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Astrolabes: The Medieval 'Smartphone'? | Seb Falk


When you have an astrolabe, when you understand an astrolabe, you've got the universe in the palm of your hand (rhythmic music) I'm Seb Falk, I'm a historian at Cambridge University and I'm the author of "The Light Ages"

(rhythmic music) People often assume that modern science began in the Renaissance or began with the Scientific Revolution, as they sometimes call it, in the 17th century or perhaps the 18th century And to an extent that's true, but we mustn't ignore the contributions of the Middle Ages, the foundation of the universities, for example, the invention of the first mechanical clocks, or work with lenses, which allowed the first eyeglasses But more important than the innovations of the Middle Ages were the ideas and the mindset of the Middle Ages, the curiosity, which allowed people to take an interest in the world around them And so, when we think about the Middle Ages, we shouldn't just be thinking about battles, and wars, and kings and queens We should be thinking about a vibrant scientific culture which ran through society, especially educated society

(pleasant music) Astronomers in the Middle Ages often liked to say that there was no way of understanding science without scientific instruments, and the central scientific instrument of the Middle Ages was this one, the astrolabe The astrolabe is a tool for scientific calculation and observation, but it's also a model of the universe It's a planisphere, which means the sphere is squashed flat, just like a map is a squashed globe The story goes that Ptolemy, the great ancient Greek astronomer, was out riding his horse one day, carrying an armillary sphere, which is a three-dimensional model of the heavens, and he dropped it by accident, and his horse trod on it and squashed it flat, and thus was produced the astrolabe Now that's a bit of a fanciful tale, but what Ptolemy did do was work out how to make a three-dimensional sky understandable and workable on a two-dimensional instrument

The stars are always fixed in relation to each other So, move about on this part, which is called the rete, and they move over the background of the heavens So how does it work? How about we want to know the time, very simple thing that we're used to being able to know every day Well, in order to know the time, simply we have to set the astrolabe for the position of the heavens as it is right now and read the time on the face of the astrolabe So the first thing we have to do is to find the position of the sun in the heavens, and we do that by turning to the back and looking at the calendar

And we say the date today is the 6th of July And we find on this scale on the back that, on the 6th of July, the sun is in the sign of Cancer, and it's at about the 14th degree of Cancer So we found that on the back But, before we turn back to the front of the astrolabe, we have to measure the height of the sun in the sky, assuming it's daytime At nighttime, you could use any star, but, in the daytime, if it's sunny, you want to measure the height of the sun in the sky using this part called the alidade

You turn the astrolabe so that it's edge on to the sun, and then you turn the alidade so that the light of the sun streams through these sights, and the upper sight casts a shadow on the lower sight And then, when you've done that, you can measure the height of the sun above the horizon So let's say, for example, the height of the sign above the horizon right now is 40 degrees We turn back onto the front and we have to find the position of the sun today Now this circle here is called the ecliptic, and it carries the zodiac signs, Sagittarius, Capricorn, Aquarius, those zodiac signs that we're all familiar with

Those are the constellations that the sun passes through in the course of the year When we found the position of the sun, I said it was the 14th degree of Cancer We can mark that for today 'cause the sun only moves about a degree a day, and I might get a bit of wax, or maybe I'll mark it with a pen Those are the things people did in the Middle Ages I'll just use a little bit of white tack or something on the ecliptic where the zodiac is

That's the position of the sun Now, I can map the sun as it rises above the horizon in the morning, as it comes up to 12 o'clock noon and it culminates, it gets to its highest point in the sky, and then as it comes down and sets again Now, in order to tell the time, all we have to do is set the position of the sun at the height above the horizon that we just measured, 40 degrees, 10, 20, 30, 40 degrees up in the sky And then we put this rule through the position of the sun on the ecliptic, and we can measure on the horizon that, at eight o'clock, a little bit after eight o'clock, maybe quarter past eight in the morning, the sun was already 40 degrees above the horizon Now an astrolabe can do so much more than that

An astrolabe can tell you where you are It can tell you the direction of north It can help you measure the height of a building It can tell you when the sun will rise It can tell you when a certain star will rise or help you identify an unknown star, if it's marked on this astrolabe

So it really is a multifunctional device, just like a little smartphone, which does things that larger, more cumbersome computers could also do, but does it in a neat little package that you can carry around with you That's why it's like a smartphone It's also like a smartphone because it's beautiful It's a design classic It's even a status symbol

And this rete that carries the stars, it's got this beautiful, intricate, brass, woven pattern, and that's not necessary to the working of the instrument That's a way for craftsmen to show off their ability, so to market their devices and to let buyers know that this is a high quality product And in that way, the astrolabe was also like a smartphone It was a status symbol But, above all, it's a model of the heavens, it's a model of the world

And that's why, when you have an astrolabe, when you understand an astrolabe, you've got the universe in the palm of your hand This is the replica astrolabe, but the first time I ever held an astrolabe in a museum was just an emotional experience, a moment of contact with the craftsmen of the Middle Ages To think that I was holding in my hands something that an astronomer and a craftsman had held back in the 14th century and the 13th century, and that I was looking at the marks that that person made I was holding the brass that that person had hammered out so painstakingly, had cut so precisely, had divided those circles into 360 exactly spaced degrees That was a moment of real emotion for me, to have that personal contact with the Middle Ages

The Middle Ages was a time of intense wonder about nature So, while it's easy to dismiss some of the myths and some of the things that we now think of as being mistaken or fanciful, it's so important to understand how an interest in nature was woven through medieval society, woven through their art and their poetry and their music and their literature And what I wanted to do in "The Light Ages" was to immerse readers in that medieval sense of wonder about the world, to allow readers to learn medieval science as somebody at the time would have learned it, to learn how to multiply Roman numerals, to learn how to cure disease medieval style, to learn how to navigate by the stars in order to understand how medieval people lived their science Science for us today is a way of understanding our place in the universe, understanding why we're here, and where we've come from, and how we fit in in the world, and that was as true in the Middle Ages as it is today (dramatic music)

Source: Youtube

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