range.
Mythbusters is usually right on the money. In a recent episode, they conclusively proved that it is possible to break a glass by singing at it, both using amplification and, with significant effort from a professional singer, just bare vocal chords. However with some myths, due to time or expense contraints, they only test a very limited number of circimstantces, and then when that fails they say the myth is busted in all possible circumstances. For example, the episode where they "busted" the myth of the cell phone/gas station fire, they only used one type of cell phone and only limited conditions of gasoline vapor, etc. They called this myth busted when in fact cell phones can indeed start a fire, and it has happened before.
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.
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The sails were probably not up. Sails were only used as a secondary power source in open water and definitely not used in battle. Naval warfare at this time was basically ramming your ship into the next one or getting close to it and trying to set it on fire. So aiming at the sails was probably a no go.
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 experiments are just as bad. The biggest problem I have is that they seem to have no awareness of significance testing. Without an evaluation of the statistical significance of their results, they can't claim to have proved or disproved anything... A negative result ("busted") could simply mean that their sample size was too small.
I love the show, but it would never pass peer review :-)
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
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.
I saw a show on TLC last week (I have no idea what it was called... caught it channel surfing while it was already started) where they were building devices by following the drawings of Leonardo daVinci.
That was one of the most fascinating hour of TV I've ever seen.
Anyway, I caught it when they were about to try the giant crossbow, and they had strayed from the design to use modern techniques which they were reffering to as much more efficient and superior to what Leonardo had access to. And they could barely move the projectile.
Then someone on the team forced them to do it right, and the thing flew out.
I could tell that the modern way was weaker than the original just by looking at it. The only thing that the modern way had going for it was that it was easier to do.
The lesson is: Newer != Better.
Just because a lot was invented since doesn't mean that they couldn't do anything with what they had.
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So, where did they store the sails hwne not in use? I doubt they removed them, they were likely just rolled up. Still easy enough to target.
... and then they built the supercollider.
There are people on the boats so if you just dump a large flammable object onto a ship it it's easy for someone to dump a bucket from the sea on it.
However, if you have 500 * 1m^2 mirros at 20% effecency your talking about 100,000 watts of power over ~1-4m^2 area which could easly burn people and set riggin ect on fire. And once the fire started they could have kept extending it to ever larger areas of a ship before moving on to the next one. So while the might have been able to keep enough watter on hand to extingush most fires it would be much harder to stop an attack like this.