Public Lecture—Archimedes: Accelerator Reveals Ancient Text

[Applause] good evening and thank you very much for coming um please join me for a journey uh which we find fascinating and which in fact from our point of view here at Stanford has just begun if you could have read the New York Times on July 16 1907 you would have found on the front page the headlines of a big literary find in Constantinople the Danish scholar Johan Ludwick hyberg had discovered an ancient a series of ancient writings ins a 12th century prayer book and it is this book with which our journey today is concerned about but let us go back another 2500 years what might look to you like the Sarah Foothills on a early summer day is in fact the location where on September 11 490 BC the fate of Western civilization was hanging on a very thin thread a huge Persian army led by King Darius had landed on the Greek Shore in the Bay of marathon estimates about the size range from 20 to 60,000 men strong after several days of discussion and consultation the Athenians decided to go to face the enemy and they sent into the valley of marathon an army of 10,000 Athenians with the help of a thousand plans being about 1,600 yards from the front line of the Persian archers the Athenians did the usual thing they organized their troops into a large felons where they protected themselves basically like a turtle with all their Shields and started to March it took about 10 minutes when they reached the range of the Persian archers to about 200 yards at that point something happened which hadn't happened in the history of warfare before rather than continuing their March and being exposed to the hail of of Aros they started to rush in a almost Sprint into the front and and did such a surprise attack avoiding the errors they got immediately into an infight and it took only part of a day before the stronger equipped Greek Athenian soldiers had beaten the persant at the end of the battle 6,400 Persian soldiers were killed and only 192 Greek Fighters upon which the persans decided to flee one of the fighters fides after fighting all day had to run 26 miles to Athens to deliver the message of Victory upon which he dropped dead there might be some people amongst you who regret that Athens is actually that far away from the Bay of Marathon the Battle of Marathon was the first victory of a new form of government it was the first victory of the ocient over the Orient and it is considered as one of the most important events marking the birth of Western culture and the beginning of the age of Classics they are no man slave and no man subject was said about the Athenians they are proud the Athenians the Victorious Democrats self-confident and ambitious approaching arrogance sounds familiar they have a mentality that leads them to enormous accomplishments in politics Arts philosophy and architecture there were the Great Greek philosophers Socrates born only 20 years after the Battle of Marathon the questioner his most famous phrase all I know is I know nothing his student Plato the idealist who wrote among many important works the Republic and his student Aristotle the taxonomist who was amongst many other accomplishments the educator of a 13-year-old boy who turned out later to be known as Alexander the Great and there were the mathematicians uklad of Alexandria his concept of space in fact of three-dimensional space has survived 2200 years until a former patent Clark of the name Albert Einstein discovered that in fact space is not three-dimensional there is a fourth dimension time multiplied with a constant the speed of light which is perpendicular to the three dimensions he later also realized that this four-dimensional SpaceTime is actually not straight but it's curved under the influence of gravity and this resulted in the general Rel theory of relativity still valid and confirmed many times it will be seen how long Einstein's concept of our universe will hold there are strong doubts it will survive 2200 years certainly string theorists don't hope so and then there were was the greatest of them all arimus of Syracuse born in the city state of Syracuse on the island of Sicily and in an unfortunate event killed at the age of 74 by a Roman soldier who didn't follow his orders arimus was famous at the time the Romans had ordered to capture him alive he was such a Val able person but supposedly deep into thoughts about mathematical problems he didn't follow the orders and was killed aimeedus as a student was sent to Alexandra to learn the teachings of ukl and actually also of Aristotle he amongst his many accomplishments in mathematics engineering Warfare and science is the famous pulley a means with which you can pull a weight many times heavier than yourself the famous Archimedes screw a pumping system still used in many places around the world with which you can pump water from a lower level to a higher level during the Siege of Syracuse aimeedus employed a combination of hooks and levers and the Roman battleships which were anchored at the K these hooks were brought underneath and they were shaken uh some of some of them tipped over and the soldiers were scared to death the most famous story about aimeedus however is his Eureka moment the king of Syracuse had asked the Goldsmith to make him a wreath and he had suspected that the Goldsmith had mixed some lesser Noble metal within the gold and which is also lighter he asked Archimedes to help him solve the problem at the time of Archimedes is it was relatively easy to weigh a an object however in in order to determine whether it's gold or not you needed to know the density and for that you need to know not only the weight but also the volume how could you ever determine the volume of such a complex object like a wreath aimeedus supposedly taking a bath all of a sudden got a great idea the water in his bathtub which he moved away with his body was exact had exactly the same volume of his own body no matter how complicated and irregular his own body was and by knowing that you had a way to measure the volume now all you had to do measure the weight so a possible experiment how to do this is you put a balance beam you put the amount of gold equal to the amount in the wreath and then you dip them both into the water if the wreath has a larger volume it it'll be it'll get a stronger lift and the balance will get out of uh out of balance in that matter the king actually realized that the Goldsmith wasn't dishonest man he had put some lesser Noble metal into the wreath Archimedes also invented the law of the lever and everyone who has played with their children on a TI TOA knows how valuable that is it tells you that the mass a and the dist times the distance a of the center on a balance equals the mass the distance B times the mass B are on the same balance in order to stay in equilibrium and I would show you now in a short version how Archimedes did the proof of this important concept I'll show it in reverse how he did it but I think it's it's better for the illustrations imagine you have two objects of equal mass at an equal distance your balance beam will be perfectly straight now of course you could replace them by uh four objects uh similarly spaced or without disturbing anything you could place these four objects close to the middle and put them in one large as long as they're always at the exact same distance from the balance now imagine you take 16 eight on either side you take four of them and replace them with one which is four times as heavy you will not bring the balance you will not dist disturb the balance you take the other ones and do the same thing in this case it's 12 and you PR you place them by 12 all you have to do now is remind yourself at which place these objects were and you know that because the this object is exactly at this location and the object of 12 is exactly in between the six on either side you can can measure that and you have the law of the lever this law has dramatic consequences of course because it tells you that in principle you could lift something extremely heavy as long as your beam is long enough and that L led to the famous saying give me where to stand and I will move the Earth which is of course not to be taken literally but arimus was well aware of the power of the of the law of the lever in fact Archimedes was so famous at its time time that as his Fame grew his challenges grew grew as well at one point the king of syracus asked him uh or at one point Archimedes uh took a combination of of levers and pulley and pulled a ship all by himself on land the King was so impressed uh and said from now on we have to believe what arimus is saying scientists sometimes hope that the reigning body today would have the same respect for them arim's most um one of his most famous mathematical accomplishments was the determination of the number Pi it is compared to the mathematical invention of the wheel Pi is the ratio of the diameter and the circumference of a circle and arimus used the following estimate he said he knew how to calculate the length of the three sides of a triangle and he said well I know that the triangle is that length has to be shorter than the sphere because all of it is inside the sphere then he said why not divide these three sides and create an hexagon and then he knew also how to calculate the side of each hexagon and if you add up all the six sides you will still get a number which is smaller than the circle because it's it's still inside the Circle however it is already much closer he continued that through through 12 sides 24 48 until 96 at that point he had a very good lower limit of the circumference and then he said let's do the same thing from the outside so he started from the outside and also went to 96 by those two methods he had an upper limit and a lower limit and he got the value to a Precision of 3.14 a value which is still used by many of who work in the construction as good enough Archimedes had a friend ostanes he was 11 years younger and and aimus was kind of a mentor for him aatosan is famous because he was the first person to measure the size of the Earth how did he do it the city of us one lies directly on the Tropic of Cancer that means on June 21st at noon there is no Shadow the sun is directly overhead and here I'll show you the situation of the Earth this is the Equator this is the north south and the topic of cancer would be this line basically this is the ray from the Sun at noon artinis who came from Alexandria also knew that at the same time on the same day there was in fact a small Shadow and he could measure it it was about a 7° angle of the sun he knew the distance between the two cities from the car Caravan traveling it was about 5,000 stadia and one stadium is about 185 M all he had to do now take that distance multiply it by 360 divide it by 7 and he got the estimate of the earth his number was falling and it's partly to the uncertainty of its angle partly to the uncertainty of what exactly one stadium is it is believed to be have fallen with between 39 and 46,000 km and the exact value is 40,000 km it's a remarkable achievement for that time before the war we know that Archimedes wrote a letter to his friend aratos greetings since I know you are diligent an excellent teacher of philosophy and greatly interested in any mathematical investigation that may come your way I thought it might be appropriate to write down and set forth for you a certain special method he later continued I presume there will be some among the present as well as future Generations who by means of the method explained will been abled to find other theorems which have not yet Fallen to our share only through a miracle if you want or through a series of fortunate circumstances that this letter actually survive until today and in fact the method which arimus describes in here is of of greatest significance which I will show you in a second in arimus time his work was written on Papyrus it was then copied also on papyrus pus scoll here you have a drawing of Archimedes writing on Papyrus scroll in the 4th Century the scribes changed their method they started to use parchment made out of mostly goat and sheep skin and they used an iron Gall ink for their writings and the Archimedes texts or the Archimedes letter in this case was then uh written on a parchment It is believed that the last time these texts were written was in the 10th Century uh in the second half of the 10th Century probably in Constantinople however in the 12th century the fourth Fourth Crusade sacked Constantinople and his parchment book was taken apart and in a common practice at the time reused for other mostly religious writings we are now in the Deep part of the Dark Ages there was no interest in mathematics and it was very hard to get bip parchment so this was an early method of recycling and here's how a palest standing palmes standing for scraped again is made you take the original book which you find with a parchment you use a acid made out of lemon juice and try to wipe it out as perfect as you can then you cut the two pages apart turn them 90° and write overwrite them with your own writings rebind them and you have your little prayer book poist it was this Palm sest which Johan Ludwick hyberg had discovered in Constantinople in 1907 it did not only contain seven of Archimedes Tre diseas two of them had been previously unknown one of them the method of mechanical theorems the letter of arimus to his friend artinis it also contained the only Greek version of arimus famous treaties on floating bodies hyberg tried to get the manuscript out of Constantinople to Copenhagen but they didn't let him do it so all he could do is travel to Constantinople and equipped with a magnifying glass that was the all the technical help he had at the day he started started to transcribe the manuscript we know now that in his transcription of the method there are significant gaps after World War I the arimus pmsis Disappeared in fact Constantinople was looted to a large extent and it was believed that it had gone forever and then oh I'm I I'm sorry I'm going ahead let me say the importance or the significance of the method and this is according to um ril Nets Who is the uh one of the leading Scholars a Stanford Professor on Archimedes and he knows the method very well in fact we work together with him in the method arimus combines pure mathematics with physical considerations for example by putting segments of a geomet of geometrical objects on a balance as I similar to what I just showed you at the law of the lever he manages to measure the area and volume of geometrical objects basically he's deriving geometrical discoveries by a physical thought experiment the second extremely important point is aimeedus is able to perform infinite sums he takes a fear for example and calculates its volume as the infinite sum of circles from which it is made this is a breakthrough comparable to the modern integral calculus and most of you if not in high school you have had to deal with that probably in college both findings are essential features of modern science in fact and it is no exaggeration to say that Archimedes method was 2,000 years ahead of its time Galileo for example was considered the first physicist who used mathematics to describe physical experiments Newton is considered the person who invented calculus and it is one can only speculate how people like Galileo Newton or DAV Vinci would have developed if they would have known about the method from aredes on October 29 1998 shortly after the arimus palmist resurfaced in Paris it it was auctioned at chrisy New York and sold to an unknown investor important to note here is that the person pledged not to limit access to an ancient manuscript and the owner was contacted by Will null from the Walters Art Museum shortly after the auction and agreed to lend the manuscript for an integrated effort of conservation and imaging in fact since 1998 there has been significant Pro progress in understanding the method because now other than a magnifying glass one could use modern technology such as UV light or multispectral Imaging to better bring out the different texts however there was a problem first of all the Palm test was in horrible conditions in fact since hyberg had read it until between hbg's 1907 and 1998 it had was attacked by mold and many of the pages uh have been have really deteriorated since then furthermore curiously four of the pages had medieval paintings on them hyberg never reported about medieval paintings they could have been they could have been real but it was suspected immediately that there's something wrong with that and indeed when looking at the manuscript GRE biblo National in France published in 1929 you can see a drawing which is almost identical to the one which was found on the arimus polymist in fact it had the identical size which suggests very much that this was just copied from someone onto the parchment we know now in fact only since about about two months that this painting was done after 1939 from the composition of the um different colors in the painting we do not know who did it and we certainly do not know whether the person who did it knew what he was actually doing whether he had any idea that there was text by arimus underneath this is when I learned for the first time about the Archimedes Palm sest in fact uh now comes Neil's introduction I was at a uh photosynthesis meeting in Germany in November 2003 and uh I stayed home for one night with my parents and my mother as many mothers do gave me a a stack of uh journals and little cop Little Snips of papers to read uh and that's when I heard about the arimus poest what struck me was the fact that the writings were done with an iron based ink I just had come from a conference where for 3 days we were talking about nothing else than spinach and in that spinach and now comes the question to you what does spinach have in common with the aimeedus PES we all know that spinach has a lot of iron in fact generation or one generation at least mine had been forced to eat a lot of spinach because of a scientific error at one point it was thought it has 10 times more than the other green leaves it's not true there's not that much iron in spinach in fact so don't worry about it if you don't eat it every day does it have more or less than the than the arimus poyy I I was sure it has less than the arimus polyes in fact the experiments we do on spinach uh show that this is really a trace element and I could not believe that even the faintest text in the arimus palest wouldn't have some traces of spinach similar some tray excuse me of iron similar than to an our spinach now what else do you need to look through meta for example through a painting it's X-rays and we all know that because we have taken we have gotten our chest x-rays done and of course the inventor of x-rays Who and the invention just celebrated the 100th birthday um is Willam conard Rin and the first really x-ray image is supposedly that of his wife's hand uh which also shows that the jewelry in that time was actually pretty big would you be able to do would you be able to image the archimedian palmes with such a device and the answer is no because this image is produced from a contrast so what you do is you shine the xpace through and the the part in this case the bones or this ring absorb much more and so it stays darker if you have something extremely thin or something of very dilute extremely dilute that contrast doesn't come out at all it is like looking at the stars in bright daylight the light of the stars is there but we won't see it why because the sunlight is so much stronger so what do we do we look at the stars at night of course and that is very similar to the technique I'm going to describe you now so please bear with me we are now traveling to the inside of an atom and I will show you here a schematic setup uh how an atom is built it has a nucleus U made out of protons and neutrons and it has a whole array of electrons zipping around the nucleus what determines an element is only given by the number of protons you have in the nuclear if you have if the nucleus has 26 protons it is iron and nothing else it doesn't matter how many neutrons it has those are different isotopes but they're all Iron if it has another amount like six it is carbon etc etc now it also has the same amount of electrons to balance this positive charge so iron has typically 26 electrons zipping around imagine now as we know that the positive protons attract the negative electrons imagine now you have a charge of 26 plus 26 putting a force on the inner electrons you can you can believe that that is a very strong force much stronger than for example a carbon nucleus which has only six electron six protons and the way how the electrons experience such a strong force is that they are much tighter bound to the nucleus in order now to remove one of those inner electrons you need for iron a lot of energy and for carbon you need you need less energy and in both cases you need x-rays to do that and I'm showing you now how it is done and then I'm showing you as well what we are using for the Imaging an x-ray comes in it knocks out the inner electron that hole is immediately Filled from the outter electron and sends out a second x-ray with a different color now I use the word color in a in a in an uh larger sense because obviously x-rays do not have any color for our eyes but but the important point is that by by looking at the color of the x-rays sent out you can unambiguously determine what element you're looking at because that color strongly depends on how much energy you need to knock out the inner one and then it the energy difference between those two gives you that particular color give me let me show it to you one more time this is another example in this case we're looking at this one and it might be a closer shell it falls in and sends out a different color the Imaging the X-ray Imaging of the arimus palmist of the iron in the arimus pal relies exactly on that method you look at a particular color of x-rays how do you do it first you need the palmes obviously you need a detector and then very intense x-ray beam and now all you have to do is you move your pmest through the X-ray beam each time when you hit an atom or a series of atoms of iron it'll send out a little fluoresence you're done with one line you go down and move to the next line in that order you basically scan your book back and forth and record each time when you get the signal you recorded in your detector and you can make a map of an iron map in that case or of any element you want of what you can see now what you need for this is an extremely intense x-ray beam as you can imagine and you need a very small x-ray beam because the size of your X-ray beam tells you how well you will be able to see the text later on so let me finish where can you find such an xray beam well um we are at the Stanford linear accelerator Center and there powerful beams here um of course the most famous is our 2 mile long linu but we also have if you if you go into this little corner here not far from here as a matter of fact the Stanford synchotron radiation Laboratory um which is a an oval or almost round shaped um device which produces very intense x-rays in fact ssrl has been one of the first in the first multi-user multi-gev that is a very high energy lab of this kind uh it started in the 1970s since then there has been a revolution with these machines there are now more than 50 operating around the world at places like harima Japan this is the largest one in the world one mile circumference is so big you you will not find a one M straight area in Japan so what did they do they build it around the hill the advanced Photon Source in Illinois 1 kilm circumference almost the sister lab beautifully located below the mountains where the 1968 Olympic Games took place in grobble the European syron radiation facility across the bay from us with a beautiful view on the Golden Gate Bridge the advanced light source in Berkeley and it's sister lab Bessie Berlin how does such a syncron radiation laboratory look on the inside basically what you do is you store an electron beam in a vacuum tube which is surrounded by series of magnets when you force the electron when you force the charge to go around to be bent around it'll send out this very intense x-ray and you have in principle two or three different sources of x-rays one of them is called bending magnet radiation it comes out like a fan similar to when you have your bicycle tire wet and you spin it fast the water comes out like a fan and it's annoying because your your back gets always dirty the other one are so-called wigglers or under lators and they in fact Force the electrons on a little slalom uh Racetrack and by doing that you can actually cimate the X-ray beam coming out even further and you get even more intense x-rays x-rays from a synchrotron are between a million and a billion times brighter than the Sun and you can imagine when I told that to the curator of the Walters Art Museum I'm going to use a beam which is a billion times brighter than the sun to put it on your arimus palmy he was very happy in fact he of course didn't give me the pals stri away we had to do several tests before and I'll show you that in a second this is the inside of a ring just to impress you a little bit these series of magnets they are remarkable machines and this are some snapshots on the experimental floor these are where the users like myself use these x-rays um you see a control station here of a hard x-ray beam line you see someone putting a sample into the X-ray beam um you see a a complicated deflectometer device and this is kind of an overview where you see that it's an amazing activity going on uh our lab for example has up to 2,000 us a year coming from around the world doing different research in our laboratory I just told you they wouldn't give me the Palm sest however uh Abigail Quant was kind enough to lend me from her own private collection a 19th century parchment uh an English will uh and you're welcome to come by after the talk and have a and and have can feel how how wonderful it is um it this one is made out of sheep skin very similar to the arimus palest and the first test we did is we wanted to see can we really image something and I'm just holding it up right here this is the word or from this text and this is our x-ray iron image from that particular word the resolution is something like of order 600 DPI some of you might be familiar with these terms um in in order to protect the arimus Palm sest from this very intense x-ray beam we had to come up with a mechanism that each time when the beam was at the end of a line we inserted a shutter to close the beam so that the ex so that the palmis was not exposed to the beam it would then move up to the next line started to move open the shut again and go back and forth by doing that we guaranteed that any given point of the palmy was no longer than about 10 to 20 milliseconds exposed to this intense beam we also had a mechanism in case something fails the shutter is just closed right away in addition we needed to come up with a air condition and humidifier system because the uh conservator from the art museum abigel Quant asked me to keep the document always at a 50% humidity level level at about 70° fah um I got a lot of help from a student Jessica Lee she's now she has now joined Stanford as a freshman and we basically built a uh we modified a commercial uh humidifier for your house uh into one which requires the string more stringent um levels of for the arimus poist let me now finally show you um the palest arrived in May and here you see page uh with a gold forgery this is Abigail who is she in she is basically was the only person who was allowed to handle these pages and she is now inside our experimental Hutch um we have take we have taken this photo through the lead window during exposure during measurements no one is allowed to be inside there is an Interlock system which keeps you out of out of that what you see in the back is kind of a plastic tent this was our very sophisticated construction for the humidification system it was hidden underneath there but it worked I'll show you a little another view abigil has now left the hutch and we are able to put the beam inside the hutch touch here basically you you see a set of filters and slits those were these very fast pneumatic slits which could drop in at an instant in case there was a problem with the x-rays and here this is a different page now um you see a view uh a little bit closer look the x-rays came through here there was a very tiny slit and created this x-ray beam which is about 40 microns that's just just about the size of your hair a little bit smaller than the size of your hair and that's what that's how how small the X-ray beam was and schematically I show you again here how we basically then raster scanned this um document back and forth you can think of it as the world's most expensive copy machine if you want let me show you now our results the first I'll show you this corner and this is the normal view you have and it is really uh hard if not impossible to imagine if or that there is any text and this is how the X-ray image looks like and I'm blowing it up right now this is what came out right of the computer the horizontal writing is from Archimedes the vertical writing is from the um is the biblical writings both of them contain iron so both of them show up also unfortunately um in the drawing itself some part of the drawing uh also contain iron and so these parts um will be a little bit harder to to read in fact we are thinking about a ways where we look at different elements in order to read these parts but certainly these parts uh you can start to find letters for example you can find a t you can find a Theta you can find maybe um maybe like a five if you're if you're an expert of ancient Greek it might help you but you can imagine as well that um it is not easy to to read the text um partly because of the quality of the image but also partly uh because of the fact that when you when the um Palm sester try to to wipe out the old text what he really did is he distributed the iron all over the place that's what we do when we take an eraser and and and take out the some of the things so so you can see actually there's iron all over the place and it is not typically in a parchment that there's iron this is this was distributed let me show you another image this is now an the exray image of uh folio 163 v stands for Versa it's the front side and I'm showing you this I'm showing you an uh uh part of it here you see again arimus text in the horizontal and the text above in the vertical and I would like to point out a remarkable feature about the x-rays um again you see some characters in this direction these are Archimedes characters and this is the uh this is the prayer book text um the xrays for the x-rays the parchment itself is actually transparent but of course if you have two texts on top of each other the amount of iron adds up you have the iron from the top layer and you have the iron from the layer beneath and you can see that here you can see that at the parts where these characters overlap you actually get more signal so in our case more signal means like a bright like a a more white look of this and this might help you to actually read underneath text which is above because you can still see it with an optical Imaging if something is above it completely blocks it out and you will never be able to read it so that can be very helpful there is one difficulty with using x-rays um because the because the parchment is transparent you will see actually both sides so it would be like looking looking for example at this page which is written on both sides looking against a light and you will see the writing from both sides so you have to um somehow try to find a way to disentangle the front side from the back side and in fact by using images from both sides so what we did is we image from that side and then turn around image from that side and then through a smart trick of one of our collaborators you can then take these data and and crunch them as we say and you will get out uh the front and the back side with different colors and here I just show you an example of that the front side writings would be in red and the back side would be in Cayenne now I would say you can take on your glasses and I have to take mine as well actually okay um please uh remember the blue goes to the um right eye that's the most important thing otherwise you see six dimensional um one of our colleagues Bob marttin he had the idea why don't we uh do some stereographic Imaging and we did that all you have to do is you come in from through two different angles just about the same angles as your two eyes are and then you can print them in two different colors and here's what you see um this is now uh a 3D image uh of uh volume 163 with a text of arimus on it the first thing which You observe is that the parchment is actually waved and you can see that very clear I I hope you can see that very clearly second of all with this 3d effect uh you can actually get an idea of which of the writings is on the front side and which of the writings are is actually on the back side and for example here on that right corner you see clearly that this text uh seems to be like it is floating above the text underneath so this is clearly from the front side and then this text is clear from the back side and I'll show you another example now you're are zooming in really to a size uh that is kind of the size the scholars like to look at these characters at uh they want to have them as big as their as big as their computer screen basically and again you can you can get a very good idea about how the different layers of text are at different components so um this method so you can take off your your glasses again this method um of using the three-dimensional uh way of looking at it or the stere as they call it stereographic way might help in some cases for the Imaging um let me now finish uh with the Outlook we have just started the Archimedes Imaging and uh the Museum will come back in March with the other forgery pages in particular of a particular important importance is page two of the introduction of the method that is underneath a fore and we hope we can read as much as we can uh of that page it is basically um the continuation of the letter of arimus to his friend aratos the pal was a busy person there was not they did not only find Archimedes in this palest there is text by a possibly unknown author and we haven't been able we don't even know yet which elements are in the ink we know there is no iron in the ink we hope we might be able to help what I was told is it is enough to read something like three to five words of any book in the world and using uh super computers you can then deduce whether that is a new text or whether that is an existing text so if we could if we would be able to read let's say one line of this unknown writer we might be able to come to a new text Hyperius uh was a contemporary of Plato and uh he is seems to be rather important for some of the scholars as well by with within the next 3 years at at the latest there will be a hopefully a full translation made available to the public of the arimus palest with all the Tre Dees particular the method and and the other uh trees as well and the Palm sest will be uh again on display and it's not uh completely decided yet exactly where it is but there's a chance it will be at the Field museum in Chicago and by uh showing you a couple of impressions of my collaborators and myself at work I would like to finish with a thought what would aimeedus think if he would be seeing us here using a huge machine to try to find the last words and characters of some of his work I think he would say something like that you fools of the 21st century I like the fact that you use these large round beautiful objects to study my work but I wish you could have recovered my treaties on flying objects that would have helped you probably a couple of centuries thank you very much [Applause] so U thank you very much for a fantastic talk we have time for just a couple of questions I don't know if U can you answer any questions absolutely yeah let's try anybody got any questions uh for are there other texts that this will be useful anal yes so the question is whether there are other text um the I believe there are many texts uh very many texts where where this technique should be useful in fact uh in England some uh similar work is actually going on on some text and uh um I I'm not a scholar but from what I heard uh from from my colleagues that that there could be many texts where this could be very helpful how much time does it take to scan one page or SE P so that's actually a very good question and it's it is surprising how long it actually takes because uh what you have to what what you have to keep in mind is that if you have a a page let's say of of this size um and you you can very easily calculate how many of those uh small 40 Micron pixels actually corresponding to the 600 DPI on it and it turns out to be something of order 10 10 million and so you can then uh you can then estimate how short you have to stay on each of them in order not to make the scanning uh take a year and uh in our case it took us about 30 hours for a half page and that seems like a very long time but but you have to compare it to about uh several month for the scholars to read to read it then so in that sense actually we are uh our time is is not that long that was another question is there another element besides iron at or is that the obvious choice um yes there are um there is um we know that there's for example also sulfur in the ink um there is um potassium in the uh not in the aimeedus ink but in the ink of the prayer book so the thought is if you use uh basically like a a subtraction method you can image the potassium and the iron and then subtract out the other text uh the problem really is that uh as I showed in this example of how to um how this x-ray fluoresence how this x-ray glow works if you go to lighter elements like sulfur the x-rays do not penetrate as much anymore and it is very difficult um uh to to look at these lighter elements but we are making an effort in fact what we would have to do is put the arimus palmes inside a helium uh atmosphere and we are currently thinking about how to do that one could humidify it for example a little bit what are the waves on the page how dides that oh the weight yeah so the weight on the page which I showed was basically a um a cartoon picture of an x-ray Photon which we call a photon part of an x-ray beam coming in and hitting the hitting the atom and knocking out the electron and and then um basically uh creating this this secondary glow now you might say how in the world is it possible to hit anything as small as an atom and atoms are indeed extremely small the the the good news is there are lots of them and so basically um if you have lots of them uh you you will hit you will hit one you will never be able to tell exactly which one but you will hit one of them so so that that was the ex what's the sensitivity of your sensor what kind of noise do you have on uh are you asking about what kinds of concentrations or are detector and the kind of noise oh okay well our detector is basically what we call it's a single photon counting detector so in other words it really counts every event coming in okay and um the in order to get an image that you can that you can really um that is useful that you can see you you need uh several thousand probably uh and and so that that gives you kind of the the limit um if you get to lower numbers it starts to get grainy very similar to a photo uh photographic exposure when you go to when when you take a photo at when it's very dark uh you get graininess and that that's just due to the fact that the signal gets lower but but the but the Sensitivity I would say you know the the way to characterize it would be is as a function of kind of how much concentration or how dilute you can be and and and uh uh so I you know I could give you more details on that other than that is there any damage to the material at all can you take another scan yes that's a that's an excellent question in fact um we we did so what we did is uh we took took the we took this um parchment this British parchment and we went uh put it in the beam and we did different times of exposure okay and then after that I actually sent these different uh these parts which have different long exposure times to Ottawa to the conservatory Institute and they looked at the fragility of the fibers in there so they they did a very stringent test in fact much better than you would see for example with a microscope and we came up with a dose of 10 to the 10 um per pixel and uh if you C if you go back to the number we used we used about um 100th of that for our current Imaging so in principle we we would be allowed to scan another 100 times over that same area and at some places in fact we might need to scan longer because if if the iron gets very dilute as as the previous question was you need to to to stay on a little bit longer in order to get a good picture it's like your exposure time in your camera basically uh do you have to match the energy of the photons with the uh sort of energy required by the electrons right well in order to knock out the photon excuse me in order to knock out the electron you all you need to do is go above the threshold to knock it out so so in fact what you do is you don't want to go you don't want to go too close to the edge because then you your detector might see a lot of of those unwanted uh x-rays which are just scattering and not doing a glow also so what so what we did is we went to an energy which was about um 30% higher than than the energy of the fluoresence and that and that gave us a nice uh clean signal from the iron maybe maybe two more questions people hold pens differently okay at different angles is does your Technique allow you to discern like a blaze angle one that is a preferred reflection or or uh uh Vector for such a thing so that you could distinguish between one set of writing and another yes in fact it does and and it's a very good point you you bring up uh when we inspected the iron image of the text you could actually see uh at at from which angle um the the pen was pushed because when you then try to wipe it out out there's always more iron left in that corner where it is pushed in and uh and in some in some cases Optical Imaging or UV Imaging also brings that out but in in other cases uh with the with the X-ray image it becomes extremely clear from which side the pen was was held if I understood you correctly P the original P was 600 years old you're looking at the yes unfortunately not it's uh the original well obviously the we are looking at a 10th Century document so the original it's actually 12200 years older than the original writing however um the scholars have a very good idea of how often uh it was copied and it is believed that the Archimedes text was no copied no more than about five times uh when it made it into the prayer book so the fact that it ancient Greek and the fact that it is such a young copy in the sense of number of repetition M makes it actually extremely valuable um so iie uh U is going to hang around so those of you who have uh more questions I'm sure he's very happy to uh answer those for you want to look at the bits of parchment that's our last lecture of the year we start again the new series in 2006 bigger and better I'd like to take the opportunity to wish you all very happy holidays our cafeteria is open if you want a drink after all of this uh so once again U thank you very much indeed uh the original well obviously the we are looking at a 10th Century document so the original it's actually 1200 years older than the original writing however um the the scholars have a very good idea of how often uh it was copied and it is believed that the Archimedes text was no copied no more than about five times uh when it made it into the prayer book so the fact that it's in ancient Greek and the fact that it is such a young copy in the sense of number of repetition M makes it actually extremely valuable um so Olie uh U is going to hang around so those of you who have uh more questions I'm sure he's very happy to uh answer those for you if you want to look at the bits of parchment that's our last lecture of the year we start again a new series in 2006 bigger and better I'd like to take the opportunity to wish you all very happy holidays our cafeteria is open if you want a drink after all of this uh so once again U thank you very much indeed [Applause] e e e e e e e e e e e e e e e e e e e e e e e

Channel: SLAC National Accelerator Laboratory

Views: 17,583

Keywords: math lecture, Archimedes, physics, antiquity, palimpsest, Department of Energy, DOE, Stanford University, science, science talk, public lecture, SLAC, accelerator, science video, physics video, SSRL, laser, photon science, x-ray fluorescence, x-ray absorption, spectroscopy, X-rays, light source, synchrotron, ancient text

Id: APDg1WE8BNM

Length: 75min 22sec (4522 seconds)

Published: Tue Jan 18 2011