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."

MIT numbering...

[by Anonymous Coward]

For the unitiated, 2.009 at MIT is a class in course 2 (mechanical engineering), called Product Engineering Processes.

./ built its own death ray...

[patio11 (857072)]

... and the server is a smoking husk before the first comment is posted.

Re:./ built its own death ray...

[Mind Socket (180517)]

I'm confused, I thought adding a lot of mirrors stopped things from catching fire around here.

Obligatory Coral link

[bcat24 (914105)]

The server seems really slow right now, try this [nyud.net].

Re:Obligatory Coral link

[cluckshot (658931)]

I don't suppose that reminding the crowd that Archamedes had quite a history building some pretty massive things and doing so using some pretty cute tricks with some really high math is in order. I am quite sure that Archamedes was aware of the solar reflection and other issues. It is my understanding that he used bronze mirrors of very large size that were essentially slightly parabolic with a focal range about 1 mile. I do know he possessed the math, and architectural skills to do this. This is typical of ratio projection used in buildings.

I do know the results in history of this man's work are pretty well established. He pretty much set about and did whatever he intended to do. As a scientist he was neither politically correct nor foolish. He was the best of his time and frankly would have been pretty good today.

The Mythbusters assumed that some things were too big to do. This would not have been a problem for a man who engineered the roofing of big Greek buildings.

Two possibilities

[jd (1658)]

It depends on how large an area the mirrors would have been placed, whether they were flat or parabolic, etc. If we assume relatively narrow, flat mirrors then the problem becomes slightly different. All you'd then need is for each mirror to be on a pole.

Since the Greeks had gears [wikipedia.org] 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.

Re:Two possibilities

[bcattwoo (737354)]

As you say, you would need a mechanism for aiming - I was imagining sights on the pole attached to the mirror that they could use to line up with a specific spot on the ship, and another to line up with the sun - it shouldn't be too difficult to come up with a simple mechanism that the troops could be trained to use.

I learned in boyscouts a very simple way to aim the reflection of the sun from a mirror at a distant object. You need a mirror that is reflective on both sides with a hole in it. Look through the hole at the target. There should be a spot of sunlight on the ground or your body from the sun shining through the hole in the mirror. Angle the mirror such that the reflection in the back of the mirror of this spot of light lines up with hole in the mirror. The suns rays will now be directed at the target. Many outdoor provisions companies sell small mirrors of this type for signalling purposes in emergencies.

Re:Obligatory Coral link

[modecx (130548)]

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.

Re:Mythbusters is a joke (probably OT)

[CoderBob (858156)]

I can only assume you were misinformed or made the wrong assumption about the show. Perhaps you are missing out on what Mythbusters is about. It's this funny little thing called "entertainment".

It is not an "Educational" program. It's about 2 guys who used to do FX work for Hollywood using their skills with "getting close" to the right thing trying to see if they can replicate urban legends.

The funny thing is, you probably missed the episodes where they revisit old myths they worked on. If the show receives enough requests from the audience or they decide they didn't do something justice, they give it another go. They did the "chicken gun" myth a couple times because they kept doubting their setup. I didn't get to catch the final conclusion, but I would say that by the time they were done, they had tried everything available to them to see what would happen.

Other examples of where they've done things incredibly right include hanging a pig carcass from a hook on a pivot and shooting it with various guns to prove that no, taking a gunshot does not make you fly back and do cartwheels, and using a ballistics gel dummy (with a pig backbone to simulate the human one) to determine if you could be injured by a ceiling fan (even the high-powered ones didn't do much until they sharpened the blades).

Yes, most people who have shot guns would understand that Hollywood fakes it, but for the average Joe who just watches movies and TV, with no physics background, it was probably something neat to see.

Yes, they blow stuff up. They put a crash test dummy through hell. Yes, they keep fuck-ups on the film, because that makes the show more approachable to the target audience- it isn't a dry, we-just-provide-the-facts-ma'am-only-the-facts show. It is supposed to feel like you and you buddies could be right there with them. You know what, though? It's entertaining. And for a channel that brings us 5 variations on "hey, we're going to destroy a room in your house by letting a half-assed decorator come in and ruin your happiness", it's a damn good show.

Many of their conclusions are valid. They've shown that pissing on the "live" rail of a 3-rail train system will not shock you (urine stream is too fragmented by the time it hits the rail for electricity to travel), exactly how many bug bombs you would have to set off in a room with an ignition source before the gas was concentrated enough to explode, and that you cannot get sucked into the intake on one of those firefighting helicopters while wearing scuba gear, only to be dumped into the fire and die.

Re:Obligatory Coral link

[agrippa_cash (590103)]

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?

Well, he did get an amazing reputation.

[Quadraginta (902985)]

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.

-------------
* 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.

Mythbusters

[fimbulvetr (598306)]

Not to argue that the mythbusters are always right, but they've disproved this in one of thier episodes. They did some pretty good convincing after building a trireme and using a few hundred mirrors and only reaching a couple of hundred degrees (F).

Mythbusters: http://dsc.discovery.com/fansites/mythbusters/myth busters.html [discovery.com]

Re:Mythbusters

[pete-classic (75983)]

I like mythbusters, but they missed the boat, so to speak, on this one.

I build a Death Ray [hutnick.com] and it works great.

-Peter

Re:Mythbusters

[HermanAB (661181)]

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.

Re:Mythbusters

[phlegmofdiscontent (459470)]

I remember an episode of Mr. Wizard from way back where they use a parabolic mirror to burn/cook a hot dog. It inspired me, but lacking a parabolic mirror, I had to make do with a magnifying glass. And lacking an available hot dog, I had to make do with ants.

Re:Mythbusters

[by Anonymous Coward]

If you check out the application [discovery.com] to develop a better death ray experiment, you see that one of the criteria for participation is:

You must not be a candidate for elected public office, and if selected as a participant, you will not become a candidate for elected public office until 12 months after the initial broadcast of the last episode of the series in which you appear.

I'm wondering if their logic is "If you can build a death ray, you can't run for office, since it would give you an unfair advantage. Who the hell is going to vote against the guy with the death ray?"

Re:Mythbusters

[skiflyer (716312)]

In case you're serious, it's because of airtime laws and public elections. If they put this person on TV and their a political candidate, then they must also allow equal airtime to their opponents.

I like your idea better though.

Re:Mythbusters

[LnxAddct (679316)]

Not to argue that the mythbusters are always wrong, but they were wrong this time. Not only does the number of mirrors count, but they must be lined along a parabolic path, must be "perfectly" flat (in this case) and as the article stated, the point of focus changes at 36 feet per hour so you have to keep the mirrors "up to date". There are a lot of factors to take into account, and optical physics to solve. You can clearly see MIT's results, setting the ship on fire, and it was made out of wood stronger than what would have been used by the Romans. The ship hit over 1100 degrees and burnt pretty well. Moral of the story: Myth Buster's results no longer matter because a contradiction to them was proven to exist.
Regards,
Steve

Re:Mythbusters

[Wavicle (181176)]

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.

Re:Mythbusters

[dangitman (862676)]

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).

Why would the greeks have tried to set fire to the wood? It would me much easier to target the sails, and they would burn much more quickly. Once the sails are burning, the wood follows. I don't understand why modern people have such problems following logic, and instead have such faith in modern products, and complex solutions rather than simple ones.

Re:Mythbusters

[jlseagull (106472)]

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.

Re:Mythbusters

[Wavicle (181176)]

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.

Re:Mythbusters

[Shamashmuddamiq (588220)]

With all due respect, I don't think the Mythbusters are as smart as Archimedes was. You shouldn't impugn someone just because they lived a long time ago.

Re:Mythbusters

[Rob the Bold (788862)]

Don't screw with Archimedes.

Re:Mythbusters

[scdeimos (632778)]

Not to argue that the mythbusters are always right, but they've disproved this in one of thier episodes.

Actually, they only disproved their own design and construction methods on this one. A properly-designed and -constructed working model was demonstrated on BBC Two's practical archeology programme, What The Ancients Did For Us [bbc.co.uk]

That's not a magnifying glass.

[by Anonymous Coward]

That's an Archimedes Death Ray, now banned from all commercial airline flights. Lame.

Earlier experiment like this

[Steve1952 (651150)]

This sort of demonstration has been done before. I remember reading an article in Time magazine in the 1960's or 70's that reported on one such earlier experiment. Many men held polished flat "shields" in the sun at the right angle, and confirmed that they could cause charring in a simulated boat target.

Solar Death Ray

[bobgoatcheese (455695)]

Not exactly the same concept, but the Solar Death Ray [solardeathray.com] always reminded me of this.

No tin foil

[complexmath (449417)]

as tin foil hadn't been invented yet, his enemies would have had no viable defense against this weapon. Devastating!

He was duped

[complexmath (449417)]

in 212 BC, Archimedes (a notably smart person) constructed a burning glass to set the Roman warships, anchored within bow and arrow range, afire.

If the enemy ships were anchored within bow and arrow range, I suspect that while Archimedes was fiddling with his mirrors, a few archers dipped their arrows in pitch and fired them at the fleet. Eventually, when Archimedes finished aiming his master weapon he was overjoyed to discover the fleet in flames. Archimedes reported his success to the king, and went down in history as the oldest recorded example of a horribly over-engineered solution to a simple problem.

Re:He was duped

[TGK (262438)]

It's worth pointing out that the availability of really useful materials for incendiary warfare was notably lacking in the ancient world at this time. Even the Romans, with their much more sophisticated war machine never managed to deploy fire based weapons of any magnitude.

Dr Lendon of the University of Virginia and a leading expert on combat in the ancient world is oft quoted in reference to the opening scenes of Gladiator as saying this:

"The opening battle is remarkably accurate for a Hollywood depiction of Roman warfare... if you think away the Napalm. The Romans didn't have anything more flammable than olive oil"

Flaming arrows, while they make good cinematography, weren't in the Greek arsenal at the time.

You're only 900 years off

[jvance (416133)]

Read your link. Greek fire was invented in 673 AD.

Does anyone else find myth busters annoying?

[TummyX (84871)]

They run these unscientific experiments (most involving explosions or decaying corpses) and then "conclusively bust" myths. Some experiments are fun and interesting, but most don't deserve the hard conclusions they assign.

It's really annoying when people take accept their "proofs" as proofs.

You obviously were not paying attention at all

[brunes69 (86786)]

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.

The Sakkas Experiment

[alanw (1822)]

In 1973, a Greek scientist, Dr. Ioannis Sakkas performed the same experiment. There is a discussion at this web site [mlahanas.de], and a link to this one. [editorialbitacora.com]

It's in Spanish, but it does have a photograph of about 40 of the 70 man-sized mirrors they used. He managed to ignite a tarred wooden boat in about 3 minutes.

I am now seeing "Forbidden" when trying to access the original MIT web page, however Google claims there is mention of the Sakkis experiment on this one [mit.edu] (also forbidden).

1000 KW "death ray"

[PhilipPeake (711883)]

General technical specifications

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 [imp.cnrs.fr]

Re:MythBuster

[Shook18 (878947)]

And Mythbusters is LAW!

Re:MythBuster

[by Anonymous Coward]

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)

Re:MythBuster

[BrookHarty (9119)]

Flash ignition!
In an instant there is a large, open flame. The volatiles liberated from the wood ignite at roughly 1100 F.
Open, sustaining flame occurred less than 10 minutes after the sun was in a clear patch of sky!
You can also clearly see that there are still 3 mirrors not aimed correctly.

Now that Mythbusters is wrong, are there other myths that could be true?

Re:MythBuster

[by Anonymous Coward]

if the ships were within arrow range... wouldn't a flaming arrow have done the job just as well... why the over engineering?

Re:MythBuster

[sik0fewl (561285)]

This is before bow 'n' arrows, back in a time when lasers were the weapon of choice.

Re:MythBuster

[writermike (57327)]

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.

You don't have to burn wood -- people will do.

[kale77in (703316)]

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.

Re:Fire good!

[jericho4.0 (565125)]

Doughtfull at best. The Antikythera Mechanism [wikipedia.org] is probably only one of hudereds or thousands of devices that existed at the time, and many people could have been making, buying and useing similar items. Our knowledge of how the ancient Greeks (and others) actually lived is so fragmentary, and we tend to fill in all the blanks with the lowest common denominator answer, ie; we see no evidence of clockwork, therefore they had no clocks. Before the discovery of the Antikythera Mechanism, the suggestion that the Greeks had clockwork would have been met with scorn.

Yes, Archimedes was a very smart cookie, but he was surrounded by other smart cookies, who were also geting up to interesting things. IMO, ancient Greece was pretty much as technologicly advanced as 15th century Europe. Why we ended up having the industrial revolution, and the Greeks did not, becomes a very interesting question.

Re:Fire good!

[jericho4.0 (565125)]

Heronas of Alexandria built it. There are references to it and other steam/hydraulic sytems being harnessed to move things, but only marvels (temple trumpets, automatic doors, etc), never coal mines or factories.

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.

Re:Glass?

[rpj1288 (698823)]

A mirror can also prevent the server from burning up.

Maybe a combination of the 2

[MoreDruid (584251)]

Maybe he devised a combination of the two. A conical mirror to catch the sunrays and aim them, then a lens to bundle them even more.

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.

Re:Maybe a combination of the 2

[Scrameustache (459504)]

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

I remember that episode, they couldn't set their replica on fire even when they poured gasoline on it and set that on fire!

Adam's credibility was busted, not Archimedes'.

Easy to aim

[ChrisMaple (607946)]

There is a technique for aiming the mirrors easily and quickly, provided that one person holds each mirror and the mirrors are reflective on both sides. Make a hole in the center of the mirror. Open only one eye. Position the mirror so that you see the target in the hole and the sun shines through the hole onto your face. Tilt the mirror so that the image of the spot of sun on your face is centered on the hole.

Re:Units

[Legion303 (97901)]

"So what's that in units that the rest of the world uses?"

You can express it as 1 getacalculator (or 10^youlazyfuck if you prefer scientific notation).