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As technology progresses,

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and as it advances,

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many of us assume that these advances

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make us more intelligent,

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make us smarter and more connected to the world.

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And what I'd like to argue

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is that that's not necessarily the case,

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as progress is simply a word for change,

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and with change you gain something,

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but you also lose something.

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And to really illustrate this point, what I'd like to do

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is to show you how technology has dealt with

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a very simple, a very common, an everyday question.

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And that question is this.

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What time is it? What time is it?

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If you glance at your iPhone, it's so simple to tell the time.

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But, I'd like to ask you, how would you tell the time

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if you didn't have an iPhone?

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How would you tell the time, say, 600 years ago?

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How would you do it?

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Well, the way you would do it is by using a device

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that's called an astrolabe.

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So, an astrolabe is relatively unknown in today's world.

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But, at the time, in the 13th century,

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it was the gadget of the day.

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It was the world's first popular computer.

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And it was a device that, in fact, is a model of the sky.

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So, the different parts of the astrolabe, in this particular type,

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the rete corresponds to the positions of the stars.

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The plate corresponds to a coordinate system.

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And the mater has some scales and puts it all together.

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If you were an educated child,

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you would know how to not only use the astrolabe,

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you would also know how to make an astrolabe.

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And we know this because the first treatise on the astrolabe,

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the first technical manual in the English language,

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was written by Geoffrey Chaucer.

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Yes, that Geoffrey Chaucer, in 1391,

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to his little Lewis, his 11-year-old son.

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And in this book, little Lewis would know the big idea.

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And the central idea that makes this computer work

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is this thing called stereographic projection.

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And basically, the concept is,

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how do you represent the three-dimensional image

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of the night sky that surrounds us

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onto a flat, portable, two-dimensional surface.

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The idea is actually relatively simple.

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Imagine that that Earth is at the center of the universe,

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and surrounding it is the sky projected onto a sphere.

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Each point on the surface of the sphere

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is mapped through the bottom pole,

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onto a flat surface, where it is then recorded.

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So the North Star corresponds to the center of the device.

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The ecliptic, which is the path of the sun, moon, and planets

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correspond to an offset circle.

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The bright stars correspond to little daggers on the rete.

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And the altitude corresponds to the plate system.

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Now, the real genius of the astrolabe is not just the projection.

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The real genius is that it brings together two coordinate systems

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so they fit perfectly.

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There is the position of the sun, moon and planets on the movable rete.

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And then there is their location on the sky

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as seen from a certain latitude on the back plate. Okay?

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So how would you use this device?

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Well, let me first back up for a moment.

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This is an astrolabe. Pretty impressive, isn't it?

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And so, this astrolabe is on loan from us

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from the Oxford School of -- Museum of History.

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And you can see the different components.

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This is the mater, the scales on the back.

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This is the rete. Okay. Do you see that?

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That's the movable part of the sky.

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And in the back you can see

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a spider web pattern.

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And that spider web pattern corresponds to the local coordinates in the sky.

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This is a rule device. And on the back

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are some other devices, measuring tools

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and scales, to be able to make some calculations. Okay?

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You know, I've always wanted one of these.

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For my thesis I actually built one of these out of paper.

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And this one, this is a replica

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from a 15th-century device.

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And it's worth probably about three MacBook Pros.

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But a real one would cost about as much as my house,

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and the house next to it, and actually every house on the block,

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on both sides of the street,

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maybe a school thrown in, and some -- you know, a church.

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They are just incredibly expensive.

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But let me show you how to work this device.

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So let's go to step one.

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First thing that you do is you select a star

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in the night sky, if you're telling time at night.

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So, tonight, if it's clear you'll be able to see the summer triangle.

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And there is a bright star called Deneb. So let's select Deneb.

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Second, is you measure the altitude of Deneb.

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So, step two, I hold the device up,

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and then I sight its altitude there

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so I can see it clearly now.

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And then I measure its altitude.

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So, it's about 26 degrees. You can't see it from over there.

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Step three is identify the star on the front of the device.

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Deneb is there. I can tell.

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Step four is I then move the rete,

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move the sky, so the altitude of the star

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corresponds to the scale on the back.

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Okay, so when that happens

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everything lines up.

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I have here a model of the sky

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that corresponds to the real sky. Okay?

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So, it is, in a sense,

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holding a model of the universe in my hands.

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And then finally, I take a rule,

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and move the rule to a date line

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which then tells me the time here.

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Right. So, that's how the device is used.

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(Laughter)

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So, I know what you're thinking:

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"That's a lot of work, isn't it? Isn't it a ton of work to be able to tell the time?"

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as you glance at your iPod to just check out the time.

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But there is a difference between the two, because with your iPod

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you can tell -- or your iPhone, you can tell exactly

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what the time is, with precision.

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The way little Lewis would tell the time

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is by a picture of the sky.

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He would know where things would fit in the sky.

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He would not only know what time it was,

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he would also know where the sun would rise,

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and how it would move across the sky.

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He would know what time the sun would rise, and what time it would set.

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And he would know that for essentially every celestial object

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in the heavens.

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So, in computer graphics

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and computer user interface design,

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there is a term called affordances.

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So, affordances are the qualities of an object

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that allow us to perform an action with it.

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And what the astrolabe does is it allows us,

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it affords us, to connect to the night sky,

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to look up into the night sky and be much more --

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to see the visible and the invisible together.

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So, that's just one use. Incredible,

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there is probably 350, 400 uses.

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In fact, there is a text, and that has over a thousand uses

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of this first computer.

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On the back there is scales and measurements

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for terrestrial navigation.

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You can survey with it. The city of Baghdad was surveyed with it.

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It can be used for calculating mathematical equations of all different types.

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And it would take a full university course to illustrate it.

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Astrolabes have an incredible history.

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They are over 2,000 years old.

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The concept of stereographic projection

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originated in 330 B.C.

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And the astrolabes come in many different

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sizes and shapes and forms.

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There is portable ones. There is large display ones.

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And I think what is common to all astrolabes

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is that they are beautiful works of art.

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There is a quality of craftsmanship and precision

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that is just astonishing and remarkable.

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Astrolabes, like every technology, do evolve over time.

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So, the earliest retes, for example, were very simple and primitive.

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And advancing retes became cultural emblems.

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This is one from Oxford.

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And I find this one really extraordinary because the rete pattern

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is completely symmetrical,

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and it accurately maps a completely asymmetrical, or random sky.

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How cool is that? This is just amazing.

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So, would little Lewis have an astrolabe?

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Probably not one made of brass. He would have one made out of wood,

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or paper. And the vast majority of this first computer

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was a portable device

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that you could keep in the back of your pocket.

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So, what does the astrolabe inspire?

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Well, I think the first thing is that

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it reminds us just how resourceful people were,

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our forebears were, years and years ago.

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It's just an incredible device.

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Every technology advances.

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Every technology is transformed and moved by others.

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And what we gain with a new technology, of course,

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is precision and accuracy.

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But what we lose, I think, is

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an accurate -- a felt sense

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of the sky, a sense of context.

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Knowing the sky, knowing your relationship with the sky,

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is the center of the real answer

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to knowing what time it is.

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So, it's -- I think astrolabes are just remarkable devices.

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And so, what can you learn from these devices?

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Well, primarily that there is a subtle knowledge

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that we can connect with the world.

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And astrolabes return us to this subtle sense

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of how things all fit together,

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and also how we connect to the world.

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Thanks very much.

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(Applause)